JP2682824B2 - Method for manufacturing grain boundary layer insulated semiconductor ceramic capacitor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a high-capacity grain boundary layer insulating semiconductor ceramic capacitor, and particularly to a chemical formula of Sr _1-xy B
SrTiO ₃ system having a perovskite structure represented by a _x Ca _y TiO ₃ (0 ≦ x ≦ 1, 0 ≦ y ≦ 1) and having a high relative dielectric constant by stabilizing the particle size to be large and uniform. The present invention relates to a method for manufacturing a grain boundary layer insulated semiconductor ceramic capacitor. [Prior Art] Grain Boundary Layer Insulated Semiconductor Ceramics Capacitor
BL type capacitor) has a structure in which a highly insulating material is uniformly biased in the grain boundary layer of semiconductor ceramics. Compared with other semiconductor ceramic capacitors,
(1) High insulation resistance, (2) Excellent moisture resistance,
(3) It has characteristics such as excellent high frequency characteristics. In particular, SrTiO ₃ -based BL type capacitors have superior stability with respect to voltage, frequency, temperature, etc., in characteristics such as apparent relative permittivity that directly affects the capacitance, as compared to BaTiO ₃ -based BL type capacitors. It is used in a wide range of electrical equipment, from industrial equipment to consumer equipment. However, since the absolute value of the apparent relative permittivity of SrTiO ₃ type BL type capacitors is lower than that of BaTiO ₃ type capacitors, it is inevitable to improve the apparent relative permittivity in order to realize a practically high capacity. . It is known that in order to increase the apparent relative permittivity of a BL type capacitor, the particle size can be increased if the composition of particles, the characteristics of grain boundary unevenness, and the thickness of the grain boundary layer are not changed. . Further, it is naturally necessary that the increased particle diameters are evenly arranged in order to eliminate variations in characteristics in practical use. However, SrTiO ₃ -based capacitors (including those in which Sr is partly replaced with Ba or Ca) are difficult to fire in a general dry method as a ceramic material, so it is difficult to arrange large and large ceramic particles. there were. That is, the chemical formula Sr _1-xy Ba _x Ca _y TiO ₃ , 0 ≦ x ≦ 1,
Perovskite-type ceramics represented by 0 ≦ y ≦ 1 (SBCT-based ceramics or simply SBCT depending on the case below)
Is generally used as a raw material powder such as SrCO.
₃ powder, BaCO ₃ powder, CaCO ₃ powder, TiO ₂ powder etc.
Compounded to have T composition, and further added as a valence control material D
y ₂ O ₃ powder, Al ₂ O ₃ powder, SiO ₂ powder, etc. are added and mixed by a dry method using a ball mill, and then, for example, 1150 ° C.
It is obtained by calcining at a certain degree to obtain SBCT powder (which also contains the metal component of the valence control material), press-molding this calcined powder, and finally calcining at about 1400 ° C. In order to increase the apparent relative permittivity of the obtained SBCT ceramics, it is necessary to increase the density of the ceramics for the following reasons. The BL type capacitor has a structure in which the highly insulating substance is uniformly biased to the crystal grain boundaries of the ceramic that is a polycrystalline body. Therefore, in the firing process, individual crystal grains grow to a large uniform size, and the only intervening structure between the crystal grains is the original crystal grain boundary, and in particular, no unbonded voids remain at triple points. is required. In order to realize such a uniform coarse-grained dense structure, it is essential to promote the adhesion and coalescence of the powder particles during the firing process to promote the shrinkage of the voids and the resulting densification. In a mere dry method in which a powder is pressed and then fired into a ceramic, the density of the ceramic strongly depends on the packing density in the pressed state before firing. Therefore, in order to improve the density of ceramics, it is necessary to improve the charge density, and for that purpose, it is necessary to make the SBCT calcined powder before pressure molding finer. However, in the above-mentioned raw material powder, the agglomeration tendency between particles rapidly increases as the refinement progresses, so the refinement becomes saturated, and eventually the SB after calcination is finished.
The miniaturization of CT powder is also saturated. Therefore, the SBCT calcined powder obtained in the past had a particle size of 1 to 2 μm or more at the smallest. Therefore, the appearance of a method for stably producing a grain boundary layer insulating semiconductor ceramic capacitor having a higher apparent relative permittivity, in which the particle size of the ceramic is large and the particles are monodispersed, and is further refined by further refining the SBCT powder There was a strong demand. [Problems to be Solved by the Invention] An object of the present invention is to prepare a submicron grade SrTiO ₃ -based modified oxide raw material powder having good dispersibility in such particle size control, and use this powder to perform a simple dry process. An excellent grain boundary layer that can be fired at a relatively low temperature, has a large particle size and is monodisperse, and has a large capacity and a small variation in capacity by mixing by the method to obtain the originally desired composition raw material. An object of the present invention is to provide a method for manufacturing an insulating semiconductor ceramic capacitor. [Means for Solving the Problems] The above-mentioned object is that the chemical formula is Sr _1-xy Ba _x Ca _y TiO ₃ , 0 ≦
As a valence control material represented by x ≦ 1, 0 ≦ y ≦ 1
Grain boundary layer insulation of perovskite composition containing compounds of at least one element of Ti, Mn, Cu, Ga, Y, Nb, In, Ta, W, Bi, La, Pr, Gd, Dy, Er, Al, and Si (1) A solution containing Sr and an appropriate amount of at least one metal component other than Sr in the chemical formula, or an appropriate amount of at least one metal component other than Ti in the chemical formula. A step of preparing a solution containing Ti, (2) a step of hydrolyzing the solution to generate a sol, and drying the sol to calcinate it at 600 to 1200 ° C. to obtain a calcined product, (3) A step of mixing the calcined product and the compounds of the remaining constituents of the perovskite composition and calcining at 700 to 1300 ° C to obtain a calcined powder, (4) reduction of the calcined powder at 1300 to 1600 ° C The step of firing into ceramics in an atmosphere, and (5) Ti, Mn, Fe, Co, Ni, Cu, B,
At least 1 element of Pb, Bi, La, Pr, and Tm is 800-1300
This is achieved by a method for manufacturing a grain boundary layer insulating semiconductor ceramic capacitor, which comprises a step of diffusing at a temperature of ° C. The present inventor has determined that the above steps (1) and (2) including the wet process
As a result of the calcination, submicron grade metamorphic powder (metamorphic oxide powder) such as SrTiO ₃ powder is obtained. This metamorphic powder has very good dispersibility, and it is unmodified such as SrCO ₃ powder used as a raw material powder in the past. , TiO ₂ powder and the like, it was found that aggregation of particles inevitably generated is unlikely to occur. Furthermore, the present inventor has conducted the modified powder (SrTiO ₃ powder in the above case) and the remaining constituents (Ba and / or Ba in this case) of the target perovskite composition by the step (3).
Compounds of Ca and valence control materials (eg Ba
When mixed with CO ₃ , CaCO ₃ , and Dy ₂ O ₃ , SiO ₂ , Al ₂ O _3, etc., the mixed powder itself does not have cohesive properties, and when it is calcined, it is still a submicron grade product with good dispersibility. SBCT calcined powder is obtained, and even if operations such as hot pressing and HIP (for example, hot gas pressure sintering) are omitted, perovskite-type SBCT ceramics obtained by molding and firing this in step (4) It has been found that the particle diameters are substantially uniform and, when diffused to the grain boundary in the step (5), the grain boundary layer-insulated semiconductor ceramic capacitor has a significantly improved apparent relative dielectric constant. The solution in step (1) is an aqueous solution or an alcohol solution. The solution is prepared by using Sr in the above chemical formula, or compound powder of at least one metal component other than Ti, Sr, or
Dissolve in a solution containing Ti, respectively, on the contrary, dissolve the latter compound powder in a solution containing the former, prepare both as a solution containing each component, or mix, or both compounds Either prepared as a powder and dissolved together in water or alcohol, or by a combination thereof. As a compound for preparing a solution containing Sr,
For example, strontium bromide, strontium chloride, strontium nitrate, strontium sulfate, diethoxystrontium, propoxystrontium, butoxystrontium, etc. are used. These Sr compounds may be used alone or in combination of two or more as long as they do not affect each other. As a compound for producing a solution containing Ti, for example, titanium tetrabromide, titanium tetrachloride, tetramethoxy titanium, tetraethoxy titanium, tetrapropoxy titanium, tetrabutoxy titanium, etc. are used. These Ti compounds may be used alone or in combination of two or more as long as they do not affect each other. The “appropriate amount” in the step (1) is an amount suitable for suppressing the aggregation of the sol generated in the step (2), and varies depending on the compound used for preparing the solution. The sol generated in the step (2) is recovered by filtration and washing, and then dried. The calcination temperature of the sol after drying is 600 to 1200 ° C. If the calcination temperature is lower than 600 ° C, agglomeration will occur remarkably, and if it exceeds 1300 ° C, the particles tend to become coarse. The calcination product thus obtained is added with a deficiency of constituent components as a perovskite composition and a valence control material, and mixed. In the above case, for example, powders of SrCO ₃ and TiO ₂ can be further mixed to obtain the desired perovskite composition. In order to obtain the effect of preventing aggregation as a mixture, at least one of the raw material powders may be a submicron-grade modified powder formed in the steps (1) and (2). Therefore,
As the compound of the remaining constituent components to be mixed in the step (3), a conventional commercially available raw material powder may be used, and the submicron-class powder formed in the same manner as described above in the steps (1) and (2) may be used. Denatured powder may be used. All of the commercially available raw material powders used in step (3) need to have a submicron class particle size. The calcination temperature of the mixture (step (3)) is 700 ° C.
A perovskite structure is formed from the vicinity, and when calcined at 1300 ° C. or more, the calcined powder particle size becomes large and the calcining characteristics are remarkably deteriorated. Therefore, it is necessary to be in the range of 700 to 1300 ° C. The powder obtained in this way is molded. The calcination temperature varies depending on the kind of the constituent components, like the calcination temperature of the above-mentioned mixture, but is generally in the range of 1300 to 1600 ° C. 1300
If the temperature is lower than ℃, the sintering will be insufficient and high density will not be obtained.
If it exceeds, the particles will be locally coarsened and the particle size will vary significantly, or volatile elements will be volatilized and lost, and the desired composition will not be obtained. The firing atmosphere is a reducing atmosphere such as N ₂ + H ₂ or CO ₂ + H ₂ . In the perovskite type SBCT ceramics obtained by firing, elements for forming a highly insulating substance at grain boundaries, namely Ti, Mn, Fe, Co, Ni, Cn, B, Pb, Bi, La, Pr, Tm. A coating agent (usually a paste) containing a compound such as MnO, CuO, MnCO ₃ , PbO, Bi ₂ O ₃ etc. is applied, and the element is bound to the grain boundaries by heating and holding at 1150 ° C, for example. Then, the highly insulating material is formed by diffusing and biasing the material. It is desirable that the temperature for selectively diffusing at the grain boundaries be in the range of 900 to 1200 ° C. The molding for finally firing into ceramics is
The step (3) may be performed immediately before the firing in the step (4).
In the above step, the powder may be calcined after mixing the various powders. In the latter case of molding in step (3), of course, it is not necessary to perform molding in step (4). Hereinafter, the present invention will be described in more detail by comparing Examples and Comparative Examples. [Example] 300 cc of strontium nitrate aqueous solution (1.5 l / mol solution) and 260 cc of titanium tetrachloride aqueous solution (1.3 l / mol solution) were mixed. This aqueous solution was hydrolyzed by holding it at 100 ° C. for 100 hours to obtain a sol containing Sr ²⁺ and Ti ⁴⁺ . This was washed and dried, and then calcined at 800 ° C. to prepare SrTiO ₃ powder. 0.687 g of commercially available BaCO ₃ and 0.320 g of TiO ₂ in 10 g of the powder,
Dy ₂ O ₃ 0.04g, SiO ₂ 0.04g, and Al ₂ O ₃ 0.04g were mixed in a ball mill all day and night, and then calcined at 1000 ° C for 1 hour to obtain Sr _0.94.
Ba _0.06 TiO ₃ powder was obtained. The particle size is 0.25 μm. The powder was molded at 0.7 ton / cm ² and after degreasing 1350 ° C, 1400 ° C, 14
Baking at 50 ° C. (in 93N ₂ -7H ₂ ) for 1 hour. After that, CuO, MnO
Was applied in an equimolar amount, and the paste was applied and heat-treated at 1150 ° C. in the atmosphere for 1 hour. Further, after this, the silver electrode was used as a baking measurement sample. (Comparative Example) Commercially available SrCO ₃ , BaCO ₃ , TiO ₂ , Dy ₂ O ₃ , Al ₂ O ₃ and SiO ₂ were weighed to have the same composition as above, and 25 g of the weighed powder was mixed in a ball mill overnight. After that, it was calcined at 1150 ° C. for 1 hour to obtain a powder of 2 μm. This was molded in the same manner as in the example, and a sample was prepared under the same conditions as in the above example. The particle size and the apparent relative permittivity of each sample prepared in (Example) and (Comparative Example) were measured. The particle diameter was measured by SEM at a magnification of 1000 on the cut surface of each sample. The apparent relative permittivity was measured by an impedance analyzer. The measurement results are shown in FIGS. 1 and 2, respectively. As is clear from FIG. 1, the particle size is remarkably increased by the method of the present invention. For example, when calcined at 1450 ° C., the particle diameter is 40 μm in the conventional method (comparative example) using only the dry method, but it is 65 in the method of the present invention (example).
.mu.m, and the variation was about. +-. 5 .mu.m, which was extremely well aligned. As a result, as apparent from FIG. 2, the apparent relative permittivity (ε _r ) is remarkably improved by the method of the present invention. For example, firing temperature 1400
In the case of ~ 1450 ℃, the conventional method is 25000 ~ 27000 (± 20
%), Whereas in the method of the present invention, 45000 (± 10
%) And about 70 to 80%, and the variation was reduced to about half. [Advantages of the Invention] According to the method of the present invention, the SB is produced by the steps (1) and (2).
Raw material powders (modified oxide powders) containing one or more constituents of CT can be submicron particles with extremely few secondary particles. The SBCT raw material powder can be obtained, and by using this as a raw material and having a large particle diameter and a uniform particle diameter, SBCT ceramics having a high capacity, that is, an apparent relative dielectric constant and no variation can be obtained. In addition, the following effects can be obtained. 1) Since the modified oxide powder obtained by the calcined product is sufficiently dispersed, the calcined product can be supplied as a raw material powder without requiring a pulverizing step. 2) SBCT powder obtained by a dry method from the calcined modified oxide powder is also obtained in a monodispersed state, and therefore has sufficiently easy sinterability and high density even if the pulverization step is omitted. 3) SB that requires extremely high capacity (apparent relative dielectric constant)
The CT-based grain boundary layer-insulated semiconductor ceramic capacitor can be obtained by simple solid-phase sintering while omitting operations such as hot pressing and HIP (for example, hot gas pressure sintering). 4) The mass production of the modified oxide powder having excellent powder characteristics makes it possible to supply the SBCT composition (powder and ceramics) having an arbitrary composition at an extremely low cost.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a graph showing the particle size of the grain boundary layer insulating semiconductor ceramic capacitor manufactured by the method of the present invention with respect to the firing temperature as compared with the case of the conventional method. FIG. 2 is a graph showing the apparent relative permittivity of each sample in FIG.

   ────────────────────────────────────────────────── ─── Continuation of front page                   (56) References JP-A-62-111412 (JP, A)                 JP-A-61-239504 (JP, A)                 JP-A-57-191231 (JP, A)

Claims (1)

(57) [Claims] The chemical formula is Sr _1-xy Ba _x Ca _y TiO ₃ , 0 ≦ x ≦ 1, 0 ≦
represented by y ≦ 1 and Ti, Mn, Cu, Ga,
In a method of manufacturing a grain boundary layer insulating semiconductor ceramic capacitor of a perovskite composition containing a compound of at least one element of Y, Nb, In, Ta, W, Bi, La, Pr, Gd, Dy, Er, Al and Si (1) A solution containing an appropriate amount of at least one metal component other than Sr in the chemical formula and Sr, or a solution containing an appropriate amount of at least one metal component other than Ti in the chemical formula and Ti (2) Hydrolyzing the solution to generate a sol, drying the sol and calcining at 600 to 1200 ° C. to obtain a calcined product, (3) the calcined product and the perovskite composition (4) a step of mixing the remaining components of the compound and calcining at 700 to 1300 ° C. to obtain a calcined powder, (4) firing the calcined powder in a reducing atmosphere at 1300 to 1600 ° C. to obtain ceramics. And (5) at the grain boundaries of the ceramic, Ti, Mn, Fe, Co, Ni, Cu, B,
At least 1 element of Pb, Bi, La, Pr, and Tm is 800-1300
A method for manufacturing a grain boundary layer insulated semiconductor ceramic capacitor, which comprises a step of diffusing at ℃. 2. The particle according to claim 1, wherein in the step (1), the aqueous solution or alcohol solution of the compound of the metal component and the aqueous solution or alcohol solution of the Sr compound are mixed to prepare the solution. Method for manufacturing boundary layer insulated semiconductor ceramic capacitor. 3. The Sr compound is strontium bromide, strontium chloride, strontium nitrate, strontium sulfate,
The method for producing a grain boundary layer-insulated semiconductor ceramic capacitor according to claim 2, comprising one or more of diethoxystrontium, propoxystrontium, and butoxystrontium. 4. The particle according to claim 1, wherein in the step (1), the aqueous solution or alcohol solution of the compound of the metal component and the aqueous solution or alcohol solution of the Ti compound are mixed to prepare the solution. Method for manufacturing boundary layer insulated semiconductor ceramic capacitor. 5. The Ti compound is composed of one or more of titanium tetrabromide, titanium tetrachloride, tetramethoxytitanium, tetraethoxytitanium, tetrapropoxytitanium, and tetrabutoxytitanium. A method for manufacturing a grain boundary layer-insulated semiconductor ceramic capacitor as set forth in the paragraph.