JPH0674173B2 - Method for producing lead zirconate titanate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to piezoelectric zirconate titanate (PZ) which is a piezoelectric ceramic material.
T), more specifically, a method for producing lead zirconate titanate using a sol-gel method.

[Conventional technology]

As a conventional PZT manufacturing method, an oxide mixing method, a PVD method,
There is a CVD method.

The oxide mixing method is a method in which PdO, ZrO ₂ and TiO ₂ are mixed in a wet manner, dried and then pellet-formed, or a binder / solvent is added to form a sheet, and these are fired at a high temperature of 1150 ° C. or higher. .

Further, as the PVD method, a sputtering method, an EB vapor deposition method, an ion plating method, etc., and as the CVD method, for example, plasma CVD
Methods using MOCVD, MOCVD, etc. are known.

[Problems to be Solved by the Invention]

In the oxide mixing method, volatilization of PbO occurs and composition change occurs, so it is essential to add excess PbO in advance or to perform firing in a PbO atmosphere, but it is difficult to control the PbO vapor pressure. In addition, there is a problem in that, when powder is mixed, contamination or the presence of agglomerated particles and the removal of the binder leave voids inside the ceramics, which prevents the densification and deteriorates the piezoelectric characteristics.

Further, although the PVD method and the CVD method can produce a dense film, it is necessary to select a substrate to be deposited. Further, it is expensive due to the device, and mass production is impossible. Further, since it has gone through the gas phase, there is a problem that composition control becomes considerably difficult.

[Means for Solving the Problems]

The present invention, in order to solve the drawbacks of the prior art such as the above-mentioned, using lead compounds other than chlorides and alkoxides and zirconium compounds and titanium alkoxides as raw materials, making a sol solution using acetic acid and water as solvents, Provided is a method for producing lead zirconate titanate, which comprises firing at a temperature of 800 ° C. or lower after gelling.

Lead zirconate titanate (PZT) has a composition represented by Pb (ZrxTi _1- x) O ₃ [where 0 ≦ x ≦ 1].

First, a sol solution of PZT raw material is prepared. The lead raw material and the zirconium raw material may be organic or inorganic compounds other than chlorides and alkoxides. For example, as lead materials, lead acetate, lead nitrate, lead carbonate, lead hydroxide, lead oxide,
Lead stearate and zirconium nitrate, zirconyl hydroxide, and zirconium acetylacetonate are preferably used as zirconium raw materials.

When chloride is used as a raw material, white precipitation occurs and a uniform sol solution cannot be prepared. It is possible to prepare an almost transparent dry gel by lowering the PZT molar concentration in the sol solution, but needle-like crystals of PbCl ₂ or PbCl ₄ are precipitated by firing, and the difference from the thermal expansion coefficient of PZT A uniform film or parc cannot be obtained because cracks that are thought to be caused are generated. Also, use of chloride as a raw material is avoided because chlorine reacts completely with lead, which is also removed by heat treatment. In addition, lead and zirconium alkoxides are not only expensive, but also easily react with water in the air to become cloudy (precipitation), and it is not easy to obtain a uniform sol solution (clear solution). Not used in the invention.

Titaso alkoxide is used as the titanium raw material. This alkoxide is subsequently polycondensed and allows gelation.
As the titanium alkoxide, titanium butoxide and titanium isopropoxide can be preferably used.

A sol solution can be prepared from these raw materials by using acetic acid and water as solvents. Lead raw material, zirconium raw material and titanium raw material are blended according to a desired PZT composition, and acetic acid and water are added thereto and stirred until a transparent sol solution is obtained. The alkoxide is easily hydrolyzed, so it is better to add it last. The concentration of acetic acid is 600 per mol of Pb
~ 1600 ml, and the concentration of the raw material composition is preferably 1 mol per 1500-3000 ml of the solution. If the concentration is deviated from these concentrations, if the concentration is high, cracks will occur in the film or bulk body during firing, resulting in a uniform
I cannot make PZT. On the other hand, if the film is thin, the film is too thin to form a film, or the bulk body does not lump and becomes a film.

In order to adjust the viscosity of the sol solution and to make it highly stable, it is desirable to add 0.5 to 2.0 mol of ethylene glycol to 1.0 mol of lead and stir it.

The first method of gelling this sol solution is to form a film on a substrate by a method such as a dip coating method, a spin coating method, an ultrasonic coating method, etc., and gels when the film is formed. The sol solution also gels when dried.

Therefore, according to the present invention, the first method for producing PZT from a sol solution is to form a gel film on a substrate by various coating methods as described above, and then 800 ° C. or lower, preferably 600 to 800.
This is a method of firing at a temperature of ℃.

The second method is a method in which the sol solution is slowly dried (eg, left at room temperature for 1 week and kept at 35 ° C for 2 weeks) to gel, and the obtained gel compact is fired at a temperature of 800 ° C or lower. is there.

[Action]

By using the sol-gel method, PZT having a uniform composition can be fired at a low temperature.

〔Example〕

FIG. 1 shows a flowchart of the manufacturing process of the sol solution.
As shown in this figure, a lead material and a zirconium material are weighed in predetermined amounts, acetic acid and pure water are added thereto, and the mixture is stirred until the solution becomes completely transparent. Next, a predetermined amount of titanium raw material is dropped using a buret or the like. To adjust the viscosity of the solution and make the solution highly stable, add 0.5 to 2.0 mol of ethylene glycol to 1.0 mol of lead and stir to form a sol solution.

Substrates such as quartz, ITO, soda glass, and Pt are immersed in this, and a gel film is formed on the pulled-up substrate at a speed of 5 to 15 cm / min. A desired film thickness is obtained by this number of pulling
A PZT film is formed. About 0.15 μm per pull
And the film thickness could be easily controlled by the number of pulling operations. The film sample thus obtained is referred to as sample A.
Here, the sample A may be a film formed by a spin coating method or an ultrasonic coating method, and the film thickness can be controlled by the spin speed and the spray time.

A powder sample obtained by drying the sol solution prepared above and baking it at 500 to 800 ° C. is referred to as Sample B.

From the results of thin film and powder X-ray diffraction, both sample A and B are 50
The perovskite phase began to break out at 0 ° C and became a single perovskite phase by heat treatment at 600 ° C. This gives 600
It was found that the PZT single phase was obtained by heat treatment above ℃.

Next, as a result of measuring the transmittance of Sample A at 300 to 800 nm, 600 nm is obtained even when the film thickness is about 3 μm.
In the vicinity, it showed a transmittance of 50% or more.

Table 1 shows the dielectric constant of each composition of PZT obtained in the above process.

Example A-1 is a sol solution of lead acetate trihydrate, zirconyl nitrate dihydrate and titanium butoxide so that Pb / Zr / Ti = 1 / 0.52 / 0.48 (mol ratio) according to the flow chart shown in FIG. Was prepared, and a gel film formed on a quartz substrate coated with ITO by the dip coating method was fired at 700 ° C.

Examples A-2 to A-4 were produced under the same conditions except that the composition ratio of A-1 and Pb / Zr / Ti was changed.

Examples A-5 to A-8 are samples fired at 750 ° C. under the same conditions as A-1 to A-4 until film formation. Examples A-9 to A-8
-12 is a sample baked at 800 ° C., which is Comparative Examples A-13 to A-1.
6 is a sample baked at 850 ° C.

As shown in the above table, when the firing temperature exceeded 800 ° C., the lead component was released from the sample, compositional variation occurred, and the characteristics deteriorated. For this reason, the sample which had a yellowish translucency up to 800 ° C became white and opaque when fired at 800 ° C or higher. It should be noted that in the case of firing at 800 ° C or lower, the same characteristics as those of the conventional method were exhibited despite the firing in the atmosphere without controlling the atmosphere. Here, the samples using the dip coating method, the spin coating method, and the ultrasonic spray method all showed the same characteristics.

It was found that the MPB of PZT according to the present invention had a composition near 53/47.

Next, Table 2 shows an example in which each raw material is changed.

Example B-1 is an example using titanium isopropoxide as a titanium raw material, Example B-2 is an example using zirconium acetylacetonate as a zirconium raw material, and Examples B-3 to
B-5 is an example in which lead nitrate, lead carbonate, and lead oxide are used as lead raw materials, respectively.

Comparative Examples B-6 to B-8 are examples in which chloride was used for each raw material.

Thus, when chloride was used as the raw material, a transparent sol solution could not be prepared due to the formation of white precipitate.

In Examples A-6 and B-1 to B-5, transparent and uniform PZT
A film could be prepared and a high dielectric constant of 1000 or more was obtained.

〔The invention's effect〕

As described above, by using the sol-gel method according to the present invention, at a low temperature of 800 ° C. or less, it has the same characteristics as the conventional method without controlling the atmosphere, and is inexpensive and has a large degree of freedom in shape. The effect is that PZT that can be mass-produced can be manufactured.

[Brief description of drawings]

FIG. 1 is a flow chart showing the steps for producing a sol solution according to the present invention.

Claims (2)

[Claims] 1. A lead compound other than chloride and alkoxide, a zirconium compound, and a titanium alkoxide are used as raw materials to prepare a sol solution using acetic acid and water as a solvent. The sol solution is gelled and then fired at a temperature of 800 ° C. or lower. A method for producing lead zirconate titanate, which comprises: 2. A lead compound as lead acetate, lead nitrate, lead carbonate,
Use of any one of lead hydroxide, lead oxide and lead stearate, any one of zirconyl nitrate, zirconyl hydroxide and zirconium acetylacetonate as a zirconium compound, and any one of titanium butoxide and titanium isopropoxide as a titanium alkoxide. The method described.