JP2957002B2 - Piezoelectric porcelain composition - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a porcelain composition, in particular, a piezoelectric porcelain composition.

[Conventional technology]

As a material for a piezoelectric sounding element such as a buzzer or a speaker, there is, for example, a piezoelectric porcelain material described in Japanese Patent Publication No. 54-36756. This piezoelectric porcelain material is made of Pb (Sn _1/3 S
b _2/3 ) _x Ti _y Zr _z O ₃ and 0.05 to 1.5% by weight of Si
And a O _2. Here, Pb (Sn _1/3 Sb _2/3 ) _x Ti _y Zr _z O
₃ satisfies the following conditions.

x + y + z = 1 0.01 ≦ x ≦ 0.5 0.01 ≦ y ≦ 0.75 0.005 ≦ z ≦ 0.9 Further, this compound includes a compound in which 20 mol% or less of Pb is substituted with Sr, Ba or Ca.

[Problems to be Solved by the Invention] The conventional piezoelectric porcelain material has a high electromechanical coupling coefficient and a high relative dielectric constant, and has a good resistance to deterioration of the output voltage against repeated pressing forces, but has a low Curie point. . A piezoelectric sounding element using a piezoelectric porcelain material having a low Curie point is depolarized in a high-temperature environment, and is therefore unsuitable for equipment such as a mobile phone that requires high reliability (characteristic stability) in a high-temperature environment. It is. Generally, it is considered that the Curie point of a piezoelectric sounding element used in such a device is preferably about twice or more the maximum temperature of the temperature environment in which the device is used.
For example, it is said that the Curie point of a piezoelectric sounding element used in a temperature environment of 85 to 125 ° C. is preferably 300 ° C. or higher.

An object of the present invention is to provide a piezoelectric porcelain composition having a high Curie point, a small mechanical quality coefficient, and a large electromechanical coupling coefficient and a large relative dielectric constant.

[Means for solving the problem]

The piezoelectric porcelain composition of the present invention comprises x moles of PbZrO ₃ and y
Moles of PbTiO ₃ and z moles of Pb (Sn _1/3 Nb _{2α / 3} Sb
_{2 (1-α) / 3} ) O ₃ and the following formula is satisfied.

x + y + z = 1 0.47 ≦ x ≦ 0.52 0.43 ≦ y ≦ 0.48 0.02 ≦ z ≦ 0.08 0.2 ≦ α ≦ 0.6 (0.450 ≦ x ≦ 0.505,0.455 ≦ y ≦ 0.510,0.02 ≦
(Except when z ≦ 0.06 and 0.2 ≦ α ≦ 0.8 are simultaneously satisfied.) ***** The piezoelectric ceramic composition of the present invention contains the following three types of piezoelectric ceramic materials.

PbZrO ₃ This component is present in the composition according to the present invention in an amount of 0.47 mol or more.
Contains up to 52 moles. When the content (x) is out of the above range, the electromechanical coupling coefficient and the relative dielectric constant of the composition become small. Therefore, it is possible to obtain only a piezoelectric element having poor deterioration resistance against the repetitive pressing force of the output voltage.

PbTiO ₃ This component is contained in the composition of the present invention in an amount of from 0.43 mol to 0.48 mol. When the proportion (y) of this substance is outside the above range, the same result as when the above-mentioned PbZrO ₃ exceeds the above range is obtained.

Pb (Sn _1/3 Nb _{2α / 3} Sb _{2 (1-α) / 3} ) O ₃ The value of α of this component is set to 0.2 or more and 0.6 or less. When the value of α is less than 0.2, the Curie point of the composition becomes low. Therefore, a piezoelectric element having stable characteristics in a high-temperature environment cannot be obtained. Conversely, when α exceeds 0.6, the Curie point becomes larger, but the electromechanical coupling coefficient and the relative permittivity decrease.

In the composition of the present invention, this substance is present in an amount of 0.02 mol or more and 0.2 mol.
Contains less than 08 moles. The ratio (z) of this substance is 0.02
If the amount is less than the mole, the electromechanical coupling coefficient and the relative permittivity decrease. On the other hand, when it exceeds 0.08 mol, the electromechanical coupling coefficient and the relative dielectric constant become larger, but the Curie point is lowered.

In the composition of the present invention, the mixing ratio is adjusted so that the sum of the above x, y and z becomes 1. When this relationship is not satisfied, it is not preferable as a sounding body material.

In the composition of the present invention, any one of MgO, Cr ₂ O ₃ and MmO ₂ or a combination thereof is used with respect to 100 parts by weight of the present composition.
0.05 to 0.2 parts by weight may be contained.

〔Example〕

Commercially available Pb ₃ O ₄ , ZrO ₂ , TiO ₂ , SnO ₂ , N with a purity of 99.0% or more
Each powder of b ₂ O ₅ and Sb ₂ O ₃ was prepared, and each powder was weighed so that x, y, z and α became the values in the table. And, after wet mixing each powder using a ball mill and drying,
It was calcined at 000 ° C for 3 hours.

Next, the obtained calcined product was wet-pulverized using a ball mill so that the specific surface area became 2 m ² / g or more.

After drying, add an organic binder, press-mold
A disk having a thickness of 1.5 mm and a thickness of 1.5 mm was manufactured. Then, in an oxidizing atmosphere, the disc was fired at 1150 to 1250 ° C. for 3 hours.

Next, the disc-shaped fired body is polished to a thickness of 1 mm,
A silver paste was baked on both sides. Then, the disc on which the silver paste was baked was immersed in insulating oil at 80 ° C., and a polarization treatment was performed by applying a DC voltage of 3 kV / mm to both surfaces.

After leaving the polarized disk for 24 hours or more, the mechanical quality coefficient, electromechanical coupling coefficient, relative permittivity and Curie point of the disk were examined. The measurement was performed according to the standard of the Electronic Materials Manufacturers Association. That is, the resonance frequency and anti-resonance frequency of the extended vibration mode, the resistance value, and the capacitance at 1 KHz were measured using an impedance analyzer, and then calculated by a calculation formula. However, as for the Curie point, the sample was immersed in silicone oil, the capacitance at 1 KHz was measured while heating, and the temperature at which this capacitance showed a maximum value was defined as the Curie point. The mechanical quality factor (Qm) is a good value when it is 200 or less. An electromechanical coupling coefficient (Kb) of 65% or more is a good value. The relative permittivity (ε ₃₃ ^{T /} ε ₀ ) is preferably 2000 or more. Further, the Curie point (Tc) is a good value at 300 ° C. or higher.

The results are shown in the table. The numbers with parentheses are comparative examples, and the numbers with <> are 0.450 ≦ x ≦ 0.505, 0.455 ≦ y ≦ 0.
510, 0.02 ≦ z ≦ 0.06, 0.2 ≦ α ≦ 0.8.

Based on the results, a triangular diagram shown in the figure was created. This triangular diagram shows the relationship between x, y, and z and the measurement result. In the figure, white circles indicate that all the measurement results were good, black circles (•) indicate that even one measurement result was defective, and large black circles (•) indicate 0.
450 ≦ x ≦ 0.505,0.455 ≦ y ≦ 0.510,0.02 ≦ z ≦ 0.06,0.2
≦ α ≦ 0.8 at the same time. The numbers attached to the arrows pointing to the black circle and the white circle are sample numbers.

As is clear from the table and the figure, when x, y and z were within the range of the present invention (within the hatched portion in the figure), good measurement results were obtained when α was within the range of the present invention. On the other hand, x, y
And when z is within the scope of the present invention but α is outside the scope of the invention, and when x, y and z are outside the scope of the invention,
No good results were obtained.

〔The invention's effect〕

The piezoelectric porcelain composition according to the present invention contains the above-mentioned three components and satisfies the above-mentioned relationships. For this reason,
According to the present invention, a piezoelectric ceramic composition having a high Curie point, a small mechanical quality coefficient, and a large electromechanical coupling coefficient and a large relative dielectric constant can be realized.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a triangular diagram showing the results of the example.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-89354 (JP, A) JP-A-59-182272 (JP, A) JP-A-3-35574 (JP, A) 36756 (JP, B2) JP 5434920 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) C04B 35/46 C04B 35/49 H01L 41/18-41/187 CA (STN) REGISTRY (STN)

Claims (1)

(57) [Claims] 1. The method according to claim 1, wherein x moles of PbZrO ₃ , y moles of PbTiO ₃ , z
A piezoelectric porcelain composition comprising: Pb (Sn _1/3 Nb _{2α / 3} Sb _{2 (1-α) / 3} ) O ₃ and satisfying the following formula: x + y + z = 1 0.47 ≦ x ≦ 0.52 0.43 ≦ y ≦ 0.48 0.02 ≦ z ≦ 0.08 0.2 ≦ α ≦ 0.6 (0.450 ≦ x ≦ 0.505,0.455 ≦ y ≦ 0.510,0.02 ≦
excluding when z ≦ 0.06,0.2 ≦ α ≦ 0.8 are satisfied simultaneously)