JPS6020915B2 - piezoelectric porcelain - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to piezoelectric porcelain having good electromagnetic properties and high mechanical strength.

When piezoelectric ceramics are used, various piezoelectric properties become an issue, and the required properties differ depending on the application.

However, in almost all applications, high mechanical strength is strictly required from the viewpoints of reliability and life as a piezoelectric element as well as an electromechanical coupling coefficient. In order to obtain piezoelectric porcelain with high mechanical strength without deteriorating the electromechanical coupling coefficient and mechanical quality coefficient, the basic composition of the present invention is
bTi03-■P Snake 3-@Pb(Ni, /3Nb2/
3) 03-■ Pb (Mm, '2Nq/2) Solid solution represented by Q (a + b + c + d 100 mol%, ■ is 40 to 5
0 mol%, ■ 40-55 mol%, ■ 3.0-9.0
mol%, ■ is within the range of 0.5 to 3.0 mol%) or Mg○ is added to a solid solution in which Pb is substituted with 2 to 10 mol% of Sr, in an amount of 0.05 to 0.5 of the total amount. It is characterized by adding % by weight.

The present invention will be explained below using examples of typical compositions.

Reagent grade PD0, Ti02, Z2, S03, Ni
203, MnCQ, and NQ05 are blended into a predetermined composition as shown in Table 1.

Pb0 is added in an amount 0.5% by weight in excess of the predetermined blending amount of Pb0, taking into account evaporation during the preheating and firing process. This was placed in a nylon pot, mixed with agate natural stone for 6 to 1q hours in a green ball mill, and after drying 1. (2) After pressure molding, it was held for 1 to 5 hours at a temperature of 800 to 90 degrees Celsius. Next, this was coarsely pulverized using a horizontal thickener, and then green-type pulverized using a ball mill for 10 to 2 feeding hours. After drying, Mg0 in the amount shown in Table 1 was thoroughly mixed using a Tachibana machine, and 3% polyvinyl alcohol was added to moisten the mixture. Next 0.3~0.8/
After being pressure-formed on the ground, it is lightly crushed and passed through a 30-60 mesh sieve into similar granules, and then pressure-formed into a 2.5-inch thick piece containing 2.3 pieces at a pressure of 1.0-1.5 t/ground. In the atmosphere,
It was fired for 3 to 8 hours at a temperature of 1200 to 1300q0.
The resulting piezoelectric porcelain was polished to a thickness of 1.5 yen, coated with silver paste on both end faces, and baked at 700 to 75 porcelain.
This was polarized by applying an electric field of 30 KV' in insulating oil at 100°C. Various properties of the obtained samples were measured as shown in Table 2.

Average grain size, broken Table 1 Table 2 A scanning electron microscope was used to observe the cross section.

The transverse rupture strength was measured by supporting the specimen at three points and pressing the steel ball on the fifth side into the center. The intragrain fracture rate is the area ratio observed with a scanning electron microscope. Further, k is the electromechanical coupling coefficient in the thickness direction, Qm is the mechanical quality coefficient, and Q is the relative dielectric constant. Note that all the samples were fired at 1250°C. The effect of increasing mechanical strength by adding Mg◯ is noticeable even when added as little as 0.05% by weight based on the total amount. The average crystal grain size is also smaller than that without additives, and the bending strength is also increased as the proportion of intragranular fractured grains increases. However, when Mg◯ is added up to 0.6% by weight, it has a negative effect on kt and Qm, and the effect on anti-resistance strength is small and is not useful. Therefore, Mg○
The effect of obtaining useful materials by adding is 0.0 of the total amount.
It is limited within the range of 5 to 0.50% by weight. The effect of adding Mg○ is the same for basic compositions within the range of other patent claims, and the dielectric constant is changed by replacing Pb with Sr and T
It can be changed almost arbitrarily by changing the mol% of i and Zr.

Furthermore, the basic composition was limited to a composition range useful as a resonator. Pb is a component of the basic composition useful as this resonator.
(Mn, /2Nb, /2)03 is a necessary component to improve insulation resistance, and the effect of including this component is to improve the withstand voltage characteristics during the operation of the resonator, as well as to improve the dielectric strength during polarization processing. It has the effect of preventing dielectric breakdown. Therefore, it has the effect of improving the yield in manufacturing vibrators. The effect of improving insulation resistance is Pb(Mn,'2NO'2)
A remarkable effect was exhibited when the composition of 03 was 0.5 mol% or more.
According to the present invention, it is possible to obtain a piezoelectric porcelain having a good electromechanical coupling coefficient and a mechanical quality factor, a desired dielectric constant, and high mechanical strength.

Claims (1)

[Claims] 1. Basic composition is (a) PbTiO_3-(b) PbZr
O_3-(c)Pb(Ni_1/_3Nb_2/_3)
O_3-(d)Pb(Mn_1/_2Nb_1/_2)
Solid solution ((a) + (b) + (c) + (
d)=100 mol%), (a) is 40 to 50 mol%, (b) is 40 to 55 mol%, and (c) is 3.0 to 9.
0 mol % and (d) is in the range of 0.5 to 3.0 mol %, MgO is added from 0.05 wt % to 0.0 mol % of the total amount.
A piezoelectric porcelain characterized by containing 50% by weight of the additive. 2. The piezoelectric porcelain according to claim 1, wherein 2 to 10 mol% of Pb is replaced with Sr.