JPS63288958A - Production of sr(ce, zr)o3 type ceramic - Google Patents

Abstract

PURPOSE:To obtain the title ceramic having high density by forming a coprecipitate contg. a part of metallic constituents except Zr constituting Sr(Ce, Zr)O3 type ceramic and contg. Zr independently, adding thereto residual constituents, and molding the mixture and sintering the molded product. CONSTITUTION:A soln. [e.g. mixture of aq. soln. of cerium (III) nitrate and zirconyl nitrate] contg. an appropriate amt. of at least one metallic constituent except Zr (e.g. Ce) constituting Sr(Ce, Zr)O3 type ceramic contg. Zr is prepd. Then, coprecipitate is formed by allowing the soln. to react with a precipitate- forming soln. (e.g. aq. ammonia). The coprecipitate is dried and calcined at 700-1,300 deg.C to obtain a powdery product having submicron level particle size and contg. scarcely agglomerates. The powdery product is mixed with a compd. of residual constituents of the Sr(Ce, Zr)O3 type ceramic, and the mixture is calcined at 500-1,300 deg.C. The title ceramic is obtained by sintering the calcined powder at 700-1,700 deg.C after molding the powder.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing 5r(Ce, Zr)O, ceramics.

5r(Ce, Zr)O, ceramics have a history of application as proton conductors in various sensors, fuel cells, etc.
It is expected to be used in a wide range of fields as functional ceramics.

[Conventional technology]

5r(Ce, Zr) (Among the raw material powders of Sr, Ce and Zr oxides, which are constituent components of h-based ceramics,
Zirconia raw material powder is extremely prone to agglomeration. Using such zirconia raw material powder, 5r (Ce,
When a Zr)0=based ceramic powder is produced, the average particle size is 3 to 5 μm or more. 5r with this level of particle size
Even when using (Ce, Zr)Q, ceramic powder, 5r(Ce, Zr)0 with high density and advanced functionality
It is difficult to obtain ° series ceramics.

[Problem that the invention seeks to solve]

The present invention was made in order to eliminate the drawbacks in the dry process synthesis of 5r(Ce, Zr)O3-based ceramics, and its purpose is to produce submicron-grade modified zirconia raw material powder with good dispersibility. 5r(Ce, Zr)O, based ceramic powder that is easy to sinter and has a high bulk density is synthesized by a simple dry method using the powder, and these powders are further sintered to produce high performance and high density of 5
The present invention provides a method for producing r(Ce, Zr)Ch ceramics.

[Means for solving problems]

As a result of intensive research to achieve the above objective, the names of unexplored towns were 5
A mixed solution of a solution containing zirconium and an appropriate amount of at least one metal component other than zirconium constituting r(Ce, Zr)Os-based ceramics and a precipitate forming solution are mixed to form a coprecipitate, and then dried. After soot, 700-1300℃
It has been found that by calcining the powder, a submicron-level powder (modified zirconia powder) containing extremely little aZtA can be obtained. Using this as a raw material, the target 5r (Ce, Zr)
By mixing the remaining components of the O= ceramic composition using a dry method, a submicron-level raw material powder with excellent powder properties can be easily obtained, and when this is molded and sintered, it becomes a sintering aid. Extremely dense 5r(Ce,
It has been found that Zr)0:+ ceramics can be easily obtained. The present invention was completed based on this knowledge.

The gist of the present invention lies in the combination of the following three steps.

(1) Prepare a solution containing zirconium and an appropriate amount of at least one component other than zirconium constituting the 5r(Ce, Zr)O, system ceramics, sufficient to suppress agglomeration of coprecipitates, and combine this with the precipitate. A step of reacting with a forming liquid to form a coprecipitate and calcining it at a temperature of 700 to 1300°C. In this step, aggregation during coprecipitate formation is avoided, and particles that do not agglomerate in subsequent steps are produced.

(2) a step of mixing the calcined product obtained in step (1) with the remaining constituent compounds of the desired 5r(Ce, Zr)O3-based ceramic composition and calcining at 500 to 1300°C; In this step, the desired compound composition is obtained by adding the remaining components.

(3) The obtained calcined powder is molded to a temperature of 700 to 1700°.
The process of firing with C.

In addition, in the present invention, these Sr components and Ce, Z
It also includes those in which the molar ratio of the r component is shifted to a value higher or lower than 1°0.

Furthermore, in order to improve the sinterability and properties of 5r(Ce, Zr)03-based ceramics, it is customary to add a small amount of additives such as Yb20z. It may be added appropriately in step (1) or (2).

Compounds for making zirconium solutions include zirconium oxychloride, zirconium oxynitrate, zirconium chloride, zirconium nitrate, and metallic zirconium.

As a solvent for the zirconium solution, water or alcohol that dissolves the above compound is used. All of the above compounds are soluble in water, zirconium oxychloride, zirconium chloride and ethanol. Furthermore, in order to create a zirconium solution, metallic zirconium was mixed with aqua regia,
It can also be used after being dissolved in HF. Examples of compounds for preparing a solution containing at least one component other than zirconium include ceric nitrate and sulfur iron nitrate. Water or alcohol is used as the solvent for this solution. The zirconium solution and the solution other than zirconium may be prepared separately, or may be prepared by dissolving each compound in the same solvent.

Examples of reagents for preparing the precipitate-forming solution include organic reagents such as ammonia, ammonium carbonate, caustic alkali, oxalic acid, ammonium oxalate, amines, and oxine. The precipitate formation reaction can be carried out at room temperature.

The coprecipitate is in a sol or slurry state. The coprecipitate is recovered by filtration and washing.

5r(Ce, Zr)0 dissolved in zirconium solution
The types and amounts of the constituent components of the 3-system ceramics are preferably such that they can effectively suppress agglomeration of the zirconia powder finally obtained by adding the constituent components. The calcination temperature of the obtained coprecipitate is 700 to 1300°C.

When the calcination temperature is lower than 700°C, significant agglomeration occurs, and 1
When the temperature exceeds 300°C, the particles tend to become larger.

To the thus obtained mixture, the remaining components other than zirconium are added and mixed. Of course, it is also necessary to replenish the missing amount of the same components as those added to zirconia. In this case, the particle size of any compound powder (mainly oxide) used is submicron grade.

The calcination temperature of these mixtures must be above the minimum temperature at which the solid phase reaction is almost or completely completed, and within the fi high temperature range at which no significant particle growth occurs;
~1300°C is good.

The powder thus obtained is shaped and sintered. The sintering temperature ranges from 700 to 1700°C. If the sintering temperature is lower than 700℃, sintering is insufficient;
If it exceeds this, the particles may become coarse or the constituent components may volatilize.

C''A Example] Ceric ammonium nitrate aqueous solution (0.5 mol/
N) 50cc and zirconium oxynitrate aqueous solution (0,5
mo I/1) 200cc were mixed. This mixed solution was gradually added to the stirring 6N ammonia water 11 to obtain a hydroxide coprecipitate of Ce'+ and Zr'+. This was washed, dried and calcined at f&1100°C to produce (Ceo, 2.Zro, a)02 powder.

The average particle size of this powder was 0.32 μm.

13.3 g of said powder and 59.05 g of commercially available 5rCO-fine powder
2g, CeO248,1936g, Yb20,3.
After mixing 9408g in a ball mill for a day and night, 110g
Calcinate at 0°C for 1 hour to give 5rCeo, ysZro-zYb
o, osOx powder was obtained. The powder had an average particle size of 0.5 .mu.m. Tablets were molded into it/cm@2 and sintered at 1500 DEG C. for 12 hours. The density of the obtained product was 5.65 g/cab', which was extremely close to the theoretical density.

〔Effect of the invention〕

According to the method of the present invention, in the first step, 5r(Ce
Zirconia powder (modified zirconia powder) containing one or more of the constituent components of Zr)Oz-based ceramics can be made into submicron particles with extremely few secondary particles, and by using this, it can be used in ordinary compaction and sintering processes. Submicron grade 5r (Ce) can be easily produced by a simple dry method using
, Zr)O3-based ceramic raw material powder is obtained, and using this as a raw material, high-density ceramics that are extremely close to the theoretical density can be obtained, and excellent effects can be achieved. The pond also has the following effects:

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

2) 5 obtained by a dry method from the calcined modified zirconia powder
The r(Ce, Zr)Os-based ceramic powder is also obtained in a monodisperse state, and therefore has characteristics of sufficiently easy sinterability and high bulk density even without the pulverization step.

3) 5r (Ce, Zr)Oz ceramics that require extremely high density
By omitting operations such as pressing and HIP (hot gas pressure sintering) and simply solid-phase sintering, and without necessarily requiring a sintering aid, a product with high density that is extremely close to the theoretical density can be obtained. .

Claims (1)

[Claims] 1. (1) A coprecipitate is produced by reacting a solution containing zirconium and a precipitate-forming solution with an appropriate amount of at least one metal component other than zirconium constituting Sr(Ce, Zr)O_3 ceramics. 700-1300 after drying the coprecipitate
(2) This calcined product and the target Sr(Ce, Zr)O
It consists of a step of mixing the remaining constituent compounds of the _3 series ceramic composition and calcining it at 500 to 1300°C, and (3) a step of molding the obtained calcined powder and sintering it at 700 to 1700°C. Sr(Ce, Zr)O characterized by
_Production method of 3 series ceramics.