JP2009242175A - Piezoelectric ceramic composition, piezoelectric element and resonator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric ceramic composition which provides sufficiently high Q<SB>max</SB>, and also, suppresses a variation in the temperature properties of oscillation frequency F<SB>0</SB>caused by variation in firing temperature when being used for a resonator utilizing the third-order harmonic mode of thickness longitudinal vibration. <P>SOLUTION: The piezoelectric ceramic composition comprises: a composite oxide containing lead titanate and an Mn element; and an Mo element, wherein the content of the Mo element expressed in terms of MoO<SB>3</SB>is >0 to 0.6 pts.mass with respect to 100 pts.mass of the compound oxide. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a piezoelectric ceramic composition, a piezoelectric element, and an oscillator.

  A piezoelectric ceramic composition has a piezoelectric effect that causes electrical polarization when subjected to pressure from the outside, and an inverse piezoelectric effect that causes distortion when an electric field is applied from the outside, so that mutual conversion between electrical energy and mechanical energy is achieved. It is used as a material for performing. Such piezoelectric ceramic compositions are used in various products such as resonators, filters, sensors, actuators, ignition elements or ultrasonic motors.

For example, Patent Document 1 below discloses that Pb _a [(Zn _1/3 Nb _1/3 ) _x Ti _y Zr _z ] O ₃ (0.96 ≦ a ≦ 1.03, x + y + z = 1, 0.05 ≦ x ≦ 0.40, 0.1 ≦ y ≦ 0.5, 0.2 ≦ z ≦ 0.6), and 0.05 to 3.00 in terms of Mo as MoO ₃ as the first subcomponent. A piezoelectric ceramic composition containing within a mass% range is disclosed.
JP 2005-132705 A

When using an oscillator comprising a piezoelectric element oscillating circuit, Q _max of the piezoelectric element in order to ensure the oscillation characteristics be large. In recent years, it is also required that the temperature characteristic of the oscillation frequency F ₀ is good. Note that Q _max is tan θ _max when the maximum value of the phase angle is θ _max (unit: deg). In other words, the resonance frequency fr and anti-resonance when X is reactance and R is resistance This is the maximum value of Q (= | X | / R) between the frequency fa. Further, “the temperature characteristic of the oscillation frequency F ₀ is good” means that when the temperature of the oscillator or the oscillation circuit including the oscillator changes, the ratio of the change amount of the oscillation frequency F _{0 to} the change amount of the temperature is small. This means that the oscillation frequency F ₀ is stable with respect to temperature change.

However, in the case of an oscillator that uses the third harmonic of the thickness longitudinal vibration (third harmonic mode of the thickness longitudinal vibration), the frequency band used is high compared to an oscillator that uses the bending vibration mode. Conventional piezoelectric ceramic compositions have not necessarily been sufficiently satisfactory in terms of the temperature characteristics of Q _max and oscillation frequency F ₀ .

Further, in the conventional piezoelectric ceramic composition, when the piezoelectric ceramic composition is formed by firing the raw material composition of the piezoelectric ceramic composition, if the firing temperature is low, the sintered density of the obtained piezoelectric ceramic composition is low. When the firing temperature is high, the composition of the piezoelectric ceramic composition is changed by evaporation of the lead component, and the temperature characteristic of the oscillation frequency F ₀ tends to be lowered. That is, in the conventional piezoelectric ceramic composition, the temperature characteristic of the oscillation frequency F ₀ tends to change greatly according to the fluctuation of the firing temperature. Therefore, there has been a problem that, during mass production of a product using the piezoelectric ceramic composition, variation in temperature characteristics of the oscillation frequency F ₀ of the product becomes large due to variation in temperature in the firing furnace.

Therefore, the present invention makes it possible to obtain a sufficiently high Q _max when used in an oscillator using the third harmonic mode of thickness longitudinal vibration, and the oscillation frequency F ₀ due to fluctuations in the firing temperature. An object of the present invention is to provide a piezoelectric ceramic composition that can suppress variations in temperature characteristics of the piezoelectric ceramic, a piezoelectric element made of the piezoelectric ceramic composition, and an oscillator using the piezoelectric element.

The piezoelectric ceramic composition of the present invention includes a composite oxide containing lead titanate and Mn element and Mo element, and the content of Mo element converted to MoO ₃ is 100 parts by mass of the composite oxide. On the other hand, it is larger than 0 mass part and below 0.6 mass part.

  The piezoelectric element of the present invention is composed of the piezoelectric ceramic composition of the present invention.

  An oscillator according to the present invention includes the piezoelectric element according to the present invention and a pair of electrodes facing each other with the piezoelectric element interposed therebetween.

In the oscillator according to the present invention, since the piezoelectric element is made of a piezoelectric ceramic composition having the above composition, a sufficiently high Q is obtained even when used as an oscillator utilizing the third harmonic mode of thickness longitudinal vibration. _{In addition} to obtaining _max , it is possible to suppress variations in the temperature characteristics of the oscillation frequency F ₀ due to fluctuations in the firing temperature.

In the piezoelectric ceramic composition of the present invention, the complex oxide is
_{(Pb α M β) (Ti} 1- (x + y + z) Zr x Mn y Nb z) O 3
[Wherein, M represents at least one selected from the group consisting of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Sr. ]
0.84 ≦ α <1.00, 0 <β ≦ 0.10, 0 ≦ x <0.40,
It is preferable to satisfy 0.02 ≦ y <0.05 and 0 ≦ z ≦ 0.1.

  Thereby, the effect by this invention is show | played especially notably.

According to the present invention, it is possible to obtain a sufficiently high Q _max when used in an oscillator that utilizes the third harmonic mode of thickness longitudinal vibration, and the oscillation frequency F ₀ caused by fluctuations in the firing temperature. There are provided a piezoelectric magnetic composition capable of suppressing variations in temperature characteristics of the piezoelectric element, a piezoelectric element composed of the piezoelectric ceramic composition, and an oscillator using the piezoelectric element. In addition, according to the present invention, since the piezoelectric ceramic composition has a high Curie temperature, it is possible to obtain a piezoelectric element that is not easily depolarized even at a high temperature.

  Hereinafter, preferred embodiments of an oscillator using the piezoelectric ceramic composition of the present invention will be described with reference to the drawings as appropriate. However, the present invention is not limited to the following embodiments.

  FIG. 1 is a perspective view showing an embodiment of an oscillator, and FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1 and 2 includes a rectangular parallelepiped piezoelectric element 2 and a pair of vibrating electrodes 3 facing each other with the piezoelectric element 2 interposed therebetween. One vibration electrode 3 is formed at the center of the upper surface of the piezoelectric element 2, and another vibration electrode 3 is formed at the center of the lower surface of the piezoelectric element 2. The piezoelectric element 2 is made of the piezoelectric ceramic composition of the present embodiment. The vibrating electrode 3 is made of a conductive material such as Ag.

  The size of the piezoelectric element 2 may be an appropriate size depending on the application, and is, for example, about 1.0 to 4.0 mm in length, 0.5 to 4.0 mm in width, and about 50 to 300 μm in thickness. The shape of the vibrating electrode 3 is usually circular, and its dimensions are, for example, a diameter of 0.5 to 3.0 mm and a thickness of about 0.5 to 5 μm.

The piezoelectric ceramic composition includes a perovskite structure type composite oxide containing lead titanate and an Mn element as a main component. Moreover, the said piezoelectric ceramic composition contains Mo element as a subcomponent. The content of Mo element when converted to MoO ₃ is greater than 0 parts by mass and less than or equal to 0.6 parts by mass, preferably 0.05 parts by mass or more and 0.6 parts by mass with respect to 100 parts by mass of the composite oxide. Less than 0.05 parts by mass, and more preferably 0.05 parts by mass or more and 0.2 parts by mass or less. When the content of Mo element converted to MoO ₃ is 0 part by mass, variation in temperature characteristics of the oscillation frequency F ₀ tends to increase. On the other hand, when the content of Mo element converted to MoO ₃ is larger than 0.6 parts by mass, variation in temperature characteristics of the oscillation frequency F ₀ tends to increase, and Q _max tends to decrease. By setting the content of Mo element converted to MoO ₃ within the above range, these tendencies can be suppressed.

The composite oxide contained in the piezoelectric ceramic composition has a composition represented by the following chemical formula (1).
_{(Pb α M β) (Ti} 1- (x + y + z) Zr x Mn y Nb z) O 3 ··· formula (1)
In formula (1), M is at least one element selected from the group consisting of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Sr. Represents. Among these elements, La or Sr is preferable as the element M because it is easy to obtain the effects of the present invention. Further, La and Sr may be used in combination as the element M.

  The composite oxide preferably satisfies 0.84 ≦ α <1.00. If α is less than 0.84, the resistivity of the piezoelectric ceramic composition is likely to decrease, and thus there is a tendency that polarization processing for imparting piezoelectricity to the piezoelectric ceramic composition is difficult at the time of manufacturing the piezoelectric element 2. . When α is 1.00 or more, the mechanical strength of the sintered body (piezoelectric element) made of the piezoelectric ceramic composition tends to decrease. By setting α within the above range, these tendencies can be suppressed. From the same viewpoint, it is preferable that 0.84 ≦ α ≦ 0.96.

The composite oxide preferably satisfies 0 <β ≦ 0.10. When the composite oxide constituting the piezoelectric ceramic composition contains M within the range of 0 <β ≦ 0.08, Q _max is improved. If β is 0, the sinterability of the piezoelectric element 2 tends to deteriorate, and piezoelectric characteristics may not be obtained appropriately. On the other hand, if β exceeds 0.10, the Curie temperature decreases, and the piezoelectric element 2 tends to be easily depolarized when heated. By setting β within the above range, these tendencies can be suppressed. From the same viewpoint, it is preferable that 0.04 ≦ β ≦ 0.09.

The composite oxide preferably satisfies 0 ≦ x <0.40. When x is 0.40 or more, the Curie temperature decreases, and when the piezoelectric element 2 is heated, it tends to be depolarized and Q _max tends to be small. By setting x within the above range, these tendencies can be suppressed. From the same viewpoint, it is preferable that 0 ≦ x ≦ 0.20.

The composite oxide preferably satisfies 0.02 ≦ y <0.05. If y is less than 0.020, Q _max tends to be small. In addition, when y is 0.05 or more, the resistivity of the piezoelectric ceramic composition is likely to decrease, and therefore, it is difficult to perform a polarization treatment for imparting piezoelectricity to the piezoelectric ceramic composition at the time of manufacturing the piezoelectric element 2. There is. By setting y within the above range, these tendencies can be suppressed. From the same viewpoint, it is preferable that 0.02 ≦ y ≦ 0.04.

  The composite oxide preferably satisfies 0 ≦ z ≦ 0.1. When z exceeds 0.1, the Curie temperature decreases, and when the piezoelectric element 2 is heated, it tends to be easily depolarized. By setting z within the above range, these tendencies can be suppressed. From the same viewpoint, it is preferable that 0 ≦ z ≦ 0.09.

  The piezoelectric ceramic composition may contain a compound other than the composite oxide having the composition represented by the chemical formula (1) as an impurity or a trace additive. Examples of such compounds include oxides of Na, Al, Si, P, K, Ca, Fe, Cu, Zn, Hf, Ta, or W. In addition, when the said piezoelectric ceramic composition contains these oxides etc., the total value of the content rate of each oxide in a piezoelectric ceramic composition is 0. 0 of the whole piezoelectric ceramic composition in conversion of the oxide of each element. It is preferable that it is 3 weight% or less. In other words, it is preferable that 99.7% by weight or more of the piezoelectric ceramic composition is an oxide represented by the formula (1). In this case, the piezoelectric ceramic composition itself has a composition represented by the formula (1).

In this embodiment, since the piezoelectric element 2 included in the oscillator 1 is formed of the piezoelectric ceramic composition, the oscillator 1 is used in an oscillation circuit as an oscillator using a third harmonic mode of thickness longitudinal vibration. Sometimes, a sufficiently high Q _max can be obtained, a satisfactory temperature characteristic of the oscillation frequency F ₀ can be achieved, and variations in the temperature characteristic of the oscillation frequency F ₀ can be suppressed. In addition, the Curie temperature of the piezoelectric ceramic composition can be set to a desired value.

  The above-described method for manufacturing the oscillator 1 according to the present embodiment mainly includes a step of granulating the raw material powder of the piezoelectric element 2, a step of pressing the raw material powder to form a formed body, and firing the formed body. A step of forming the sintered body, a step of polarizing the sintered body to form the piezoelectric element 2, and a step of forming the vibrating electrode 3 on the piezoelectric element 2. Hereinafter, a method for manufacturing the oscillator 1 will be specifically described.

First, a starting material for preparing a piezoelectric ceramic composition is prepared. As the starting material, oxides of each element constituting the composite oxide having the perovskite structure represented by the above chemical formula (1) and / or compounds that become these oxides after firing (carbonate, hydroxide, oxalic acid) Salt, nitrate, etc.). As a specific starting material, PbO, a compound of a lanthanoid element (for example, La ₂ O ₃ , La (OH) _3, etc.), TiO ₂ , ZrO ₂ , MnO _2, MnCO ₃ , Nb ₂ O ₅ or the like can be used. That's fine. Each of these starting materials is blended in a weight ratio such that a composite oxide having a composition represented by the above chemical formula (1) is formed after firing. Further, a Mo compound (for example, MoO ₃ or the like), which is a subcomponent, is added to the blended starting material. In the piezoelectric ceramic composition obtained after firing, the addition amount of the Mo compound is such that the content of Mo element converted to MoO ₃ is greater than 0 parts by mass and 0.6 parts by mass with respect to 100 parts by mass of the composite oxide. Adjust so that:

  Next, the blended starting materials are wet mixed by a ball mill or the like. The wet-mixed starting material is temporarily molded to form a temporary molded body, and the temporary molded body is temporarily fired. By this temporary baking, the temporary baking body containing the piezoelectric ceramic composition of this embodiment mentioned above is obtained. The calcination temperature is preferably 700 to 1050 ° C., and the calcination time is preferably about 1 to 3 hours. If the pre-baking temperature is too low, the chemical reaction tends not to proceed sufficiently in the temporary molded body. If the temporary baking temperature is too high, the temporary molded body starts to sinter, and the subsequent pulverization tends to be difficult. is there. The pre-baking may be performed in the air, or may be performed in an atmosphere having a higher oxygen partial pressure or in a pure oxygen atmosphere than in the air. Further, the wet-mixed starting material may be temporarily fired as it is without being temporarily formed.

  The obtained calcined product is slurried and finely pulverized (wet pulverized) with a ball mill or the like, and then dried to obtain a fine powder. If necessary, a binder is added to the obtained fine powder to granulate the raw material powder. In addition, it is preferable to use alcohol, such as water and ethanol, or a mixed solvent of water and ethanol, as a solvent for slurrying the calcined body. Examples of the binder added to the fine powder include commonly used organic binders such as polyvinyl alcohol, polyvinyl alcohol added with a dispersant, and ethyl cellulose.

  Next, a compact is formed by press molding the raw material powder. What is necessary is just to set the load at the time of press molding to 100-400 Mpa, for example.

  The resulting molded body is subjected to binder removal treatment. The binder removal treatment is preferably performed at a temperature of 300 to 700 ° C. for about 0.5 to 5 hours. The binder removal treatment may be performed in the air, or may be performed in an atmosphere having a higher oxygen partial pressure than the air or a pure oxygen atmosphere.

  After the binder removal treatment, the compact is fired to obtain a sintered body (piezoelectric ceramic composition). The firing temperature may be about 1050 to 1250 ° C., and the firing time may be about 1 to 8 hours. In addition, the binder removal treatment and firing of the molded body may be performed continuously or separately.

  Next, the sintered body is cut into a thin plate, and this is lapped and surface-treated. When the sintered body is cut, a cutting machine such as a cutter, a slicer, or a dicing saw can be used. After the surface processing, provisional electrodes for polarization treatment are formed on both surfaces of the thin plate-like sintered body. As the conductive material constituting the temporary electrode, Cu is preferable because it can be easily removed by etching with a ferric chloride solution. For forming the temporary electrode, it is preferable to use a vacuum deposition method or sputtering.

  A polarization electric field is applied to a thin plate-like sintered body on which a temporary electrode for polarization treatment is formed, and polarization treatment is performed. The conditions for the polarization treatment may be appropriately determined according to the composition of the piezoelectric ceramic composition contained in the sintered body. Usually, the temperature of the sintered body subjected to the polarization treatment is 150 to 300 ° C., and a polarization electric field is applied. The time may be 1 to 30 minutes, and the magnitude of the polarization electric field may be 0.9 times or more the coercive electric field of the sintered body.

  After the polarization treatment, the temporary electrode is removed from the sintered body by etching or the like. Then, the sintered body is cut into a desired element shape to form the piezoelectric element 2. By forming the vibrating electrode 3 on the piezoelectric element 2, the resonator 1 of the present embodiment is completed. For the formation of the vibrating electrode 3, it is preferable to use a vacuum deposition method or sputtering.

  The preferred embodiments of the piezoelectric ceramic composition and the oscillator according to the present invention have been described above, but the present invention is not necessarily limited to the above-described embodiments.

  For example, the piezoelectric ceramic composition of the present invention includes a filter, an actuator, an ultrasonic cleaner, an ultrasonic motor, a vibrator for an atomizer, a fish detector, a shock sensor, an ultrasonic diagnostic device, and a waste toner sensor in addition to an oscillator. It may be used for a gyro sensor, a buzzer, a transformer or a lighter.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

(Sample 2)
As starting materials for Sample 2, lead oxide (PbO), lanthanum hydroxide (La (OH) ₃ ), titanium oxide (TiO ₂ ), zirconium oxide (ZrO ₂ ), manganese carbonate (MnCO ₃ ), niobium oxide (Nb ₂₎ O _5), molybdenum oxide _(MoO 3), we were prepared each powder raw material of strontium carbonate (SrCO _3). These powder raw materials were weighed and blended so that the piezoelectric ceramic composition constituting the ceramic sample (sintered body) after the main firing had the composition of “Sample 2” in Table 1. In addition, the compounding quantity of molybdenum oxide (MoO ₃ ) shown in Table 1 is the main component (composite oxide) of the completed piezoelectric ceramic composition (Pb _α La _β1 Sr _β2 ) (Ti _{1- (x + y + z)} Zr _x Mn _y Nb _z ) Value (unit: part by mass) relative to 100 parts by mass of O ₃ .

  Next, the blended powder raw material mixture and pure water were mixed with a Zr ball by a ball mill for 10 hours to obtain a slurry. This slurry was sufficiently dried and then press-molded, and this was temporarily fired at 1000 ° C. to obtain a temporarily fired body. Next, the calcined product was finely pulverized with a ball mill, and then dried and granulated by adding an appropriate amount of PVA (polyvinyl alcohol) as a binder. About 3 g of the obtained granulated powder was placed in a 20 mm long × 20 mm wide mold and molded using a uniaxial press molding machine with a load of 245 MPa. The molded sample was heat-treated to remove the binder, and then subjected to main firing at 1200 to 1240 ° C. for 2 hours to obtain a porcelain sample (sample 2) which is a sintered body composed of the piezoelectric ceramic composition. A plurality of porcelain samples as “Sample 2” were prepared by the same operation.

One of the obtained porcelain samples was flattened to a thickness of 0.4 mm with a double-sided lapping machine, and then cut into a size of 6 mm length × 6 mm width with a dicing saw. A pair of Ag electrodes having a size of 5 mm × 5 mm was formed by vacuum-depositing an Ag paste on both ends of the cut ceramic sample. After installing the porcelain sample on which the Ag electrode is formed in the electric furnace, the LCR meter is used to measure the temperature at which the capacitance of the porcelain sample reaches the maximum value in the temperature raising process and the temperature lowering process. The Curie temperature _Tc was determined from the average value. The results are shown in Table 1. In order for the oscillator to function normally even at a high temperature, the piezoelectric element (the porcelain sample of the sample 2) needs to maintain piezoelectricity even at a high temperature. Therefore, the higher the Curie temperature _Tc is preferable.

A voltage of 200 V is applied to a porcelain sample (sample 2) similar to the measurement sample of Curie temperature _Tc in a silicon oil bath maintained at 120 ° C., and the current value between the Ag electrodes is measured. The resistivity (specific resistance) was calculated.

In addition, a porcelain sample (sample 2) different from the one used for measuring the Curie temperature _Tc is planarized to a thickness of 0.4 mm with a double-sided lapping machine, and then cut into a size of 16 mm length × 16 mm width with a dicing saw. did. A pair of temporary electrodes for polarization treatment having a size of 15 mm × 15 mm was formed by applying an Ag paste to both ends of the cut ceramic sample. The porcelain sample on which the temporary electrode was formed was subjected to polarization treatment by applying a polarization electric field twice the coercive electric field for 15 minutes in a silicon oil bath at a temperature of 120 ° C. After the polarization treatment, the porcelain sample from which the temporary electrodes had been removed was again polished to a thickness of about 0.25 mm with a lapping machine, and processed into a 7 mm × 4.5 mm piezoelectric element 2 with a dicing saw. Next, the vibrating electrodes 3 were formed on both surfaces of the piezoelectric element 2 using a vacuum vapor deposition apparatus, and the oscillator 1 having the same configuration as that shown in FIGS. The vibrating electrode 3 was composed of a 1.5 μm Ag layer.

Next, using an impedance analyzer (4294A manufactured by Agilent Technologies), the Q _max of the oscillator 1 in the third harmonic mode of thickness longitudinal vibration near 30 MHz was measured. The results are shown in Table 1. Q _max contributes to stable oscillation and is preferably as large as possible.

(Sample 1, 3-16)
Samples 1 and 3 to 16 were the same as Sample 2 except that the piezoelectric ceramic composition constituting the ceramic sample (sintered body) after the main firing had the composition shown in Table 1. A porcelain sample and an oscillator were prepared, and their Curie temperature T _c , resistivity, and Q _max were measured. The results are shown in Table 1.

As shown in Table 1, the content of Mo element, which includes a complex oxide containing lead titanate and Mn, and Mo element and converted to MoO ₃ is 0 with respect to 100 parts by mass of the complex oxide. Greater than 0.6 parts by weight and less than 0.6 parts by weight, and the composite oxide
_{(Pb α La β1 Sr β2)} (Ti 1- (x + y + z) Zr x Mn y Nb z) O 3
0.84 ≦ α <1.00, 0 <β ≦ 0.10 (where β = β1 + β2), 0 ≦ x <0.40, 0.02 ≦ y <0.05 In Samples 2 to 5 and 7 to 12 that satisfy 0 ≦ z ≦ 0.1, it was confirmed that both the Curie temperatures T _c and Q _max were high.

On the other hand, in the sample 6 in which the Mo element content converted to MoO ₃ is 0.8 parts by mass with respect to 100 parts by mass of the composite oxide, the Q _max is lower than those of the samples 2 to 5 and 7 to 12. Was confirmed.

In the sample 13 where x is 0.400, it was confirmed that both the Curie temperatures T _c and Q _max were lower than those of the samples 2 to 5 and 7 to 12.

  In sample 14 where y is 0.050, the resistivity of the porcelain sample was low, so that sufficient piezoelectricity could not be imparted to the porcelain sample by the polarization treatment.

In sample 15 in which α was 1.000, the mechanical strength of the porcelain sample was low, so the porcelain sample was cracked during processing of the porcelain sample, and the Curie temperatures Tc and _Qmax could not be measured.

  In sample 16 in which α is 1.000 and β is 0, the piezoelectric ceramic composition was not sufficiently sintered, and a porcelain sample could not be obtained.

(Sample 1a)
Each powder raw material was weighed and blended in the same manner as in Sample 1, and the same method as Sample 2 was used except that the main firing was performed at 1200 ° C. (hereinafter referred to as “T ₁ ° C.”). An oscillator 1 was produced.

Next, as shown in FIG. 3, parallel capacitors C _L1 and C _L2 having a predetermined capacitance were connected to the oscillator 1 to form a Colpitts oscillation circuit 20 together with the IC. In the Colpitts oscillation circuit 20, Rf is a feedback resistor and Rd is a limiting resistor. The Colpitts oscillation circuit 20 was connected to a predetermined DC power source (not shown). The Colpitts oscillation circuit 20 was placed in a constant temperature bath at 25 ° C., and the oscillation frequency (hereinafter referred to as F ₀ (25 ° C.)) when the temperature in the bath was stabilized at 25 ° C. was measured. Further, the temperature of the thermostatic chamber containing the Colpitts oscillation circuit 20 is set to −40 ° C., and the oscillation frequency (hereinafter referred to as F ₀ (−)) when the temperature in the bath (temperature of the oscillator 1) is stabilized at −40 ° C. 40)), and the temperature of the thermostatic chamber containing the Colpitts oscillation circuit 20 is set to 85 ° C., and the oscillation frequency when the temperature in the bath is stabilized at 85 ° C. (hereinafter referred to as F ₀ (85 ° C.)). ) Was measured. Oscillation frequencies F ₀ (25 ° C.), F ₀ (−40 ° C.), and F ₀ (85 ° C.) were measured using a frequency counter (53181A manufactured by Agilent Technologies).

Based on the measured oscillation frequencies F ₀ (25 ° C.), F ₀ (−40 ° C.), and F ₀ (85 ° C.), the temperature characteristics of the oscillation frequency F ₀ are calculated using the following formulas (1) and (2). Values F ₀ TC1 and F ₀ TC2 (unit: ppm / ° C.) were determined. The smaller F ₀ TC1 and F ₀ TC2 are, the more stable the oscillation frequency F ₀ is with respect to temperature change, which means that the temperature characteristics of F ₀ are better. Therefore, F ₀ TC1 and F ₀ TC2 are preferably as small as possible.

F ₀ TC1 (ppm / ° C.) = {F ₀ (25 ° C.) − F ₀ (−40 ° C.)} / [{25 ° C .− (− 40 ° C.)} × F ₀ (25 ° C.)] × 10 ^6.・ Formula (1)

F ₀ TC2 (ppm / ° C.) = {F ₀ (85 ° C.) − F ₀ (25 ° C.)} / {(85 ° C.−25 ° C.) × F ₀ (25 ° C.)} × 10 ⁶ Formula (2 )

In the following, F ₀ TC1 and F ₀ TC2 of a sample manufactured at a main firing temperature of T ° C. are _{denoted as} F ₀ TC1 (T) and F ₀ TC2 (T), respectively. Therefore, since F ₀ TC1 and F ₀ TC2 of the sample 1a are T = T ₁ = 1200 ° C., they are expressed as F ₀ TC1 (T ₁ ) and F ₀ TC2 (T ₁ ), respectively.

(Sample 1b)
Each powder raw material was weighed and blended in the same manner as in Sample 1, and the same method as Sample 2 was used except that the main firing was performed at 1220 ° C. (hereinafter referred to as “T ₂ ° C.”). An oscillator 1 was produced. In addition, F ₀ TC1 (T ₂ ) and F ₀ TC2 (T ₂ ) of Sample 1b were obtained by the same method as Sample 1a.

(Sample 1c)
Each powder raw material was weighed and blended in the same manner as Sample 1, and the same firing as Sample 2 was performed, except that the main firing was performed at 1240 ° C. (hereinafter referred to as “T ₃ ° C.”). An oscillator 1 was produced. Further, F ₀ TC1 (T ₃ ) and F ₀ TC2 (T ₃ ) of Sample 1c were obtained by the same method as Sample 1a.

Next, F ₀ TC1 (T ₁ ), F ₀ TC2 (T ₁ ), F ₀ TC1 (T ₂ ), F ₀ TC2 (T ₂ ), F ₀ TC1 (T ₃ ), and F ₀ TC2 (T ₃₎ ), The characteristic values ΔF ₀ TC1 / ΔT and ΔF ₀ TC2 / ΔT (unit: ppm · ° C. ⁻² ) of the oscillation frequency F ₀ defined by the following formulas (3) and (4) were obtained. . The results are shown in Table 2.

ΔF ₀ TC1 / ΔT (ppm · ° C. ⁻² ) = {F ₀ TC1 (T _x ) −F ₀ TC1 (T _y )} / (T _x −T _y ) (3)

ΔF ₀ TC2 / ΔT (ppm · ° C. ⁻² ) = {F ₀ TC2 (T _x ) −F ₀ TC2 (T _y )} / (T _x −T _y ) (4)

In Formula (3) and Formula (4), T _x and T _y are each T ₁ (1200 ° C.), T ₂ (1220 ° C.), or T ₃ (1240 ° C.). In Table 2, T _x = T ₂ = 1220 ° C., T _y = T ₁ = 1200 ° C., and T _x = T ₃ = 1240 ° C., T _y = T ₂ = 1220 ° C. , ΔF ₀ TC1 / ΔT and ΔF ₀ TC2 / ΔT were determined, respectively.

ΔF ₀ TC1 / ΔT and ΔF ₀ TC2 / ΔT are values indicating the amount of change in temperature characteristic value (ΔF ₀ TC1 or ΔF ₀ TC2) of the oscillation frequency F ₀ with respect to the amount of change in the main firing temperature (ΔT). . Therefore, as ΔF ₀ TC1 / ΔT and ΔF ₀ TC2 / ΔT are smaller, the temperature characteristic of the oscillation frequency F ₀ is more stable with respect to the change in the main firing temperature, and the variation in the temperature characteristic of the oscillation frequency F ₀ is suppressed. Means that Therefore, ΔF ₀ TC1 / ΔT and ΔF ₀ TC2 / ΔT are preferably as small as possible.

(Samples 2a, 2b, 2c)
Similarly to sample 2, each powder raw material was weighed and blended, and oscillator 1 of sample 2a was created in the same manner as sample 2, except that the main firing was performed at 1200 ° C. (T ₁ ° C.). Similarly to sample 2, each powder material is weighed and blended, and oscillator 1 of sample 2b is created in the same manner as sample 2, except that the main firing is performed at 1220 ° C. (T ₂ ° C.). did. Further, each powder raw material was weighed and blended in the same manner as in Sample 2, and the oscillator 1 of Sample 2c was prepared in the same manner as Sample 2 except that the main firing was performed at 1240 ° C. (T ₃ ° C.). did. Similarly to the samples 1a, 1b, and 1c described above, ΔF ₀ TC1 / ΔT and ΔF ₀ TC2 / ΔT were obtained using the oscillator 1 of the samples 2a, 2b, and 2c. The results are shown in Table 2.

(Samples 3a, 3b, 3c)
Similarly to sample 3, each powder raw material was weighed and blended, and oscillator 1 of sample 3a was prepared in the same manner as sample 2, except that the main firing was performed at 1200 ° C. (T ₁ ° C.). Similarly to sample 3, each powder raw material is weighed and blended, and oscillator 1 of sample 3b is prepared in the same manner as sample 2, except that the main firing is performed at 1220 ° C. (T ₂ ° C.). did. Further, each powder raw material was weighed and blended in the same manner as in sample 3, and oscillator 1 of sample 3c was prepared in the same manner as sample 2, except that the main firing was performed at 1240 ° C. (T ₃ ° C.). did. Similarly to the samples 1a, 1b, and 1c described above, ΔF ₀ TC1 / ΔT and ΔF ₀ TC2 / ΔT were obtained using the oscillator 1 of the samples 3a, 3b, and 3c. The results are shown in Table 2.

(Samples 4a, 4b, 4c)
The oscillator 1 of the sample 4a was prepared in the same manner as the sample 2 except that each powder raw material was weighed and blended in the same manner as the sample 4 and the main firing was performed at 1200 ° C. (T ₁ ° C.). In addition, each powder raw material was weighed and blended in the same manner as in sample 4, and oscillator 1 of sample 4b was created in the same manner as sample 2, except that the main firing was performed at 1220 ° C. (T ₂ ° C.). did. Further, each powder raw material was weighed and blended in the same manner as in Sample 4, and the oscillator 1 of Sample 4c was prepared in the same manner as Sample 2 except that the main firing was performed at 1240 ° C. (T ₃ ° C.). did. Similarly to the samples 1a, 1b, and 1c described above, ΔF ₀ TC1 / ΔT and ΔF ₀ TC2 / ΔT were obtained using the oscillator 1 of the samples 4a, 4b, and 4c. The results are shown in Table 2.

(Samples 5a, 5b, 5c)
The oscillator 1 of the sample 5a was prepared in the same manner as the sample 2 except that each powder raw material was weighed and blended in the same manner as the sample 5 and the main firing was performed at 1200 ° C. (T ₁ ° C.). Similarly to sample 5, each powder raw material was weighed and blended, and oscillator 1 of sample 5b was prepared in the same manner as sample 2, except that the main firing was performed at 1220 ° C. (T ₂ ° C.). did. Further, each powder raw material was weighed and blended in the same manner as in sample 5, and oscillator 1 of sample 5c was prepared in the same manner as sample 2 except that the main firing was performed at 1240 ° C. (T ₃ ° C.). did. Similarly to the samples 1a, 1b, and 1c described above, ΔF ₀ TC1 / ΔT and ΔF ₀ TC2 / ΔT were obtained using the oscillator 1 of the samples 5a, 5b, and 5c. The results are shown in Table 2.

As shown in Table 2, oscillation using a porcelain sample containing Mo at least when the main firing temperature fluctuates in the range of 1200 to 1220 ° C or fluctuates in the range of 1220 to 1240 ° C. It was confirmed that ΔF ₀ TC1 / ΔT and ΔF ₀ TC2 / ΔT were smaller in the child 1 than in the resonator 1 using the porcelain sample not containing Mo. That is, in the oscillator 1 using the porcelain sample containing Mo, the temperature characteristic of the oscillation frequency F ₀ is more stable with respect to the change of the main firing temperature than the oscillator 1 using the porcelain sample not containing Mo. It was confirmed that variation in the temperature characteristics of the oscillation frequency F ₀ was suppressed.

Next, the oscillation frequencies F ₀ (−20 ° C.), F ₀ (−10 ° C.), F ₀ (0 ° C.), F ₀ (25 ° C.) F ₀ (50) of the sample 3a whose main firing temperature was 1200 ° C. ° C.), F ₀ (70 ° C.), and F ₀ (85 ° C.), respectively. These oscillation frequencies F ₀ were measured by the same method as in the case of the sample 1a. The oscillation frequency F ₀ of the oscillator 1 when the temperature in the oscillation frequency measurement tank (temperature of the oscillator 1) is stabilized at T ° C. is expressed as F ₀ (T ° C.).

Next, by substituting the measured value of F ₀ (25 ° C.) into F ₀ (T ₀ ) of the following formula (5) and substituting the measured value of F ₀ (−20 ° C.) into F ₀ (T). , RF ₀ (−20 ° C.) (unit:%) was calculated. RF ₀ (T) is the rate of change (unit: ppm) of the oscillation frequency F ₀ when the temperature of the oscillator 1 changes from the temperature T ₀ to the temperature T, and is the absolute value of RF ₀ (T) Means that the oscillation frequency F ₀ is more stable with respect to temperature change, and the temperature characteristic of F ₀ is better.
RF ₀ (T) = {F ₀ (T) −F ₀ (T ₀ )} / F ₀ (T ₀ ) × 10 ⁶ (5)

Furthermore, in the same manner as RF ₀ (−20 ° C.), RF ₀ (−10 ° C.), RF ₀ (0 ° C.), RF ₀ (25 ° C.), RF ₀ (50 ° C.), RF ₀ (70 ° C.) , And RF ₀ (85 ° C.) were obtained.

Next, with respect to the temperature T of the oscillator 1, RF ₀ (−20 ° C.), RF ₀ (−10 ° C.), RF ₀ (0 ° C.), RF ₀ (25 ° C.), RF ₀ (50 ° C.), RF ₀ (70 ℃), and was determined _RF 0 (T) curve by plotting the _RF 0 (85 ℃). The results are shown in FIG.

In the sample 3a and a similar method was determined _RF 0 (T) curve of the sample 3b the sintering temperature was 1220 ° C., and _RF 0 sample 3c was the sintering temperature is 1240 ° C. The (T) curve, respectively . The results are shown in FIG.

Further, in the sample 3a and a similar method, the _RF 0 (T) curve of the sintering temperature was 1200 ° C. Samples 1a, _RF 0 (T) curve of the sample 1b the sintering temperature was 1220 ° C., and the The RF ₀ (T) curves of Sample 1c whose firing temperature was 1240 ° C. were determined. The results are shown in FIG.

4A and 4B, in the oscillator 1 using the porcelain sample containing Mo (samples 3a, 3b, and 3c), the oscillator 1 using the porcelain sample not containing Mo is used. Compared to (Samples 1a, 1b, 1c), the absolute value of the rate of change RF ₀ (T) of the oscillation frequency F ₀ is small, and the shape of the rate of change RF ₀ (T) curve with respect to the change in the main firing temperature is It was stable and it was confirmed that the variation of the change rate RF ₀ (T) was suppressed.

From the above experimental results, according to the present invention, it is possible to obtain a sufficiently high Q _max when used in an oscillator that utilizes the third harmonic mode of thickness longitudinal vibration, and the variation in the firing temperature. It was confirmed that an oscillator capable of suppressing the variation in temperature characteristics of the oscillation frequency F ₀ caused by the oscillation frequency is provided.

1 is a perspective view showing an oscillator according to an embodiment of the present invention. It is sectional drawing along the II-II line of FIG. It is. It is a Colpitts oscillation circuit diagram provided with an oscillator. 4 (a) is porcelain samples containing Mo with respect to the temperature T of the oscillator using the (piezoelectric ceramic), graph plotting the rate of change RF ₀ of the oscillation frequency _{F 0 (RF} 0 (T) curve) 4B is a graph (RF ₀ (T ₀ (T ₀ )) plotting the rate of change RF ₀ of the oscillation frequency F ₀ against the temperature T of the resonator using the porcelain sample (piezoelectric ceramic) not containing Mo. ) Curve).

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Oscillator, 2 ... Piezoelectric element, 3 ... Vibrating electrode.

Claims (4)

A composite oxide containing lead titanate and Mn element, and Mo element,
The piezoelectric ceramic composition, wherein the Mo element content converted to MoO ₃ is greater than 0 parts by mass and equal to or less than 0.6 parts by mass with respect to 100 parts by mass of the composite oxide. The composite oxide is
_{(Pb α M β) (Ti} 1- (x + y + z) Zr x Mn y Nb z) O 3
[Wherein, M represents at least one selected from the group consisting of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Sr. ]
Having a composition represented by
0.84 ≦ α <1.00,
0 <β ≦ 0.10,
0 ≦ x <0.40,
0.02 ≦ y <0.05, and 0 ≦ z ≦ 0.1
The piezoelectric ceramic composition according to claim 1, wherein:   A piezoelectric element comprising the piezoelectric ceramic composition according to claim 1.   An oscillator comprising the piezoelectric element according to claim 3 and a pair of electrodes facing each other with the piezoelectric element interposed therebetween.

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