JP2001302348A - Piezoelectric ceramic composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric ceramic composition having a large piezoelectric displacement under a high electric field, a small temperature change of a specific dielectric constant and an excellent insulation property. SOLUTION: The piezoelectric ceramic composition is composed of a mother component, which is expressed by a composition formula, aPbTiO3+bPbZrO3+ cPb(Ni1/3Nb2/3)O3, (a+b+c=100) and exists on a line formed by connecting point I (a=35 mol%, b=30 mol%, c=35 mol%), point J (a=44 mol%, b=16 mol%, c=40 mol%), point K (a=50 mol%, b=4 mol%, c=10 mol%) and point L (a=40 mol%, b=50 mol%, c=10 mol%) and in the region surrounded by the 4 points, in which the Pb content is adjusted and auxiliary components are added to improve d33.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric ceramic composition containing lead zirconate titanate as a main component, and in particular, has a large piezoelectric displacement under a high electric field and a change in relative permittivity with temperature. The present invention relates to a piezoelectric ceramic composition which is small and has excellent insulation properties.

[0002]

2. Description of the Related Art Conventionally, PbTi has been used as a piezoelectric ceramic material.
Piezoelectric ceramics containing O ₃ or PbZrO ₃ as a main component (hereinafter referred to as PZT-based piezoelectric ceramics) and multi-component PZT-based piezoelectric ceramics in which composite perovskites are dissolved as third and fourth components are used as piezoelectric constants. Is widely used as a material for actuators including piezoelectric vibrators.

[0003] Materials of these systems generally have a piezoelectric constant (d) at a composition near the morphotopic phase boundary (MPB).
As a material for actuators, piezoelectric ceramic materials having a composition in the vicinity of the MPB have been widely used as a material for an actuator because the characteristics contributing to piezoelectric displacement such as a constant are improved.

[0004]

However, the piezoelectric constant is a value obtained by a resonance-anti-resonance method generally shown by EMAS-6100 or the like, and is basically a low electric field (about several hundred V / (approximately m) when applied. On the other hand, the driving electric field in an actual piezoelectric actuator is several hundred kV / m to several thousand kV / m, and the piezoelectric constant obtained by the above method may not have a practical meaning. Furthermore, with the expansion of the range of use of piezoelectric actuators in recent years, there has been a demand for characteristic stability over a wide temperature range, particularly temperature stability of capacitance. For example, when a piezoelectric actuator is used as a component for an automobile, the stability of characteristics in a wide temperature range of −40 ° C. to 170 ° C. may be required depending on the use environment. On the other hand, in general, the piezoelectric ceramic material having a composition near the MPB has a large variation in the relative dielectric constant with temperature, and thus has a problem in the stability of the actuator characteristics in a wide temperature range, particularly in the stability of the capacitance.

[0005] PbTiO ₃ -PbZrO ₃ -Pb (Ni
_1/3 Nb _{2/3) O 3} system (hereinafter, the piezoelectric ceramic composition is referred to as PNN-PZT system) has a large d constant, is utilized as a piezoelectric ceramic material for Akuyueta element.

However, as the range of application of the piezoelectric actuator is expanded, a material having a larger d constant is required. Further, the piezoelectric ceramic material of this system has a relatively small electric resistivity, and when used for an element having a thickness of about 100 μm, such as a laminated piezoelectric element, the voltage that can be applied cannot be increased, and sufficient characteristics can be obtained. There are problems such as being unable to be pulled out and causing dielectric breakdown during use.

Further, since the PNN-PZT piezoelectric ceramic material has a large variation in electric resistivity with temperature, there is a problem that the reliability is further lowered particularly when used in the above-mentioned wide temperature range. there were.

Therefore, one technical problem of the present invention is that the piezoelectric strain constant when a high voltage is applied is large, the change in relative permittivity with temperature is small, and the electric resistivity in a high temperature range is large. An object of the present invention is to provide a piezoelectric ceramic composition having stable properties in a temperature range and excellent in insulating properties.

A special technical object of the present invention is to provide a piezoelectric ceramic composition which is extremely useful as a material for an actuator.

[0010]

Means for Solving the Problems The present inventor has proposed a composition formula aP
bTiO ₃ + bPbZrO ₃ + CPb (Ni _1/3 Nb
As a result of various investigations on the piezoelectric displacement characteristics of the piezoelectric ceramic composition represented by _2/3 ) O ₃ (a + b + c = 100), the composition range was within a predetermined range, and the Pb amount was reduced.
By adding a lanthanoid element such as La and Nd and an alkaline earth element such as Sr as subcomponents, a piezoelectric displacement when a DC electric field of 500 kV / m is applied in the same direction as the polarization axis (hereinafter, d33 (500 kV)) ) Has been found to be improved as compared with the case where only the base component is used, and to have less deterioration in the temperature change of the relative dielectric constant in the range of −40 ° C. to 170 ° C. In addition, for the piezoelectric ceramic material described above,
Converting Mn to an oxide represented by MnO, 0 to 0.0
It has been found that the content of 5 wt% (excluding 0) improves the insulating properties of the piezoelectric ceramic composition,
The present invention has been accomplished.

That is, according to the present invention, the composition formula aPbTi
O ₃ + bPbZrO ₃ + cPb (Ni _1/3 N
b _2/3 ) O ₃ (a + b + c = 100), and its composition range is point I (a = 35 mol%, b = 30 in FIG. 1).
mol%, c = 35 mol%), J point (a = 44 mol)
%, B = 16 mol%, c = 40 mol%), point K (a
= 50 mol%, b = 40 mol%, c = 10 mol
%) And L point (a = 40 mol%, b = 50 mol)
%, C = 10 mol%), and the range defined as a region surrounded by these four points on the line connecting the respective composition points was used as a mother component, and the amount of Pb was reduced in the range of 0 to 3 mol% (excluding 0). When a DC electric field of 500 kV / m is applied in the same direction as the polarization axis, the piezoelectric displacement shows 500 pm / V or more, and the temperature change of the relative dielectric constant is 300% in the range of -40 ° C to 170 ° C. A piezoelectric ceramic composition characterized by the following is obtained.

Further, according to the present invention, in the piezoelectric ceramic composition, at least one of a lanthanoid element such as La and Nd and an alkaline earth element such as Sr is 0 to 7 mol% (0 Excluding)
And a piezoelectric displacement of 500 pm / V or more when a DC electric field of 500 kV / m is applied in the same direction as the polarization axis with the Pb content reduced in the range of 0 to 5 mol% (excluding 0); In addition, a piezoelectric ceramic composition characterized in that the temperature change of the relative dielectric constant is 300% or less in the range of 40 ° C to 170 ° C.

Further, according to the present invention, the composition formula aPbTi
O ₃ + bPbZrO ₃ + cPb (Ni _1/3 N
b _2/3 ) O ₃ (a + b + c = 100), and its composition range is point I (a = 35 mol%, b = 30 in FIG. 1).
mol%, c = 35 mol%), J point (a = 44 mol)
%, B = 16 mol%, c = 40 mol%), point K (a
= 50 mol%, b = 40 mol%, c = 10 mol
%) And L point (a = 40 mol%, b = 50 mol)
%, C = 10 mol%) on the line connecting the respective composition points and a range surrounded by the four points is defined as a mother component, and La,
One or more of lanthanoid elements such as Nd and alkaline earth elements such as Sr are added in the range of 0 to 5 mol% (excluding 0).
The piezoelectric displacement when applying a DC electric field of 500 pm /
The piezoelectric ceramic composition is characterized in that the piezoelectric ceramic composition exhibits a temperature of not less than V and a temperature change of the relative dielectric constant of 300% or less in a range of -40 ° C to 170 ° C.

According to the present invention, in any of the piezoelectric ceramic compositions described above, Mn is converted to an oxide represented by MnO in an amount of 0 to 0.05 wt% (0 is included) based on the total amount. And a specific resistance at −40 ° C. to 170 ° C. of 1.0 × 10 ¹¹ Ω · cm or more.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the piezoelectric ceramic composition of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing the composition of the mother component of the piezoelectric ceramic composition of the present invention in triangular coordinates.

The piezoelectric ceramic composition of the present invention has a composition formula aPb
TiO ₃ + bPbZrO ₃ + cPb (Ni _1/3 Nb
_2/3 ) O ₃ (a + b + c = 100), and its composition range is point I in FIG. 1 (a = 35 mol%, b = 30 m
ol%, c = 35 mol%), J point (a = 44 mol)
%, B = 16 mol%, c = 40 mol%), point K (a
= 50 mol%, b = 40 mol%, c = 10 mol
%) And L point (a = 40 mol%, b = 50 mol)
%, C = 10 mol%) on a line connecting the respective composition points and a range surrounded by these four points is defined as a mother component.

One example of the piezoelectric porcelain composition of the present invention is to reduce the amount of Pb in the range of 0 to 3 mol% (excluding 0) from this base component, so that 500 k in the same direction as the polarization axis.
When a DC electric field of V / m is applied, the piezoelectric displacement is 500
It is a piezoelectric ceramic composition which shows pm / V or more and has a relative dielectric constant with a temperature change of 300% or less in a range of -40 ° C to 170 ° C.

Another example of the piezoelectric ceramic composition of the present invention is the piezoelectric ceramic composition, wherein at least one of a lanthanoid element such as La and Nd and an alkaline earth element such as Sr is used with respect to a mother component. Seed is 0-7 mol% (0
), And the Pb content is 0 to 5 mol%
(Excluding 0), the piezoelectric displacement when a DC electric field of 500 kV / m is applied in the same direction as the polarization axis shows 500 pm / V or more, and 4
In the range of 0 ° C to 170 ° C, the temperature change of the relative dielectric constant is 300
% Or less.

Further, still another example of the piezoelectric ceramic composition of the present invention is a piezoelectric ceramic composition according to the present invention, wherein one or more of lanthanoid elements such as La and Nd and alkaline earth elements such as Sr are contained in the mother component with respect to the total amount. By adding in the range of 0 to 5 mol% (excluding 0), 500% in the same direction as the polarization axis.
The piezoelectric displacement when applying a DC electric field of kV / m is 50
A piezoelectric ceramic composition exhibiting 0 pm / V or more, and having a temperature change in relative dielectric constant of 300% or less in a range of -40 ° C to 170 ° C.

Further, another example of the piezoelectric ceramic composition of the present invention is that a lanthanoid element such as La and Nd and an alkaline earth element such as Sr are used with respect to the mother component. A DC electric field of 500 kV / m in the same direction as the polarization axis by adding Pb in the range of 0 to 7 mol% (except 0) and decreasing the amount of Pb in the range of 0 to 5 mol% (except 0). Is greater than 500 pm / V, and 40 ° C. to 1
The piezoelectric ceramic composition has a relative dielectric constant with a temperature change of 300% or less in a temperature range of 70 ° C.

Further, another example of the piezoelectric ceramic composition of the present invention is the piezoelectric ceramic composition of any of the above-described piezoelectric ceramic compositions, wherein Mn is converted to an oxide represented by MnO with respect to a total amount of 0 to 0.
It is contained at a rate of 0.05 wt% (excluding 0), and has a specific resistance of 1.0 at -40 ° C to 170 ° C.
It is a piezoelectric ceramic composition having × 10 ¹¹ Ω · cm or more.

Next, an embodiment of the present invention will be described.

(First Embodiment) Titanium oxide (TiO)
₂ ), raw materials of zirconium oxide (ZrO ₂ ), nickel oxide (NiO), niobium oxide (Nb ₂ O ₅ ) and lead oxide (PbO) with a reduced Pb content are weighed so as to have a target composition, and these raw materials are weighed. The powder was placed in an acrylic pot together with zirconia balls and wet mixed for 20 hours.

Next, after dehydrating and drying these mixed powders, they were pre-fired in an alumina mortar, and each pre-fired powder was wet-pulverized with zirconia balls in an acrylic pot for 15 hours.
Subsequently, a binder was mixed with the pre-fired pulverized powder obtained by dehydration and drying, and the mixture was pressurized to give a diameter (φ) of 20 × thickness (T) of 3 mm.
Molded. This molded body is heated at 1100 ° C. to 1300 ° C. for 2 hours.
After firing for a time, each sintered body was processed to a thickness of 1 mm, silver paste was applied to both surfaces and baked at 450 ° C. to form electrodes, thereby obtaining samples having different compositions. Each sample obtained in this way was polarized at 3 kV / mm, and was subjected to a 1
Temperature characteristics of relative permittivity εr of kHz were measured. The temperature characteristics are in the range of -40 ° C to 400 ° C.
After holding for one minute, εr at 1 KHz at each temperature was measured. For d33 (500 kV), a voltage of OV → 500 V → 0 V is applied to the sample supported at the center point at a constant speed for 2 seconds, and the displacement in the sample thickness direction is measured using a fringe counter type laser displacement meter. Was measured and calculated.

FIG. 2 is a diagram showing an example of measurement of d33 (500 kV). As shown in FIG. 2, when a DC voltage of 500 V was applied to a measurement sample having a thickness of 1 mm (electric field strength of 500 kV
/ M) was calculated as d33 (500 kV).

Samples 1 to 26 in Tables 1 and 2 below show the parent component and the d33 (500 kV) of the Pb-reducing material at -40 ° C.
The temperature change rate of εr at 170 ° C. is shown. In the table, sample Nos. Indicates outside the scope of the present invention.

From Table 1 above, the following can be read. That is, an improvement in d33 (500 kV) is observed while maintaining the temperature characteristics by reducing the amount of Pb. d33 (5
The improvement of 00 kV) gradually decreases with the peak amount of Pb decreasing at about 1.5 mol%. If the amount of Pb reduction is excessive, the sinterability of the sample starts to decrease, the sintering temperature increases, and the characteristics of the sample deteriorate, which is not preferable. Sample No. 25,2
6 means that the value of d33 (500 kV) is 500p
Since it is less than m / V, it is not included in the scope of the present invention. From these results, it can be seen that the target characteristics of the present invention are achieved when the Pb reduction amount is in the range of 0 to 3 mol% (excluding 0).

(Second Embodiment) Lead oxide (PbO),
Titanium oxide (TiO ₂ ), zirconium oxide (Zr
O ₂ ), nickel oxide (NiO), niobium oxide (Nb ₂
O ₅₎ mother ingredient material and additive element as a lanthanum oxide _{(La 2 O} 3) of neodymium oxide _{(Nd 2 O} 3), strontium carbonate (SrCO ₃₎ was weighed so as to target composition, the first embodiment Samples were prepared and various characteristics were evaluated in the same manner as in the above embodiment.

Sample Nos. In Tables 1 and 2 below 27-39
In addition, d33 (500 kV) of the additive sample and -40 ° C
The temperature change rate of εr at 170 ° C. is shown. Sample No. marked with * in Tables 1 and 2 below. Indicates outside the scope of the present invention. The following can be read from Table 1 below. In other words, d33 (500 k
V), and the value of Δεr deteriorates. Sample No. to which Sr was excessively added. 30 is Δεr 3
Since it exceeds 00%, it is excluded from the claims. The sample No. Sample No. 39 was damaged during sample preparation and could not be measured.

(Third Embodiment) Lead oxide (PbO),
Titanium oxide (ZrO ₂ ), zirconium oxide (Zr
O ₂ ), nickel oxide (NiO), niobium oxide (Nb ₂
First, lanthanum oxide (La ₂ O ₃ ), neodymium oxide (Nd ₂ O ₃ ), and strontium carbonate (SrCO ₃ ) were weighed to obtain the target composition and the additive element of O ₅ ). Samples were prepared in the same manner as in the form, and various characteristics were evaluated. Sample No. in Table 2 below. 40 to 64 show d33 (500 kV) of the sample and the temperature change rate of εr at −40 ° C. to 170 ° C. Sample No. marked with * in Table 2
Indicates outside the scope of the present invention. The following can be read from Table 2 below. By decreasing the amount of Pb together with the addition of the additive, a larger amount of the additive can be added as compared with the case where the additive is simply added, and the deterioration of Δεr is small. Further, the sample No. having a balance of about 0.99 mol by adding the Pb reduction amount and the addition amount. 42, 47, 54, etc. show good d33 (500 kV) even if the added amount is relatively small.

[0032]

[Table 1]

[0033]

[Table 2]

(Fourth Embodiment) Lead oxide (PbO),
Titanium oxide (TiO ₂ ), zirconium oxide (Zr
O ₂ ), nickel oxide (NiO), niobium oxide (Nb ₂
O ₅₎ mother ingredient material and additive element as a lanthanum oxide _{(La 2 O} 3) of neodymium oxide _{(Nd 2 O} 3), strontium carbonate (SrCO _3), manganese carbonate (MnC
O ₃ ) was weighed so as to have a target composition, a sample was prepared in the same manner as in the first embodiment, and the specific resistance was measured at −40 ° C. and 170 ° C., respectively. FIG. 3 shows an example of the result.
From FIG. 3, although the specific resistance decreases in the constant temperature region, Mn
It can be seen that the specific resistance is remarkably improved only by adding a very small amount of MnCO ₃ as O, and the target value of the present invention is satisfied. Further, it was found that when the amount of MnO added exceeds 0.05 wt%, no further improvement in the specific resistance can be expected. Excessive addition of MnO also tends to degrade the piezoelectric properties such as the piezoelectric constant, so it can be determined that 0.05 wt% or less is an appropriate value for the target of the present invention.

[0035]

As described above, according to the present invention, the piezoelectric strain constant at the time of applying a high voltage is large, the change in the relative dielectric constant with temperature is small, and the electric resistivity in the high temperature range is large. It can provide a piezoelectric ceramic composition having stable characteristics over a wide temperature range and excellent insulation properties, and is extremely useful as a material for an actuator.

[Brief description of the drawings]

FIG. 1 is a diagram showing the composition of a mother component of a piezoelectric ceramic composition of the present invention in triangular coordinates.

FIG. 2 shows d33 shown in the first embodiment of the present invention.
FIG. 4 is a diagram illustrating a concept of a (500 kV) measuring method, and is a diagram illustrating a relationship between an applied voltage and a piezoelectric displacement.

FIG. 3 is a diagram showing a relationship between an added amount of MnO and a specific resistance according to a fourth embodiment of the present invention.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yoichi Mamiya 6-7-1, Koriyama, Taishiro-ku, Sendai, Miyagi Prefecture Tokin Co., Ltd. (72) Inventor Yoshihiro Kawakami 231 Sugazawa, Yamazaki-cho, Shiso-gun, Hyogo Tokin F-term (reference) in Ceramics Co., Ltd. 4G031 AA02 AA05 AA07 AA09 AA11 AA12 AA14 AA19 AA23 AA32 BA09 BA10 GA02

Claims (4)

[Claims] 1. Composition formula aPbTiO ₃ + bPbZrO <sub>3
+ CPb (Ni 1/3 Nb</sub> 2/3) O 3 (a + b + c =
100), and the composition range of the point I (a =
35 mol%, b = 30 mol%, c = 35 mol
%), J point (a = 44 mol%, b = 16 mol%, c
= 40 mol%), point K (a = 50 mol%, b = 40)
mol%, c = 10 mol%) and L point (a = 40
mol%, b = 50 mol%, and c = 10 mol%) on the line connecting the respective composition points and the range defined by the area surrounded by these four points is defined as the mother component, and the Pb content is 0 to 3 mol% (excluding 0). Reduced in range, in the same direction as the polarization axis, 500
The piezoelectric displacement when applying a DC electric field of kV / m is 50
A piezoelectric ceramic composition exhibiting 0 pm / V or more, and having a temperature change of relative permittivity of 300% or less in a range of -40 ° C to 170 ° C. 2. The piezoelectric ceramic composition according to claim 1, wherein at least one of a lanthanoid element such as La and Nd and an alkaline earth element such as Sr is 0 to 7 mol% (excluding 0) based on the mother component. ) And Pb
The amount was reduced in the range of 0 to 5 mol% (excluding 0),
When a DC electric field of 500 kV / m is applied in the same direction as the polarization axis, the piezoelectric displacement shows 500 pm / V or more, and the temperature change of the relative dielectric constant is 300% or less in the range of 40 ° C. to 170 ° C. A piezoelectric ceramic composition characterized by the following. 3. Composition formula aPbTiO ₃ + bPbZrO <sub>3
+ CPb (Ni 1/3 Nb</sub> 2/3) O 3 (a + b + c =
100), and the composition range of the point I (a =
35 mol%, b = 30 mol%, c = 35 mol
%), J point (a = 44 mol%, b = 16 mol%, c
= 40 mol%), point K (a = 50 mol%, b = 40)
mol%, c = 10 mol%) and L point (a = 40
mol%, b = 50 mol%, c = 10 mol%) on the line connecting the respective composition points and the range defined by the area surrounded by these four points as mother components, and lanthanoid elements such as La and Nd and alkaline earths such as Sr. One or more of the class elements
When a DC electric field of 500 kV / m is applied in the same direction as the polarization axis in a range of 5 mol% (excluding 0), the piezoelectric displacement is 500 pm / V or more, and -40.
Temperature change of relative permittivity is 300% in the range of ℃ ~ 170 ℃
A piezoelectric ceramic composition characterized by the following. 4. The piezoelectric ceramic composition according to claim 1, wherein Mn is MnO based on the total amount.
0 to 0.05 wt% (0
Wherein the specific resistance at −40 ° C. to 170 ° C. is 1.0 × 10 ¹¹ Ω · cm or more.