JP3259677B2 - Piezoelectric ceramic composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a piezoelectric ceramic composition, and more particularly to a piezoelectric ceramic composition useful as a material for a piezoelectric ceramic element such as a piezoelectric ceramic filter or a piezoelectric ceramic oscillator.

[0002]

As a piezoelectric ceramic composition used for the piezoelectric ceramic element such Background Art Piezoelectric ceramic filters, mainly lead zirconate titanate _{(Pb (Ti x Zr 1-} x) O 3) or lead titanate (PbTiO ₃₎ Piezoelectric ceramic compositions as components are widely used. In such a piezoelectric ceramic composition containing lead zirconate titanate or lead titanate as a main component, lead oxide is generally used in the production process, but due to evaporation of the lead oxide, Product uniformity decreases.

On the other hand, a composition formula: (K _1-xy Na _x
Li _y ) A piezoelectric ceramic composition mainly composed of potassium sodium lithium niobate represented by NbO ₃ or the like does not contain lead oxide, and thus does not encounter the above-described problems.
Further, in the piezoelectric ceramic composition composed mainly of potassium sodium niobate lithium, electromechanical coupling coefficient K _p is large, it is what is considered to be promising as a material such as a piezoelectric ceramic filters and piezoelectric ceramic oscillator Exists.

However, such a piezoelectric ceramic composition containing potassium sodium lithium niobate as a main component has a smaller relative dielectric constant than lead zirconate titanate or lead titanate, and therefore a piezoelectric ceramic filter or piezoelectric ceramic When used as a material for an oscillator or the like, impedance matching with a circuit provided with such a piezoelectric ceramic filter or a piezoelectric ceramic oscillator or the like is not good, and circuit design may be difficult.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems encountered in piezoelectric ceramic compositions containing potassium sodium lithium niobate as a main component, and has a dielectric constant of 1000 or more. And contains no lead and has a sufficient electromechanical coupling coefficient K _P (25%
The present invention aims to provide a piezoelectric ceramic composition which shows the above.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned technical problems by the general formula: (1-n) (K _{1-
xy Na x Li y) m (} Nb 1-z Ta z) O 3 -nM1
As a main component a composition represented by M2O _3, a piezoelectric ceramic composition, in the above general formula, M1 consists bivalent metal element, M2 consists of tetravalent metal elements, also,
x, y, z, m and n are respectively 0.1 ≦ x, y ≦ 0.3, x + y <0.75, 0 ≦ z ≦ 0.3, 0.98 ≦ m ≦ 1.0, And 0 <n <0.1.

The above-described ranges of x, y, z, m, and n
The reasons for limiting the box are as follows. x and y
Respectively, to limit 0.1 ≦ x and y ≦ 0.3
The reason is that if it is out of these ranges, a good sintered body can be obtained.
Because you can't do that. Also, let x + y <0.75.
The reason is that when 0.75 ≦ x + y, the electromechanical coupling coefficient K _P
Is less than 25%, the piezoelectric ceramic filter, pressure
It is difficult to use it as a material for electroceramic oscillators.
That's because.

[0008] With respect to z, 0 ≦ z ≦ 0.3 means that if the value is outside this range, the Curie point drops to 200 ° C. or less, and the temperature stability of the element constituted by the piezoelectric ceramic composition is reduced. This is because a problem arises in the point. Also, m
The reason why 0.98 ≦ m ≦ 1.0 is that if it is out of this range, the polarization treatment becomes difficult.

Further, regarding n, 0 <n <0.1 means that when n is 0.1 or more, the electromechanical coupling coefficient K
_P is less than 25%, piezoelectric ceramic filter,
This is because it becomes difficult to use the piezoelectric ceramic oscillator as a material. In the present invention, preferably, M1 in the above general formula is at least one selected from the group consisting of Mg, Ca, Sr, and Ba;
2 is at least one selected from the group consisting of Ti, Zr, Sn, and Hf.

[0010]

EXAMPLE First, K was used as a starting material._TwoCO_Three, Na_Two
CO_Three, Li_TwoCO_Three, Nb_TwoO _Five, Ta_TwoO_Five, Ca
CO_Three, SrCO_Three, BaCO_Three, TiO_Two, Zr
O_Two, And SnO_TwoPrepare these raw materials, general
Formula: (1-n) (K_1-xyNa _xLi_y)_m(Nb_1-z
Ta_z) O_Three-NM1M2O_ThreeAs shown in Table 1
Weighed to obtain a suitable composition and used a ball mill for about 4
Wet mix in alcohol for hours and dry the resulting mixture
After that, it was calcined at a temperature of 700C to 900C. Next
After coarsely pulverizing these dry mixtures, the organic binder is removed.
Add an appropriate amount and wet crush for 4 hours using a ball mill.
The particle size was adjusted through a mesh sieve.

Next, 1000 kg of the powder whose particle size has been adjusted
After molding into a disk having a diameter of 12 mm and a thickness of 1.2 mm at a pressure of / cm ² , firing was performed at a temperature of 1050 ° C. to 1300 ° C. using a normal firing method to obtain a disk-shaped porcelain. . Next, a silver paste is applied and baked on both main surfaces of these porcelain disks by a usual method to form silver electrodes, and then 2 to 10 kV / in an insulating oil at 50 ° C. to 150 ° C.
A DC voltage of 10 mm was applied for 10 to 30 minutes to perform polarization treatment, and a piezoelectric ceramic disk as a sample was obtained.

Next, the relative permittivity, the electromechanical coupling coefficient K _P , and the Curie point of each sample were measured. The results are also shown in Table 1.

[0013]

[Table 1]

In Table 1, samples with an asterisk (*) are out of the scope of the present invention. In Table 1,
0.1 ≦ x, y ≦ 0.3, x + y <0.75, 0 ≦ z ≦
For samples satisfying all the conditions of 0.3, 0.98 ≦ m ≦ 1.0, and 0 <n <0.1, that is, samples according to the examples of the present invention in which sample numbers are not marked with *, All show good characteristics such as a relative dielectric constant of 1000 or more, an electromechanical coupling coefficient K _P of 25% or more, and a Curie point exceeding 200 ° C.

On the other hand, 0.1 ≦ x or y ≦ 0.
Samples 14 and 15 that do not satisfy the condition 3 have sintering failure. In addition, the above-mentioned 0.1 ≦ x or y ≦
In Sample 1, which satisfies the condition of 0.3 but does not satisfy x + y <0.75, the electromechanical coupling coefficient K _P is 22.0%, and the electromechanical coupling coefficient K _P of 25% or more cannot be achieved. . In this sample 1, the relative dielectric constant was 850,
Dielectric constant of 1000 or more is not achieved.

Sample 3 not satisfying 0 ≦ z ≦ 0.3
In Curie point 2, the Curie point is 160 ° C., and a Curie point exceeding 200 ° C. cannot be realized. Also, 0.98 ≦ m ≦
The sample 37 that does not satisfy the condition of 1.0 cannot achieve the desired polarization. Also, among the samples that do not satisfy the condition of 0 <n <0.1, the samples 5, 9, 13, and 1 where n is 0.1 or more.
In 9, 23, 27, 31, 36, 40, 43, 46 and 49, the electromechanical coupling coefficient K _P is smaller than 25%. Samples 2, 6, 10, 1 where n is 0
6, 20, 24, 28, and 33 did not achieve a relative dielectric constant of 1000 or more.

Although the present invention has been described with reference to the embodiments, the piezoelectric ceramic composition falling within the scope of the present invention is not limited to such embodiments, but departs from the spirit of the present invention. The composition can be variously changed within a range not to do. For example, in the embodiment described above, M1 is C
a, Ba and Sr are used, and M2
At least one of Ti, Zr and Sn was used, but for M1, the same effect can be obtained even if Mg is used and M2 is Hf. Has been confirmed. For M1, another divalent metal element may be used, and for M2, another tetravalent metal element may be used.

[0018]

As described above, according to the present invention, the relative dielectric constant is 1000 or more, and the electromechanical coupling coefficient K _P is 25%.
As described above, a piezoelectric ceramic composition exhibiting good properties such as a Curie point exceeding 200 ° C. can be obtained,
Using this piezoelectric ceramic composition, a piezoelectric ceramic element such as a piezoelectric ceramic filter or a piezoelectric ceramic oscillator can be advantageously produced.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-9-165262 (JP, A) JP-A-7-82024 (JP, A) JP-A-59-88322 (JP, A) JP-A-51- 5600 (JP, A) JP-A-49-33907 (JP, A) JP-A-48-81096 (JP, A) JP-A-48-38483 (JP, A) (58) Fields investigated (Int. ⁷ , DB name) C04B 35/495-35/499 H01L 41/187

Claims (2)

(57) [Claims] 1. The general formula: (1-n) (K _1-xy Na _x L)
i _{y) m} (as a main component a composition represented by _{Nb 1-z Ta z) O} 3 -nM1M2O 3, the piezoelectric ceramic composition. Here, M1 is a divalent metal element, M2 is a tetravalent metal element, and 0.1 ≦ xy ≦ 0.3 x + y <0.750 0 ≦ z ≦ 0.3 0.98 ≦ m ≦ 1.00. <N <0.1. 2. The M1 is at least one selected from the group consisting of Mg, Ca, Sr, and Ba, and the M2 is at least one selected from the group consisting of Ti, Zr, Sn, and Hf. The piezoelectric ceramic composition according to claim 1, which is one kind.