JP2003201171A - Piezoelectric porcelain composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric porcelain composition having excellent piezoelectric characteristics by using an inexpensive material not containing a lead component. <P>SOLUTION: The piezoelectric porcelain composition is expressed by the chemical formula [Bi<SB>a</SB>(Na<SB>1-x</SB>K<SB>x</SB>)<SB>1-a</SB>]<SB>b</SB>[Ti<SB>1-y</SB>(Mg<SB>c</SB>Ta<SB>1-c</SB>)<SB>y</SB>]<SB>b</SB>O<SB>3</SB>, in which x and y are 0<x<1, 0<y≤0.3. <P>COPYRIGHT: (C)2003,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] TECHNICAL FIELD The present invention relates to a vibrator, an actuator,
Pressure suitable for piezoelectric devices such as etas and sensors
It relates to a porcelain composition. [0002] 2. Description of the Related Art Ceramics conventionally used for piezoelectric devices
Material is PT (PbTiO_Three) Or PZT
(Pb (Ti, Zr) O_ThreeContains lead as typified by
Most do. [0003] However, these leads are
The contained ceramic is a lead component in the manufacturing process
The volatilization of is inevitable. In addition, these lead in industrial waste
Ash or ash
Environmental pollution due to elution is possible. Therefore, lead component
Measures that do not release to the external environment are required,
Occurs. For these reasons, lead-free piezoelectric materials are provided.
This is extremely beneficial not only in terms of environmental measures but also in terms of manufacturing costs.
It is for. However, the lead-free pressure obtained so far
In electrical materials, piezoelectric properties or dielectric properties
However, it is not always practically sufficient. [0006] Accordingly, the present invention provides a safety device containing no lead component.
Piezoelectric ceramic compositions with excellent piezoelectric properties
The task is to provide. [0007] [MEANS FOR SOLVING THE PROBLEMS]
The piezoelectric ceramic composition of the present invention is_a(Na_1-xK _x)
_1-aTi_1-y(Mg_cTa_1-c)_yO_ThreeRepresented by the chemical formula
Where x and y are molar ratios, 0 <x <1, 0 <y ≦ 0.3.
By doing so, it becomes an excellent piezoelectric ceramic composition that does not contain lead.
You. [0008] The present invention relates to a Bi—Na—Ti based piezoelectric material.
Then, part of Na is replaced with K, and part of Ti is further replaced with Mg.
_1/3Ta_2/3Substitution with piezoelectric properties and dielectric
This is to improve the characteristics. [0009] The respective replacement amounts are 0 <x <1, 0 <y ≦
The reason for setting the ratio to 0.3 is that the piezoelectric characteristics are deteriorated outside this range.
That's because. The reason for this is unknown, but M
Greater than the composition range near PB (morphotropic phase boundary)
The cause seems to be that it comes off easily. [0010] By the way, in the piezoelectric ceramic composition of the present invention,
Is slightly different from stoichiometry (stoichiometric ratio)
Excellent piezoelectric properties can be obtained even for crystals that have been grown. The cause
As the precipitation of a different phase, the replacement of constituent elements with another site,
Precipitation at grain boundaries, oxygen vacancies, or valence of constituent elements
Change and the like. The deviation of the composition ratio at that time is about ± 5%.
Is possible. That is, the composition of the piezoelectric ceramic composition of the present invention
By adding a, b, c and d in addition to the above x and y,
[Bi _a(Na_1-xK_x)_1-a]_b[Ti_1-y(Mg_c
Ta_1-c)_y]_dO_ThreeWhere a is the value of a
About ± 5% around 0.5, and the value of b is 1.0
Approximately ± 5% around 0, and the value of c around 1/3
About ± 5%, and as the value of d, around ± 1.00
Changes up to about 5% are possible. Further, as a method for producing ceramics,
Any production method may be used.
Absent. [0013] Next, the present invention will be described by way of examples. [0014] As an invention, a chemically pure Bi
_TwoO_Three, Na_TwoCO_Three, K_TwoCO_Three, TiO_Two, MgO, Ta_Two
O_FiveAnd Bi_0.5(Na_1-xK_x)_0.5Ti_1-y(Mg
_1/3Ta_{2 / Three})_yO_Three, (0 <x <1, 0 <y ≦ 0.3)
And a ball mill using alcohol.
For 40 hours. [0015] This is dried, at 900 ° C for 1 hour in the air
Calcined. Next, wet mixing was performed for 20 hours using a ball mill.
Was. The powder obtained by drying is coated with polyvinyl alcohol.
Granulated as an inder, pressure 1.5 ton / cm^TwoUniaxial addition
Formed into a disc with a diameter of 20 mm and a thickness of 1 mm by pressing.
Shaped. The firing is performed at 1,000 to 1200 ° C. for 2 hours.
Was. The upper and lower surfaces of the obtained sintered body are polished in parallel, and
A silver electrode is applied and baked.
Apply a direct current of 4-7 kV / mm for 15 minutes in the
Polarized in the thickness direction. Also, as a comparative product, the same manufacturing method as the invention product is used.
A composition having a composition outside the range described in the claims was produced by the method. Table 1 shows the electromechanical coupling between the invention product and the comparison product.
Several kp and kt, mechanical quality factor Qm, relative permittivity ε₃₃
^T/ ε_oIs shown. Characteristics are impedance analyzer
Was calculated by the resonance-anti-resonance method. Part of Na
Part of K and Ti (Mg_1/3Ta_{2 / Three}) In the claim
The inventions substituted within the range have piezoelectric and dielectric properties.
Has been improved. [0019] [Table 1][0020] As described above, according to the present invention, B
i_0.5(Na_1-xK_x)_0.5Ti_1-y(Mg_1/3Ta_2/3)
_yO_ThreeWhere x and y are molar ratios and 0 <x <
1, 0 <y ≦ 0.3, excellent lead-free content
A piezoelectric ceramic composition having characteristics can be obtained.

Claims (1)

Claims: 1. Bi _0.5 (Na _{1 -x} K _x ) _0.5 Ti _{1 -y} (M
g _1/3 Ta _2/3) represented by the chemical formula of _y O _3, x, piezoelectric ceramic composition characterized by y is 0 <x <1,0 <y ≦ 0.3 in molar ratio.