JPH01252509A - Production of compound having perovskite type structure - Google Patents

Abstract

PURPOSE:To obtain a high-density and readily sintering compound having perovskite type structure at low cost, by producing the compound having perovskite type structure by a specific process. CONSTITUTION:Oxides or carbonates of A and B are used as starting substances, both the compounds are separately and gradually poured to aqueous solutions of nitric acid to give saturated aqueous solutions. These saturated aqueous solutions are blended so as to make the aimed composition of ABO3. A precipitating solution is prepared from ethanol, water and oxalic acid and the previously made mixed solution is gradually dripped into the precipitating solution. The resultant solution is maintained at 50-80 deg.C for >=10hours after the dripping and the precipitated particles are aged. After the filtration, the particles are dried at 50-120 deg.C. The powder is calcined under conditions including at least the following three stages of (I) at 160-250 deg.C for 0.5-2hours, (II) at 450-550 deg.C for 0.5-3hours and (III) 750-850 deg.C for >=10hours.

Description

Detailed Description of the Invention The general formula ABO3 is widely used as functional ceramics in the electronics field, etc. as electronics materials and sensor materials (where A represents one or more oxygen-12-coordinated metal elements, and B The present invention relates to a method for producing a compound having a perovskite structure represented by one or more oxygen hexacoordinated metal elements.

Conventional methods for preparing raw material powder include (1) dry method, (2) sol-gel method, and (3) wet coprecipitation method.

(1) The dry method is a method in which the constituent raw materials (oxides, carbonates) are mixed dry or wet (using water, alcohol, etc.) in a mortar, etc., and then calcined.

(2) The Zoldan method is a method of converting a mixed solution sol into a gel to create a fine powder, but in a broader sense it is a method of hydrolysis and polymerization of organometallic compounds, and a colloidal sol method (precipitation and stabilization of fine particles). It also includes methods such as

(3) Wet coprecipitation method uses a water-soluble salt as a starting material,
Mix and use as an aqueous solution. A precipitant is added and coprecipitated to create a raw material powder. Forms such as hydroxide and oxalate are used for precipitation.

Problems to be Solved by the Invention However, the methods (1) to (3) above each have their own problems.

(1) The dry method is the simplest method and is often used in the laboratory, but it is difficult to obtain raw material powder with a uniform composition, the chemical reaction cannot be completed completely unless the calcination temperature is high, and the raw material The shape and size distribution of the powder is large, and the average particle size is also large, so there are drawbacks such as insufficient sinterability.

In addition, (2) raw material powders made by the sol-gel method generally have good uniformity and excellent sinterability, but the cost of raw material powders is high, as seen in the alkoxide method as a typical example. This is a drawback. Furthermore, (3) the wet coprecipitation method is generally cited as a drawback. Although it is easy to obtain a powder with excellent uniformity, the particles may aggregate during drying and calcination to form secondary particles, resulting in poor sinterability. Furthermore, when a precipitant is added and coprecipitated, the precipitate forming ability of the solution differs depending on the component, so it may not be possible to completely precipitate all the components, resulting in a disadvantage that the desired composition may differ. There is also.

The object of the present invention is to eliminate the above-mentioned conventional drawbacks, and to provide a manufacturing method that allows raw material powder to be prepared at low cost, and that produces easily sinterable and high-density ceramics.

Means for Solving the Problems The present invention achieves the above object, and its technical means is based on the general formula ABO3 (where A represents one or more oxygen-12-coordinated metal atoms, and B The purpose of the present invention is to produce a compound having a perovskite structure represented by (representing one or more oxygen hexacoordination metals) through the following series of steps.

(1) Dilute concentrated nitric acid with water. Add the starting material A to the nitric acid solution.
Alternatively, the oxide or carbonate of B is gradually added to prepare aqueous nitric acid solutions of A and B, respectively. Saturation A,
When B is no longer dissolved, add concentrated nitric acid to maintain near saturation.

(2) Check the concentration of the solution thus prepared by evaporating the solution and burning it to produce oxides of A and B.

These nitric acid aqueous solutions are mixed to have the desired composition of ABO.

(3) Make a precipitation solution from ethanol, water, and oxalic acid.

(4) Co-precipitate A and B in the form of oxalate in a solution of ethanol and water. Slowly drop the stock solution prepared in (2) using a pipette or the like.

In this case, stir gently. Vigorous stirring prevents precipitation.

(5) After dropping, heat at 50-80℃ using a water bath etc.
The precipitated particles are aged by holding for 10 hours or more. (Filtration is possible because the particles are large) (6) After filtration, the residual solvent bath is dried by heating at 50 to 120° C. without any particular washing. At this time, if the temperature is raised, secondary agglomeration occurs, which has an adverse effect.

(7) This powder is calcined under the following conditions.

(i) 05-2 hours at 160-250°C (ii)
05-3 hours at 450-550°C (iii) 75
If unreacted substances are still found by X-ray analysis etc. after 10 hours or more at 0 to 850° C., the powder is further wet-mixed with ethanol or the like and subjected to the heat treatment of 1ii).

The powder thus obtained is further pulverized if necessary, then molded and main fired.

Effects According to the present invention, by producing a compound having a perovskite structure through the steps (1) to (7) above, it is possible to obtain a compound having a low cost, easy sinterability, and high density.

Example Examples of the present invention will be shown in detail below.

Lao and 5Sro are examples of the ceramics we want to make.
, 5Coo・ will be taken up. As a starting material, Lat
O., 5rCOs, (Coco-)z3Co(OH
)t·xH2O was used.

A nitric acid solution was prepared by mixing water and concentrated nitric acid in a 1:1 ratio. The raw material was added to this liquid until it was nearly saturated. After filtering out insoluble matter, the concentration of the solution was examined. solution 1
Place the sample in a platinum crucible, and after drying and melting, calculate the difference between before and after.
The concentration was determined by measuring.

The concentration of the can liquid is 0.106988 mot/10 in La solution.
0.0644mot/100g with 0g SSr solution,
The Co solution was 0.11742m04/100g.

The liquid from the can was mixed so that 5 g of the solution was obtained with the following composition: Lao, 6 Sr O, 5 Cool.

The precipitation solution was 30 l of ethanol, 100 ml of water, and 10 g of oxalic acid.

Slowly drop the stock solution into the precipitate using a pipette for 10 minutes. The precipitate is slowly stirred using a starter. After precipitation, the beaker was placed in a water bath maintained at 70°C and left for one day. After filtering the rollers 10
Dry on a hot plate set at 0°C. This is 2
IOH heat treatment was performed at 20°C, IH at 1500°C, and 3H at 1800°C, and X-ray analysis revealed that a perovskite structure was formed. When this powder was molded into a 13 nm pellet using a press and treated at 1100° C. for 2 hours, it had a density equivalent to that of a physical density, and the electrical conductivity was also 5×10n7'an. this is,
It was equivalent to dry-mixed powder treated at 1300°C for 2 hours.

The general formula of the present invention is La, Sr, C
Rare earth elements such as a, Pb, Ba, B is Co, Fe
, Ni, Mn, Cr.

Examples include Ti, Zr, At, Sn, Bi, etc.

Effects of the Invention As described above, the present invention uses the above-mentioned preparation of raw material powder and firing method to produce general formulas A B with high density at low temperatures.
Qs' (where A is one or more oxygen-12-coordinated metal elements, and B is one or two oxygen-6-coordinated metals).
It has now become possible to obtain ceramics having a perovskite-type structure represented by (representing species or more).

Claims (1)

[Claims] Perovskite represented by the general formula ABO_3 (where A represents one or more 12-coordination metal elements of oxygen, and B represents one or more 6-coordination metals of oxygen). 1. A method for producing a compound having a perovskite-type structure, the method comprising producing a compound having a perovskite-type structure through the following steps. (1) Using oxides or carbonates of A and B as starting materials, each is gradually added to an aqueous nitric acid solution to create a substantially saturated aqueous solution. (2) Mix the saturated aqueous solution so that it has the desired composition of ABO_3. (3) The precipitation solution is composed of ethanol, water, and cyanic acid. (4) Slowly drop the mixture prepared in (2) above into the precipitate prepared in (3) above. (5) Maintain this liquid at 50 to 80°C for 10 hours or more. (6) The precipitate obtained in (5) above is filtered and heated to a temperature of 50 to 120°C to dry the precipitate. (7) The powder is calcined under conditions including at least the following three steps. (i) 0.5-2 hours at 160-250℃ (ii) 0.5-3 hours at 450-550℃ (iii)
10 hours or more at 750-850°C.