JPH0457615B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for producing raw material powder of perovskite and its solid solution. Perovskites and their solid solutions are piezoelectric materials,
It is widely used as functional ceramics for dielectrics, semiconductors, sensors, optoelectronic materials, etc. Recently, there has been a desire to further improve this function, and raw material powders of perovskite and its solid solution that are easily sinterable, uniform, high bulk density, and low cost are available in large quantities to meet these demands. There is a need for the development of technology that can produce these products. Recently, there has also been a demand for capacitor materials that can be sintered at low temperatures. The present invention particularly relates to the production of material powders that exhibit excellent properties as capacitor materials. (Prior Art and its Problems) Conventionally, dry methods and coprecipitation methods are known as methods for producing perovskite raw material powders. The dry method is a method in which compounds of constituent raw materials are mixed in a dry method and then calcined. However, with this method, it is difficult to obtain a raw material powder with a uniform composition, so it is difficult to obtain a perovskite with excellent functionality, and the sinterability is also not sufficient. The coprecipitation method is a method in which a mixed solution is prepared by combining all of the constituent components, a precipitate-forming liquid such as an alkali is added to the mixed solution to cause coprecipitation, and the coprecipitate is dried and calcined. According to this coprecipitation method, it is easy to obtain powder with excellent uniformity, but because of its uniformity, the particles coagulate to form secondary particles during precipitate formation, drying, or calcination, resulting in poor sinterability. The problem was that the quality was not good. In addition, in the coprecipitation method, if the precipitate forming ability of each component in the precipitate forming solution is not the same, for example, one component will form substantially 100% of the precipitate, while other components will form substantially all of the precipitate. Therefore, it was difficult to obtain a desired composition. especially
It is extremely difficult to quantitatively precipitate Mg and Zn components. Since the amounts of these components greatly affect the physical and electrical properties of the sintered body, it is very important to add them quantitatively. When used as a capacitor material, it is preferable to have a high proportion of perovskite in the powder stage, but in all of the above methods, the proportion of perovskite was low, which was not preferable. (Objective of the Invention) An object of the present invention is to provide a method capable of solving the problems of the dry method and coprecipitation method and producing a raw material powder of a perovskite capacitor material having a desired composition. More specifically, it satisfies easy sinterability, uniformity, and low cost, and has a perovskite ratio close to 100%.
The object of the present invention is to provide a method that can efficiently produce a raw material powder for a perovskite capacitor material that can quantitatively contain components such as Mg component and Zn component. (Technical Means for Solving the Problems) The inventors of the present invention have conducted intensive research to achieve the above-mentioned object, and as a result, have arrived at the present invention. The present invention _is based _on the general formula _{Pb 1 - X A} Indicates at least one type of Zn, x = 0.01 to 0.50, y = 0.50
It has a value of ~1.0. ) When producing raw material powder of perovskite and its solid solution represented by
After preparing the powder of the Nb-O-based composite oxide in advance, (1) the powder of the B-Nb-O-based composite oxide is dispersed in the liquid phase, and then the solution of the remaining component compounds is brought into contact with the precipitation forming solution. or (2) bring the solution of the remaining component compound into contact with the precipitate forming solution to form a precipitate, which is then combined with B-Nb-O.
A low-temperature sinterable perovskite characterized by preparing a mixture of a B-Nb-O-based composite oxide and a precipitate of the remaining components by mixing powders of the B-Nb-O-based composite oxide, and calcining the mixture. The present invention relates to a method for producing raw material powder for type capacitor materials. In the present invention, the term "solution" refers to a solution in which soluble substances are dissolved or a suspension in which insoluble substances are dispersed. A of the perovskite and its solid solution represented by the general formula Pb _1-X A _X (B _1/3 Nb _2/3 ) _y Ti _1-y O ₃ in the present invention
The component is at least one of Ba, Sr and Ca, the B component is at least one of Mg and Zn, and the Pb _1-x A _x component and (B _1/3 Nb _2/3 ) _y Ti The atomic ratio of _{the 1-y} component is usually 1.0, but nonstoichiometric perovskites in which this atomic ratio is shifted to a value higher or lower than 1.0 are also included. In addition, x and y in the above general formula are x=0.01~
0.50, y=0.50 to 1.0, and if it deviates from this range, it will cause problems in terms of characteristics, so it is not preferable. The B-Nb-O composite oxide of the present invention can be produced by mixing the oxide powder of the B component and niobium oxide powder using an oxide solid phase method, and calcining the mixture, or by using a semi-wet method in a liquid phase. Either niobium oxide powder or niobium hydroxide is suspended in the liquid phase, and a solution of nitrate, chloride, etc. of component B is brought into contact with a precipitate forming liquid to form a precipitate, or the oxide powder of component B is suspended in the liquid phase. A precipitate is formed by suspending and contacting a niobium chloride solution with a precipitate-forming liquid, or by adding niobium hydroxide, and then calcining the obtained precipitate, or by a wet method. A solution of a soluble substance of Nb and a precipitate forming solution are brought into contact to form a precipitate,
It is prepared by calcining this. Examples of the precipitate-forming liquid include solutions of ammonia, ammonium carbonate, ammonium oxalate, caustic alkali, and the like. In any of the oxide solid phase method, semi-wet method, and wet method, calcination is performed in air at a temperature of 500 to 1300°C. Using the B--Nb--O composite oxide powder thus obtained, a composition represented by the above general formula can be obtained by the following method. (1) Disperse B-Nb-O composite oxide powder in a liquid phase containing a precipitant, and add Pb while stirring.
Components, solutions of Ba component and Ti component are dropped,
to form those precipitates or B-
Dispersing Nb-O composite oxide powder in the liquid phase,
Next, at the same time as or after dropping the solution of the Pb component, Ba component, and Ti component, a precipitate is added to form a precipitate, or (2) the solution of the Pb component, Ba component, and Ti component is precipitated. These precipitates are formed by contacting with the forming liquid, and then the precipitates and the B--Nb--O complex oxide powder are mixed in a dry or wet manner. The mixture of the precipitates of Pb, Ba and Ti components and the B-Nb-O complex oxide obtained by these methods is washed with water etc. by a normal washing method such as a decanting method. , Separately, after drying, calcining. The raw materials used in the precipitation reaction are not particularly limited as long as they are soluble, such as inorganic salts such as hydroxides, carbonates, oxysalts, sulfates, nitrates, and chlorides, acetates, and oxalic acids. It is appropriately selected from organic acid salts such as salts, oxides, etc. These are generally used as an aqueous solution, but if they are not soluble in water, they can be made soluble by adding an acid, and insoluble raw materials may be used as a suspension solution. Precipitation forming liquids include ammonia, ammonium carbonate, ammonium oxalate, caustic alkali,
Examples include solutions such as: If the calcination temperature is too low, the dehydration and thermal decomposition of the precipitate will be insufficient, and if it is too high, the powder will become coarse.
A range of 1000°C is preferred. (Example) The present invention will be explained in more detail by showing Examples and Comparative Examples below. In addition, characteristic evaluation in Examples was performed by the following method.・Powder particle size: Transmission electron microscope ・Perovskite ratio: From the peak intensity of the (110) plane of perovskite in X-ray diffraction I _perp and the peak intensity of the (222) plane of virochlore I _pyrp Perovskite ratio = I _perp /I _pyrp +I _perp ×100 ・Density: Archimedes method ・Electrical characteristics: LCR meter (1KHz) Example 1 Pb _0.9 Ba _0.1 (Zn _1/3 Nb _2/3 ) _0.1 (Mg _1/3 Nb _2/3 ) _0.8 Ti _{0 .
1
O3} zinc oxide (ZnO) 0.0033 mol and magnesium acetate (MgO) 0.027 mol and niobium hydroxide [Nb(OH)
₅ ] 0.060 mol was added to 50 ml of water, and the slurry was ball milled using zirconia balls for 10 hours. The slurry was dried and solidified using a dryer, ground in a mortar, and then fired at 1000°C. The obtained Zn-Mg-Nb-O composite oxide was
_{- Titanium tetrachloride} ( _{TiCl 4} ) A solution of 0.01 mol dissolved in 200 ml of water was added dropwise to form a precipitate. Let this precipitate-containing liquid stand still, remove the supernatant liquid, and add fresh water.
After adding 2,000 ml and thoroughly stirring, the mixture was allowed to stand again and the supernatant liquid was removed. The decanting operation was repeated three times, and finally a precipitate was obtained separately. Next, the precipitate was dried in a drier and then calcined in an electric furnace at 800°C for 2 hours. The obtained powder was ball milled in the presence of ethanol, and part of the powder was observed using a transmission electron microscope, and the particle size was uniform at about 0.4 μm. Furthermore, when the percentage of perovskite structure was investigated by X-ray diffraction, it was found to be 99%. 0.8% by weight of polyvinyl alcohol in the above powder
The density of the sintered body was 99% of the theoretical density as a result of adding it and molding it at 1 t/cm ² and sintering it at 950°C for 10 hours. Furthermore, when the electrical properties were measured at room temperature,
The dielectric constant was 14,500 and the dielectric loss (tan δ) was 0.8%. Examples 2 to 7 Products having the compositions shown in Table 1 were manufactured by the same method as in Example 1, and their electrical properties were measured. The results are shown in Table 2. Comparative example 1 Pb _0.9 Ba _0.1 (Zn _1/3 Nb _2/3 ) _0.1 (Mg _1/3 Nb _2/3 ) _0.8 Ti _0.
1
O3 lead oxide (PbO), barium carbonate ( _BaCO3 ), zinc oxide (ZnO), magnesium oxide ( _MgO ), niobium oxide ( _Nb2O5 ) and titanium oxide ( _TiO2 )
were weighed to have the above composition, thoroughly mixed in a ball mill, and then calcined at 800°C for 2 hours. The particle size of the obtained powder was 0.5 to 5 μm with a wide distribution. After adding 0.8% by weight of polyvinyl alcohol to this powder and molding it at 1 t/cm ² , it was sintered at 950°C for 10 hours. The density of the sintered body was 94% of the theoretical density, and the electrical properties were a dielectric constant of 8100 and a tan δ of 85.2%.

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Claims (1)

_[ Claims _{] 1} General formula _{Pb 1 -X A} B represents at least one of Mg and Zn, and the values are x = 0.01 to 0.50, y = 0.50 to 1.0. In the production of B-Nb-O complex oxide powder is prepared in advance, (1) the B-Nb-O complex oxide powder is dispersed in the liquid phase, and then a solution of the remaining component compounds is added. (2) Contact a solution of the remaining component compound with a precipitate forming solution to form a precipitate, and then combine this with B-Nb-O.
A low-temperature sinterable perovskite characterized by preparing a mixture of a B-Nb-O-based composite oxide and a precipitate of the remaining components by mixing powders of the B-Nb-O-based composite oxide, and calcining the mixture. A method for producing raw material powder for type capacitor materials.