JPH0566896B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a ceramic composition for piezoelectric material, which has a large radial electromechanical coupling coefficient, dielectric constant, and piezoelectric constant, and is suitable as a material for piezoelectric actuators and piezoelectric buzzer towers that utilize piezoelectric distortion. . (Prior Art) Lead zirconate titanate Pb(ZrTi)O ₃ porcelain composition has been known as a piezoelectric material. This compound has advantages such as high piezoelectricity, being usable up to high temperatures, and the ability to obtain highly modified porcelain by substituting or adding a third component. In particular, some of Zr and Ti are mixed with Mg.
Pb substituted with Nb (Mg _1/3 Nb _2/3 )O ₃ −PbTiO ₃ −
The three-component piezoelectric material PbZrO ₃ is easy to sinter, with little evaporation of PbO, and it is possible to provide various piezoelectric properties by adding various additives to the main component. It has been used as a material for filters, piezoelectric ignition elements, ultrasonic vibrators, etc. In recent years, the need for precise displacement elements has increased in the fields of precision machinery, optical instruments, etc., and attempts have been made to use displacement driving elements that utilize piezoelectric distortion. Piezoelectric materials used in such fields are required to have a large radial electromechanical coupling coefficient, dielectric constant, and piezoelectric constant. Among the conventionally known materials, Pb (Mg _1/3
Nb _2/3 ) O ₃ −PbTiO ₃ −PbZrO ₃ (Special Publication No. 42-9716
(No. 2) has a radial electromechanical coupling coefficient of 50 to 70%.
Although it has a large value, its relative permittivity is only about 2500 at most. As a material for increasing the relative dielectric constant, a material in which part of the Pb in the above composition is replaced with Sr, Ba, and Ca has been proposed (Japanese Patent Publication No. 17103/1983). Also, JP-A-49-122512, JP-A-62-
Publication No. 17065 describes Pb(Mg _1/3 Nb _2/3 )O ₃ −Pb(Ni _1/3
A four-component piezoelectric material of Nb2 _/3 ) _O3 - _PbTiO3 - _PbZrO3 has been proposed, and a piezoelectric ceramic with high specificity in terms of radial electromechanical coupling coefficient, dielectric constant, and piezoelectric constant has been obtained. Piezoelectric constant of this kind of material
d ₃₁ is approximately 300 to 314×10 ⁻¹² m/v. (Problems to be Solved by the Invention) However, the piezoelectric materials described above do not have sufficient characteristics to meet the recent demands for higher performance of piezoelectric materials. That is, conventional piezoelectric materials have a small dielectric constant, an electromechanical coupling coefficient, or a piezoelectric constant. Therefore, when these materials are used as a piezoelectric actuator, there are disadvantages in that the amount of displacement is small and the drive voltage is large. An object of the present invention is to provide a piezoelectric material that has a large relative dielectric constant, a radial electromechanical coupling coefficient, and a piezoelectric constant, and can obtain a large piezoelectric strain. (Means for Solving the Problems) The present inventors developed Pb(Mg _1/3 Nb _2/3 )O ₃ −PbTiO ₃ −PbZrO ₃ , which has been recognized to have good properties.
The ternary composition of Pb(Mg _1/3 Nb _2/3 )O ₃ −Pb
(Ni _1/3 Nb _2/3 ) O ₃ - PbTiO ₃ - PbZrO ₃ is the basic four-component system composition, and some of the Pb is added to the elements in order to increase the radial electromechanical coupling coefficient as a piezoelectric material. After adding Sr with the assumption that it would be replaced with Sr, the effects of other additives were investigated. the result,
It was discovered that in a three-component composition of SnO ₂ , ZnO, Bi ₂ O ₃ , by simultaneously adding an appropriate amount of NiO, a material with high relative dielectric constant, radial electromechanical coupling coefficient, and piezoelectric constant could be obtained. . The gist of the present invention based on the above knowledge is the following piezoelectric material composition. The content of each element is within the following range in weight%
Pb, Ti, Zr, Mg, Nb, Ni, Sr, Sn, Zn, Bi
and a porcelain composition for piezoelectric material, characterized by comprising oxygen and inevitable impurity elements. 1.8 ≦Nb≦11.0 0.05≦Bi≦6.5 Above The composition is the basic three-component composition [Pb
(Mg _1/3 Nb _2/3 )O ₃ −PbTiO ₃ −PbZrO ₃ ] of Pb 10
Substituting atomic percent or less with Sr and adding SnZn, Bi, and Ni, and the basic four-component composition [(Mg _1/3 Nb _2/3 )O ₃ −Pb(Ni _1/3 Nb _{2/ 3} ) _O3−
10 atomic% of Pb in PbTiO ₃ −PbZrO ₃ ]
This corresponds to the one in which Sn, Zn, and Bi are added. When the amount of Pb replaced by Sr exceeds 10 atomic %, the radial electromechanical coupling coefficient and piezoelectric constant decrease. Furthermore, the reason why Ti, Zr, Mg, and Nb are limited to the above range is that outside this range, the relative permittivity and piezoelectric constant become small. Other additives, SnO ₂ , ZnO, Bi ₂ O ₃ and NiO in the three-component composition, and SnO ₂ , ZnO and Bi ₂ O ₃ in the four-component composition, are each compound of one kind, two or three. Even if a combination of species is added, the dielectric constant, electromechanical coupling coefficient, and piezoelectric constant may be lower than those of a composition without additives, or the improvement effect is small. However, in a three-component composition, the above-mentioned 4
In the case of seed and four-component compositions, when the above-mentioned three types are added at the same time and the content of each element is within the above-mentioned range (including substitution for Mg in the case of Ni), improvements in each property are observed. If this condition is violated, some of the characteristics will deteriorate. The composition of the present invention can be manufactured by blending and forming oxides, carbonates, hydroxides, etc. of each element so as to have the above-mentioned composition, and then sintering the composition. In addition, Fe, Ca, Na,
Impurity elements such as Si and Ba may be mixed in. However, the content of these elements in the piezoelectric material composition is at a level not exceeding 0.005 wt%. Example 1 The basic four-component composition was αPb(Mg _1/3 Nb _2/3 )O ₃
−βPb(Ni _1/3 Nb _2/3 )O ₃ −γPbTiO ₃ −δPbZrO ₃ (However, α+β+γ+δ=1), PbO, ZrO ₂ ,
_TiO2 , MgO, _NiO , _Nb2O5 , _SrCO3 , _SnO2 ,
Each raw material of ZnO and Bi ₂ O ₃ was weighed so as to have the composition shown in 1 of Table 1, and thoroughly mixed using a ball mill. Note that 2 in Table 1 shows the blending amounts of elements other than oxygen and unavoidable impurity elements in weight %. The obtained mixed powder was calcined at 900 to 1100° C. for about 2 hours, and the calcined product was thoroughly ground and mixed again in a ball mill, and then an organic binder was mixed and granulated. This granulated powder is heated to a diameter of 20 mm with a pressure of approximately 1000 kg/cm ^2.
mm and thickness of 2 mm, and baked at a temperature of 1200 to 1300°C for 2 hours. Silver electrodes were formed on both sides of the obtained disk-shaped sintered body, and polarization treatment was performed by applying a DC voltage of 2 kV/mm in silicone oil at 100°C. The piezoelectric properties of the porcelain obtained in this way are
It is shown in Table 2. In addition, ε ^T ₃₃ /ε ₀ in the table is the relative dielectric constant,
k _r is the radial electromechanical coupling coefficient and d ₃₁ is the piezoelectric constant.

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【table】

[Table] ○ mark: maximum value of the example of the present invention, × mark: same minimum value In Table 1, samples Nos. 1 to 16 have αPb (Mg _1/3
Nb _2/3 )O ₃ −βPb(Ni _1/3 Nb _2/3 )O ₃ −γPbTiO ₃ −
The α, β, γ, and δ (mol%) of δPbZrO ₃ are changed. (However, α+β+γ+δ=1) In view of the test results of each characteristic, 0.1≦α0.55 0.025≦δ≦0.6 0.01≦β≦0.28 0.3≦γ≦0.5 are appropriate. Outside this range, d ₃₁ becomes small. Samples Nos. 17 to 19 are samples in which the amount of Pb replaced by Sr is changed, but when the amount of Sr substitution exceeds 10 at%, the relative dielectric constant increases, but conversely k _r decreases, resulting in d ₃₁ will also become smaller. Samples Nos ^. 20 _to 38 are samples in which the amounts _of SnO ₂ , _{ZnO ,} and Bi ₂ O ₃ added are changed. ₂ and Bi ₂ O ₃ are required to be in the ranges of 0.1≦ZnO≦5, 0.05≦Bi ₂ O ₃ ≦5, 0.1≦SnO ₂ ≦5, respectively, in terms of mol%.
Furthermore, if only one or two of these are added, ε ^T ₃₃ /ε ₀ , k _r , and d ₃₁ all decrease,
In order to increase the size of all of these, it is necessary to add three types at the same time. Example 2 Basic three-component composition Pb (Mg _1/3 Nb _2/3 ) O ₃ −
Part of Pb in PbTiO ₃ −PbZrO ₃ is replaced with Sr,
When adding NiO, SnO ₂ , ZnO, and Bi ₂ O ₃ , the above composition is expressed as αPb(Mg _1/3 Nb _2/3 )O ₃ −γPbTiO ₃ −δPbZrO ₃ (α+γ+δ=1), and PbO, _ZnO2 , _TiO2 , MgO, _{Nb2O5 ,}
Each raw material of SrCO ₃ , NiO, SnO ₂ , ZnO, and Bi ₂ O ₃ was weighed so as to have the composition shown in 1 of Table 2. Incidentally, in Table 2, 2 shows the blending amounts of elements other than oxygen and inevitable impurity elements in weight %. Hereinafter, mixing, calcination, molding, and
After baking to form a silver electrode, polarization treatment was performed and piezoelectric properties were measured. Its properties are shown in Table 2.

【table】

【table】

【table】

[Table] ○ mark: maximum value of the example of the present invention, × mark: same minimum value In 1 of Table 2, samples No. 30 to 40 are αPb
α of (Mg _1/3 Nb _2/3 )O ₃ −γPbTiO ₃ −δPbZrO ₃ ,
γ and δ (mol%) are changed (however, α+γ+δ1). From the test results, 0.1≦α≦0.55, 0.3≦γ≦0.5, 0.025≦δ≦0.6 are suitable, and d ₃₁ becomes small outside these ranges. Samples No. 28 to 29 are samples in which the amount of Pb replaced by Sr is changed, but as in Example 1, when the amount of Sr substitution exceeds 10 atomic %, k _r decreases, and as a result, d ₃₁ also decreases. Samples Nos. 1 to 27 have different amounts of NiO, SnO ₂ , ZnO, and Bi ₂ O ₃ , but ε ^T ₃₃ /ε ₀ , k _r , d ₃₁
To obtain a large one, use NiO, SnO ₂ ,
It can be seen that ZnO and Bi ₂ O ₃ need to be in the ranges of 0.1≦NiO≦5, 0.1≦SnO ₂ ≦5, 0.1≦ZnO≦0.05≦Bi ₂ O ₃ ≦5. Furthermore, if these additives are added alone or in combination of two or three, ε ^T ₃₃ /ε ₀ ,
All of k _r and d ₃₁ decrease, and in order to increase them all, it is necessary to add four types at the same time. In the sintered bodies obtained in Examples 1 and 2, the change in chemical composition during sintering was negligible, and the blended composition was the same value as the sintered body composition. The weight proportions of each element in the sintered body are determined as follows from the appropriate values of the blending proportions determined from the above investigation results. The ranges of each element below are determined from the maximum and minimum values in Examples of the present invention (described in the notes column of each table) in Tables 1 and 2. 1.8 ≦Nb≦11.0 0.05≦Bi≦6.5 Remaining amount :0 (oxygen) and inevitable impurity elements (effects of the invention) As shown in the examples, the ceramic composition of the present invention has excellent properties in all of the radial electromechanical coupling coefficient, dielectric constant, and piezoelectric constant. It is extremely useful as a material for the various uses mentioned at the beginning.

Claims (1)

[Claims] 1. The content of each element is in the following range in weight%.
Pb, Ti, Zr, Mg, Nb, Ni, Sr, Sn, Zn, Bi
and a porcelain composition for piezoelectric material, characterized by comprising oxygen and inevitable impurities. 0.02 ≦Zn≦1.0 0.05≦Bi≦6.5