JPH11349379A - Piezoelectric ceramic material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a piezoelectric ceramic material having a proper electromechanical coupling coefficient and mechanical quality factor, showing excellent characteristics of temperature stability of mechanical quality factor and resonance frequency, consequently providing an inexpensive high-precision piezoelectric vibration gyroscope drivable at a low voltage. SOLUTION: This piezoelectric ceramic material is shown by the compositional formula: Fb[(Mna Sb1-b )b Tic Zrd ]O3 in which (a), (b), (c) and (d) satisfy relations of 0.333<a<=0.60, 0.01<=b<=0.22, 0.19<=c<=0.61, 0.35<=d<=0.58 and b+c+d=1, respectively. Preferably a×b>0.012. Further a piezoelectric ceramic material comprises a main component composed of the piezoelectric ceramic material and at least one of (e) wt.% of Ln2 O3 (with the proviso that Ln is at least one of lanthanoids; (e) is a number of 0<e<=5) and (f) wt.% of SiO2 (with the proviso that (f) is a number of 0<f<5) when the weight of the main components is 100 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a piezoelectric ceramic material, and more particularly, to a piezoelectric ceramic material used for a piezoelectric vibrator gyro.

[0002]

2. Description of the Related Art In recent years, small and inexpensive gyros using piezoelectric vibrators have been provided to the market, and have been used for hand-held camera and hand-held camera shake correction, car navigation systems, and ABS systems. I have. These piezoelectric gyros are currently roughly described in (a) ~
They are classified into four types (d), and all of them have been put to practical use.

(A) A vibrator in which a piezoelectric ceramic is stuck to a tuning fork made of a constant elastic metal, using two orthogonal vibration modes, one of which is driven and the other is induced by Coriolis force generated at an angular velocity. A method used to detect angular velocity from vibrations in the orthogonal direction. (B) A piezoelectric ceramic is bonded to a quadrangular prism made of a constant elastic metal to generate bending vibration of a rod and orthogonal bending vibration generated by Coriolis force is applied to another piezoelectric ceramic. (C) A vibrator formed by forming and polarizing a tolerance finger electrode in the length direction on the surface of a piezoelectric ceramic cylinder. One set of electrodes generates bending vibration in one direction, and the other two sets A configuration in which the voltage generated by the electrodes is detected, and the output voltage difference is detected from the unbalance of the output on the detection side by the effect of the orthogonal vibration generated according to the Coriolis force. (D) The above (b) and (c) ) A piezoelectric ceramic plate is bonded three sheets triangular prism aspect of sexual metal, for driving one, method of using the other two for the detection is over.

Here, the above-mentioned method (c) (hereinafter referred to as a ceramic round bar method) has an advantage that the structure is simple and the reliability is high without requiring an adhesion step. On the other hand, since all of the vibrator characteristics are determined by the material characteristics of the piezoelectric ceramic, the selection range of usable materials is significantly limited.

More specifically, first, the mechanical quality factor Qm is proportional to the magnitude of the sensitivity. Generally, however, the temperature change of the mechanical quality factor of the piezoelectric ceramic (ΔQm / Qm, based on the room temperature value) Is large, and some materials can be several hundred percent in the operating temperature range. In this case, the temperature fluctuation of the sensitivity increases, and a practical problem occurs. As a countermeasure, the drive voltage has a temperature characteristic opposite to the temperature change of Qm, and the temperature change of the output can be controlled by correcting the temperature change of the sensitivity.

However, in this case, the driving voltage fluctuates depending on the temperature, and it is difficult to obtain a stable operation. In particular, in the case of application to car navigation, there is a practical problem that a change in null voltage causes an error in position accuracy, but a change in drive voltage is a major factor in the change in null voltage.

Second, the temperature change of the resonance frequency fr also causes a change in the drive frequency, and also causes a change in the sensitivity and the null voltage.

[0008] Third, Q is a factor that determines sensitivity.
There is an absolute value of m and an electromechanical coupling coefficient. Basically, Q
It is preferable that m is large and the electromechanical coupling coefficient is large.

Generally, a piezoelectric material is PbTiO.
By dissolving one or more compound perovskite compounds in a solid solution of _3- PbZrO ₃ (binary PZT ceramic), the dielectric and piezoelectric properties that were not obtained with a binary component are improved, and the product is widely used. Has been offered to.

[0010] Therefore, considering the gyro _{material, PbTiO 3 -PbZrO 3 -Pb (Mn} 1/3 which is dissolved a _{Pb (Mn 1/3 Sb 2/3) O} 3 as a third component
The Sb _2/3 ) O ₃ -based piezoelectric ceramic is desirable in that it has a characteristic of a hard material that can obtain several hundred to several thousand Qm and high dielectric and piezoelectric characteristics. However, (ΔQ
m / Qm) was determined only by the amount of the third component, and when the amount of the third component was 5 mol% or more, (ΔQm / Qm) was deteriorated, so that it could not be used as a gyro material.

Therefore, conventionally, the third component Pb (Mn _x
(ΔQm / Qm) was improved by changing the ratio of Mn to Sb of Sb _1-x ) O ₃ . That is, Pb
(Mn _1/3 Sb _2/3 ) O ₃ has Mn: Sb = 1: 2, but (ΔQm / Qm) is reduced by reducing the Mn ratio x to 0.15 to 0.333. And achieves the required levels of the gyro sensitivity and the temperature stability of the null voltage (Japanese Patent Application No. Hei 8-2).
67380).

[0012]

However, in the case of a material for a vibrating gyroscope of a round bar type used for camera shake correction of a video camera or the like, Qm is required to be driven at a low voltage.
Is required to be higher. That is, in order to obtain sufficient sensitivity even at low voltage drive,
Qm is 100 over the entire operating temperature range (-40 ° C to + 80 ° C)
Must be maintained at 0 or more.

Further, as a material for a round bar type vibration gyro compatible with camera shake correction, it is necessary that the basic characteristics satisfy the requirements shown in Table 1 below.

However, on the other hand, in the conventional material,
The level of Qm did not reach the required condition, and it was not possible to provide a vibrating gyroscope capable of driving at a low voltage.

As described above, in order to obtain a round bar vibrating gyroscope that can be driven at a low voltage, the basic characteristics of the piezoelectric material must satisfy the requirements shown in Table 1 below.
This condition has been difficult to achieve with conventional materials.

[0016]

[Table 1]

Therefore, a general technical problem of the present invention is to
An object of the present invention is to provide a piezoelectric ceramic material having the characteristics shown in Table 1 above.

A special technical problem of the present invention is that Qm
Is to provide a piezoelectric ceramic material having a temperature of 600 or more in the entire temperature range of use (−40 ° C. to + 80 ° C.) and having both temperature stability of Qm and fr.

[0019]

Means for Solving the Problems] As a result of various studies for solving the above technical problem, the present inventors, the compositional formula _{Pb [(Mn a Sb 1-} a) b Ti c Zr d) In a porcelain material represented by O ₃ and a, b, c, and d each satisfy a relationship expressed by the following equation 2, the porcelain material is used as a main component, and Ln ₂ O ₃ (Ln : Ln is a porcelain material containing at least one of the lanthanoid elements), and it has been found that a piezoelectric ceramic material capable of providing a gyro having high temperature stability can be obtained, which has led to the present invention.

That is, according to the present invention, the composition formula Pb [(M
n _a Sb is represented by _{1-a) b Ti c Zr} d) O 3, a,
A piezoelectric ceramic material is obtained in which b, c, and d each satisfy a relationship represented by the following equation (2).

[0021]

(Equation 2)

Further, according to the present invention, when the weight of the main component made of the piezoelectric ceramic material and the weight of the main component as an auxiliary component added thereto is 100%, L% by weight of e
₂ O ₃ (where Ln is at least one of lanthanoid elements, e is a number of 0 <e <6.0) and f% by weight
SiO ₂ (where, f is 0 <f <number 5) of the piezoelectric ceramic material is obtained which comprises at least one of the.

The Mn content (a ×
It was confirmed that when b) was a fixed amount, that is, 0.012 or less, the Qm level was reduced.

When the ratio of PbTiO ₃ to PbZrO ₃ exceeds the above range, it was confirmed that Kp and εr were lowered, and sufficient sensitivity could not be obtained.

Further, in the present invention, a range in which the temperature change (Tkfr) of the resonance frequency is large is included in only the main component, and in this case, Tkfr is improved to 85 ppm / ° C.
It is necessary to prevent the sensitivity and the temperature stability of the null voltage from being lowered by the following.

In the present invention, the improvement of Tkfr is achieved by using Ln ₂ O ₃ (Ln: Y, Sc, La,
Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, D
It has been found that this can be achieved by adding the above-mentioned appropriate amount of at least one of the lanthanoid elements y, Ho, Er, Tm, Tb and Lu).

Further, in the present invention, it has been found that the Qm temperature characteristic can be achieved by adding the above-mentioned appropriate amount of SiO ₂ as an auxiliary component.

[0028]

Embodiments of the present invention will be described below.

(First Embodiment) PbO, TiO ₂ , ZrO ₂ , MnC
O ₃ , Sb ₂ O ₃ , La ₂ O ₃ , Nd ₂ O ₃ , Sm ₂ O
₃ and the like were weighed to obtain a desired composition. Put this raw material powder in an acrylic pot with zirconia balls,
Wet mixed for 20 hours. After the mixed powder was dehydrated and dried, it was prefired in an alumina mortar at 800 ° C. for 2 hours. The prefired powder was wet-pulverized with zirconia balls in an acrylic pot for 15 hours. Subsequently, the mixture was evaporated to dryness, and the obtained prefired and ground powder was mixed with bain and pressed to form a φ20 × 15 mm thick. The molded body was fired at 1200 ° C. to 1260 ° C. for 2 hours, and the obtained sintered body was processed into a thickness of 1 mm. Then, a silver paste was applied to both sides and baked at 450 ° C. to form an electrode. And

The sample obtained in this way was
Polarization treatment at 4kV / mm for 15 minutes.
r, electromechanical coupling coefficient Kp, and mechanical quality coefficient Qm were measured. Further, this sample was cut into a 2 × 10 mm rectangular plate, and Qm and resonance frequency fr were measured in a temperature range of −40 ° C. to + 80 ° C., and ΔQm / Qm and Tkfr were determined. The measurement results are shown in Table 2 below.

[0031]

[Table 2]

From Table 2 above, the following unsuitable items (A) to (D) to be excluded can be listed as reasons for determining the composition range of the piezoelectric material of the present invention.
That is, εr ≧ 500 and Kp ≧ 30 described in Table 1 above.
%, Qm ≧ 600, ΔQm / Qm ≦ 65%, Tkfr ≦
If the condition of 85 ppm / ° C was not satisfied, it was excluded from the scope of the present invention.

(A) When the Mn ratio a is 0.333 or less and the third component amount b is less than 0.01, Qm is low, which is not desirable (Nos. 1, 5 in Table 2). Further, when a is 0.
When it exceeds 60 or b exceeds 0.22, ΔQm / Qm
Or Tkfr becomes higher than 85 ppm / ° C., which is not preferable (No. 4, 8,
10-12). Further, the ratio of Mn to the whole (a ×
b) is preferably larger than 0.012 (No.
13).

(B) the amount c of PbTiO ₃ is less than 0.19;
When the amount d of PbZrO ₃ exceeds 0.58, εr and K
This is not preferable because p decreases (Nos. 9, 10). When c exceeds 0.61 and d is less than 0.35, Kp
Is not preferable because of low values (No. 15, 1
6).

(C) If the amount e of Ln ₂ O ₃ exceeds 5.5 wt%, Qm and Kp decrease, which is not suitable (No. 2).
0). In addition, when only one type was added, a remarkable effect was recognized when e was 2 wt% or more (Nos. 21 to 24).

(D) SiO ₂ has improved Qm temperature characteristics, but when the SiO ₂ amount f exceeds 5 wt%, it is not preferable because a hetero phase is formed (No. 31).

[0037] For the above reasons, the composition formula Pb [(Mn _a
Represented by _{Sb 1-a) b Ti c} Zr d) O 3, a, b,
A piezoelectric ceramic material in which c and d were expressed by the following equation (3) was obtained.

(Equation 3)

Further, the compositional formula _{Pb [(Mn a Sb 1-} a) b
Ti _c Zr _d ) O ₃ , wherein a, b, c, and d are each represented by the following equation (4), and the weight of the main component is 100%. Ln ₂ O ₃ added in the range of 0 <e ≦ 5 wt% (where Ln is Y, Sc, La, Ce,
Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, H
and at least one of the lanthanoid elements o, Er, Tm, Tb, and Lu).

[0039]

(Equation 4)

[0040]

As described above, the piezoelectric ceramic material according to the present invention has an appropriate electromechanical coupling coefficient and mechanical quality coefficient, and has excellent mechanical quality coefficient and temperature stability of resonance frequency. As a result, the use of the material of the present invention makes it possible to provide a high-precision, inexpensive, low-voltage driven piezoelectric vibrating gyroscope.

Claims (2)

[Claims] 1. A composition formula _{Pb [(Mn a Sb 1-} a) b Ti
_c Zr _d) is represented by O _3, piezoelectric ceramic materials a, b, c, d are each, characterized characterized by satisfying the relationship represented by equation (1) below. (Equation 1) 2. A method according to claim 1 and a main component consisting of a piezoelectric ceramic material according the weight of the main component is 100% as an auxiliary component which is added thereto, e wt% of Ln ₂ O ₃ (where , Ln is at least one of the lanthanoid elements, e is a number of 0 <e <6.0) and f wt% of SiO ₂
(However, f is a number of 0 <f <5).