JPS63292614A - Manufacture of grain boundary layer type semiconductor ceramics capacitor - Google Patents

Abstract

PURPOSE:To obtain a ceramics capacitor enabling firing at a relatively low temperature and having large capacity with small dispersion of capacity, by making an SrTiO3 system of denatured oxide raw material powder of a submicron order having good dispersibility in grain diameter control for making this powder into a composite raw material by mixing this powder. CONSTITUTION:A solution which contains a proper quantity of at least one kind of metallic components except Sr or Ti of the chemical formula expressed by Sr1-x-yBaxGayTiO3 and Sr or Ti is made. Next, this solution is hydrolyzed to generate a sol and this sol is dried and temporarily fired at 600-1200 deg.C to be made into a calcined substance. As a result, denatured powder of a submicron order, for instance, SrTiO3 powder is obtained as the calcined substance, and this denatured powder has extremely good dispersion so as to be hard to generate cohesion of grains. Subsequently, this temporary-fired substance and a compound of the remaining constitutive components of perovskite structure are mixed to be temporary-fired at 700-1300 deg.C for being made into calcined powder. The calcined powder is fired in a reducing atmosphere of 1300-1600 deg.C to be made into a ceramic. Ti, Mn, Fe, Co, Ni, Cu, B, Pb, Bi, La, Pr and Tm are diffused in a grain boundary at 800-1300 deg.C to obtain the intended ceramic capacitor.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a high-capacity grain boundary layer insulated semiconductor ceramic capacitor, particularly when the chemical formula is Sr+-x
-yBaXCayTiOa (0≦X≦1.0≦y≦1
The present invention relates to a method for manufacturing a SrTiO3-based grain boundary layer insulated semiconductor ceramic capacitor having a perovskite structure represented by ) and having a high and stable dielectric constant by increasing and equalizing particle diameters.

[Conventional technology]

Grain boundary layer insulated semiconductor ceramic capacitor (usually B
L-type capacitors (abbreviated as L-type capacitors) have a structure in which a highly insulating material is uniformly segregated in the grain boundary layer of semiconductor ceramics, and compared to other semiconductor ceramic capacitors, (]) insulation resistance is (2) Excellent moisture resistance;
(3) Features include excellent high frequency characteristics.

In particular, 5rTiO, system B I-type capacitors are BaT
Compared to i0a series BL type capacitors, characteristics such as apparent iJ dielectric constant, which directly affects capacitance, have excellent stability with respect to voltage, frequency, temperature, etc., so it can be used in everything from industrial equipment to consumer equipment. Used in a wide range of electrical equipment. However, since the absolute value of the dielectric constant of 5rTi03 type Bl type capacitors is apparently lower than that of BaTi0a type capacitors,
In order to achieve a sufficiently high capacity for practical use, it is inevitable to improve the apparent dielectric constant.

It is known that in order to increase the apparent dielectric constant of a BL type capacitor, it is sufficient to increase the particle size if the particle composition, characteristics of grain boundary segregates, and thickness of the grain boundary layer remain unchanged. There is. Furthermore, it is naturally necessary that the increased particle size be uniform without variation in order to eliminate variations in properties in practice.

However, BL type capacitors based on 5rTiO (including those in which part of the Sr is replaced with Ba or Ca) are difficult to sinter using the general dry method as a ceramic material, so it is difficult to make the ceramic particles large and aligned. there were.

That is, the chemical formula Sr, -X-yBaxCayTiO+
, 0 ≦
CaCO3 powder, TiO□ powder, etc. are blended to obtain the desired 5BCT composition, and Dy2 is further added as a valence control material.
Off powder, A 12 zo3 powder, SiO2 powder, etc. are added and mixed using a dry method using a ball mill, etc., and then calcined at, for example, about 1150°C to obtain 5BCT powder (
This calcined powder is press-molded and finally fired at, for example, about 1400°C.

In order to increase the apparent dielectric constant of the obtained 5BCT ceramics, it is necessary to increase the density of the ceramics for the following reasons. The BL type capacitor has a structure in which a highly insulating substance is uniformly segregated at the grain boundaries of a polycrystalline ceramic as described above. Therefore, during the firing process, individual crystal grains grow to a large and uniform size, and the structure intervening between each crystal grain is only the original grain boundary,
In particular, it is necessary that no unbonded voids remain at triple points or the like. In order to realize such a uniform coarse-grained and dense structure, it is essential to promote adhesion and coalescence of powder particles during the firing process to promote shrinkage of voids and thereby densification.

In the dry method, in which powder is pressure-formed and then fired into ceramics, the density of the ceramic is strongly dependent on the packing density in the pressure-formed state before firing. Therefore, in order to improve the density of ceramics, it is necessary to improve the packing density, and for this purpose, it is necessary to further refine the 5BCT calcined powder before pressure molding. However, as the raw material powder described above is refined, the tendency to agglomerate between particles rapidly increases, so the refinement reaches saturation, and eventually the
The refinement of BCT powder also reaches saturation. Therefore, the 5BCT calcined powder obtained conventionally has a minimum of 1 to 2
It was more than μm.

Therefore, by further refining the 5BCT powder,
There has been a strong demand for a method for stably manufacturing grain boundary layer insulated semiconductor ceramic capacitors with large, monodisperse ceramic particles and a higher apparent dielectric constant.

(Problems to be Solved by the Invention) The purpose of the present invention is to create a submicron-class SrTiO3-based modified oxide raw material powder with good dispersibility, and to use this powder to perform a simple dry process. By mixing the desired composition raw materials, it is possible to bake at a relatively low temperature, and the particle size is large and monodisperse, providing a large capacity and excellent grain boundary layer insulation with small variation in capacity. An object of the present invention is to provide a method for manufacturing a type semiconductor ceramic capacitor.

[Means for solving problems]

For the above purpose, the chemical formula is Sr+-x-yBaxcay
TiO: +, expressed as 0≦X≦1.0≦y≦1, and as a valence control material Ti, Mn+Cu, Ga, Y, Nb,
In4a+W+old, La+Pr+Gd, Dy, E
In a method for manufacturing a grain boundary layer insulated semiconductor ceramic capacitor having a perovskite composition containing a compound of at least one element of r, Aβ, and Si, (1) an appropriate amount of at least one metal component other than Sr in the chemical formula and Sr; or a solution containing Ti in the chemical formula
(2) hydrolyzing the solution to produce a sol, drying the sol to a temperature of 600 to 12
(3) mixing the calcined product with compounds of the remaining components of the perovskite composition and calcining at 700 to 1300°C to obtain a calcined powder; (4) firing the calcined powder in a reducing atmosphere at 1,300 to 1,600°C to form a ceramic; and (5) containing Ti, Mn, Pe, and Co at the grain boundaries of the ceramic.

Ni, CutB+Pb, Bi+La, Pr, and T
This is achieved by a method for manufacturing a grain boundary layer insulated semiconductor ceramic capacitor, which comprises a step of diffusing at least one element of m at 800 to 1300°C.

The present inventor has discovered that a submicron grade modified powder (modified oxide powder) such as 5rTi0,1 powder is obtained as a calcined product through the above steps (1>-(2) including a wet process, and this modified powder is highly dispersed. For example, unmodified 5rCOs powder, Ti0, which has good properties and has been conventionally used as raw material powder.
It has been found that agglomeration of particles, which inevitably occurs with Z powder, is less likely to occur. Furthermore, the present inventors also combined the modified powder (5rTi03 powder in the above case) with the remaining constituent components of the target perovskite composition (Ba and/or Ca in this case, and the valence control material) through step (3). When mixed with compounds such as BaCO3, CaCO3, and Dyz (h+5iOz, ^1 zoi, etc.), the mixed powder itself has no agglomeration, and when calcined, it becomes submicron-grade 5BCT with good dispersibility. Even if a calcined powder is obtained and operations such as hot pressing or HIP (for example, hot gas pressure sintering) are omitted, a perovskite mold 5 can be obtained by molding and firing it in step (4).
It has been found that BCT ceramics have large particle sizes, and when diffused into grain boundaries in step (5), a grain boundary layer insulated semiconductor ceramic capacitor has a significantly improved apparent dielectric constant.

The solution in step (1) is an aqueous solution or an alcoholic solution. The solution is prepared by dissolving a metal compound powder of at least one metal component other than Sr or Ti in the above chemical formula in a solution containing Srs or Ti, or conversely, in a solution containing the former. Either the latter compound powder is dissolved, both are prepared as solutions containing their respective components and mixed together, or both are prepared as compound powders and dissolved together in water or alcohol, or both are prepared as compound powders and dissolved together in water or alcohol. This is done by a combination of

As a compound for creating a solution containing Sr,
For example, strontium bromide, strontium chloride, strontium nitrate, strontium sulfate, jetoxystrontium, propoxystrontium, butoxystrontium, etc. are used. These Sr compounds may be used alone, or two types may be used as long as they do not affect each other.
More than one species may be used together. Examples of compounds for preparing a Ti-containing solution include titanium tetrabromide,
Titanium tetrachloride, tetramethoxytitanium, tetraethoxytitanium, tetrapropoxytitanium, tetrabutoxytitanium, etc. are used. These Ti compounds may be used alone, or two or more types may be used together as long as they do not affect each other.

The "appropriate amount" in step (1) is an amount suitable for suppressing aggregation of the sol produced in step (2), and varies depending on the compound used to create the solution.

The sol produced in 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℃, agglomeration will occur significantly, and l3
When the temperature exceeds 00°C, particles tend to become coarse.

To the thus obtained calcined product, the missing components of the perovskite composition and a valence control material are added and mixed. In the above case, for example, 5rCO, TiO□
The powders can be further mixed to obtain the desired perovskite composition.

In order to obtain the agglomeration prevention effect as a mixture, at least one of the raw material powders may be a submicron-grade modified powder formed in steps (1) and (2). Therefore, as the remaining constituent compounds to be mixed in step (3), conventional commercially available raw material powders may be used, and submicron powders formed in the same manner as above in steps (1) and (2) may be used. Grade modified powders may also be used. All commercially available raw material powders used in step (3) must have submicron particle sizes.

The calcination temperature of the mixture (step (3)) is 700°C.
A perovskite structure is formed from the vicinity, and if calcined at a temperature higher than 1300°C, the calcined powder particle size will increase and the firing characteristics will be significantly deteriorated, so the temperature should be in the range of 700 to 1300°C.

The powder thus obtained is molded. The calcination temperature, like the calcination temperature of the mixture described above, varies depending on the types of constituent components, but is generally in the range of 1300 to 1600°C. If it is lower than 1300°C, sintering will be insufficient and high density will not be obtained, and if it exceeds 1600°C, the particles will locally coarsen and the particle size will vary significantly, or volatile elements will evaporate and be lost. The desired composition is not achieved.

What is the firing atmosphere? 'Jz 1H2, Co□+H2, etc. reducing atmosphere.

The perovskite-type 5BCT ceramic obtained by firing is injected with elements for forming a highly insulating substance at grain boundaries, namely Ti, Mn, Fe, Co+Ni, Cu,
B, Pb, Bi, La.

Compounds such as Pr, Tm (e.g., Cu, MnC,
0a, PbO.

A coating agent (iJT+ usually in paste form) containing Bi2O3, etc.) is applied and heated and held at, for example, 1150°C to diffuse and segregate the element in the grain boundaries to form the highly insulating substance.

The temperature for selective diffusion to grain boundaries is 900-1200℃
It is desirable that it be within the range of .

The shaping for final firing to form ceramics may be performed immediately before the firing in step (4), or may be performed after mixing the various powders in step (3) and then calcined. In the latter case of molding in step (3), it is of course unnecessary to perform molding in step (4).

The present invention will be explained in more detail below by comparing Examples and Comparative Examples.

〔Example〕

Strontium nitrate aqueous solution (1,5β/mail solution)
300cc and titanium tetrachloride aqueous solution (1,3It/mo
(!Solution) 260cc were mixed. This aqueous solution, 1
Hydrolysis is carried out by holding at 00°C for 100 hours,
A sol containing S r'' and Ti'' was obtained. After washing and drying this, it was calcined at 800°C to produce 5rTi (1+ powder).

0.687 g of commercially available BaCO3 was added to 10 g of the powder,
TiOz: 0.320 g, DyzO: + 0.0
4 g, SiO□0.04 g, A p 20
After mixing 30.04g in a ball mill for a day and night, 10
Calcined at 00℃ for 1 hour, Sro, q4Bao, o
6Tio3 type powder was obtained. The particle size is 0.25 μm. The powder was molded at 0.7 ton/cjA, and after degreasing, 1
350℃, 1400℃, 1450℃ (93N2-7H2
(medium) for 1 hour. Thereafter, a paste containing equimolar amounts of Cub and MnO was applied and heat treated at 1150° C. in the air for 1 hour. Further, after this, the silver electrode was baked and used as a measurement sample.

(Comparative example) Commercially available 5rC03, BaCO3, Ti0z, mouth VzO8
+8 I! 203,5i02 was weighed to have the same composition as above, and 25 g of the weighed powder was mixed in a ball mill overnight and then 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.

For each sample prepared in (Example) and (Comparative Example), the particle diameter and apparent dielectric constant were measured.

Measurement of particle size was performed using SE at 1000x magnification on the cut surface of each sample.
It was done by M. The apparent dielectric constant was measured using an impedance analyzer. The results of each measurement are shown in FIG. 1 and FIG. 2, respectively.

As is clear from FIG. 1, the particle size is significantly increased by the method of the present invention. For example, when fired at 1450°C, the particle size is 40 μm in the conventional method (comparative example) using only a dry method, but in the method of the present invention (example)
In this case, it increases to 65μm, and the variation is ±5μm.
They were very well aligned, about m. As a result, as is clear from FIG. 2, the apparent dielectric constant (Sr) is significantly improved by the method of the present invention. For example, firing temperature 1
In the case of 400 to 1450℃, the conventional method
~27,000 (±20%), whereas in the method of the present invention, it is 45,000 (±10%), about 70-80%.
Excellent characteristics were obtained, with improved characteristics and variations reduced by about half.

〔Effect of the invention〕

According to the method of the present invention, 5B
The raw material powder (modified oxide powder) containing one or more of the constituent components of CT can be made into submicron particles with extremely few secondary particles. 5BCT raw material powder was obtained, and by using this powder as a raw material, the particle size was large and uniform, so 5BCT ceramics with a high capacity, that is, an apparent dielectric constant, and no variation were obtained, which was an excellent effect. It will be done. In addition, the following effects can also be obtained.

1) Since the modified oxide powder obtained by the calcined product is obtained in a sufficiently dispersed manner, it can be supplied as a raw material powder without the need for a particular pulverization step of the calcined product.

2) 5OC obtained from the calcined modified oxide powder by a dry method
T powder is also obtained in a monodisperse state, and therefore has sufficient sinterability and high density even without the pulverization step.

3) Extremely high capacitance (apparent dielectric constant) is required 5
A BCT-based grain boundary layer insulated semiconductor ceramic capacitor can be obtained simply by solid-phase sintering, omitting operations such as hot pressing and HIP (for example, hot gas pressure sintering).

4) 5BCT compositions (powders and ceramics) of arbitrary compositions can be supplied at extremely low cost by mass producing modified oxide powders with excellent powder properties.

[Brief explanation of drawings]

FIG. 1 is a graph showing the grain size of a grain boundary layer insulated semiconductor ceramic capacitor manufactured by the method of the present invention as a function of firing temperature in comparison with that of a conventional method. FIG. 2 is a graph showing the apparent dielectric constant of each sample in FIG. 1.

Claims (1)

[Claims] 1. The chemical formula is Sr_1_-_x_-_yBa_xCa
_yTiO_3, expressed as 0≦x≦1, 0≦y≦1 and containing Ti, Mn, Cu, Ga, Y, N as a valence control material
b, In, Ta, W, Bi, La, Pr, Gd, Dy,
In a method for manufacturing a grain boundary layer insulated semiconductor ceramic capacitor having a perovskite composition containing a compound of at least one element of Er, Al, and Si, (1) an appropriate amount of at least one metal component other than Sr in the chemical formula and Sr;
or a solution containing Ti and an appropriate amount of at least one metal component other than Ti in the chemical formula; (2) hydrolyzing the solution to produce a sol; a step of drying the sol and then calcining it at 600 to 1200°C to obtain a calcined product; (3) mixing the calcined product and compounds of the remaining constituent components of the perovskite composition and calcining the mixture at 700 to 1300°C; (4) firing the calcined powder in a reducing atmosphere at 1,300 to 1,600°C to produce a ceramic; and (5) adding Ti, Mn, Fe, Co, Ni
, Cu, B, Pb, Bi, La, Pr, and Tm at 800 to 1300°C. 2. In the step (1), the solution is prepared by mixing an aqueous solution or an alcoholic solution of the compound of the metal component and an aqueous solution or an alcoholic solution of the Sr compound. A method for manufacturing a grain boundary layer insulated semiconductor ceramic capacitor. 3. Claim 2, wherein the Sr compound is comprised of one or more of strontium bromide, strontium chloride, strontium nitrate, strontium sulfate, diethoxystrontium, propoxystrontium, and butoxystrontium. A method for manufacturing a grain boundary layer insulated semiconductor ceramic capacitor as described in 1. 4. In the step (1), the solution is prepared by mixing an aqueous solution or an alcoholic solution of the compound of the metal component and an aqueous solution or an alcoholic solution of the Ti compound. A method for manufacturing a grain boundary layer insulated semiconductor ceramic capacitor. 5. The Ti compound is titanium tetrabromide, titanium tetrachloride,
The method for manufacturing a grain boundary layer insulated semiconductor ceramic capacitor according to claim 4, characterized in that the capacitor is made of one or more of tetramethoxytitanium, tetraethoxytitanium, tetrapropoxytitanium, and tetrabutoxytitanium. .