JP2006327863A - Piezoelectric ceramic material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric ceramic material which is lead-free but has a high mechanical quality factor Qm and properties suitable to be used for an ultrasonic vibrator or the like. <P>SOLUTION: The piezoelectric ceramic material contains elements Bi, Na, Ba, Ti, Mn, Nb, and O, and is represented by the general formula: (1-x-y)(Bi<SB>0.5</SB>Na<SB>0.5</SB>)TiO<SB>3</SB>-xBaTiO<SB>3</SB>-y(Bi<SB>0.5</SB>Na<SB>0.5</SB>)(Mn<SB>1/3</SB>Nb<SB>2/3</SB>)O<SB>3</SB>(wherein x is 0.01≤x≤0.20 and y is 0<y≤0.05). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a piezoelectric ceramic material that does not use lead.

Conventionally, as a piezoelectric ceramic material, barium titanate (BaTiO ₃ ), lead titanate (PbTiO ₃ ), lead zirconate titanate (Pb (ZrTi) O ₃ ), and the like are known. Among them, many piezoelectric ceramic materials mainly composed of lead zirconate titanate are used. Since this lead zirconate titanate can change the mechanical quality factor Qm, relative dielectric constant ε ₃₃ ^T / ε ₀ , piezoelectric strain constant d _33, etc. by appropriately selecting additives, it is used for a washing machine. And ultrasonic transducers for ultrasonic processing machines, ultrasonic sensors, pressure sensors, frequency filters, and the like.

  However, lead zirconate titanate-based piezoelectric ceramic materials are polluted because lead compounds are decomposed during firing and sintering processes and lead is released into the atmosphere, and lead is released into water during powder manufacturing and molding processes. It is necessary to take measures. In addition, there is a possibility that lead is eluted from the waste.

In recent years, therefore, research and development have been conducted on piezoelectric materials that do not contain lead. For example, a Bi _0.5 Na _0.5 TiO ₃ (BNT) -based piezoelectric ceramic material is known (Patent Document 1).

JP-A-11-180769

However, in the piezoelectric ceramic material of Patent Document 1, in order to obtain a large displacement, it is intended to obtain a so-called soft piezoelectric ceramic material having a large relative dielectric constant ε ₃₃ ^T / ε ₀ and a large K ₃₃ and d _33. is doing. For this reason, although the relative permittivity ε ₃₃ ^T / ε ₀ is large, the mechanical quality factor Qm is low due to its softness, so that it is a bolt-clamped Langevin type ultrasonic vibrator for a washing machine or a processing machine, a fish detector, etc. Therefore, it was not suitable for an element used in the ultrasonic vibrator.

  The present invention has been made in view of such problems, and is a lead-free piezoelectric ceramic material that has a high mechanical quality factor Qm and has characteristics suitable for use, for example, an ultrasonic vibrator. The purpose is to provide.

Its solution is, elements include Bi, Na, Ba, Ti, Mn, Nb, and O, the general formula: (1-x-y) (Bi 0.5 Na 0.5) TiO 3 -xBaTiO 3 -y (Bi 0.5 Na _0.5 ) (Mn _1/3 Nb _2/3 ) O ₃ , a piezoelectric ceramic material in which x and y satisfy the following formulas (1) and (2).
0.01 ≦ x ≦ 0.20 (1)
0 <y ≦ 0.05 Formula (2)

The piezoelectric ceramic material of the present invention is a lead-free piezoelectric ceramic material containing elements Bi, Na, Ba, Ti, Mn, Nb, and O. Moreover, when expressed by the above general formula, x and y have a composition satisfying the above conditional expressions (1) and (2). This piezoelectric ceramic material has other characteristics such as a high mechanical quality factor Qm and a relatively large value of relative dielectric constant ε ₃₃ ^T / ε ₀ when used in an ultrasonic vibrator. It will be a thing.

X and y are coefficients indicating the abundance ratio (molar ratio) of (Bi _0.5 Na _0.5 ) TiO ₃ , BaTiO ₃ and (Bi _0.5 Na _0.5 ) (Mn _1/3 Nb _2/3 ) O ₃ .

Examples of the piezoelectric ceramic material according to the present invention will be described together with comparative examples.
Commercially available high-purity chemical reagents Bi ₂ O ₃ , NaHCO ₃ , BaCO ₃ , TiO ₂ , MnCO ₃ , and Nb ₂ O ₅ are represented by the general formula: (1-xy) (Bi _0.5 Na _0.5 ) TiO ₃ -xBaTiO ₃ −y (Bi _0.5 Na _0.5 ) (Mn _1/3 Nb _2/3 ) O ₃ is weighed in a predetermined amount, mixed and calcined, pulverized, granulated, molded, sintered, Dimensional processing, electrode baking, and polarization were performed to prepare samples (piezoelectric ceramic material, 12 mmφ × 0.8 mmt) according to Examples 1 to 10 and Comparative Examples 1 to 6.
About this sample, mechanical quality factor Qm etc. were measured using impedance analyzer (HP4194: made by Agilent Technologies). The results are shown in Table 1.
In each table and below, (Bi _0.5 Na _0.5 ) TiO ₃ may be abbreviated as BNT, BaTiO ₃ as BT, and (Bi _0.5 Na _0.5 ) (Mn _1/3 Nb _2/3 ) O ₃ as BNMN. .

  Among Examples 1 to 10 and Comparative Examples 1 to 6 shown in Table 1, when the abundance ratio (molar ratio) y of BNMN is fixed at y = 0.001 (Examples 1 to 5, Comparative Examples 1 and 2) ) Are shown again in Table 2.

According to Table 2, when y = 0.001, when the abundance ratio (molar ratio) x of BT satisfies the following formula (1) (Examples 1 to 5), the electromechanical coupling coefficient kt is kt ≧ 40%, mechanical quality factor Qm is Qm ≧ 300, relative permittivity ε ₃₃ ^T / ε ₀ is ε ₃₃ ^T / ε ₀ ≧ 400, dielectric loss tan δ is tan δ ≦ 1.2%, Curie temperature Tc Any of Tc ≧ 250 ° C. can be satisfied. Thus, if the above equation (1) is satisfied, the electromechanical coupling coefficient kt, the mechanical quality factor Qm, the relative dielectric constant ε ₃₃ ^T / ε ₀ and the Curie temperature Tc are relatively suitable for use in an ultrasonic transducer. It can be seen that the piezoelectric ceramic material has a large and well-balanced characteristic.
0.01 ≦ x ≦ 0.20 (1)

  Specifically, if it is within a range of 0.01 ≦ x ≦ 0.20, kt ≧ 40% can be obtained. However, in the case of x = 0.005 (Comparative Example 1), kt <40%, which indicates that sufficient characteristics cannot be obtained. When x = 0.25 (Comparative Example 2), kt <40% and Tc <250 ° C., indicating that sufficient characteristics cannot be obtained.

  Next, among Examples 1 to 10 and Comparative Examples 1 to 6 shown in Table 1, when the abundance ratio (molar ratio) x of BT is fixed at x = 0.15 (Examples 4, 6 to 10, Comparative Examples) 3 and 4) are listed and re-displayed in Table 3.

According to Table 3, when x = 0.15 is fixed and the abundance ratio (molar ratio) y of BNMN satisfies the following formula (2) (Examples 4, 6 to 10), the electric machine Coupling coefficient kt is kt ≧ 40%, mechanical quality factor Qm is Qm ≧ 300, relative permittivity ε ₃₃ ^T / ε ₀ is ε ₃₃ ^T / ε ₀ ≧ 400, dielectric loss tan δ is tan δ ≦ 1.2%, Curie The temperature Tc can satisfy any of Tc ≧ 250 ° C. Thus, if the above equation (2) is satisfied, the electromechanical coupling coefficient kt, the mechanical quality factor Qm, the relative dielectric constant ε ₃₃ ^T / ε ₀ and the Curie temperature Tc, which are suitable for the ultrasonic vibrator, are relatively large, It can be seen that the piezoelectric ceramic material has a good balance of properties.
0 <y ≦ 0.05 Formula (2)

  Specifically, when it is within the range of 0 <y ≦ 0.05, kt ≧ 40% can be obtained. However, in the case of y = 0 (Comparative Example 3), it can be seen that kt <40% and Qm <300, and sufficient characteristics cannot be obtained. In this case, Qm is particularly low (Qm = 112). That is, it can be seen that Qm can be significantly increased in Example 4 or the like in which even a slight amount is added (y> 0) as compared with Comparative Example 3 in which BNMN is not added. Further, in the case of Comparative Example 2 (y = 0.060) in which a large amount of BNMN is added, it can be seen that Qm <300, and sufficient characteristics cannot be obtained.

  Further, according to Table 1, in the sample of Comparative Example 5 where x = 0.005, y = 0, and thus 1-xy = 0.993, Qm <300 (specifically, Qm = 107). became. Further, in the sample of Comparative Example 6 in which x = 0.25, y = 0.060, and 1-xy = 0.690, Tc <250 (specifically, Tc = 235). Therefore, it can also be seen from Comparative Examples 5 and 6 that satisfactory characteristics cannot be obtained with samples that do not satisfy the above formulas (1) and (2).

Thus, from the results shown in Tables 1, 2, and 3, the general formula: (1-xy) (Bi _0.5 Na _0.5 ) TiO ₃ —xBaTiO ₃ —y (Bi _0.5 Na _0.5 ) (Mn _1/3 Nb _{2 / 3} ) In the piezoelectric ceramic material represented by O _3, it is found that 0.01 ≦ x ≦ 0.20 and preferably 0 <y ≦ 0.050. The piezoelectric ceramic material having this composition is used for, for example, powerful ultrasonic application equipment such as a bolt-clamped Langevin type ultrasonic vibrator for a cleaning machine or a processing machine, or an ultrasonic vibrator for a fish detector or the like. It is suitable as an element.

  In the above, the present invention has been described in accordance with each example shown in Table 1 (Tables 2 and 3). However, the present invention is not limited to the piezoelectric ceramic material having the composition shown in the above example, and the gist thereof is described. Needless to say, the present invention can be changed and applied as appropriate without departing from the scope of the present invention.

Claims (1)

Including the elements Bi, Na, Ba, Ti, Mn, Nb, and O;
A piezoelectric ceramic material represented by the general formula: (1-xy) (Bi _0.5 Na _0.5 ) TiO ₃ —xBaTiO ₃ —y (Bi _0.5 Na _0.5 ) (Mn _1/3 Nb _2/3 ) O ₃ And
A piezoelectric ceramic material in which x and y satisfy the following formulas (1) and (2).
0.01 ≦ x ≦ 0.20 (1)
0 <y ≦ 0.05 Formula (2)