JP6463238B2 - Kiln tools - Google Patents

Description

  The present invention relates to a kiln tool. The kiln tool of the present invention is suitably used for firing electronic parts, for example.

  One of the manufacturing processes of electronic components such as a multilayer ceramic capacitor (MLCC), a piezoelectric element, and a thermistor includes a firing process. In the firing step, a plurality of workpieces to be fired are placed on, for example, a plate-shaped refractory kiln tool called a shelf board, and firing is performed in that state. In such an electronic component firing process, as a result of miniaturization of the component, the electronic component to be fired is taken out of the furnace by putting it in a very high temperature furnace together with a firing kiln tool for a short time. Rapid firing processes, which are firing with rapid heating and / or rapid cooling to complete firing, are becoming mainstream. Along with this, the kiln tools for firing are required to have further higher thermal shock resistance and lower heat capacity. As a result, the material of the kiln tool has changed from alumina to silicon carbide (SiC). Although the SiC material satisfies the above-mentioned characteristics of thermal shock resistance and low heat capacity, it may react with electronic components. Therefore, in order to prevent this, a zirconia coating layer is usually provided on the surface. This zirconia-based coating layer has a drawback that it is easily peeled off from a SiC-based substrate during use of the kiln tool.

For example, in Patent Document 1, Al ₂ O ₃ , Al ₂ O ₃ —SiO ₂ material, Al ₂ O ₃ —SiO ₂ is provided between a first layer which is a SiC substrate and a third layer such as ZrO _{2. 2} -MgO _{quality, MgO-Al 2 O 3 -ZrO} 2 the thermal provided a second layer consisting of selected ceramic from quality jig is described. This document describes that providing the second layer provides the effect of preventing the coating layer from peeling off.

In Patent Document 2, a coating layer is formed on the surface of a substrate made of ceramic such as SiC, and the coating layer is formed of Al ₂ O ₃ or Al ₂ O having a porosity of 10% or less on the surface of the substrate. ₃ and an intermediate layer mainly composed of -SiO ₂ quality for electronic components firing jig porosity is composed of a surface layer of zirconia such as 20 to 70 percent is described. This document describes that peeling of the surface layer can be prevented by increasing the porosity of the surface layer.

JP 2003-306392 A JP 2006-183972 A

  However, the conventional kiln tools have not been sufficiently prevented from peeling off the surface zirconia coating layer so as to cope with recent rapid firing.

  Therefore, the subject of this invention is providing the kiln tool which can eliminate the various fault which the prior art mentioned above has.

The present invention relates to a kiln having a mullite coating layer that forms an interface with the base material of a ceramic containing SiC, and a zirconia coating layer on the surface side of the mullite coating layer. A tool,
A kiln tool in which the average pore diameter of the mullite coating layer is 1 μm or more and 50 μm or less is provided.

  The kiln tool of the present invention is excellent in that peeling of the zirconia-based coating layer hardly occurs. Therefore, since the kiln tool of the present invention can withstand repeated thermal cycles with severe heating and cooling conditions, it can be used for a long time when used as a kiln tool for firing electronic components. .

It is the SEM photograph of the cross section before the temperature rising-cooling cycle test of the kiln tool obtained in Example 1 and Comparative Example 1, respectively. (A) is sectional drawing of the kiln tool of Example 1, (b) is sectional drawing of the kiln tool of the comparative example 1. FIG. It is a SEM photograph of a section after repeating a temperature rising-cooling cycle concerning a kiln tool obtained in Example 1 and comparative example 1, respectively. (A) is sectional drawing of the kiln tool of Example 1, (b) is sectional drawing of the kiln tool of the comparative example 1. FIG.

Hereinafter, the present invention will be described based on preferred embodiments thereof.
The kiln tool of the present invention has a mullite-based coating layer that forms an interface with the base material made of ceramics containing SiC, and a zirconia-based coating layer on the surface side of the mullite-based coating layer. Have Hereinafter, each configuration will be sequentially described.

<Base material>
The base material forms the outer shape of the kiln tool of the present invention, and examples of the shape thereof include a plate-like shape called a shelf plate and a three-dimensional container shape called a sheath or a pot. Not limited to these.

  The substrate is composed of ceramics, and the silicon carbide (SiC) contained in the ceramics includes recrystallized SiC, atmospheric pressure sintered SiC, silicon nitride bonded SiC, silicate bonded SiC, silicon impregnated SiC, and the like. Any silicon carbide conventionally used in the technical field can be used without particular limitation.

  The content of silicon carbide (SiC) in the substrate is preferably 60% by mass or more, more preferably 70% by mass or more, and particularly preferably 85% by mass or more. Moreover, although the upper limit of content of silicon carbide (SiC) in a base material is 100 mass%, it is preferable from viewpoints of the availability of a base material, for example that it is 99 mass% or less. The content of silicon carbide (SiC) in the substrate can be measured by fluorescent X-rays.

  In the kiln tool of the present invention, the base material made of ceramics containing SiC forms an interface with the mullite coating layer. In such a kiln tool of the present invention, the SiC material exposed on the surface of the base material is usually arranged in a state of being in direct contact with the mullite coating layer without being interposed in a layer of a material other than mullite. .

<Mullite coating layer>
The mullite coating layer is made of mullite with a focus on mullite (3Al ₂ O ₃ .2SiO ₂ ). The mullite coating layer is sufficient if at least the material to be fired on the surface of the base material is formed on the placement portion, but preferably forms an interface with the entire surface of the base material.

  The present inventors diligently studied the ease of peeling of the zirconia coating layer in a kiln tool having a ceramic substrate containing SiC and a surface zirconia coating layer. As a result, the average pore diameter of the mullite coating layer when the mullite coating layer is provided as an intermediate layer between the substrate and the zirconia coating layer is located on the surface side of the mullite coating layer. It was found that this is strongly related to the ease of peeling of the zirconia coating layer. Here, the surface side refers to the side facing the outer surface rather than the substrate side when the coating layer is used as a reference. It has been found that by setting the average pore diameter in a specific range, it is possible to effectively improve the difficulty of peeling off the zirconia coating layer in the kiln even under severe heat cycles. The term “peeling of the zirconia coating layer” as used herein refers not only to the case where the zirconia coating layer peels from another coating layer located on the substrate side of the coating layer, but also to the zirconia coating layer. When the layer is peeled off from the base material together with the mullite coating layer or the mullite coating layer and the alumina coating layer (intermediate layer), or the zirconia coating layer is coated with the alumina coating layer (intermediate layer). All cases where the layer is peeled off from the mullite coating layer are also included.

  Specifically, it is important that the average pore diameter of the mullite coating layer is 1 μm or more and 50 μm or less. From the viewpoint of further enhancing the effect of improving the difficulty of peeling, the average pore diameter based on the number of pore diameters is preferably 5 μm or more and 40 μm or less, and preferably 10 μm or more and 30 μm or less. Particularly preferred. In the present specification, the average pore diameter based on the number of the above-mentioned pore diameters is referred to as the average pore diameter. This average pore diameter is measured by an intercept method based on a photomicrograph of the cross section of the coating layer. . For example, it measures by the method as described in the Example mentioned later.

In the present invention, in order to set the average pore diameter of the mullite coating layer in the above range, a mullite coating layer is formed using two or more mullite powders having different particle sizes, Moreover, what is necessary is just to adjust the particle size and usage-amount of 2 or more types of powder in that case. Specifically, the raw material powder for forming the mullite coating layer preferably contains two different specific particle size range powders. Two different specific particle size ranges are an average particle size d _{50 in} the range of 1 μm to 10 μm and an average particle size d _{50 in} the range of 20 μm to 100 μm. The kiln tool of the present invention has a mullite coating layer in which the grain size distribution of crystal grains is adjusted, so that the zirconia coating layer is more reliably prevented from peeling off. In the present specification, the average particle size d ₅₀ of the powder is measured, for example by laser diffraction scattering particle size distribution analyzer (manufactured by Nikkiso Co., Ltd. or Microtrac Bell Co. Microtrac MT3000II). d ₅₀ is a 50% diameter in the volume-based integrated fraction.

In addition to the average pore size of the mullite coating layer, the kiln tool of the present invention has a specific pore size distribution in the coating layer. This is preferable in that it can hardly occur. Specifically, in the pore size distribution, the cumulative pore size (D ₅₀ ) at 50% cumulative distribution is preferably 2 μm or more and 70 μm or less, more preferably 5 μm or more and 60 μm or less, and more preferably 10 μm or more and 50 μm or less. It is particularly preferred.

Further, in the mullite coating layer, from the viewpoint of more surely achieving the effects of the present invention, the pore size distribution is preferably such that the cumulative pore size (D ₁₀ ) in the cumulative distribution 10% from the small diameter side is in a specific range. . Specifically, it is preferable that the above D ₁₀ in the coating layer of mullite is 1μm or more 15μm or less, more preferably 2μm or more 10μm or less, and particularly preferably 5μm or 9μm or less.

Further, from the viewpoint of more reliably achieving the effects of the present invention, the pore size distribution is preferably such that the cumulative pore size (D ₉₀ ) in the cumulative distribution 90% from the small diameter side is in a specific range. Specifically, the D ₉₀ in the mullite coating layer is preferably 1 μm or more and 200 μm or less, more preferably 3 μm or more and 150 μm or less, and particularly preferably 30 μm or more and 100 μm or less.

D ₅₀ , D ₁₀ and D ₉₀ are obtained by taking a micrograph of the cross-section of the coating layer, measuring the pore diameter by the intercept method based on the photograph, and obtaining 50 or more pore diameter data from the pore diameter (μm). It can be measured by plotting the accumulation of the number of data on the axis and plotting the distribution on the axis. For example, it can be obtained by the method described in Examples described later.

In the present invention, in order to set the pore size distribution of the mullite coating layer within the above range, a mullite coating layer is formed using two or more mullite powders having different particle sizes, Moreover, what is necessary is just to adjust the particle size and usage-amount of 2 or more types of powder in that case. Specifically, the two specific ranges are an average particle diameter d _{50 in} the range of 1 μm to 10 μm and an average particle diameter d _{50 in} the range of 20 μm to 100 μm. The kiln tool of the present invention has a mullite coating layer in which the grain size distribution of crystal grains is adjusted, so that the zirconia coating layer is more reliably prevented from peeling off.

In the present invention, also important that the value of the ratio of the average pore diameter to the value of the cumulative pore diameter (D ₅₀₎ of the coating layer of mullite "average pore diameter / cumulative pore diameter (D _50)" is a specific range It is. The value of average pore diameter / cumulative pore diameter (D ₅₀ ) is usually 1 or less. When it is larger than 1, the adhesiveness of the coating layer is weak, and it is easily worn and peeled off. Furthermore, the present inventors have found that peeling of the zirconia-based coating layer can be more easily prevented by setting the average pore diameter / cumulative pore diameter (D ₅₀ ) within a certain range. Although the reason for this is not clear, the present inventors presume that the two points of the adhesiveness of the coating layer and the relaxation of thermal expansion are influential. Specifically, the average pore diameter / cumulative pore diameter (D ₅₀ ) value of the coating layer is more preferably 0.5 or more and 0.9 or less, and preferably 0.7 or more and 0.85 or less. Further preferred. In the present invention, in order to set the average pore diameter / cumulative pore diameter (D ₅₀ ) of the mullite coating layer within the above range, two or more mullite powders having different particle diameters are used. A quality coating layer may be formed, and the particle size and amount used of two or more powders may be adjusted.

  The mullite coating layer preferably has a porosity of 10% to 50% in addition to the average pore diameter being in the above range. It is preferably 10% or more from the viewpoint of preventing peeling of the mullite coating layer and the zirconia coating layer, and 50% or less is preferable from the viewpoint of preventing wear of the substrate and the mullite coating layer. . From these viewpoints, the porosity of the mullite coating layer is more preferably 15% or more and 45% or less, and still more preferably 20% or more and 40% or less. The porosity can be measured by the method described in Examples described later using an intercept method. In order to set the porosity of the mullite coating layer within the above range, the kiln tool of the present invention may be manufactured according to the manufacturing method described later.

Where as mullite described above represented by _{3Al 2 O} 3 · 2SiO 2, the coating layer of mullite is preferably from the viewpoint of preventing peeling contain _Al 2 _{O 3} less 75 mass% 70 mass% or more, 72 It is particularly preferable that the content is from 74% by weight to 74% by weight. The mullite coating layer preferably contains 25% by mass or more and 30% by mass or less of SiO ₂ from the same viewpoint, and particularly preferably contains 26% by mass or more and 28% by mass or less. From the same viewpoint, the mass ratio of SiO ₂ / Al ₂ O ₃ in the mullite coating layer is preferably in the range of 70/30 to 75/25, more preferably 72/28 to 74/26. The content of Al ₂ O _{3 and} the content of SiO ₂ are determined by cutting out a mullite coating layer from a kiln tool and performing fluorescent X-ray analysis.

  The thickness of the mullite coating layer is preferably 30 μm or more from the viewpoint of enhancing the effect of the present invention. The thickness of the mullite coating layer is preferably 150 μm or less from the viewpoint of preventing peeling of the mullite coating layer. From these viewpoints, the thickness of the mullite coating layer is more preferably 50 μm or more and 120 μm or less, and further preferably 70 μm or more and 110 μm or less. The thickness can be measured by the method described in Examples described later.

<Zirconia coating layer>
The zirconia coating layer is formed on the surface side of the mullite coating layer. The zirconia coating layer may form an interface with the mullite coating layer. Alternatively, another layer is provided between the zirconia coating layer and the mullite coating layer, and the zirconia coating layer and the mullite coating layer are separated by this separate layer, and the interface is separated. It may be in a state where it is not formed. The zirconia coating layer may cover substantially the entire base material and / or mullite coating layer, or may cover a part thereof. The kiln tool of the present invention may or may not have another layer on the surface side of the zirconia layer. When the other layer is not provided on the surface side of the zirconia layer, the zirconia-based coating layer is located on the outermost surface of the kiln tool of the present invention.

  As described above, in the present invention, the average pore diameter of the mullite coating layer is important.In addition to this, if the average pore diameter of the zirconia coating layer is within a specific range, the kiln tool of the present invention, It is preferable in terms of making the zirconia-based coating layer even more difficult to peel off and preventing wear. The average pore diameter of the zirconia coating layer is preferably 1 μm or more and 50 μm or less, more preferably 5 μm or more and 40 μm or less, and particularly preferably 10 μm or more and 30 μm or less.

In the kiln tool of the present invention, in addition to the average pore size of the mullite coating layer being in the above range, the pore size distribution in the coating layer of the zirconia layer is also specific. Peeling of the zirconia-based coating layer can be made even more difficult, and this is preferable in terms of wear. For example, in the pore size distribution, the cumulative pore size (D ₅₀ ) is preferably 2 μm or more and 70 μm or less, more preferably 5 μm or more and 60 μm or less, and particularly preferably 10 μm or more and 50 μm or less.

  The zirconia-based coating layer preferably has a porosity of 10% to 50%. 10% or more is preferable from the viewpoint of peeling, and 50% or less is preferable from the viewpoint of wear. From these viewpoints, the porosity of the zirconia-based coating layer is more preferably 15% or more and 45% or less, and still more preferably 20% or more and 40% or less.

The average pore diameter of the coating layer of zirconia, each cumulative pore diameter (D ₅₀₎ and porosity, average pore diameter of the coating layer of mullite, as measured by the cumulative pore diameter (D ₅₀₎ and porosity similar manner The

Examples of the zirconia (zirconium oxide, ZrO ₂ ) material include unstabilized zirconia, partially stabilized zirconia and stabilized zirconia, or a mixture thereof. Stabilization or partial stabilization can be achieved by adding yttria (Y ₂ O ₃ ), calcia (CaO), magnesia (MgO), or the like to zirconia.

  The thickness of the zirconia-based coating layer is preferably 50 μm or more from the viewpoint of enhancing the effects of the present invention and the reaction resistance with the object to be fired. The thickness of the zirconia coating layer is preferably 250 μm or less from the viewpoint of preventing peeling of the mullite coating layer. From these viewpoints, the thickness of the zirconia coating layer is more preferably 50 μm to 200 μm, and still more preferably 70 μm to 150 μm. The thickness can be measured by the method described in Examples described later.

  As described above, the kiln tool of the present invention can provide an intermediate layer between the mullite coating layer and the zirconia coating layer. For example, an alumina coating layer is provided as the intermediate layer. It is preferable.

<Alumina coating layer>
The alumina-based coating layer is made of alumina (Al ₂ O ₃ ). The alumina coating layer preferably forms an interface with the mullite coating layer. The alumina-based coating layer may cover substantially the entire base material and / or mullite-based coating layer, or may cover a part thereof. The alumina coating layer preferably forms an interface with the zirconia coating layer located on the surface side.

  As described above, the average pore diameter of the mullite coating layer is important in the present invention, and in addition to this, if the average pore diameter of the alumina coating layer is within a specific range, the kiln tool of the present invention, This is preferable in that the zirconia coating layer can be further prevented from peeling off. The average pore diameter of the alumina coating layer is preferably 1 μm or more and 50 μm or less, more preferably 5 μm or more and 40 μm or less, and particularly preferably 10 μm or more and 30 μm or less.

In the kiln tool of the present invention, the average pore size of the mullite coating layer is in the above range, and the pore size distribution in the coating layer of the alumina layer is also specific. It is preferable in that the quality of the coating layer can be further prevented from peeling off. For example, in the pore size distribution, the pore size D _{50 at a} cumulative frequency of 50% is preferably 2 μm or more and 70 μm or less, more preferably 5 μm or more and 60 μm or less, and particularly preferably 10 μm or more and 50 μm or less.

  The alumina-based coating layer preferably has a porosity of 10% to 50%. 10% or more is preferable from the viewpoint of peeling, and 50% or less is preferable from the viewpoint of wear. From these viewpoints, the porosity of the alumina coating layer is more preferably 15% or more and 45% or less, and still more preferably 20% or more and 40% or less.

The average pore diameter of the coating layer of alumina, each cumulative pore diameter (D ₅₀₎ and porosity, average pore diameter of the coating layer of mullite, as measured by the cumulative pore diameter (D ₅₀₎ and porosity similar manner The

  The thickness of the alumina coating layer is preferably 50 μm or more from the viewpoint of enhancing the effect of the present invention. The thickness of the alumina-based coating layer is preferably 200 μm or less from the viewpoint of preventing peeling of the alumina-based coating layer. From these viewpoints, the thickness of the alumina coating layer is more preferably from 50 μm to 150 μm, and still more preferably from 70 μm to 120 μm. The thickness can be measured by the method described in Examples described later.

<Manufacturing method>
The preferred manufacturing method of the kiln tool of the present invention includes a step of manufacturing a base material, a step of forming a mullite coating layer on the surface of the base material, and a zirconia coating layer on the surface side of the mullite coating layer. Forming the step.

  A base material can be manufactured by various methods according to the shape. For example, a molded body may be manufactured by press molding, extrusion molding, cast molding, hydraulic molding, cast molding, vibration molding, and the like, and the molded body may be fired.

Next, a mullite coating layer is directly formed on the surface of the obtained substrate. The mullite raw material powder contains a mullite powder having an average particle diameter d _{50 in} the range of 1 μm or more and 10 μm or less, and a mullite powder having an average particle diameter d _{50 in} the range of 20 μm or more and 100 μm or less.
The content of SiO ₂ in the raw material powder of mullite, the content of Al ₂ O _3, as the preferred ranges of the weight ratio of _{SiO 2 / Al 2 O 3,} SiO coating layer of mullite obtained using it _As the preferred range of the content ratio of _2, the content ratio of Al ₂ O ₃ , and the mass ratio of SiO ₂ / Al ₂ O ₃ , the same ranges as those mentioned above can be mentioned.

  Examples of a method for forming a mullite coating layer on a base material using mullite raw powder include a spray coating method, a thermal spraying method, a CVD (Chemical Vapor Deposition) method, and a PVD (Physical Vapor Deposition) method. For example, when a mullite coating layer is formed by a spray coating method, a liquid medium and a binder as necessary are mixed with the raw material powder to form a slurry, and this slurry is spray coated on the substrate surface. As the liquid medium, water or the like can be used, and it is preferably used at a concentration of, for example, 10 parts by mass to 40 parts by mass with respect to 100 parts by mass of the mullite raw material powder. PVA and methyl cellulose can be used as the binder. The binder is preferably used at a concentration of, for example, 1 part by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the raw material powder. In the case of thermal spraying, the raw material powder can be sprayed as it is or in the form of a slurry. As the thermal spraying method, for example, as long as it is a plasma spraying method, water plasma spraying, gas plasma spraying, and the like are known, and any spraying method may be adopted.

  A zirconia coating layer is formed directly on the surface of the obtained mullite coating layer, or an intermediate layer such as an alumina coating layer is formed, and then a zirconia coating layer is formed.

Examples of the method for manufacturing a kiln tool of the present invention include the following methods (1) to (3), but are not limited thereto.
(1) (i): A mullite raw material powder is sprayed on the surface of the substrate to form a coating layer which is a mullite sprayed film. (ii): Alumina raw material powder is sprayed on the surface of the mullite coating layer obtained in (i) to form a coating layer which is an alumina sprayed film. (iii): A zirconia raw material powder is sprayed on the surface of the alumina coating layer obtained in (ii) to form a coating layer which is a zirconia spray coating.
(2) (i): A slurry containing mullite raw material powder is spray-coated on the surface of the substrate to form a mullite coating layer. (ii): A slurry containing an alumina raw material powder is spray-coated on the surface of the mullite coating layer obtained in (i) to form an alumina coating layer. (iii): A slurry containing zirconia raw material powder is spray-coated on the surface of the mullite coating layer obtained in (ii) to form a zirconia coating layer. (iv): The base material on which the mullite, alumina and zirconia coating layers obtained in (iii) are formed is fired.
(3) (i): A slurry containing mullite raw material powder is spray coated on the surface of the substrate to form a mullite coating layer. (ii): A slurry containing zirconia raw material powder is spray-coated on the surface of the mullite coating layer obtained in (i) to form a zirconia coating layer. (iii): The base material on which the mullite and zirconia coating layers obtained in (ii) are formed is fired.

  As a calcination temperature in a calcination process, 1200 ° C or more and 1500 ° C or less are preferred, for example. Examples of the firing atmosphere include an oxygen-containing atmosphere such as air. The firing time is preferably 1 hour or more and 50 hours or less under the condition that the firing temperature is within the above range.

  The kiln tool of the present invention thus obtained can effectively prevent peeling of the zirconia coating layer even under conditions where the heating and cooling rates are large and the thermal cycle is severe. For this reason, it is suitably used when firing in the manufacturing process of various electronic parts that are to be fired, such as dielectrics, multilayer capacitors, ceramic capacitors, multilayer ceramic capacitors (MLCC), piezoelectric elements, thermistors, inductors, etc. . And the durability of repeated use of a kiln tool improves by using the kiln tool of this invention for manufacture of such an electronic component.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the scope of the present invention is not limited to such examples. Unless otherwise specified, “%” means “mass%”.

[Example 1]
As the substrate, a plate-like substrate made of recrystallized SiC having a length of 100 mm, a width of 100 mm, and a thickness of 2 mm was used. This base material was obtained by molding SiC powder as a raw material by a casting molding method and firing the obtained molded body, and the SiC content was 98% by mass. A mullite raw material powder (Al ₂ O ₃ content 72% / SiO ₂ content 28%) was used as a material for forming the mullite coating layer. The mullite raw powder had a substantially spherical particle shape. Raw material powder of the mullite has an average particle diameter and d ₅₀ of the mullite of 8μm powder, average particle size d ₅₀ is the mass ratio of the powder of mullite of 75 [mu] m (the former: the latter) 3: 7 in a mixing Met. To 100 parts by mass of the mullite raw material powder, 25 parts by mass of water as a liquid medium and 5 parts by mass of PVA as a binder were mixed to form a slurry. This slurry was spray coated on the substrate surface and dried at 100 ° C. to form a mullite coating layer. The thickness of the mullite coating layer was adjusted to 55 μm after firing, which is a subsequent process.
The obtained substrate with a coating layer was baked at 1200 ° C. for 8 hours by the above process. After firing, the mixture was allowed to stand for 72 hours and cooled to room temperature. An alumina coating layer was formed on the surface of the mullite coating layer obtained by firing by plasma spraying, and a zirconia coating layer was further formed on the surface of the alumina coating layer by plasma spraying. As the plasma spraying conditions, Ar was used as the working gas. The alumina coating layer having a thickness of 65 μm and the zirconia coating layer having a thickness of 52 μm were formed on the current value and the spraying time of plasma spraying.
The kiln tool of Example 1 was obtained by the above process.

[Example 2]
The average particle diameter d _{50 of} the two kinds of mullite powders constituting the mullite raw powder and the mixing ratio (mass ratio, the same applies hereinafter) of the two kinds of powders are as described in Table 1. A mullite coating layer was formed by thermal spraying, and the thicknesses of the mullite coating layer, the alumina coating layer, and the zirconia coating layer were adjusted to the thicknesses shown in Table 1. Except for these points, a kiln tool was obtained in the same manner as in Example 1.

Example 3
The average particle diameter d _{50 of} the two kinds of mullite powder constituting the mullite raw powder and the mixing ratio of the two kinds of powders are as shown in Table 1. The formation of each of the mullite, alumina and zirconia coating layers was performed by spray coating. Firing was performed after each coating layer was spray coated. The thicknesses of the mullite coating layer, the alumina coating layer, and the zirconia coating layer were adjusted to the thicknesses shown in Table 1. Except for these points, a kiln tool was obtained in the same manner as in Example 1.

Example 4
The average particle diameter d _{50 of} the two kinds of mullite powder constituting the mullite raw powder and the mixing ratio of the two kinds of powders are as shown in Table 1. The thicknesses of the mullite coating layer, the alumina coating layer, and the zirconia coating layer were adjusted to the thicknesses shown in Table 1. Except for these points, a kiln tool was obtained in the same manner as in Example 3.

Example 5
The average particle diameter d ₅₀ and the mixing ratio of the two kinds of powders constituting the mullite powder are as shown in Table 1. The thicknesses of the mullite coating layer, the alumina coating layer, and the zirconia coating layer were adjusted to the thicknesses shown in Table 1. Except for these points, a kiln tool was obtained in the same manner as in Example 3.

Example 6
The average particle diameter d ₅₀ and the mixing ratio of the two kinds of powders constituting the mullite powder are as shown in Table 1. The formation of the alumina coating layer was performed by spray coating, and the firing was performed after the mullite coating layer and the alumina coating layer were spray coated. The kiln tool was prepared in the same manner as in Example 1, except that the thicknesses of the mullite coating layer, the alumina coating layer, and the zirconia coating layer were adjusted to the thicknesses shown in Table 1. Obtained.

Example 7
The average particle diameter d ₅₀ and the mixing ratio of the two kinds of powders constituting the mullite powder are as shown in Table 1. Formation of the zirconia coating layer was performed by spray coating. The firing was performed in the same manner as in Example 1 except that the thicknesses of the mullite coating layer, the alumina coating layer, and the zirconia coating layer were adjusted to the thicknesses shown in Table 1. Got.

Example 8
As the base material, normal pressure sintered SiC was used. This base material was obtained by molding SiC powder as a raw material by a CIP molding method and firing the obtained molded body, and contained 98% by mass of SiC. The average particle diameter d ₅₀ and the mixing ratio of the two kinds of powders constituting the mullite powder are as shown in Table 1. The thicknesses of the mullite coating layer, the alumina coating layer, and the zirconia coating layer were adjusted to the thicknesses shown in Table 1. Except for these points, a kiln tool was obtained in the same manner as in Example 1.

Example 9
As the substrate, silicon nitride-bonded SiC was used. This base material was obtained by forming powders of Si and SiC as raw materials by a casting method, and firing the obtained molded body, and contained 70% by mass of SiC. The average particle diameter d ₅₀ and the mixing ratio of the two kinds of powders constituting the mullite powder are as shown in Table 1. The thicknesses of the mullite coating layer, the alumina coating layer, and the zirconia coating layer were adjusted to the thicknesses shown in Table 1. Except for these points, a kiln tool was obtained in the same manner as in Example 1.

Example 10
The average particle diameter d ₅₀ and the mixing ratio of the two kinds of powders constituting the mullite powder are as shown in Table 1. After spraying the base material with a mullite raw material powder and firing, the zirconia raw material powder was sprayed without spraying the alumina raw material powder. The thicknesses of the mullite coating layer and the zirconia coating layer were adjusted to the thicknesses shown in Table 1. Except for these points, a kiln tool was obtained in the same manner as in Example 1.

[Comparative Example 1]
Example 1 except that the base material was not spray-coated with mullite raw powder and the thicknesses of the alumina coating layer and the zirconia coating layer were adjusted to the thicknesses shown in Table 2. Similarly, a kiln tool was obtained.

[Comparative Example 2]
The average particle diameter d ₅₀ of the two powders constituting the mullite powder and the mixing ratio thereof are as shown in Table 2. The thicknesses of the mullite, alumina, and zirconia coating layers were adjusted to the thicknesses shown in Table 2. Except for these points, a kiln tool was obtained in the same manner as in Example 1.

[Comparative Example 3]
The average particle diameter d ₅₀ of the two powders constituting the mullite powder and the mixing ratio thereof are as shown in Table 2. The thicknesses of the mullite, alumina and zirconia coating layers were adjusted to the thicknesses shown in Table 2. Except for these points, a kiln tool was obtained in the same manner as in Example 1.

[Evaluation]
About the kiln tools obtained in Examples 1 to 10 and Comparative Examples 1 to 3, the average porosity of the mullite coating layer, the cumulative pore diameter (D ₅₀ , D ₁₀ , D ₉₀ ), the pores by the following methods In addition to determining the rate, the porosity of the zirconia and alumina coating layers was determined. Moreover, the thickness of each coating layer was confirmed. Further, the peel resistance was examined by the following method. The results are shown in Tables 1 and 2.

<Average pore diameter, cumulative pore diameter (D ₅₀ , D ₁₀ , D ₉₀ ) and porosity>
The kiln tool was cut with a diamond cutter to obtain a cross section along the thickness of the kiln tool. After this section is filled with resin and polished with a polishing board, the section is observed with a scanning electron microscope (JSM-6380, manufactured by JEOL Ltd., magnification 200 times), and a section photograph is taken. The pore diameter of each coating layer was measured. Specifically, horizontal (horizontal) lines were drawn at 1 cm intervals from the obtained SEM photograph (12 cm long by 9 cm wide in the photo dimensions). The length of the portion where this line intersects with the pores was defined as the pore diameter (μm). By this method, 50 or more pore diameters were determined for one coating layer, and the average value thereof was defined as the average pore diameter (μm). For 50 or more pore diameter data, a pore diameter distribution was obtained with the pore diameter (μm) as the horizontal axis and the cumulative pore diameter as the vertical axis. 50% of the cumulative pore diameter in the obtained distribution was defined as the cumulative pore diameter (D ₅₀ ) (μm). Further, the cumulative pore diameter (D ₁₀ ) (μm) of 10% of the pore diameter from the small particle side and the cumulative pore diameter (D ₉₀ ) (μm) of 90% of the pore diameter from the small particle side were also determined.

The SEM photograph of the cross section of the kiln tool obtained in Example 1 and Comparative Example 1 is shown in FIG. In the mullite coating layer in FIG. 1, the portions shown in black are pores. The porosity (%) was measured by calculating the ratio of the pore diameter length to the raw material length by the same intercept method in the SEM photograph. Specifically, the porosity was calculated according to the following formula.
Porosity (%) = total pore diameter length / (total pore diameter length + total raw material length) × 100
Here, the sum of the pore diameter lengths means the sum of 50 or more pore diameters determined by the above-described intercept method. The sum of the raw material lengths refers to the sum of the raw material lengths of 50 or more (the same number as the pore diameter used for the sum of the pore diameters) obtained by the intercept method. A raw material here means the material particle which comprises each coating layer, and the sum total of raw material length is the photograph formed by observing the kiln tool at a magnification of 200 times with a scanning electron microscope about a cross section along the thickness direction. In this case, the particle diameter of the material particles is determined by measuring by the same intercept method as described above.

<Thickness>
The thickness of each coating layer was measured by observing the longitudinal section of the kiln tool with a microscope (JSM-6380 manufactured by JEOL Ltd.) (50 times magnification).

<Peeling resistance (cycle test)>
A kiln tool was placed in a furnace at room temperature, and the temperature was increased at a rate of temperature increase of 2 ° C./min in an air atmosphere. After raising the temperature to 1200 ° C., the temperature was maintained at 1200 ° C. for 1 hour. Thereafter, the furnace was cooled. The above was made into 1 cycle, and the said cycle was repeated until peeling of the surface layer was observed. Tables 1 and 2 show the presence or absence of peeling and the number of times peeling was observed. When “None” is described, it indicates that no peeling was observed even after repeating the cycle 100 times or more. After repeating the cycle 20 times, the cross section of the kiln tool obtained in Example 1 and Comparative Example 1 was obtained in the same manner as the method of measuring the pore diameter described above, and the SEM photograph was taken. . FIG. 2 shows this SEM photograph. As is clear from FIG. 2, in the kiln tool of Example 1, no peeling was observed between each coating layer and between the coating layer and the substrate after 20 heating / cooling cycles. On the other hand, in the kiln tool of Comparative Example 1, peeling between the coating layer and the base material after 20 heating / cooling cycles was remarkable.

From the description in Table 1, it can be seen that the kiln tool of each example in which the average pore diameter in the mullite coating layer is 1 μm or more and 50 μm or less has very high peel resistance. On the other hand, from the description in Table 2, the kiln tool of each comparative example in which the average pore diameter in the mullite coating layer is outside the range of the present invention is inferior in peeling resistance. Therefore, the kiln tool of the present invention is excellent in repeated use under rapid firing conditions and is useful as a kiln tool for firing electronic parts.

Claims (18)

A kiln tool having a ceramic material containing SiC as a base material, a mullite coating layer that forms an interface with the base material, and a zirconia coating layer on a surface side of the mullite coating layer. ,
A kiln tool in which an average pore diameter of the mullite coating layer is 1 μm or more and 50 μm or less, and a porosity of the zirconia coating layer is 10% or more and 50% or less . A kiln tool having a ceramic material containing SiC as a base material, a mullite coating layer that forms an interface with the base material, and a zirconia coating layer on a surface side of the mullite coating layer. ,
The kiln tool in which the average pore diameter of the mullite coating layer is 1 μm or more and 50 μm or less, and the average pore diameter of the zirconia coating layer is 1 μm or more and 50 μm or less . A kiln tool having a ceramic material containing SiC as a base material, a mullite coating layer that forms an interface with the base material, and a zirconia coating layer on a surface side of the mullite coating layer. ,
The kiln tool in which the average pore diameter of the mullite coating layer is 1 μm or more and 50 μm or less, and the cumulative pore diameter (D ₅₀ ) in the pore diameter distribution of the zirconia coating layer is observed in the range of 2 μm or more and 70 μm or less. . A kiln tool having a ceramic material containing SiC as a base material, a mullite coating layer that forms an interface with the base material, and a zirconia coating layer on a surface side of the mullite coating layer. ,
An average pore diameter of Ri der least 50μm or less 1 [mu] m, range average pore diameter / cumulative pore diameter of the coating layer of the mullite (D ₅₀₎ value of 0.5 to 0.9 of the coating layer of the mullite A kiln tool. A kiln tool having a ceramic material containing SiC as a base material, a mullite coating layer that forms an interface with the base material, and a zirconia coating layer on a surface side of the mullite coating layer. ,
Ri average pore diameter der than 50μm below 1μm of the coating layer of the mullite, kiln cumulative pore diameter (D ₅₀₎ is observed in 70μm or less the range of 2μm in pore diameter distribution of the coating layer of the mullite tool. The kiln tool according to any one of claims 2 to 5 , wherein a porosity of the zirconia-based coating layer is 10% or more and 50% or less. The kiln tool according to any one of claims 3 to 5 , wherein an average pore diameter of the zirconia-based coating layer is 1 µm or more and 50 µm or less. The kiln tool according to claim 4 or 5 , wherein a cumulative pore diameter (D ₅₀ ) in a pore diameter distribution of the zirconia-based coating layer is observed in a range of 2 µm to 70 µm. A kiln furniture according to claim 5 wherein the average pore diameter / cumulative pore diameter (D ₅₀₎ of a mullite coating layer of value is in the range of 0.5 to 0.9. The kiln tool according to any one of claims 1 to 9 , wherein a porosity of the mullite coating layer is 10% or more and 50% or less. The kiln tool according to any one of claims 1 to 10 , wherein a thickness of the mullite coating layer is 30 µm or more and 150 µm or less. The kiln tool according to any one of claims 1 to 11 , wherein a thickness of the zirconia-based coating layer is 50 µm or more and 250 µm or less. Between the covering layer of the covering layer and the zirconia of the mullite, as claimed in any one of claims 1 to 12 having a coating layer of alumina forming the coating layer and the interface of the mullite further Kiln tools. The kiln tool according to claim 13 , wherein an average pore diameter of the alumina-based coating layer is 1 µm or more and 50 µm or less. The kiln tool according to claim 13 or 14 , wherein a cumulative pore diameter (D ₅₀ ) of the alumina-based coating layer is observed in a range of 2 µm to 70 µm. The kiln tool according to any one of claims 13 to 15 , wherein a porosity of the alumina-based coating layer is 10% or more and 50% or less. The kiln tool according to any one of claims 13 to 16 , wherein the thickness of the alumina coating layer is 50 µm or more and 150 µm or less. The kiln tool according to any one of claims 1 to 17 , which is used for firing electronic components.