JPS62162623A - Production of fine powder of lead titanate zirconate - Google Patents

Abstract

PURPOSE:To easily produce the titled readily sintering fine powder having prescribed composition, by precipitating 3-kinds of elements (Pr, Zr and Ti) in >=2 steps from aqueous solutions containing each element under radiation of ultrasonic wave. CONSTITUTION:An aqueous solution containing compounds of one or more elements selected from Pb, Zr and Ti [e.g. ZrO(NO3)2 and TiCl4] is dripped into excess precipitation liquid (e.g. ammonia water) in an ultrasonic bath under stirring to form a precipitate [e.g. hydroxides of Zr and Ti] containing the above 1-2 kinds of elements. An aqueous solution containing compounds of remaining 2-1 kinds of elements of the above 3-kinds of elements (e.g. lead nitrate) is dripped into the liquid containing the precipitation liquid containing the (co)precipitate in dispersed state in the ultrasonic bath. If necessary, the precipitation operation is repeated several times until the 3-kinds of elements are completely precipitated. The precipitate containing the 3-kinds of elements is calcined at 550-750 deg.C to obtain the titled fine powder having a composition of formula I (0.9<=x<=1.2; 0.1<=A<=0.98).

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is suitable for manufacturing a sintered body of titanate zirconate button (hereinafter referred to as rPZTJ) used as a piezoelectric material, pyroelectric material, etc. Concerning powder manufacturing method.

[Conventional technology]

Conventionally, methods for manufacturing PZT sintered bodies include lead (pb),
After mixing zirconium (Zr) and titanium (Ti) oxides in the required proportions and calcining them, they are crushed and molded, and the molded product is heated for 12 hours in air containing lead oxide (pbo) or in oxygen.
A dry method of sintering at a temperature of about 0.000C has been used. In this dry method, the raw material powder obtained by calcination has low uniformity of composition and has a large average particle size of several μI, so a high temperature of about 1200° C. is required for sintering.

On the other hand, from the viewpoint of improving the quality of the obtained PZT sintered body and improving the ease of sintering for energy saving, a fine raw material powder with a uniform composition and an average particle size on the submicron order is desired. ing.

Recently, as a method for producing easily sinterable PZT fine powder, a wet method has been used to obtain a fine powder having a desired composition by precipitation formation. Co-precipitation, which is one of the wet methods, involves simultaneously forming a precipitate of three elements by simultaneously mixing an aqueous solution containing the required amount of each elemental compound of Pb, Zr, and Ti with a precipitate-forming solution containing an alkali to obtain the desired composition. The law is known.

[Problem that the invention seeks to solve]

However, since the precipitate forming ability of each element in a single precipitate forming solution (for example, the solubility product of the precipitate of each element at a constant pH) is different, it is not necessarily possible to obtain precipitated fine particles with the same composition as the charged composition. Not limited.

In addition, when forming a precipitate, it tends to aggregate and form secondary particles,
As a result, there was a problem in that there was a limit to the improvement in sinterability. Furthermore, although it is desirable to use inexpensive titanium tetrachloride as a raw material compound for titanium, there is also the drawback that chlorine ions cannot be used because they react with lead to form a white precipitate.

[Means for solving problems]

The present invention solves the problems of the conventional coprecipitation method, and involves the step of extracting the one or two elements selected from Pb, Zr, and Ti from an aqueous solution containing a compound of one or two elements in ultrasonic waves. A precipitate containing the elements is formed.

Next, in a state in which the obtained precipitate is dispersed, an aqueous solution containing a compound of the remaining two or one of the three elements is subjected to ultrasonic waves containing the remaining two or one of the elements. The operation for forming a precipitate is performed a necessary number of times to precipitate all three types of elements.

Next, the obtained precipitate containing the three types of elements was
After calcining at 750℃, 1 composition is Pbx'1rATi1-A
O3 (however, 0.9≦x≦1.2.0.1≦A≦0.9
The present invention provides a method for producing PZT fine powder, which comprises obtaining a fine powder represented by 8).

The production method of the present invention is a method in which the three elements Pb, Zr, and Ti are not precipitated (co-precipitated) at the same time when forming a precipitate, but the precipitate formation is performed in two or more stages (hereinafter referred to as multi-stage wet method). ”). Specifically, for example, these three
Among the seed elements, one element is precipitated in the first stage and the second element is precipitated.
A method in which the remaining two elements are co-precipitated in the first stage, and vice versa, a method in which the two elements are co-precipitated in the first stage and one element remaining in the second stage is precipitated. Examples include a method in which precipitate formation is performed sequentially for each element, thus forming the precipitate in three stages, and a method in which the precipitate is formed in four or more stages. Usually, precipitation is formed in two or three stages.

Another feature of the present invention is that all of these two or more steps of precipitation formation are carried out under ultrasonic waves.

It can be used as a raw material in the production method of the present invention.

Examples of compounds of Pb, Zr and Ti include salts of organic or inorganic acids such as oxychlorides, carbonates, oxynitrates, sulfates, nitrates, acetates, formates, and oxalates of these elements; Examples include, but are not limited to, oxides, chlorides, and oxides.

If the compound to be used is not water-soluble, it can be used by solubilizing it by adding a mineral acid or the like.

Since the present invention employs a multi-stage wet method, compounds that cannot be used in conventional coprecipitation methods due to poor compatibility can be used in combination.

For example, the aforementioned titanium tetrachloride can also be used if Ti and PB are precipitated in separate steps.

The precipitate is formed by mixing an aqueous solution containing the raw material compound with an excess amount of the precipitate forming liquid. Examples of the precipitation forming liquid used include ammonia, ammonium carbonate,
Examples include solutions of caustic alkali, soda carbonate, oxalic acid, ammonium oxalate, and organic reagents such as oxins and amines.

You can choose from these.

If the precipitate forming liquid used for the first stage precipitate formation and the second stage precipitate formation is the same, the aqueous solution containing the precipitate obtained in the first stage precipitate formation is used for precipitation in the second stage. It is sufficient to mix an aqueous solution containing the elements, and in this case, since an excessive amount of the precipitate forming liquid has already been added, there is no need to add it again depending on the case. In addition, if the precipitate forming liquid in the second stage is different from the precipitate forming liquid in the first stage, and it is desirable that the precipitate forming liquid used in the first stage does not exist in the second stage, the precipitate forming liquid in the first stage Thereafter, the precipitate may be washed and then dispersed in water or an aqueous solution containing the element to be precipitated in the second step, and the second step of precipitate formation may be carried out.

The thus obtained precipitated particles are formed in ultrasonic waves, and as a result, the formation of secondary particles due to aggregation is extremely suppressed, and the average particle size is fine, on the order of several tens of particles.

The obtained precipitate is subjected to the next calcination after washing and drying, and it is preferable to use an alcohol such as ethanol for washing, so that agglomeration during drying and calcination can be further suppressed.

The obtained precipitate is calcined in air or oxygen at a temperature of 550 to 750°C, preferably 600 to 700°C, and the calcining time may be approximately 1 to 2 hours. By this calcination, a fine powder consisting of a single phase of PZT and having an average particle size of 1 μm or less is obtained. If the calcination temperature is lower than 550° C., phases of PbTi01 and PbZrO3 coexist, and a PZT single phase in which the solid phase reaction is completed does not occur.

Furthermore, if the temperature exceeds 750°C, grain growth becomes significant, making it impossible to obtain easily sinterable fine powder.

In order to produce a sintered body using the PZT fine powder of the present invention obtained in this way, the fine powder is preferably pulverized and then molded, and the molded product is heated to a temperature of 900 to Sinter at 1200°C.

If the sintering temperature is less than 900°C, a high-density sintered body with a relative density of 95% or more cannot be obtained, and if it exceeds 1200°C, PbO
evaporation becomes significant, resulting in changes in composition and abnormal grain growth, making it impossible to obtain a uniform high-density sintered body. The PZT fine powder of the present invention is advantageous in that a high-density sintered body can be obtained even at a temperature of 900 to 1000°C, which is 1000°C or lower. Furthermore, according to such low temperature sintering,
There is extremely little evaporation of PbO during the sintering process, so it is easy to produce a sintered body with the desired composition.
Since there is no need to use a containing atmosphere, the operation of loading the sample into the crucible in the furnace becomes extremely simple. In addition, it is possible to obtain a uniform sintered body with small grain size and less likely to cause abnormal grain growth. In particular, when manufacturing laminated elements used in pyroelectric films, piezoelectric films, or piezoelectric actuators by screen printing, abnormal grain growth is difficult to occur.
A film with uniform particle size can be produced, and the film is not easily deformed.

In addition, when printing electrode paste on a pellet-like molded body or a thick film molded body and sintering this (for example, for a laminated device), there are advantages such as being able to use an inexpensive Ag-based electrode material. Yes, PZT obtained by the production method of the present invention
The industrial significance of fine powder is extremely large.

The sintering time during the above sintering is preferably 2 to 100 hours, particularly 20 to 100 hours when sintering at 900 to 1000°C.
~100 hours is preferred.

[For production]

When ultrasonic waves are applied to the precipitate formation process, a vibration field and cavitation phenomenon are generated in the liquid, and mechanical force is applied, making it possible to stir extremely small areas. For example, when ultrasonic waves are applied to a precipitation forming solution and an aqueous solution of a compound of an element to be precipitated is dropped, the solution immediately reacts and forms precipitated particles. It is considered that the agglomeration of the precipitated particles is minimized by the mechanical force of the continuously applied ultrasonic waves. In the precipitate formation process from the second stage onward, the fine particles dispersed by the ultrasonic wave are used as nuclei to form precipitates on top of them, and grains grow.

It is surmised that since the new precipitated particles are generated and mixed with the already dispersed fine particles, extremely microscopic mixing of each element is possible.

In this way, a precipitate is obtained in which the three types of elements are microscopically mixed as fine particles of about several dozen particles, and as a result, they are easily converted into PZT particles in the next calcination step, and are easily sintered in the submicron order. It is considered that a concreted PZT fine powder is obtained.

〔Example〕

The present invention will be specifically explained below using examples.

Example 2.535 g of zirconium oxynitrate and 1 part of titanium tetrachloride
．． An aqueous solution of 922 g dissolved in 500 mR of water was added dropwise to 600+nQ of 5N ammonia water in an ultrasonic bath with stirring to form a precipitate of zirconium and titanium hydroxides. 200 mfl of an aqueous solution containing 6.983 g of lead nitrate was added dropwise to the solution in which the coprecipitate was dispersed in an ultrasonic bath to obtain hydroxide precipitates of zirconium, titanium, and buttons.

After washing and drying the precipitate, the precipitate was calcined at 600° C. for 1 hour to obtain a raw material powder consisting of only a PZT single phase of PbZro, 52Tio, and 4aOz from X-ray diffraction.

The raw material powder was molded at 2t/aJ, and the molded product was heated to a temperature of 900 to 1200 in an oxygen atmosphere containing saturated PBO vapor.
Sintered at various temperatures within the range of °C.

The sintered density of the obtained sintered body was measured and the theoretical density (~8g
/ff1) was determined. In addition, the presence or absence of abnormal grain growth in the sintered body was investigated, and the average grain size was measured. These results are shown in Table 1.

As is clear from Table 1, a PZT high-density sintered body with a relative density of 95% or more relative to the theoretical density (>8 g/a#) was obtained. Further, there was no abnormal grain growth, and a uniform, high-density sintered body was obtained with a small, uniform, and high-density average grain size at 900°C of 3.0 μm.

Comparative Example Raw material powder was obtained in the same manner as in Example 1, except that the precipitate formation process was not carried out in ultrasonic waves. 1 Sintered at various temperatures and under the same conditions as in Example 1, the obtained sintered bodies were The results shown in Table 2 were obtained.

A high-density sintered body was obtained at a sintering temperature of 1000°C or higher, but no high-density sintered body was obtained at a sintering temperature of 900°C.

Table 1 Table 2 [Effect of the invention] By using a multi-stage wet method, Pb, Zr and T
Considering the precipitate forming ability (solubility product, etc.) of each precipitate in i, the charged composition of each element can be easily adjusted so as to obtain a fine powder having the desired composition.

The obtained PZT fine powder has high sinterability because it consists of submicron-order particles made of a single PZT phase, and a high-density sintered body can be produced by sintering at a temperature of 1000°C or less. .

Claims (1)

[Claims] (1) A precipitate containing the one or two elements selected from lead, zirconium, and titanium is generated from an aqueous solution containing a compound of one or two elements selected from lead, zirconium, and titanium using ultrasonic waves; An operation of generating a precipitate containing the remaining two or one of the three elements using ultrasonic waves from an aqueous solution containing a compound of the remaining two or one of the three elements in a state where the precipitate is dispersed. is repeated a necessary number of times to precipitate all the three types of elements, and then the obtained precipitate containing the three types of elements is
Calcined at 750℃, the composition is Pb_xZr_ATi_1
＿−＿AO_3 (However, 0.9≦x≦1.2, 0.1≦
A method for producing a fine powder of lead zirconate titanate, which comprises obtaining a fine powder represented by A≦0.98).