JP2589179B2 - Method for producing lead-based ceramic powder - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a lead-based ceramic powder, and more particularly to a technique for obtaining a perovskite-type lead oxide powder.

[Prior art] Provskite-type lead-based ceramics represented by PZT, PLZT, PMN, etc. are expected to have many uses in the field of electronics. Methods for producing these ceramic raw material powders include an oxide mixing method, a neutralization coprecipitation method, and an alkoxide method. In the oxide mixing method, the main processing equipment is only a pulverizer and mixer, and it is the cheapest and suitable for mass production. In addition, although the control conditions are small, a powder with constant characteristics can be obtained relatively stably. However, since the raw material powder finally obtained depends on the particle size of the oxide of the starting material, the particle size becomes coarse, and Poor sintering and poor composition uniformity. The neutralization coprecipitation method can obtain a fine powder with a uniform composition, but it requires a large facility, so the cost is higher than the oxide mixing method. ， Many conditions must be controlled. In the alkoxide method, a fine powder having a uniform composition can be obtained as in the neutralization coprecipitation method. However, the alkoxide method is the least economical of these three methods because there are many control conditions and the price of the raw material alkoxide is expensive. Further, the raw material alkoxide is hydrolyzed by moisture in the air, and is therefore difficult to handle.

As described above, each synthesis method has its own characteristics. However, to date, the perovskite-type lead oxide powder has been mainly produced on an industrial scale by the oxide mixing method and the neutralization coprecipitation method. ing.

[Problems to be Solved by the Invention] PbO, PbO ₂ , Pb ₂ O ₃ , and the like are used as a lead source when a lead-based ceramic raw material powder is obtained by an oxide mixing method. In the calcination for obtaining lead-based ceramic powder, it is necessary to suppress the temperature to 800 ° C or less from the viewpoint of composition stability because lead evaporates at high temperatures. However, in the oxide mixing method, it is difficult to obtain a raw material powder composed of a single crystal phase by calcination in a temperature range of 800 ° C. or less. This is because the homogenization of the composition proceeds by the solid-phase reaction between the powders, and when such powders are used for molding and sintering, the local sintering rate is formed inside the compact during the sintering process. And it is difficult to obtain a dense sintered body with few pores. On the other hand, when the calcination temperature exceeds 800 ° C, the composition becomes uniform, but it is necessary to obtain a powder consisting of a single crystal phase.
In many cases, calcining at a temperature higher than 900 ° C is required.
At these temperatures, the stability of the composition in every production deteriorates due to the remarkable evaporation of lead. Calcination at a high temperature promotes grain growth, and it is difficult to obtain easily sinterable raw material powder.

For the reasons described above, a lead-based ceramic raw material powder having a single crystal phase, which has an easy sintering property, and has good composition uniformity has not been obtained by the oxide mixing method. The present invention has been made to solve the above-mentioned drawbacks in the oxide mixing method, and has made it possible to obtain a lead-based ceramic raw material powder composed of a single crystal phase by calcination at a temperature of 800 ° C. or less, It is an object of the present invention to provide a method capable of inexpensively producing a lead-based ceramic raw material powder having good composition uniformity having easy sinterability on an industrial scale.

[Constitution of the Invention] That is, the present invention solves the above problems,
In a process of producing a raw material powder for ceramics by using lead oxide as one of the starting materials, pulverizing and mixing the raw material with other oxides and inorganic salts, and firing the mixture, nitrate ions or organic acid ions are present. Lead-based ceramic powder characterized by crushing and mixing all starting materials in an aqueous solution of PH7-11, transforming lead oxide into a basic lead composition, and then calcining at 500-900 ° C In the production method of the above, and in the step of producing a raw material powder for ceramics by pulverizing and mixing the above raw material and other oxides and inorganic salts with lead oxide as one of the starting raw materials, and then firing the mixture, nitrate ions or Lead oxide is crushed in advance in an aqueous solution of PH7 to 11, in which organic acid ions are present, to transform it into a basic lead composition, which is filtered or filtered, dried, or other starting materials are added as they are. , Crushing, Performs a case processing, 500 ℃ ~90
The present invention relates to a method for producing a lead-based ceramic powder, which is calcined at a temperature of 0 ° C.

[Detailed Description of the Invention] Lead sources used in the present invention include PbO, PbO ₂ , Pb ₂ O ₃ , and the like. The present inventors crushed these lead oxides in an aqueous solution of PH7 to PH11 in which nitrate ions exist in order to solve the above problems. As a result, it was found that these lead oxides changed from the original color to white. Intensive studies on this phenomenon revealed that this reaction occurred in an aqueous solution containing nitrate ions in the range of pH 7 to 11, and that the reaction proceeded rapidly in the presence of mechanical force. Then, the whitened product was dried. This was a basic lead nitrate composition, and was found to be a thermally unstable substance whose particle size changes significantly with drying temperature.
Figure 1 shows the X-ray diffraction pattern (b) and SEM photograph (a) of PbO.
FIG. 2 shows an X-ray diffraction pattern (b) and an SEM photograph (a) of the basic lead nitrate composition obtained therefrom.

In the X-ray diffraction pattern, the horizontal axis is the diffraction angle of Cu to Kα radiation,
The vertical axis is the X-ray intensity (cps). Fig. 1 shows the index of each diffraction peak by reflection of orthorhombic PbO called Mascot from the JCPDS card. Fig. 2 shows Pb ₂ (NO ₃ ) (OH) ₃
Index can be assigned by reflection of. From this, it is clear that PbO is altered. A similar reaction was observed for organic acids such as acetic acid. Then, when the lead oxide is formed into such a basic lead composition at the beginning or during the mixing of the lead oxide, the temperature is 500 ° C to 900 ° C, preferably 700 ° C to
It was found that calcining at 800 ° C could produce lead-based ceramic powder with good composition uniformity. In the present invention, the lead oxide and the other starting materials are pulverized and mixed together in the aqueous solution of PH7 to 11 in which nitrate ions or organic acid ions are present. PH7 containing nitrate or organic acid ions
The mixture may be ground and mixed in an aqueous solution of No. 11 to 11 to form a basic lead composition, to which other starting materials may be added and further ground and mixed under appropriate conditions. Other starting materials may be metal oxides or inorganic salts. Aqueous solution of PH7~11 the nitrate ions are present, or mixed nitric acid and ammonia water, to use NH ₄ NO ₃ aqueous solution PH adjusted desired. A similar production method is desirable for the aqueous solutions of PH7 to PH11 in which organic acid ions are present. As a device for pulverization and mixing, a ball mill, a grinder, a vibration mill, a bead mill and the like are generally used. The organic acids used in the present invention are mainly organic carboxylic acids such as acetic acid and acrylic acid. The important point in the present invention is to sufficiently modify the lead oxide, and the conditions of the concentration of nitrate ion or organic acid ion and the PH of the aqueous solution or the pulverization and mixing are determined on the premise of this. . The reason that the sinterable lead-based ceramic powder consisting of a single crystal phase, which has not been obtained conventionally, can be obtained by the oxide mixing method at the calcination temperature of 500 to 900 ° C according to the present invention is that nitrate or organic acid It is thought that the Hedvall effect occurred during the decomposition of the salt, and the composition uniformity of the powder during the reaction was improved. Hereinafter, embodiments of the present invention will be described in detail.

[Example] Take 62.81 g of PbO, 4.53 g of La ₂ O _3, 24.21 g of ZrO _{2, and} 8.45 g of TiO ₂ ,
It was pulverized and mixed in a ball mill for 15 hours together with a PH8.3 aqueous NH ₄ NO ₃ solution (concentration: 100 g / l). This was washed with aqueous ammonia, dried at 80 ° C., and calcined at 800 ° C. for 2 hours. This was pulverized again in an alcohol using a ball mill, dried, calcined at 700 ° C. for 2 hours, and pulverized to obtain a PLZT raw material powder. FIG. 3 shows an X-ray diffraction pattern of this powder.

The vertical and horizontal axes of the X-ray diffraction pattern are the same as in FIGS. Each diffraction peak can be indexed approximately by cubic PLZT. It can be seen that the powder was PLZT single phase despite calcining below 800 ℃. Thereby, preferable treatment can be performed under the condition that the evaporation of lead is small. The specific surface area of this powder measured by the BET method is 5 m ² / g, which is almost twice the specific surface area of the PLZT powder obtained by the oxide mixing method of the comparative example described later, and the powder sinterability is also improved. I understood.

[Comparative Example] Take 62.81 g of PbO, 4.53 g of La ₂ O _3, 24.21 g of ZrO _{2, and} 8.45 g of TiO ₂ .
The mixture was ground and mixed for 15 hours in a ball mill together with water of PH7.
This was dried at 80 ° C and calcined at 900 ° C for 2 hours.
This is crushed again in alcohol using a ball mill,
After drying, the powder was calcined at 700 ° C. for 2 hours and dissociated to obtain a PLZT raw material powder. FIG. 4 shows an X-ray diffraction pattern of this powder.

The vertical and horizontal axes of the X-ray diffraction pattern are shown in FIG. 1, FIG.
It is the same as the figure. In the figure, clear Pb is indicated by the arrow.
TiO ₃ peak is observed. This powder is a mixture of PLZT and PbTiO ₃ despite being calcined at a high temperature of 100 ° C. as compared with the example. The specific surface area of this powder determined by the BET method was 3 m ² / g.

[Effects of the Invention] As described above, according to the present invention, a lead-based ceramic raw material powder having a single sintered phase by an oxide mixing method can be obtained by calcination at 500 ° C to 900 ° C. By lowering the calcination temperature,
The specific surface area of the obtained powder is larger than that of the powder obtained by the conventional oxide mixing method, and the powder is easily sintered. This means that the oxide mixing method can be suitably implemented to expand the electric and optical applications of perovskite-type lead-based ceramics.
This contributes to mass production of raw material powder and cost reduction.

[Brief description of the drawings]

FIG. 1 (a) is a photograph of the particle structure of PbO, one of the starting materials, and FIG. 1 (b) is an X-ray diffraction pattern. FIG. 2A is a photograph of the particle structure of the basic lead nitrate composition, and FIG. 2B is an X-ray diffraction pattern. FIG. 3 is an X-ray diffraction pattern of the PLZT raw material powder obtained by the example. FIG. 4 is an X-ray diffraction pattern of the PLZT raw material powder obtained by the comparative example.

Claims (2)

(57) [Claims] 1. A process for producing a raw material powder for ceramics by using lead oxide as one of the starting materials, pulverizing and mixing the raw material with other oxides or inorganic salts, and then firing the mixture to form nitrate ions or organic compounds. All the starting materials are ground and mixed in an aqueous solution of PH7-11 in which acid ions are present, lead oxide is transformed into a basic lead composition, and then calcined in the range of 500-900 ° C. For producing lead-based ceramic powder. 2. A process in which lead oxide is used as a starting material, and the raw material and other oxides and inorganic salts are pulverized, mixed, and fired to produce a ceramic raw material powder. In an aqueous solution of PH7 to 11 in which acid ions are present, lead oxide is preliminarily pulverized to be transformed into a basic lead composition, which is filtered or filtered, dried, or other starting materials are added as it is, A method for producing a lead-based ceramic powder, comprising crushing and mixing, and calcining at a temperature of 500 to 900 ° C.