JPH0649575B2 - Method for producing piezoelectric ceramic powder - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a piezoelectric ceramic powder used in various electronic components such as filters, vibrators, ignition elements, delay elements, buzzers and the like.

Configuration of Conventional Example and its Problems Conventionally, piezoelectric ceramic powders are composed of PbO, TiO ₂ , Z
Three main components of rO ₂ and MgO, Nb ₂ O ₅ , Zn
Various additives such as O and MnO ₂ are blended in a composition according to the target characteristics, mixed in a wet ball mill, dried, calcined to cause a solid phase reaction, pulverized in a wet ball mill, and dried. To manufacture. A flowchart of this process is shown in FIG. This method is called the simple mixing method. The disadvantage of this method is bad from the viewpoint of microscopic uniformity of composition, and it is difficult to obtain high-purity ceramic powder. In addition, it is also possible that fine particles cannot be obtained.

Therefore, a co-precipitation method, which is a type of liquid phase method, is known as a method for producing a ceramic powder that compensates for these drawbacks. This method
Since the precipitation agent is added from the state of being melted to the solution and the particles are simultaneously precipitated, the mixing degree of each element is uniform, and the fine particles can be obtained with high purity. However, the disadvantage of this coprecipitation method is that
Since the PH region in which precipitation is generated differs depending on each element, it is difficult to simultaneously precipitate the multi-component constituent elements such as practical ceramic powder.

Addition of MnO ₂ to the lead zirconate titanate-based piezoelectric material composition has advantages such as improved sinterability and improved mechanical quality factor (Q _M ). However, if this composition is attempted to be produced by the coprecipitation method, the PH region in which Pb ²⁺ produces precipitation is 7-1.
1, Zr ⁴⁺ is 4 or more, Ti ⁴⁺ is 3 or more, Mn ²⁺ is 10 or more, and Pb, Ti, Z is first added to a strong acid of PH 3 or less.
Although ammonia water is usually used as a precipitating agent after each of the starting materials for r and Mn is melted, the pH of the ammonia must be 10-11 by dropping the ammonia water.
A large amount of ammonia water is required, and the reaction vessel becomes large, which is not practical.

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a method for producing a piezoelectric ceramic powder in which manganese is added to a lead zirconate titanate system by a liquid phase method.

To achieve this object, the present invention is to coprecipitate a composite of lead, titanium, and zirconium elements, calcining this, and then dispersing this powder in an aqueous solution to prepare an aqueous solution of manganese nitrate. A method for producing a piezoelectric ceramic powder, characterized in that manganese is added by adding and precipitating using ammonia water as a precipitating agent. Also,
In a preferred embodiment, lead nitrate, tetraisopropyl orthotitanate, and zirconium oxynitrate are used as starting materials for each element of lead, titanium, and zirconium, and coprecipitated using an aqueous ammonia solution as a precipitation agent, which is then calcined. After that, this powder is dispersed in an aqueous solution, an aqueous solution of manganese nitrate is added, and manganese is added by precipitating with ammonia water as a precipitating agent, which is a method for producing a piezoelectric ceramic powder. The reason for doing this is to use fine particles of lead zirconate titanate prepared by the coprecipitation method or secondary particles in which primary particles are collected,
This is for uniformly dispersing manganese.

Description of Examples PbTi _0.48 Zr _0.52 O ₃ +0.25 wt% Mn by coprecipitation method
A piezoelectric ceramic powder having a composition of O ₂ was synthesized. As a starting material, special grade lead nitrate (Pb (N
O _{3) 2)} Similarly, EP tetraisopropyl orthotitanate _{([(CH 3)} 2 CHO] ₄ Ti), likewise GR zirconium oxynitrate _{(ZrO (NO 3) 2 ·} 2H
₂ O) was used to prepare an aqueous solution of lead nitrate and zirconium oxynitrate, tetraisopropyl orthotitanate was dissolved in an aqueous solution of nitric acid, and the three materials were weighed so as to have a desired composition to prepare a mixed aqueous solution of nitric acid. Using a mixer, the above-mentioned mixed nitric acid solution and aqueous ammonia are added to aqueous ammonia while stirring while adjusting the pH to a range of 7 to 8. The precipitate obtained by this operation was washed excessively, then dispersed in pure water and spray-dried. This powder was calcined in an electric furnace at 600 ° C. for 2 hours to produce lead zirconate titanate. Next, using a mixer, in an aqueous ammonia solution,
The calcined powder is dispersed and stirred, and then added to the special grade manganese nitrate (Mn (NO ₃ ) ₂ · n manufactured by Kanto Kajia Co., Ltd.
The H ₂ O) aqueous solution was weighed in such an amount that the added amount of MnO ₂ was 0.25 wt%, and was added under the condition that the PH was about 11. The precipitate thus prepared was washed, washed and dried. A flow chart of the manufacturing process of the piezoelectric ceramic powder of this embodiment is shown in FIG.

On the other hand, for comparison, a powder was prepared by a conventional piezoelectric ceramic powder manufacturing method. As a starting material, lead monoxide (P
hO), titanium oxide (TiO ₂ ), zirconium oxide (ZrO ₂ ), and manganese dioxide (MnO ₂ ) are weighed to a target composition, wet ball mill mixed, dried, and temporarily stored in an electric furnace at 900 ° C. for 2 hours. Baked, wet ball milled and dried. The composition is PbTi _1-x Zr _x O ₃ +0.2
It was carried out at x = 0.51, 0.52, 0.53 at 5 wt%.
For comparison, a precipitate of lead, titanium, and zirconium produced by the coprecipitation method as in this example was spray-dried,
After calcination at 600 ° C., 0.25 wt% of manganese dioxide was added, mixed by a wet ball mill, and dried powder was also prepared. These powders are granulated, molded and fired to obtain 16mmφ,
It is processed into a disk of 0.5 mmt, coated with a silver electrode, baked at 700 ° C, and in silicon oil at 100 ° C, 3 KV / mm.
Then, a direct current electric field of (3) was applied and polarization was performed for 30 minutes. The characteristic measurement results are shown in the table below. Although the characteristics vary depending on the composition, the piezoelectric ceramic powder produced by the method of the present invention is fluorescent X.
As a result of elemental analysis by lines, it was confirmed that there was no compositional deviation. In addition, in the conventional method, even if MnO ₂ was added after calcination, the characteristics were the same as when added before mixing. As described above, according to the method of the present invention, the coupling coefficient Kp is 0.44 → 0.
This is a significant improvement of 54 and 23%.

In addition, the method of adding MnO ₂ to the powder obtained by coprecipitating lead, titanium, and zirconium and calcined as a comparative example by the conventional method did not show such an improvement in the coupling coefficient. Only by coprecipitating lead, titanium, and zirconium, and calcining to prepare a powder of lead zirconate titanate, and adding manganese to this powder by the liquid phase method, the coupling coefficient Kp is remarkably improved as described above. I was able to do it. The powder obtained by the coprecipitation method has a perovskite phase of lead zirconate titanate formed at a calcination temperature of about 550 ° C. or higher, and a perovskite phase of lead zirconate titanate formed on the conventional method at a temperature of about 850 ° C. or higher. However, the calcination temperature becomes lower than that. In the case of the coprecipitation method, the calcination temperature is preferably 550 ° C to 700 ° C. Other starting materials for lead, titanium, and zirconium are also conceivable, for example, titanium tetrachloride (TiCl ₄ ) aqueous solution may be considered as a starting material for titanium. In this case, precipitation of PbCl ₂ is generated and coprecipitation occurs. Is not suitable because it becomes uneven. Lead nitrate, tetraisopropyl orthotitanate, and zirconium oxynitrate were the most suitable starting materials.

EFFECTS OF THE INVENTION As described above, according to the method of the present invention, a high-performance piezoelectric ceramic powder having a significantly improved coupling coefficient can be obtained as compared with the conventional method, and the industrial value is great.

[Brief description of drawings]

FIG. 1 is a flowchart showing a conventional method for producing a piezoelectric ceramic powder, and FIG. 2 is a flowchart showing a method for producing a piezoelectric ceramic powder according to an embodiment of the present invention.

Claims (2)

[Claims] 1. A complex of lead, titanium and zirconium elements is co-precipitated, calcined, and then the powder is dispersed in an aqueous solution. An aqueous solution of manganese nitrate is added thereto to add ammonia water to the precipitation agent. A method for producing a piezoelectric ceramic powder, which comprises depositing manganese and adding manganese. 2. Lead nitrate, starting materials for each of the elements zirconium, lead nitrate, tetraisopropyl orthotitanate,
The method for producing a piezoelectric ceramic powder according to claim 1, wherein zirconium oxynitrate is used and an aqueous ammonia solution is used as a precipitation agent.