JP6232827B2 - Manufacturing method of ceramic composite - Google Patents

Description

  The present invention relates to a method for producing a ceramic composite having a structure in which two or more crystal phases produced by unidirectional solidification of an eutectic oxide melt are continuously and three-dimensionally entangled with each other. . Specifically, the ceramic composite used as a structural member of a heat engine exposed to a high temperature, and the ceramic composite used as a selective emitter member having a strong emissivity at a selective wavelength used in thermophotovoltaic power generation technology. The present invention also relates to a method for producing the ceramic composite used as a light conversion member in a white light emitting diode or the like used for a display, illumination, backlight light source or the like.

  A ceramic composite with a structure in which two or more crystal phases produced by unidirectional solidification of an eutectic oxide melt is continuously and three-dimensionally intertwined is selected as a high-temperature structural member It is known to have excellent characteristics as an emitter member or a light conversion member (Patent Documents 1 to 5). Among them, the ceramic composite used as a light conversion member can be used as a light conversion member by itself, and is industrially useful suitable for use in combination with a high-power light-emitting diode having both high emission intensity and heat resistance. It is a ceramic composite with particularly high properties.

  In recent years, research and development of white light emitting diodes using a blue light emitting element using a nitride compound semiconductor as a light source has been actively conducted. White light-emitting diodes are light in weight, do not use harmful substances such as mercury, and have a long lifetime, so that demand is expected to increase rapidly in the future.

  The most commonly performed method for converting blue light of a blue light emitting element into white light is, for example, as described in Patent Document 6, in which a part of blue light is placed on the front surface of a blue light emitting element. By providing a coating layer containing a phosphor that absorbs and emits yellow light, and a mold layer for mixing the blue light of the light source and the yellow light from the coating layer, and mixing the complementary blue and yellow colors A pseudo white color is obtained. Conventionally, a mixture of yttrium aluminum garnet (YAG: Ce) powder activated with cerium and an epoxy resin is employed as the coating layer. Currently, as the use of white light-emitting diodes expands, high-intensity white light-emitting diodes with high emission intensity are demanded and are being developed.

  In order to improve the light emission intensity of the white light emitting diode, it is necessary to apply a higher output current. However, application of a high output current generates heat in the blue light emitting diode as a light emitting source, causing deterioration of the phosphor and the coating resin, leading to a decrease in light emission intensity.

  In order to solve this problem, research and development of phosphors that do not use a resin has been conducted. Two or more types of crystal phases produced by unidirectional solidification of an oxide melt having a eutectic composition, which can be used as a light conversion member, have a structure in which they are intertwined with each other continuously and three-dimensionally. Ceramic composites (ceramic composites for light conversion) have extremely high heat resistance compared to resins, and do not cause deterioration of the phosphor due to heat generation, and can maintain high fluorescence intensity (Patent Document 4, 5).

  The above-mentioned ceramic composite is usually moved by a crucible containing a melt composed of components constituting the ceramic composite in a furnace having an appropriate temperature gradient, and the Bridgman method is used to solidify the melt in one direction. Manufactured by. As the crucible, a crucible made of a refractory metal such as iridium (hereinafter referred to as Ir), tungsten (hereinafter referred to as W), molybdenum (hereinafter referred to as Mo), or the like can be used.

  Further, as shown in FIG. 3 or FIG. 4 of Patent Document 7, the structure inside the crucible is positioned above the unitized crystal growth chamber and the unitized crystal growth chamber, and the straight body portion extends from the unitized crystal growth chamber. And a structure using a nesting having a large volume space between the inner wall and the crucible inner wall, and further disclosed in Example 5 of Patent Document 7. Thus, by using the ceramic composite itself as a seed crystal, it is possible to obtain a ceramic composite free from cracks with a high yield.

Japanese Patent No. 3216683 Japanese Patent No. 3412381 JP 2000-272955 A Japanese Patent No. 4609319 Japanese Patent No. 5029362 JP 2000-208815 A JP 2004-238254 A JP 2011-216543 A

  However, even if a ceramic composite without cracks can be obtained with a high yield by the above method, the crucible holding the melt at a high temperature is worn out during the unidirectional solidification, and the crucible structure is changed from the crucible to the melt. Ingredients may be mixed. The mixed components of the crucible remain as contaminants in the ceramic composite after solidification, particularly from the seed crystal to the lower part of the ceramic composite, and the ceramic composite does not exhibit the original color at the contaminated site. In addition, the original characteristics of the ceramic composite may not be exhibited. Moreover, it may remain in the form of flakes or the like in the vicinity of the surface of the ceramic composite.

  If the crucible constituents mixed in the unidirectional solidification process remain in the ceramic composite as described above, the contaminated portion contaminated by the crucible constituents does not exhibit the original characteristics of the ceramic composite and is removed. In such a case, the product yield is reduced, and the removal process is required, which increases the manufacturing cost of the ceramic composite.

  Accordingly, the present invention grows a ceramic composite having a structure in which two or more crystal phases are continuously and three-dimensionally entangled with each other using a seed crystal from an oxide melt having a eutectic composition by the Bridgman method. An object of the present invention is to provide a method for producing a ceramic composite that enables a ceramic composite that is free from cracks and less contaminated by impurities to be produced with a high yield.

  In order to achieve the above object, the present inventors conducted extensive research. As a result, first, the melt was maintained at a higher temperature than before, and specifically, the seed crystal composed of the ceramic composite was completely formed. It has been found that when the ceramic composite is grown after the melting temperature is reached, contamination due to the constituent components of the crucible hardly remains in the ceramic composite. However, when all the seed crystals are melted, the resulting ceramic composite is easily polycrystallized, resulting in a problem that the yield for obtaining a ceramic composite free from cracks is reduced.

  Therefore, as a result of further extensive research, the present inventors have used a single crystal of the same base as the crystal of any one of the crystal phases constituting the ceramic composite for the seed crystal, so that the seed crystal is not a ceramic composite. Even if the melt is unidirectionally solidified while maintaining the temperature at which all the seed crystals are melted, that is, the temperature above the melting point of the ceramic composite, the seed crystals are not melted completely. It has been found that the ceramic composite can be grown, and that the generation of cracks associated with the crystallization of the ceramic composite can be suppressed.

  As described above, the present inventors use a single crystal of the same matrix as any one of the crystal phases constituting the ceramic composite for the seed crystal, thereby maintaining the melt at a higher temperature than before. It was found that ceramic composites can be grown from seed crystals even if unidirectional solidification is carried out in this way, and that ceramic composites free from cracks and less contaminated by impurities can be obtained with a high yield. Invented.

  That is, the present invention relates to a ceramic composite having a structure in which two or more crystal phases are continuously and three-dimensionally entangled with each other using a seed crystal from an oxide melt having a eutectic composition by the Bridgman method. A method for growing a body, wherein the seed crystal is a single crystal having the same matrix as any one of crystal phases constituting the ceramic composite. Is the method.

  Further, the present invention is the method for producing a ceramic composite according to the above, wherein the seed crystal is a single crystal having the same base as the base crystal of the crystal phase having the highest melting point among the crystal phases. .

According to the present invention, the ceramic composite is a first crystal composed of an Ln ₃ Al ₅ O ₁₂ (Ln is at least one element of Y, Tb, Dy, Ho, Er, Tm, Yb and Lu) phase. phase and a method for manufacturing a ceramic composite body, characterized in that it is composed of a second crystalline phase made of Al ₂ O _3.

  In the present invention, the first crystal phase is a crystal phase that emits fluorescence, and the ceramic composite converts a part of the received light into light having a wavelength different from that of the received light. It is a manufacturing method of the said ceramics composite body characterized by the above-mentioned.

  In the ceramic composite according to the present invention, the Ln is at least one element of Y or Tb, and the first crystal phase is a crystal phase containing Ce as an activator. It is a manufacturing method.

  Further, the present invention is the method for producing a ceramic composite according to the above, wherein Ln is Y.

In addition, the present invention provides the method for producing a ceramic composite as described above, wherein the seed crystal is a single crystal of Al ₂ O ₃ .

  According to the method for producing a ceramic composite according to the present invention, two or more kinds of crystal phases are continuously and three-dimensionally formed by using a seed crystal from an oxide melt having a eutectic composition by the Bridgman method. In the method of growing a ceramic composite having a structure intertwined with each other, the temperature of the melt near the seed crystal can be increased without completely melting the seed crystal, so that there is no crack and contamination by impurities from the crucible is avoided. A small number of ceramic composites can be produced with a high yield.

It is a schematic diagram of a crucible used in the present invention. It is a figure which shows the installation form of the thermocouple which measures the temperature just under the seed crystal of a crucible outer side. It is a schematic diagram of a crucible in a state in which seed crystals are loaded and a melting raw material is charged. It is a photograph of the growth direction cross section of the seed crystal vicinity part (including nesting) of the ceramic composite according to the present invention. It is a figure which shows the position which extract | collected the disk-shaped sample for extract | collecting an internal quantum efficiency measurement sample in the ceramic composite_body | complex which concerns on this invention. It is a figure which shows the location which extract | collected the internal quantum efficiency measurement sample in the disk-shaped sample.

  First, the ceramic composite according to the present invention will be described.

  The ceramic composite according to the present invention is specifically disclosed in, for example, Patent Documents 1 to 5, and has a structure in which two or more crystal phases known per se are continuously and three-dimensionally entangled with each other. Is a ceramic composite that can be suitably used as a high-temperature structural material or a functional material having good mechanical properties at high temperatures.

The ceramic composite according to the present invention includes a first crystal phase composed of an Ln ₃ Al ₅ O ₁₂ (Ln is at least one element of Y, Tb, Dy, Ho, Er, Tm, Yb, and Lu) phase. In the case of a ceramic composite composed of a second crystal phase made of Al ₂ O ₃ , a high-temperature structural material having particularly good mechanical properties at high temperatures and a high emissivity at a selective wavelength at high temperatures It is suitable as a selective emitter material.

  The ceramic composite according to the present invention is a ceramic composite for light conversion in which the first crystal phase is a crystalline phase that emits fluorescence, and a part of the received light is converted into light having a wavelength different from that of the received light. Is preferable because it is suitably used as a light conversion member in various light emitting devices.

  Further, when Ln is at least one element of Y or Tb and the first crystal phase is a ceramic composite for light conversion that is a crystal phase containing Ce as an activator, the first crystal phase is The received blue light is converted into yellow light, the second crystal phase transmits blue light as it is, and white light mixed with yellow light and blue light can be emitted, so it is used in combination with a blue light emitting diode. It is suitable as a light conversion member for a white light emitting diode, and is particularly preferable.

In the case where Ln is Y, that is, the ceramic composite according to the present invention is a crystalline phase that emits fluorescence, a first crystal phase composed of a Y ₃ Al ₅ O ₁₂ phase activated by Ce, and Al ₂ O _In the case of a ceramic composite for light conversion having a structure in which the second crystal phase composed of ₃ is continuously and three-dimensionally entangled with each other, the internal quantum efficiency is particularly high. It is particularly suitable as a light conversion member for the white light emitting diode used. Further, the first crystal phase composed of the Y ₃ Al ₅ O ₁₂ phase activated by Ce can contain Gd. When the first crystal phase contains Gd, the wavelength of the fluorescence emitted from the first crystal phase can be increased.

  Next, a method for producing a ceramic composite according to the present invention will be described.

  The ceramic composite according to the present invention is manufactured by unidirectionally solidifying a raw material oxide melt using a seed crystal by the Bridgeman method and growing the crystal.

The method for producing a ceramic composite according to the present invention is characterized in that a seed crystal made of a specific single crystal is used in unidirectional solidification of an oxide melt having a eutectic composition by the Bridgman method. That is, the method for producing a ceramic composite of the present invention is a structure in which two or more crystal phases are continuously and three-dimensionally intertwined from a melt having a eutectic composition using a seed crystal by the Bridgman method. The seed crystal is a single crystal having the same base material as any one of the crystal phases constituting the ceramic composite. The host is a host crystal in the phosphor crystal, and refers to, for example, a Y ₃ Al ₅ O ₁₂ crystal when the phosphor crystal is Y ₃ Al ₅ O ₁₂ : Ce.

  Since the ceramic composite according to the present invention is obtained by solidifying a melt having a eutectic composition as described later, a single crystal having the same matrix as any one of the crystal phases constituting the ceramic composite is The melting point is higher than that of the ceramic composite. Therefore, when the single crystal according to the present invention is used for the seed crystal, the melt near the seed crystal can be maintained at a higher temperature than when the same ceramic composite is used for the seed crystal. When the ceramic composite itself is used as a seed crystal, all the seed crystals are melted when the temperature of all the seed crystals is higher than the melting point of the melt. However, if the single crystal according to the present invention is used as a seed crystal, the seed crystals are melted. Even if all the temperatures are higher than the melting point of the melt, the seed crystals are not completely melted up to the melting point of the single crystal according to the present invention. Therefore, if the single crystal according to the present invention is used for the seed crystal, the ceramic composite can be grown from the seed crystal even in a state where the melt is melted at a higher temperature than before.

  Since the seed crystal used in the present invention is a single crystal having the same matrix as any one of the crystal phases constituting the ceramic composite, the orientation of the crystal phase constituting the ceramic composite can be arbitrarily determined by the orientation of the seed crystal. It is possible to control the direction. In addition, since there is no mismatch with the lattice spacing of the crystal phase constituting the ceramic composite, the ceramic composite is less likely to be polycrystallized and cracks are generated, and precise orientation control is possible.

The seed crystal used in the present invention may be a single crystal having the same matrix as any one of crystal phases constituting the ceramic composite. For example, the ceramic composite has a structure in which a first crystal phase composed of Y ₃ Al ₅ O ₁₂ : Ce and a second crystal phase composed of Al ₂ O ₃ are continuously and three-dimensionally entangled with each other. In the case of a ceramic composite for light conversion, not only a single crystal of Al ₂ O _{3 and} a single crystal of Y ₃ Al ₅ O ₁₂ : Ce but also a single crystal of Y ₃ Al ₅ O ₁₂ not containing Ce is used as a seed. It can be used as a crystal. Even if part of the seed crystal with a composition different from that of the ceramic composite melts and enters the melt and remains in the ceramic composite, the seed crystal is composed of some of the constituent elements of the resulting ceramic composite. In addition, since the ratio of the seed crystal to the obtained ceramic composite is usually very small, it does not affect the yield and characteristics of the obtained ceramic composite.

  In the present invention, a ceramic composite is grown from an oxide melt having a eutectic composition. If the composition of the melt is a eutectic composition, the crystal phase constituting the eutectic grows while crystallizing almost simultaneously when the ceramic composite is solidified, so that the specific crystal phase constituting the eutectic may become coarse. It is possible to produce a ceramic composite having a uniform structure. Here, the eutectic composition in the present invention is not only the eutectic point, but also a composition near the eutectic point where a specific crystal phase constituting the eutectic is not coarsened and cracks are generated in the ceramic composite. Specifically, it refers to a composition in the range of ± 7 mol% from the eutectic point. If the composition of the melt is within this range, the specific crystal phase constituting the eutectic does not become extremely coarse. The composition of the melt is more preferably within the range of ± 5 mol% from the eutectic point.

  The seed crystal used in the present invention is preferably a single crystal having the same base as the base crystal of the crystal phase having the highest melting point among the crystal phases constituting the ceramic composite. This is because as the melting point of the seed crystal is higher, the temperature of the melt can be increased and a ceramic composite with less contamination by impurities can be obtained.

The ceramic composite according to the present invention includes a first crystal phase composed of an Ln ₃ Al ₅ O ₁₂ (Ln is at least one element of Y, Tb, Dy, Ho, Er, Tm, Yb, and Lu) phase. In the case of a ceramic composite having a structure in which the second crystal phase composed of Al ₂ O ₃ is continuously and three-dimensionally entangled with each other, the seed crystal may be a single crystal of Al ₂ O ₃ preferable. The melting point of the single crystal of Al ₂ O ₃ is higher than the melting point of the single crystal of Ln ₃ Al ₅ O ₁₂ (Ln is at least one element of Y, Tb, Dy, Ho, Er, Tm, Yb, and Lu). Because it is expensive.

The ceramic composite according to the present invention first emits fluorescence composed of Ln ₃ Al ₅ O ₁₂ (Ln is at least one element of Y, Tb, Dy, Ho, Er, Tm, Yb and Lu). A ceramic composite having a structure in which a crystal phase and a _second crystal phase made of Al ₂ O ₃ are continuously and three-dimensionally entangled with each other, and the ceramic composite receives a part of received light. In the case of a ceramic composite for light conversion that converts light having a wavelength different from that of the received light, the seed crystal is preferably an Al ₂ O ₃ single crystal. When Ln is at least one element of Y or Tb and the first crystal phase is a crystal phase containing Ce as an activator, the seed crystal is an Al ₂ O ₃ single crystal. It is preferable.

When an Al ₂ O ₃ single crystal is used as a seed crystal, the crystal orientation of the Al ₂ O ₃ phase constituting the resulting ceramic composite can be precisely controlled. When producing a general cylindrical ceramic composite as the shape of a solidified body obtained by the Bridgman method, the crystal orientation of the Al ₂ O ₃ phase constituting the ceramic composite can be precisely controlled, so that Al ₂ O ₃ It becomes possible to easily collect a wafer-like sample having a uniform diameter from the ceramic composite with a high yield by adjusting the crystal orientation of the phase to the target orientation. For example, in a light emitting diode substrate in which a ceramic composite layer for light conversion and a single crystal layer disclosed in Patent Document 5 are directly bonded, the single crystal layer is a layer made of a single crystal of Al ₂ O ₃ , light conversion When the ceramic composite layer for a wafer is a layer made of the ceramic composite for light conversion according to the present invention, a wafer-like ceramic composite for light conversion in which the crystal orientation of the Al ₂ O ₃ phase is adjusted to the target orientation is obtained. The ability to collect with good yield brings about the effects described below.

By using a single crystal of Al ₂ O ₃ having the same orientation as the plane orientation of the single crystal layer as a seed crystal to grow a ceramic composite for light conversion, an Al ₂ O ₃ phase on a plane perpendicular to the growth direction can be obtained. A ceramic composite for light conversion that is oriented in the same direction as the plane orientation of the single crystal layer of the substrate for a light emitting diode disclosed in Patent Document 8 can be produced. By slicing the ceramic composite for light conversion in a direction perpendicular to the growth direction, a ceramic composite layer for light conversion in which the plane orientation of the Al ₂ O ₃ phase is the same as that of the single crystal layer is prepared. can do. And Al ₂ O ₃ phase ceramic composite layer for light conversion, if the plane orientation of the junction surface of the single crystal of Al ₂ O ₃ single crystal layer is the same, light-emitting diode of constant high quality bonding strength Since the substrate is easily obtained with a high yield, in the present invention, when a single crystal of Al ₂ O ₃ is used as the seed crystal, the light emitting diode substrate having a high quality and a constant quality can be manufactured with a high yield. As described above, when the ceramic composite of the present invention is a ceramic composite for light conversion that converts a part of the received light into light having a wavelength different from that of the received light, the seed crystal is particularly Al ₂ O. ₃ is preferable.

  The method for growing a ceramic composite by the Bridgman method of the present invention will be specifically described.

  The melting raw material used in the ceramic composite growth step according to the present invention, that is, the unidirectional solidification step by the Bridgeman method can be prepared by the following method. First, the raw material powder is mixed at a ratio that produces a ceramic composite having a desired component ratio to obtain a mixed powder. There is no particular limitation on the mixing method, and either a dry mixing method or a wet mixing method can be employed. As a medium when using the wet mixing method, alcohol such as methanol or ethanol is generally used. When the wet mixing method is adopted, the used medium is removed by a rotary evaporator or the like. Subsequently, the mixed powder is melted in a crucible made of Mo, the melt is poured into a mold having a predetermined shape, and after cooling, it is taken out from the mold to obtain a melting raw material to be subjected to a unidirectional solidification process. .

  Growth of the ceramic composite by the Bridgman method, that is, unidirectional solidification by the Bridgman method is performed by the following method.

  As the unidirectional solidification device, any Bridgman device that can be heated above the melting point of the ceramic composite and can control the atmosphere can be used without any particular limitation. In the present invention, the crucible is accommodated in the vacuum chamber so as to be movable in the vertical direction, a high frequency induction coil for heating in the vacuum chamber, a graphite heat insulating material and a high frequency induction coil inside the high frequency induction coil A graphite susceptor, which can be heated by the above, is installed, and a Bridgman device known per se is used, which is equipped with a high-frequency power source and a vacuum pump for reducing the pressure inside the container.

  The crucible may be any shape as long as it can be loaded with a seed crystal and can grow from the seed crystal, and a known crucible for single crystal growth can be used. The crucible may be made of any material as long as it has heat resistance that does not melt at a temperature equal to or higher than the melting point of the ceramic composite and does not react with the melt, but Mo can be preferably used. In FIG. 1, the schematic diagram of the well-known crucible 1 used for this invention is shown. The crucible is a known crucible described in Patent Document 7, and is located in the unitized crystal growth chamber 3 and the upper part of the unitized crystal growth chamber 3, and the straight barrel portion extends from the unitized crystal growth chamber 3. 4 and a nesting portion 2 having a shape in which a large volume space is provided between the inner wall and the crucible inner wall. Hereinafter, an embodiment of the present invention will be described based on an embodiment using a known crucible 1, but the present invention is not limited thereto.

  FIG. 2 shows an example of a state in which the crucible 1 is installed in the vacuum chamber of the Bridgeman device used in the present invention. The crucible 1 is installed on a crucible support 7 installed on a chill plate 6. Further, a tungsten-rhenium thermocouple 8 is attached to the outside of the bottom of the crucible 1 so that the temperature immediately below the seed crystal can be measured by a tungsten-rhenium thermocouple 8 fixed to the crucible support 7.

  FIG. 3 shows a schematic diagram of the crucible 1 in a state where the seed crystal 9 is loaded and the melting raw material 10 is charged. As shown in FIG. 2, the crucible 1 fixed on the crucible support 7 installed on the chill plate 6 and fitted with the tungsten-rhenium thermocouple 8 is attached to the seed crystal as shown in FIG. 9 is charged, and the molten raw material 10 is charged. Thereafter, the inside of the vacuum chamber of the Bridgeman device is depressurized by a vacuum pump, and when a predetermined pressure is reached, the high frequency induction coil is energized to start heating the graphite susceptor. The temperature measured by a thermocouple installed on the outside of the crucible directly under the seed crystal (hereinafter referred to as the temperature immediately below the seed crystal) is composed of a single crystal of the same matrix as any one crystal of the crystal phase constituting the ceramic composite. While making sure that the temperature does not reach the point at which the seed crystals completely melt, adjust the output of the high-frequency power source to melt the melting raw material. Then, the temperature immediately below the seed crystal is maintained for a certain period of time while maintaining the temperature at which the seed crystal is not completely melted. Here, the temperature immediately below the seed crystal when the melt is kept in the melt is a temperature at which contamination in the vicinity of the seed crystal of the ceramic composite is almost eliminated, and is a temperature higher than that. Set to a temperature that does not completely melt.

  Thereafter, the crucible is pulled down, the crucible is cooled from the lower part, that is, from the seed crystal side, and the melt is unidirectionally solidified to grow a ceramic composite.

  Unidirectional solidification of the melt is possible under normal pressure as long as the components of the crucible and Bridgman apparatus are not oxidized and consumed, but in order to easily obtain a material with few defects, the pressure is 4000 Pa or less. It is preferable to carry out, and it is particularly preferable to carry out at 0.13 Pa or less.

  The crucible pulling rate, that is, the growth rate of the ceramic composite is appropriately set depending on the melt composition and melting conditions, but is usually 50 mm / hour or less, preferably 1 to 20 mm / hour.

The effect of the present invention is visually confirmed by the yield of the ceramic composite that does not generate cracks and the fact that almost the entire ceramic composite exhibits the original color (there is no partial coloration due to contamination from the crucible). can do. Further, in addition to visual confirmation, it can also be confirmed that almost the entire ceramic composite exhibits original characteristics. In the present invention, the ceramic composite is a light conversion composed of a first crystal phase composed of a Y ₃ Al ₅ O ₁₂ phase containing Ce as an activator and a second crystal phase composed of Al ₂ O _3. The effect of the present invention is confirmed as follows for the ceramic composite for use.

20 production experiments of a ceramic composite for light conversion composed of a first crystal phase composed of Y ₃ Al ₅ O ₁₂ phase containing Ce as an activator and a second crystal phase composed of Al ₂ O ₃ In this case, the effect of the present invention is confirmed from the yield at which a ceramic composite for light conversion free from cracks is obtained and the internal quantum efficiency measurement results at a plurality of locations of the ceramic composite for light conversion free from cracks.

  The internal quantum efficiency of the ceramic composite for light conversion was measured by using a quantum efficiency measurement system QE-1100F (manufactured by Otsuka Electronics Co., Ltd.) to process the ceramic composite for light conversion into 8 mm × 8 mm and a thickness of 1.5 mm. This is done for plate samples. Quantum efficiency is defined as the ratio of the number of photons emitted by fluorescence (fluorescence photon number) to the number of photons of excitation light absorbed by the sample (excitation photon number). The internal quantum efficiency is calculated from the excitation photon number. It represents the ratio of the fluorescence photon number to the absorbed photon number that subtracts the number of photons (reflected photon number) by the reflected light from the sample.

  The procedure for measuring the internal quantum efficiency of the ceramic composite for light conversion according to the present invention is as follows. First, without setting a sample in the integrating sphere attached to the quantum efficiency measurement system, the intensity of the excitation light to be used is measured, and the excitation quantum number is calculated. Next, the plate sample processed with the ceramic composite for light conversion according to the present invention is placed in the integrating sphere attached to the system so that all of the excitation light is irradiated to the sample, and the excitation light is applied to the sample. Irradiate. The fluorescence intensity of the fluorescence emitted from the sample receiving the excitation light is measured, the fluorescence light quantum number and the absorption light quantum number are calculated from the fluorescence intensity, and the internal quantum efficiency is calculated. In the internal quantum efficiency measurement in the present invention, light having a wavelength of 460 nm, which is a kind of light emitted from a general blue LED, is used as excitation light.

The ceramic composite according to the present invention is composed of a first crystal phase composed of a Y ₃ Al ₅ O ₁₂ phase containing Ce as an activator and a second crystal phase composed of Al ₂ O ₃ . In the case of a ceramic composite, the present invention was carried out as follows and the effect was confirmed.

(Confirmation of the temperature at which the seed crystal of the ceramic composite for light conversion completely melts)
In order to reduce the crack generation rate due to polycrystallization of the ceramic composite for light conversion, it is necessary to grow the ceramic composite for light conversion from the seed crystal. Therefore, it is necessary to grasp the temperature at which all seed crystals are melted and to produce a ceramic composite for light conversion at a lower temperature. When the ceramic composite for light conversion was used as a seed crystal, the temperature at which the seed crystal completely melted was measured by the following method.

As shown in FIG. 2, a Mo crucible equipped with a tungsten-rhenium thermocouple and having an inner diameter of 54 mm, a length of 200 mm, and a bottom thickness of 4.0 mm was prepared. As shown in FIG. 3, the bottom part of the crucible, which is installed in the vacuum chamber of the Bridgman apparatus used in the present invention and equipped with a tungsten-rhenium thermocouple as shown in FIG. 2, has a diameter of 4 mm and a height. A 30 mm cylindrical ceramic composite for light conversion was loaded as a seed crystal, and subsequently, a melting raw material produced by the method described in Example 1 described later was charged into a crucible. Thereafter, the inside of the vacuum chamber of the Bridgeman apparatus was depressurized, and the crucible and the melting raw material were heated while gradually increasing the output of the high-frequency power source, thereby melting the melting raw material under a pressure of 1.33 × 10 ⁻³ Pa. Further, the temperature was increased until the temperature immediately below the seed crystal reached 1,600 ° C., and the temperature immediately below the seed crystal was maintained at 1,600 ° C. for 3 hours.

Next, while keeping the output of the high frequency power source constant, the crucible is pulled down at a speed of 5 mm / hour in the same atmosphere to solidify the melt unidirectionally from the bottom of the crucible, and the Y ₃ Al ₅ O ₁₂ : Ce phase And a ceramic composite for light conversion having a diameter of 54 mm and a straight body portion height of 100 mm, comprising an Al ₂ O ₃ phase.

  The center of the nesting taken out from the crucible was cut and a cross section in the height direction of the seed crystal was observed, and the height at which the seed crystal remained without melting was measured. The height of the seed crystal remaining unmelted is visually determined by the presence of a linear boundary between the seed crystal remaining unmelted and the ceramic for light conversion grown from the seed crystal in this unidirectional solidification. You can find out at The seed crystal, which is the ceramic for light conversion of the present invention itself, and the ceramic for light conversion in a slight linear region immediately after growing from the seed crystal have different tissue sizes, which is a difference in transparency. It can be confirmed visually. When the temperature immediately below the seed crystal was 1,600 ° C., the height at which the seed crystal remained without melting was 7 mm.

  Subsequently, a ceramic for light conversion was produced in the same manner as when the temperature immediately below the seed crystal was 1,600 ° C., except that the temperature immediately below the seed crystal was 1,620 ° C. When the cross section of the seed crystal in the height direction was observed, the boundary between the seed crystal and the produced ceramic for light conversion was not confirmed. It was found that even if the temperature immediately below the seed crystal was 1,600 ° C., the seed crystal was not completely melted, but when the temperature was 1,620 ° C., the seed crystal was sometimes completely melted.

(Confirmation of the temperature at which contamination of the ceramic composite for light conversion is eliminated)
An experiment for producing a ceramic composite for light conversion by increasing the temperature immediately below the seed crystal at an interval of 10 ° C. from 1,620 ° C. at which it was confirmed that the seed crystal was completely melted was conducted. Was performed in the same manner as described in the confirmation of the temperature at which the glass melts completely. The lower the temperature just below the seed crystal, the more the contaminated part of the resulting light conversion ceramic composite that is supposed to be a constituent of the Mo crucible remains. Contamination that is visually confirmed as the temperature immediately below the seed crystal increases. There were fewer sites. When the temperature immediately below the seed crystal was 1,670 ° C., the contaminated portion was hardly confirmed in the obtained ceramic composite for light conversion.

Example 1
The α-Al ₂ O ₃ powder (purity 99.99%) and Y ₂ O ₃ powder (purity 99.999%) were mixed at a molar ratio of 82:18, and CeO ₂ powder (purity 99.99%) was added. It was weighed so as to be 0.03 mole Y ₃ Al ₅ O ₁₂ 1 mol of product by unidirectional solidification. These raw material powders were wet mixed with a ball mill for 16 hours using ethanol as a medium, and then the ethanol was removed using an evaporator to obtain a mixed powder. The mixed powder is put into a Mo crucible, heated and melted at 1,950 ° C. in a vacuum furnace, the melt is poured into a mold of a predetermined shape, cooled, taken out of the mold, and subjected to a unidirectional solidification process. A melting raw material was prepared.

Next, at the bottom of a Mo crucible with an inner diameter of 54 mm, a length of 200 mm, and a bottom thickness of 4.0 mm installed in the vacuum chamber of the Bridgeman apparatus, a diameter of 4 mm and a height of 30 mm as shown in FIG. , (11-20) A cylindrical Al ₂ O ₃ single crystal having a plane perpendicular to the longitudinal direction was charged as a seed crystal, and then a melting raw material was charged into the crucible. Thereafter, the inside of the vacuum chamber of the Bridgeman apparatus is depressurized, the crucible and the melting raw material are heated, and the melting raw material is melted under a pressure of 1.33 × 10 ⁻³ Pa. Thereafter, the temperature immediately below the seed crystal is 1,670. The temperature was raised to 0 ° C.

Next, while keeping the output of the high frequency power source constant, the crucible is pulled down at a speed of 5 mm / hour in the same atmosphere to solidify the melt unidirectionally from the bottom of the crucible, and the Y ₃ Al ₅ O ₁₂ : Ce phase And a ceramic composite for light conversion having a diameter of 54 mm and a straight body portion height of 100 mm, comprising an Al ₂ O ₃ phase.

The light conversion ceramic composite production experiment was performed 20 times under the above-described conditions, and 20 light conversion ceramic composites having a diameter of 54 mm and a straight body portion height of 100 mm were produced. After 20 experiments, it was confirmed that a part of the seed crystal remained unmelted in all the ceramic composites for light conversion, and the height of the unmelted seed crystal was 3 to 15 mm. All of the ceramic composites for light conversion were not confirmed to be colored from the crucible, and the occurrence of cracks was 1 in 20 and the crack generation rate was 5%. FIG. 4 shows a photograph of a cross section obtained by cutting a portion in the vicinity of one seed crystal of the obtained ceramic composite for light conversion in the growth direction along with the nest. It can be seen that part 8 of the seed crystal composed of the Al ₂ O ₃ single crystal remains without being completely melted.

  The internal quantum efficiency of the obtained ceramic composite for light conversion was measured as follows. In the straight body portion of the ceramic composite for light conversion, four 1 mm-thick disk samples for collecting the internal quantum efficiency measurement samples were collected at intervals of 30 mm as shown in FIG. From the disk-like sample, a sample for measuring internal quantum efficiency having a size of 10 mm × 10 mm and a thickness of 0.2 mm was cut out as shown in FIG. The internal quantum efficiency was measured at a total of 8 locations per ceramic composite for light conversion. With respect to 19 ceramic composites for light conversion excluding the ceramic composite for light conversion in which cracks occurred, the above-described internal quantum efficiency measurement was performed, and the average value at each location was calculated. The results are shown in Table 1. High internal quantum efficiencies are obtained at all points, and in the method for producing a ceramic composite for light conversion of Example 1, a ceramic composite for light conversion with no cracks and few parts with poor optical properties can be obtained with a high yield. I found out I was able to get it.

Further, the crystal orientation of the ceramic composite for light conversion was measured by the following method. As the measurement sample, a disk-shaped sample on the upper part of the ceramic composite for light conversion shown in FIG. 5 collected from the obtained ceramic composite for light conversion was used. Using a multifunctional X-ray diffractometer ATX-G for surface structure evaluation (manufactured by Rigaku Corporation), complete pole figure measurement of the (300) plane of Al ₂ O ₃ at the center of the disk-shaped sample was performed. After that, using the analysis software “Pole figure and stereo projection display program” (manufactured by Noel Engineering Co., Ltd.), the pole figure of the (300) plane of Al ₂ O ₃ measured and the simulation figure of Al ₂ O ₃ By rotating and tilting the simulation diagram so as to overlap the (300) plane, a stereo projection diagram of the crystal orientation of the ceramic composite for light conversion was created. From the stereo projection, it was confirmed that the (11-20) plane of Al ₂ O ₃ coincided with the orientation of the main surface of the disk-shaped sample. That is, the (11-20) plane of Al ₂ O ₃ is perpendicular to the growth direction of the ceramic composite for light conversion, and the crystal orientation of the Al ₂ O ₃ phase of the ceramic composite for light conversion is the crystal of the seed crystal. It was confirmed that the direction was reflected. It was confirmed that the crystal orientation of the Al ₂ O ₃ phase of the ceramic composite for light conversion reflected the crystal orientation of the seed crystal for all the ceramic composites for light conversion in which no crack was generated.

(Comparative Example 1)
A ceramic composite for light conversion was produced in the same manner as in Example 1 except that the ceramic composite for light conversion obtained in Example 1 was used for the seed crystal. In the same manner as in Example 1, 20 light conversion ceramic composites were manufactured 20 times, and 20 light conversion ceramic composites having a diameter of 54 mm and a straight body portion height of 100 mm were manufactured. After 20 experiments, it was confirmed that all seed crystals were not melted and remained in all the ceramic composites for light conversion. All of the ceramic composites for light conversion were not confirmed to be colored from the crucible, and the number of cracks generated was 4 out of 20 and the crack generation rate was 20%. The internal quantum efficiency of the obtained ceramic composite for light conversion was measured by the same method as in Example 1. The results are shown in Table 1. Although the measurement result was similar to that of Example 1, it was confirmed that the yield was reduced due to the occurrence of cracks.

In addition, when a crack is confirmed the crystal orientation of all the light converting ceramic composite which did not occur in the same manner as in Example 1, the Al ₂ O ₃ (11-20) plane of the light converting ceramic composite It was distributed in a range inclined by 10 to 30 ° from a plane perpendicular to the growth direction, and it was confirmed that there was variation in the crystal orientation of the Al ₂ O ₃ phase.

(Comparative Example 2)
A ceramic composite for light conversion was produced in the same manner as in Comparative Example 1 except that the temperature immediately below the seed crystal was 1,600 ° C. In the same manner as in Comparative Example 1, 20 light conversion ceramic composites were manufactured 20 times, and 20 light conversion ceramic composites having a diameter of 54 mm and a straight body portion height of 100 mm were produced. After 20 experiments, it was confirmed that a part of the seed crystal remained unmelted in all the ceramic composites for light conversion, and the height of the unmelted seed crystal was 5 to 15 mm. All of the ceramic composites for light conversion were confirmed to be colored from the crucible, and the occurrence of cracks was 1 in 20 and the crack generation rate was 5%. The internal quantum efficiency of the obtained ceramic composite for light conversion was measured by the same method as in Example 1. The results are shown in Table 1. In the lower part of the ceramic composite for light conversion, it was confirmed that although the internal quantum efficiency is low and the ceramic composite for light conversion without cracks can be obtained with a high yield, there are many parts with poor optical characteristics.

In addition, when a crack is confirmed the crystal orientation of all the light converting ceramic composite which did not occur in the same manner as in Example 1, (11-20) plane of Al ₂ O ₃ is, for light conversion ceramic composite It was confirmed that the crystal orientation of the Al ₂ O ₃ phase of the ceramic composite for light conversion reflects the crystal orientation of the seed crystal.

DESCRIPTION OF SYMBOLS 1 Crucible 2 Nesting 3 Unification crystal growth room 4 Straight body part (Crucible) 5 Connection part 6 Chill plate 7 Crucible support base 8 Tungsten-rhenium thermocouple 9 Seed crystal 10 Melting raw material 11 Photoelectric conversion ceramic composite Part of seed crystal consisting of Al ₂ O ₃ single crystal remaining unmelted after production

Claims (6)

By Bridgman method
From an oxide melt of eutectic composition, using seed crystals,
A first crystal phase composed of Ln ₃ Al ₅ O ₁₂ (Ln is at least one element of Y, Tb, Dy, Ho, Er, Tm, Yb and Lu) and a _second crystal composed of Al ₂ O ₃ . A method of growing a ceramic composite having a structure in which a crystalline phase is continuously and three-dimensionally entangled with each other,
The method for producing a ceramic composite, wherein the seed crystal is a single crystal having the same base as any one of crystal phases constituting the ceramic composite.   2. The ceramic composite according to claim 1, wherein the seed crystal is a single crystal having the same base as the base crystal of the crystal phase having the highest melting point among the crystal phases constituting the ceramic composite. Manufacturing method. The first crystal phase is a crystal phase emitting fluorescence;
The ceramic composite according to claim 1 or 2 , wherein the ceramic composite is a ceramic composite for light conversion that converts a part of received light into light having a wavelength different from that of the received light. Production method. Ln is at least one element of Y or Tb;
The method for producing a ceramic composite according to claim 3 , wherein the first crystal phase is a crystal phase containing Ce as an activator. Wherein Ln is, the manufacturing method of the ceramic composite body according to any one of claims 1 to 4, characterized in that a Y. The method for producing a ceramic composite according to any one of claims 1 to 5 , wherein the seed crystal is a single crystal of Al ₂ O ₃ .

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