JPH03232755A - Production of piezoelectric porcelain - Google Patents

Abstract

PURPOSE:To easily obtain the title porcelain with the component of the formula by calcination of wet-ground raw material powder at low temperatures into a calcined product with the solid phase reaction completed, which is then pulverized to enhance the activity and formed into a sheet which is then calcined at specified low temperatures. CONSTITUTION:Using a medium-agitating mill, raw material powder is put to wet-grinding and mixing, drying and then calcination at 700-1000 deg.C to effect completion of the solid phase reaction. The resulting calcined product powder is put to wet-grinding using a medium-agitating mill to enhance the activity with an average size of <=0.6mum and made into a sheet form. This sheet is then calcined at 1000-1400 deg.C, thus easily obtaining the objective piezoelectric porcelain with the component of the general formula [x, y and z represent each mol%, x+y+z=100; a and b represent each mol% based on (x+y+z=100), a is 0.01-5 and b is 0-40].

Description

[Detailed description of the invention] Industrial applications The present invention is a seven ramic filter and a piezoelectric acoustic element.

The present invention relates to a method of manufacturing piezoelectric ceramics used for actuators, resonators, etc.

BACKGROUND OF THE INVENTION Conventionally, coprecipitation methods and solid phase methods have been known as methods for producing piezoelectric raw material powder.

The coprecipitation method is a method in which a mixed solution of all the constituent components is prepared, a precipitate forming liquid such as an alkali is added to this solution, and the coprecipitate is dried and calcined. This coprecipitation method yields a fine powder with excellent uniformity and easy sinterability, but it requires large-scale manufacturing equipment and high costs, and the precipitate forming ability of each component is not the same in the precipitate forming liquid. In some cases, for example, the acid component causes substantially 10% precipitation, but the other components may not produce substantially all of the precipitation, and the desired composition may not be obtained. In particular, the Mq component, N
It was difficult to substantially precipitate the i component and the Mn component by 100%.

The solid-phase method is a method in which the constituent raw material compounds are mixed dry or wet and then calcined. However, when conventional mixing using a ball mill is used, the grinding efficiency of the raw materials is poor, and when using general commercially available raw materials, The grain size was coarse and the sinterability was not good.

Furthermore, since it is difficult to obtain a raw material powder with a uniform composition, there are problems in that advanced properties cannot be obtained and that the properties of the product vary widely.

Problems to be Solved by the Invention The present invention improves the solid-phase method described above, and achieves high density and high uniformity by pulverizing the raw material using a medium stirring mill and molding the fine powder raw material with high density and high homogeneity by sheet forming. The present invention aims to provide a method for efficiently manufacturing a piezoelectric ceramic that satisfies four requirements: low cost, and high performance piezoelectric properties.

Means for Solving the Problems The manufacturing method of the present invention is based on the general formula x CPb (Mg, 1
<INb%)032y(PbTiO)-z(PbZrO
3-a (MnO2) b (N 10 ) (However,
x, y and 2 represent mortise, z + y + z
= 100, and a and b are z + y + 2 = 1
molar ratio to oO, a = 0.01~6゜b
When manufacturing piezoelectric ceramics represented by =o to 4o, commercially available solid phase raw materials are processed into submicron order by using small-diameter boulders and a medium agitation mill in which the amount of liquid serving as a dispersion medium is kept to the minimum amount possible to form a slurry. After finely pulverizing and mixing the product, it is calcined, then finely pulverized again using a media stirring mill, an organic binder, a deflocculating agent, an antifoaming agent, etc. are added to form a slurry, and this is further made into a green sheet using a doctor blade method. The number of sheets for the required thickness is laminated by thermocompression,
It is characterized in that it is fired after being punched into the required shape.

Function In the present invention, "e" and "2" in the general formula can take various values depending on the use of the piezoelectric material, but usually I is 5.
~9o, y is preferably selected from the range of 6-'-80, and Z is preferably selected from the range of 6 to 80 mol. If it deviates from this range, the piezoelectric properties or sinterability may deteriorate, which is not preferable. a and b are molar ratios to x + y + 2 = 1oO, and a is 0.01 to 6. It is desirable to select b from the range of 0.01 to 4o. Both Mn and Ni have the effect of improving the mechanical quality constant Qm, but if added in excess of the above range, the sinterability will deteriorate and the dielectric constant will decrease, which is not preferable.

There are ball mills, vibration mills, etc. for pulverizing ceramic powder, but they take a long time to pulverize,
There were problems such as a large amount of impurities mixed in from the cobblestones used as the grinding medium. There is a method of efficiently finely pulverizing the ceramic powder in wet pulverization using a media agitation mill by reducing the volume of the liquid to four times or less than that of the ceramic powder, adding a dispersant, and using cobblestones with a diameter of 1FF or less. (Tokuko Showa 64-9
Publication No. 0045). According to this method, it is possible to grind ceramic powder into fine particles of submicron size or less in a short time, and it is possible to improve reactivity and dispersibility when mixing raw materials, and when grinding calcined powder, it is possible to It is possible to increase the activity of the particles, lower the sintering temperature, improve the sintered density, and improve the overall sinterability. Therefore, if the finely ground solid phase raw material is calcined by this method, a uniform solid phase reaction can be realized at a lower temperature. Here, the calcination temperature should be in a temperature range where the solid phase ff reaction is completed and sintering between particles does not occur, and a range of 700 to 1000°C is preferable.

The calcined raw material obtained in this way is again finely pulverized using a media stirring mill and then molded. Since the raw ceramic powder becomes fine particles, it is difficult to produce a dense and uniform molded product using the dry press molding method. It is difficult to obtain, and there are problems such as variations in porcelain density after firing and easy cracking. Naturally, the piezoelectric properties of the porcelain also varied or deteriorated accordingly.

In view of this point, the inventors of the present invention conducted extensive studies and found that sheet molding is effective for molding such fine powder raw materials. In other words, by selecting an appropriate dispersant, it is possible to obtain a slurry that is much better dispersed than solid phase granulated powder.
By spreading this uniformly on a conveying film using the doctor blade method and drying it, a sheet with uniform composition and packing density can be obtained.Furthermore, this sheet can be laminated by pressure bonding and made into a dry press molded product. The result is a much more uniform molded product. Therefore, by firing this sheet molded body, it is possible to obtain a porcelain that is dense, has little variation, and has good piezoelectric properties. Here, the dispersion medium used for molding may be water or an organic solvent, but water is preferable when performing wet pulverization using water as a medium using a media stirring mill. This is because an organic binder, antifoaming agent, etc. can be added directly to the slurry obtained after pulverization using a media stirring mill, and it is possible to create a slurry that can be drawn into sheets without agglomerating the pulverized ceramic raw material fine powder. It is. When using an organic solvent-based dispersion medium, it is necessary to completely dry and remove the water in the slurry.
Recombination of the crushed fine particles occurs, and the dispersibility and tight packing properties of the sheet are inferior to systems using water as the dispersion medium.

EXAMPLES Below, Examples and Comparative Examples will be shown to explain the present invention in more detail.

Example 1 37,5(Pb(Mg3ANb2.)03)-3
7, s (PbT l03) 25.0 (PbZr03)
-1,9(MnO2)-2,2(Nip) Purity 98%
Above (D P b○, M gO, T iO2, Z
r○2゜Using Nb2O6, MnCO3, and NtO (the average particle size of these powders is 2.6 μm), weigh them to the above molar ratio, and then calculate the true volume of these ceramic powders. After mixing in a ball mill with pure water of 0.75 to 7 times the volume of the ceramic powder and a polycarboxylic acid type dispersant of 1 to 2 wt% (in terms of solid content) of the weight of the ceramic powder to form a slurry, about 100 ml of the slurry was prepared.

CC was converted into a flow tube type media stirring mill with an internal volume of 600 CC (rotation speed 200 Orpm, 12 rO27, gitator Deinuk 96
φ, Z r O2 boulder 0.6-1.0φ-420CG)
was circulated at a rate of 5 to 10 CC/min, and ground and mixed for 16 minutes. When the particle size distribution of this was measured using a sedimentation type particle size distribution analyzer, it was found that the average particle size was 0.48 μm and the specific surface area was 3.42 om/l. Here, the obtained slurry was dried and then placed in an alumina porcelain crucible and calcined at 850° C. for 2 hours to form a single phase. This was coarsely ground using a grinder. This powder (average particle size 1.32 μm) was wet-pulverized using a media stirring mill (eoocc slurry, circulation introduction rate 5 to 10 CCZ minutes for 20 minutes) under the same conditions as the raw material. The particle size distribution of the obtained slurry was 0.46μm in average particle size and 2.430n// in specific surface area.
It was l. Next, after drying this slurry, it was pulverized using a grinder and placed in an alumina porcelain crucible at 600°C.
The dispersant was removed by baking for a period of time, and the powder was crushed again using a sieve machine. Polyvinyl butyral 609 as a binder, dibutyl phthalate 30% and acetic acid n-FK 350F were added to 100 of the calcined powder. ,
1oφZr○2 balls 900 in 2 liter polypot
Ball mill mixing was performed for 24 hours with f. Next, this slurry was passed through a ≠250 nylon mesh, degassed under vacuum, and formed into a doctor blade sheet. After laminating 12 green sheets with a thickness of 100 μm obtained here and thermo-compression bonding at 60°C and 1200 Kg/cnl, 20φ
It was punched out into a disc shape. This molded body was fired at 1260° C. for 1 hour in a pbo atmosphere. The density of the obtained sintered body was measured using the Archimedes method.7. s2r/
~, which was close to the theoretical density. After polishing this sintered body into a disk shape of 16φ-0.5t,
After baking the q electrode and polarizing it at 100° C. in an electric field of 3 Kv/ma, piezoelectric properties were measured using an impedance analyzer, and the following results were obtained.

Specific dielectric constant ε33/ε. 1o60 Electromechanical coupling constant Kp 5B, 2 Mechanical quality factor Qm 211゜Example 2 3wt% of solid water-soluble polyvinyl butyral was added to the slurry containing the calcined powder finely pulverized by the media stirring mill obtained in Example 1. , 0.1 wt% polycarboxylic acid dispersant, 0.1 wt% polyglycol antifoaming agent, pure water (so that the total water content is 1°wt% based on the solid content) was added and kneaded together with 1oφZ r O2 cobblestones in a polypot for 24 hours, passed through a ≠250 nylon mesh, degassed under vacuum, and formed into a doctor blade sheet. Twelve green sheets with a thickness of 100 μm obtained here were laminated, thermocompression bonded at 60° C. with a ratio of 9/- to 120, and then punched into a disc shape of 20φ. This molded body is pb
○ It was baked at 1160°C in an atmosphere for 1 hour. The density of the obtained sintered body was measured by the Archimedes method and was 7.8.
The density was 69/Crd, which was close to the theoretical density. After polishing this sintered body into a disk shape of 16φ-O, St, Aq electrodes were baked on both sides and 3Kv//++ was heated at 100℃.
After polarization treatment in an electric field of +1 for 30 minutes, piezoelectric properties were measured, and the following results were obtained.

Specific dielectric constant ε33/ε. 1125 Electromechanical coupling constant K 60.4% Mechanical quality factor Qfn 222゜Example 3 to Example 8 In the manufacturing method of Example 1 (M solvent based sheet) and Example 2 (water based sheet), the constituent elements Piezoelectric ceramics were manufactured by changing the ratios as shown in Table 1. The average particle size, density and piezoelectric properties of the sintered body after pulverization of the calcined powder using a media stirring mill were as shown in Table 2.

<Table> x[Pb(M(J3ANb%)03]V(PbT
103)z(PbZrO3) a(MnO2)-b(NiO) <Table> Comparative Example 1 37.5 [Pb(Mg3.Nb%) 03] 37-5
(PbT iO3)25.0 (PbZrO
3) 1.9 (Mn 02 ) 2-2 (NN
iO) PbO, MgO, TiO2, Z with a purity of 98% or more
rO2゜Nb2052MnCO3, N10 (the average particle size of these powders is 2.5 μm) was weighed at the above molar ratio to give a total of 3 kg, and 3 kg was added in a 6-liter pot.
Kg of agate boulder, 40 cc of polycarboxylic acid dispersion, and 1500 cc of pure water were crushed and mixed for 48 hours. The particle size distribution of the obtained slurry was 1.46 μm in average particle size.

The specific surface area was 0.998y//f. After drying, this slurry was roughly pulverized using a grinder, and then placed in an alumina porcelain crucible and calcined at 85° C. for 2 hours.

After pulverizing this powder again using a miller, 2 kg of calcined powder and 27 kg of polycarboxylic acid dispersant were added to a 6-liter pot.
CC, 1500 CC of pure water, and 3 kg of boulders were crushed for 48 hours. The particle size distribution of the slurry thus obtained was 1.44 μm in average particle size and 0.71 in specific surface area.
077//f! Met. After drying this slurry, it was crushed using a sieve machine, 6 wt% of the solid content was added to a 10% aqueous polyvinyl alcohol solution, and the slurry was granulated to produce 1 ton.
A 20φ-1t disk sample was molded at a pressure of /ci. When this compact was fired at 1200°C for 1 hour, the density of the sintered compact was 7.76? /cttl. Polarization was performed in the same manner as in Example 1, but most of the samples cracked during polarization, and even those that were polarized had poor piezoelectric properties as shown below.

Relative dielectric constant ε /ε 985 33 0 Electromechanical coupling constant K 42.1% Mechanical quality factor Q! n 1640 Comparative Example 2 0.8 wt% polyvinyl alcohol and 0.9 wt% wax emulsion in terms of solid content were added to the nullary containing the calcined raw material finely pulverized with a media stirring mill in Example 1, mixed in a ball mill, and then mixed in a ball mill. Granulated. Then, 1
A 2oφ-1t disk sample was molded at a pressure of 115 ton/CJ and subjected to binder removal baking at 450°C for 10 hours.
After firing at 0°C for 1 hour, more than half of the samples had cracks. The density of the obtained sintered body was measured by the Archimedef method and was found to be 7.79 f/crd. After polishing a crack-free sample to 16φ-0.5t, Aq electrodes were baked on both sides, and the piezoelectric properties were measured as shown below.

Specific dielectric constant ε33/ε. 1015 Electromechanical coupling constant K 46 Mechanical quality factor Q. 1816 Effects of the Invention The present invention provides the general formula x[Pb(Mqp, NbB)03]y(
PbTio3)-z(PbZros)-a(MnO2)
-b (N i○) (I, y and 2 represent molti, x+y+z=100, a and b are x
+y+z=molar ratio to 100, aO,01-
6, b=o-4Of) When manufacturing piezoelectric ceramics expressed by Using a small amount of media stirring mill,
By uniformly mixing and pulverizing the raw material powder in a short period of time and calcining it in a state that increases the activity and uniform dispersibility of the raw material powder, the solid phase reaction is completed at a low temperature, and then the material is pulverized again using a media stirring mill. By using a powder raw material with high activity and easy sinterability, and molding and firing it using a sheet forming method with excellent dense and uniform filling properties, sintering at low temperatures is possible.
It has the excellent effect of being able to produce porcelain that is dense and has excellent piezoelectric properties at low cost and with little variation.

Claims (1)

[Claims] General formula x (Pb[Mg_1_/_3Nb_2_/_3)
O_3]-y(PbTiO_3)-z(PbZrO_3
)-a(MnO_2)-b(NiO) (where x, y
and z represents mol%, x+y+z=100, a and b are molar ratios to x+y+z=100, a=0.01-5, b=0-40). The method comprises wet-pulverizing raw material powder in a media agitation mill, mixing it, drying it,
A first step of calcining at 0°C, and a second step of wet-pulverizing the obtained calcined powder with a media stirring mill to reduce the average particle size to 0.6 μm or less, forming it into a sheet, and firing it at 1000 to 1400°C. A method for manufacturing piezoelectric ceramic, comprising: