JP2006021960A - Piezoelectric ceramic material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric ceramic material having electromechanical coupling coefficient and mechanical quality factor satisfying a level not less than a specific value and having high stability of piezoelectric characteristics to the change of a temperature. <P>SOLUTION: The piezoelectric ceramic material has a composition formula expressed by Pb<SB>x</SB>[(Co<SB>1/3</SB>Nb<SB>2/3-y</SB>)<SB>a</SB>(Sb<SB>1/2</SB>Nb<SB>1/2</SB>)<SB>b</SB>Ti<SB>c</SB>Zr<SB>d</SB>]O<SB>3</SB>+(e) wt.% R<SB>2</SB>O<SB>3</SB>(where, a+b+c+d=1 and R expresses a rare earth element) and the composition range is 0.92≤x≤1.00, 0<y≤0.03, 0.03≤a≤0.30, 0<b≤0.10, 0.40≤c≤0.53, 0.25≤d≤0.52, 0≤e≤1.50. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a piezoelectric ceramic material used for various piezoelectric devices, and in particular, a piezoelectric ceramic material having an electromechanical coupling coefficient and a mechanical quality factor of a certain level or more and high stability of piezoelectric characteristics against temperature changes. Involved.

  Various devices using piezoelectric ceramic materials have been developed, commercialized, and widely used in the market. In general, a piezoelectric material having a high electromechanical coupling coefficient or a high mechanical quality factor is regarded as a material having high characteristics. In addition to this, temperature stability of the piezoelectric characteristics is also an important point. This is because if the piezoelectric characteristics change greatly with temperature, the stability of the device characteristics is directly affected.

  In addition, in the manufacturing process of a product on which a piezoelectric device is mounted, the piezoelectric device itself may be processed at a high temperature of 200 ° C. or higher. If the piezoelectric characteristics greatly change before and after the processing, It becomes difficult to design that satisfies the above standards.

For this reason, a material having high stability with respect to temperature change of piezoelectric characteristics and small characteristic fluctuation after high temperature processing is required. As an example of stabilizing temperature characteristics, Patent Document 1 discloses that a predetermined element is contained in a Pb (Co _1/3 Nb _2/3 ) O ₃ —PbZrO ₃ —PbTiO ₃ based piezoelectric ceramic material. It is described that the temperature coefficient of the resonance frequency is lowered while maintaining a high electromechanical coupling. Patent Document 2 also includes a predetermined element in a Pb (Co _1/3 Nb _2/3 ) O ₃ —PbZrO ₃ —PbTiO ₃ based piezoelectric ceramic material, thereby reducing the temperature coefficient of the resonance frequency, It is described that characteristic fluctuation after high temperature treatment is also reduced.

Japanese Patent Laid-Open No. 10-338572 Japanese Patent Application Laid-Open No. 11-147663

  An object of the present invention is to provide a piezoelectric ceramic material having an electromechanical coupling coefficient and a mechanical quality coefficient at a certain level or more and high stability in piezoelectric characteristics against temperature changes.

According to the present invention, the composition formula is Pb _x [(Co _1/3 Nb _{2 / 3-y} ) _a (Sb _1/2 Nb _1/2 ) _b Ti _c Zr _d ] O ₃ (where a + b + c + d = 1) The composition range is 0.92 ≦ x ≦ 1.00, 0 <y ≦ 0.03, 0.03 ≦ a ≦ 0.30, 0 <b ≦ 0.10, 0.40 ≦ c. ≦ 0.53, 0.25 ≦ d ≦ 0.52, and the weight of the main component is 100, and the rare earth oxide is converted into R ₂ O ₃ (R is a rare earth element) as a subcomponent. Thus, a piezoelectric ceramic material containing 1.50 or less in weight (one or more rare earth elements may be added and the total addition amount is within this range) is obtained.

Further, according to the present invention, the piezoelectric ceramic material having the above composition has a radial electromechanical coupling coefficient K _p of 0.30 or more, a relative dielectric constant ε _r of 400 or more, and a mechanical quality factor Q _m of 300 or more. The change in the temperature range of −40 ° C. to + 80 ° C. when the mechanical quality factor Q _m is 20 ° C. is ± 50% or less, and −40 when the resonance frequency _fr is 20 ° C. as a reference. ° C. ~ + 80 changes in the temperature range ° C. temperature characteristic variation of ± 1% or less _{Q m (-40 ℃ ~ + 80} ℃, 20 ℃ basis) ± 50% or less, the temperature characteristic variation of the resonance frequency f _r (-40 A piezoelectric ceramic material having a temperature of ± 1% or less is obtained.

Also, according to the present invention, the rate of change of the mechanical quality factor Q _m (reference before heat treatment) before and after the heat treatment which is kept at 260 ° C. for 1 hour and left to stand at room temperature for 24 hours is 10% or less, and the resonance frequency _fr. A piezoelectric ceramic material having a change rate of 0.5% or less is obtained.

With the above structure, a piezoelectric ceramic material according to the invention, the electromechanical coupling coefficient K _p, the mechanical quality factor Q _m is increased, and the temperature characteristic variation of Q _m, small temperature characteristic variation of the resonance frequency f _r, a heat treatment before and after Q _m, the characteristic variation of the f _r is small. As a result, it is possible to develop a highly stable product using the piezoelectric ceramic material of the present invention and contribute to the improvement of the reliability, so that the industrial value is great.

The piezoelectric ceramic material of the present invention has a composition formula of Pb _x [(Co _1/3 Nb _{2 / 3-y} ) _a (Sb _1/2 Nb _1/2 ) _b Ti _c Zr _d ] O ₃ (where a + b + c + d = 1), and the composition range is 0.92 ≦ x ≦ 1.00, 0 <y ≦ 0.03, 0.03 ≦ a ≦ 0.30, 0 <b ≦ 0.10, 0.40. ≦ c ≦ 0.53, 0.25 ≦ d ≦ 0.52, and when the weight of the main component is 100, a rare earth oxide as a subcomponent is R ₂ O ₃ (R is a rare earth element) ) Is a piezoelectric ceramic material containing 1.50 or less by weight. One or more rare earth elements such as Sc, Y, La, Ce, Pr, Nd, Sm, Gd, and Yb, which are subcomponents, may be used, and the total weight when converted as an oxide of R ₂ O ₃ is within this range. I just need it.

Further, in the present invention, the piezoelectric ceramic material having the above composition, and the piezoelectric device further has piezoelectric characteristics, a radial electromechanical coupling coefficient K _p of 0.30 or more, a relative dielectric constant ε _r of 400 or more, Mechanical quality factor Q _m is 300 or more and Q _m temperature characteristic change is ± 50% or less (change in temperature range of −40 ° C. to + 80 ° C. when mechanical quality factor Q _m is based on 20 ° C. There follows 50% ±), the resonance frequency f temperature characteristic variation of _r is ± 1% or less (the resonance frequency f _r of 20 ℃ -40 ℃ ~ + 80 changes in the temperature range ° C. is ± 1% of the time relative to the The Q _m change rate (reference before heat treatment) after a heat treatment held at 260 ° C. for 1 hour and left at room temperature for 24 hours is 10% or less, and the _fr change rate is 0.5% or less. A certain piezoelectric ceramic material is desirable.

  Next, the reason why the compounding ratio (composition ratio) of each compound is limited will be described below. When the amount x of Pb is 1 or less, the electromechanical coupling coefficient is improved. However, when the amount is less than 0.92, the electromechanical coupling coefficient is decreased. Therefore, the range of 0.92 ≦ x ≦ 1.00 is preferable.

  The reduction amount Nb of y increases the electromechanical coupling coefficient and the relative dielectric constant by reducing Nb. However, if it exceeds 0.03, the characteristics deteriorate due to the formation of a different phase, and so 0 <y ≦ 0 A range of 0.03 is preferred.

As for the amount a of cobalt niobate, the electromechanical coupling coefficient and the mechanical quality factor are low when the amount of (CO _1/3 Nb _{2 / 3-y} ) is less than 0.03. The range of 0.03 ≦ a ≦ 0.30 is preferable because the temperature is low and the characteristic stability under high temperature conditions is poor.

The amount b of antimony niobate increases as the amount of (Sb _1/2 Nb _1/2 ) increases, but if it exceeds 0.10, the mechanical quality factor deteriorates, so that 0 <b A range of ≦ 0.10 is preferred.

  Since the amount of Ti and the amount of Zr d are in the regions other than 0.40 ≦ c ≦ 0.53 and 0.25 ≦ d ≦ 0.52, any of the characteristic items deteriorates. preferable.

Furthermore, the rare earth element oxide R ₂ O ₃ , which is a subsidiary component, has an effect of improving the electromechanical coupling coefficient and stabilizing the temperature characteristics, but the addition amount exceeds 1.50% by weight. Since a heterogeneous phase is generated and the electromechanical coupling coefficient and relative dielectric constant deteriorate, the range of 1.50% by weight or less is desirable.

  Hereinafter, the present invention will be described according to examples.

First, PbO, ZrO ₂ , TiO ₂ , Co ₃ O ₄ , Nb ₂ O ₅ , Sb ₂ O ₃ , La ₂ O ₃ , Sm ₂ O ₃ , Nd ₂ O ₃ , Yb ₂ O ₃ as starting materials Was used. In actual production, easily available raw materials may be used from various oxides, hydroxides, carbonates and the like.

  A predetermined amount of each raw material powder was weighed and wet mixed by a ball mill, and then the collected mixed powder was dried and calcined in the atmosphere. Thereafter, the calcined powder was wet pulverized with a ball mill and dried. Further, the obtained powder was mixed with a binder, pressed into a cylindrical mold, debindered, and fired to produce a sintered body.

Further, the produced sintered body was sliced into a disk shape, and silver electrodes were formed on both sides to be polarized to obtain a sample. The sample was allowed to stand at room temperature for 24 hours after the polarization treatment, and then the specific dielectric constant ε _r , the radial electromechanical coupling coefficient K _p , and the mechanical quality factor Q _m were measured and evaluated for characteristics.

Further, the temperature characteristic variation of Q _m, the temperature characteristic variation of the resonance frequency f _r, measured in the range of + 80 ° C. from -40 ° C., was evaluated for a highest variation when relative to the value of 20 ° C. .

For the evaluation of the change in characteristics due to the heat treatment, after the above characteristic evaluation, the sample was held at 260 ° C. for 1 hour, then left at room temperature for 24 hours, and then Q _m and _fr were measured and compared with the characteristic values before the heat treatment.

  Table 1 shows the evaluation results. A sample marked with * indicates that the sample is outside the scope of the present invention.

From the results in Table 1, it can be seen that the mechanical quality factor decreases when the amount x of Pb is out of the range. Similarly, it can be seen that the mechanical quality factor is also reduced when the Nb reduction y is out of the range. In addition, when the amount a of cobalt niobate is small, the electromechanical coupling coefficient and the mechanical quality factor are low. As the amount b of antimony niobate increases, the mechanical quality factor decreases. When the amount c of Ti is small, the mechanical quality factor is low, and when it is too large, the electromechanical coupling factor is lowered. When the amount d of Zr is small, the change in characteristics due to heat treatment is large, and when it is too large, the electromechanical coupling coefficient and the mechanical quality factor are low. Furthermore, it can be seen that the electromechanical coupling coefficient decreases as the addition amount e of the rare earth oxide R ₂ O ₃ increases.

Claims (3)

Represented _{by the} composition formula Pb _x [(Co _1/3 Nb _{2 / 3-y} ) _a (Sb _1/2 Nb _1/2 ) _b Ti _c Zr _d ] O ₃ (where a + b + c + d = 1), and its composition range 0.92 ≦ x ≦ 1.00, 0 <y ≦ 0.03, 0.03 ≦ a ≦ 0.30, 0 <b ≦ 0.10, 0.40 ≦ c ≦ 0.53,. With respect to a main component satisfying 25 ≦ d ≦ 0.52 and a weight of 100 of the main component, a rare earth oxide as an auxiliary component is converted into R ₂ O ₃ (R is a rare earth element), and the weight is 1.50 or less. A piezoelectric ceramic material comprising: When the radial electromechanical coupling coefficient K _p is 0.30 or more, the relative dielectric constant ε _r is 400 or more, the mechanical quality factor Q _m is 300 or more, and the mechanical quality factor Q _m is 20 ° C. 40 ° C. ~ + 80 changes in the temperature range ° C. is ± 50% or less, the change in the temperature range of -40 ℃ ~ + 80 ℃ when referenced to 20 ° C. of the resonance frequency f _r is less than 1% ± The piezoelectric ceramic material according to claim 1. And held 1 hour to 260 ° C., before and after the heat treatment for further 24 hours standing at room temperature, the rate of change of the mechanical quality factor Q _m is 10% or less, the rate of change of the resonance frequency f _r is less than 0.5% The piezoelectric ceramic material according to claim 2.