JP2010235345A - Dielectric ceramic composition and oscillator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dielectric ceramic composition which can improve temperature characteristics of electrostatic capacitance, can reduce dielectric loss and can lower relative dielectric constant. <P>SOLUTION: The dielectric ceramic composition is used as a dielectric ceramic composition for a load capacitance element in an oscillator provided with a piezoelectric element and the load capacitance element and comprises a multiple oxide of perovskite type which has a composition represented by the chemical formula (A): Pb<SB>a</SB>[Zn<SB>b</SB>Nb<SB>c</SB>Ti<SB>ä1-(b+c+d)}</SB>Zr<SB>d</SB>]O<SB>3</SB>(A) and satisfies 0.98≤a≤1.01, 0.01≤b≤0.02, 0.02≤c≤0.04 and 0.48≤d≤0.51, and Ni element, wherein a content of the Ni element expressed in terms of NiO is 0.01 to 0.3 pts.mass per 100 pts.mass of the multiple oxide and a content of Co element expressed in terms of Co<SB>3</SB>O<SB>4</SB>is 0 pts.mass or more and less than 0.1 pts.mass per 100 pts.mass of the multiple oxide. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a dielectric ceramic composition and an oscillator.

  An oscillator including a piezoelectric element as shown in Patent Document 1 below is widely used in electronic devices such as an HDD device and a DVD recording / reproducing device as a component that generates a reference signal for a microcomputer. The piezoelectric element is an element including a piezoelectric ceramic composition and a pair of electrodes facing each other with the piezoelectric ceramic composition interposed therebetween.

In a general oscillator, a piezoelectric element is incorporated in a Colpitts oscillation circuit 20 as shown in FIG. The piezoelectric element P in the Colpitts oscillation circuit 20 can be replaced with an equivalent circuit E shown in FIG. The Colpitts oscillation circuit 20 includes load capacitive elements C _L1 and C _L2 together with the piezoelectric element P. The load capacity of the oscillator is determined by each capacity of the load capacity elements C _L1 and C _L2 . An element having a piezoelectric element and a load capacitor element integrated with the piezoelectric element is called a load capacitor built-in type resonator.

JP-A-10-190400

The oscillation frequency F ₀ (unit: Hz) of the resonator including the Colpitts oscillation circuit 20 shown in FIG. 1A is calculated by the following formula (1).
F ₀ = F _r × {1 + C ₁ / (C ₀ + C _L )} ^1/2 (1)
In the above formula (1), _Fr is the resonance frequency of the oscillator. Further, C ₀ is the capacity of the capacitor C _{0 included in} the equivalent circuit E of FIG. 1B, and C ₁ is the capacity of the capacitor C ₁ included in the equivalent circuit E. A relationship of C _d = (C ₀ + C ₁ ) is established between the capacitance C _{d of the} piezoelectric element and C ₀ and C ₁ . Further, C _L is defined by the formula C _L = C _L1 / 2. Here, C _L1 is the capacitance (parallel capacitance) of the load capacitance element C _L1 , and C _L2 is the capacitance (parallel capacitance) of the load capacitance element C _L2 . Further, it is assumed that C _L1 ≈C _L2 holds between C _L1 and C _L2 .

In recent years, stabilization of the oscillation frequency F ₀ of a reference signal generated by an oscillator has been demanded as electronic devices have been improved in performance. To stabilize the oscillation frequency F ₀ is to improve the temperature characteristic of the oscillation frequency F ₀ is required. The "temperature characteristic of the oscillation frequency F _0" is quantified as "the ratio of the amount of change of the oscillation frequency F ₀ for the amount of change in temperature of the piezoelectric ceramic composition or oscillator piezoelectric element comprising", its value smaller, has excellent temperature characteristic of the oscillation frequency F _0.

As is clear from the above formula (1), the oscillation frequency F ₀ changes according to the resonance frequency F _r derived from the piezoelectric element, the capacitances C ₀ and C ₁ , and the capacitances C _L1 and C _L2 of each load capacitance element. To do. Therefore, in order to improve the temperature characteristics of the oscillator F ₀ , it is necessary to develop a piezoelectric element having F _r , capacitances C ₀ and C ₁ that hardly change with temperature change, or change with temperature change. It is necessary to develop load capacitance elements C _L1 and C _L2 having difficult capacitances C _L1 and C _L2 . Specifically, for example, by improving the piezoelectric ceramic composition having the piezoelectric element, or to improve the temperature characteristics of the F _r, by improving the dielectric ceramic composition load capacitor element has a temperature of C _L1 and C _L2 It is conceivable to improve the characteristics. Note that the smaller the variation in the temperature characteristic of the resonance frequency _Fr derived from the piezoelectric element and the variation in the temperature characteristic of the capacitances C _L1 and C _L of the load capacitance element, the smaller the oscillation frequency F _{0 in} mass production of the resonator. easily suppress variations, easily controlled within narrow tolerances the oscillation frequency F _0. Therefore, the temperature characteristic of the oscillation frequency F ₀ is easily mass-produced good oscillator.

Conventionally, in order to stabilize the oscillation frequency F ₀ , various properties of the piezoelectric element can be obtained by adding an additive to the piezoelectric ceramic composition or by replacing some elements of the piezoelectric ceramic composition with other elements. Attempts have been made to improve. However, conventionally, the dielectric ceramic composition for the purpose of stabilizing the oscillation frequency F ₀ has not been sufficiently improved.

In order to stabilize the oscillation frequency F ₀ by improving the dielectric ceramic composition, it is necessary to improve the temperature characteristics of the capacitance of the load capacitive element. The “temperature characteristic of the capacitance of the load capacitor element” is quantified by “the ratio of the change amount of the capacitance to the change amount of the temperature of the dielectric ceramic composition included in the load capacitor element”, and the value The smaller the is, the better the temperature characteristics of the capacitance of the load capacitive element. In order to stabilize the oscillation frequency F ₀ , it is necessary not only to improve the temperature characteristics of the capacitance, but also to reduce the dielectric loss of the load capacitance element. This is because when the dielectric loss is large, the oscillation may stop under a low voltage. In recent years, with the miniaturization of electronic devices, there has been a demand for miniaturization of oscillators and load capacitance elements. In order to reduce the size of the oscillator and the load capacitance element, it is necessary to reduce the relative dielectric constant of the dielectric ceramic composition.

  However, with the conventional dielectric ceramic composition, it has been difficult to achieve all of improvement in the temperature characteristics of capacitance, reduction in dielectric loss, and reduction in relative dielectric constant.

  Accordingly, the present invention provides a dielectric ceramic composition capable of improving the temperature characteristics of capacitance, reducing dielectric loss, and lowering the dielectric constant, and an oscillation device comprising a load capacitive element having the dielectric ceramic composition. The purpose is to provide children.

A dielectric ceramic composition according to the present invention is a dielectric ceramic composition of a load capacitive element in an oscillator including a piezoelectric element and a load capacitive element,
Pb _a [Zn _b Nb _c Ti _{{1- (b + c + d)}} Zr _d ] O ₃
0.98 ≦ a ≦ 1.01, 0.01 ≦ b ≦ 0.02, 0.02 ≦ c ≦ 0.04, and 0.48 ≦ d ≦ 0.51 A perovskite-type composite oxide satisfying the above requirements, Ni element, and the content of Ni element converted to NiO is 0.01 to 0.3 parts by mass with respect to 100 parts by mass of the composite oxide, and Co The content of Co element converted to ₃ O ₄ is 0 part by mass or more and less than 0.1 part by mass with respect to 100 parts by mass of the composite oxide.

  Since the present invention has the above composition, it is possible to improve the temperature characteristics of the capacitance in the load capacitor element, to reduce the dielectric loss, and to reduce the relative dielectric constant of the dielectric ceramic composition. it can.

The present invention, the content of Co element in terms of _Co 3 _{O 4} is preferably a 0 to 0.05 parts by mass relative to the composite oxide 100 parts by weight. This makes it easier to improve the temperature characteristics of the capacitance.

The resonator according to the present invention includes a piezoelectric element and a load capacitive element, and the load capacitive element includes the dielectric ceramic composition according to the present invention. In the resonator according to the present invention, since the load capacitor element includes the dielectric ceramic composition according to the present invention, the temperature characteristic of the oscillation frequency F ₀ can be improved.

  In the resonator according to the present invention, the piezoelectric element and the load capacitance element are preferably integrated. Thereby, the size of the oscillator can be reduced.

  According to the present invention, a dielectric ceramic composition capable of improving the temperature characteristics of capacitance, reducing dielectric loss, and reducing the relative dielectric constant, and an oscillation device comprising a load capacitive element having the dielectric ceramic composition A child is provided.

FIG. 1A is a schematic diagram showing a Colpitts oscillation circuit including a load capacitance element having a dielectric ceramic composition according to an embodiment of the present invention and a piezoelectric element, and FIG. It is an equivalent circuit of the piezoelectric element shown to (A). 1 is an exploded perspective view of a load capacity built-in type oscillator according to an embodiment of the present invention. It is. 1 is a perspective view of a load capacitor built-in type resonator according to an embodiment of the present invention.

  Hereinafter, a preferred embodiment of the present invention will be described with reference to the drawings as appropriate.

As shown in FIGS. 1A and 1B, the resonator according to the present invention is an LC composed of a piezoelectric element P, load capacitive elements C _L1 and C _L2 , a feedback resistor Rf, and a limiting resistor Rd. A Colpitts oscillation circuit is provided. A predetermined DC power supply (not shown) is connected to the Colpitts oscillation circuit 20. Each of the load capacitance elements C _L1 and C _L2 is a capacitor including a sintered body of the dielectric ceramic composition according to the present embodiment and a pair of electrodes sandwiching the sintered body.

The dielectric ceramic composition according to the present embodiment includes a perovskite complex oxide having a composition represented by the following chemical formula (A) and Ni element.
Pb _a [Zn _b Nb _c Ti _{{1- (b + c + d)}} Zr _d ] O ₃ (A)

  In the chemical formula (A), 0.98 ≦ a ≦ 1.01. When a is less than 0.98, the sinterability of the dielectric ceramic composition is deteriorated and the relative dielectric constant is increased. When a is larger than 1.01, the dielectric loss of the load capacitive element increases. In the present embodiment, since 0.98 ≦ a ≦ 1.01, these problems can be prevented.

  In the chemical formula (A), 0.01 ≦ b ≦ 0.02. When b is less than 0.01, the temperature characteristics of the capacitance of the load capacitive element are deteriorated, and the dielectric loss is increased. When b is greater than 0.02, the relative dielectric constant increases. In the present embodiment, since 0.01 ≦ b ≦ 0.02, these problems can be prevented.

  In the chemical formula (A), 0.02 ≦ c ≦ 0.04. When c is less than 0.02, the temperature characteristic of the capacitance is deteriorated and the dielectric loss is increased. When c is larger than 0.04, the relative dielectric constant increases. In this embodiment, since 0.02 ≦ c ≦ 0.04, these problems can be prevented.

  In the chemical formula (A), 0.48 ≦ d ≦ 0.51. When d is less than 0.48, the relative dielectric constant increases. When d is larger than 0.51, the temperature characteristic of the capacitance is deteriorated and the dielectric loss is increased. In the present embodiment, since 0.48 ≦ d ≦ 0.51, these problems can be prevented.

  In the dielectric ceramic composition, the content of Ni element converted to NiO is 0.01 to 0.3 parts by mass with respect to 100 parts by mass of the composite oxide. This improves the temperature characteristics of the capacitance. When the content of Ni element is less than 0.01 parts by mass, the sinterability of the dielectric ceramic composition is deteriorated and the relative dielectric constant is increased. When the content of Ni element is larger than 0.3 parts by mass, the temperature characteristics of the capacitance are deteriorated and the dielectric loss is increased. In this embodiment, since content of Ni element is 0.01-0.3 mass part, these malfunctions can be prevented.

In the dielectric ceramic composition, the content of Co element converted to Co ₃ O ₄ is 0 part by mass or more and less than 0.1 part by mass with respect to 100 parts by mass of the composite oxide. In the present embodiment, even when the dielectric ceramic composition does not contain a Co element, the effects of the present invention can be achieved. However, the dielectric loss further decreases when the dielectric ceramic composition contains a Co element. . When the content of Co element is 0.1 parts by mass or more, the temperature characteristic of the capacitance is deteriorated. In the present embodiment, the temperature characteristic of the capacitance can be improved by setting the content of Co element to less than 0.1 parts by mass.

In the dielectric ceramic composition, the content of Co element converted to Co ₃ O ₄ is preferably 0 to 0.05 parts by mass with respect to 100 parts by mass of the composite oxide. This makes it easier to improve the temperature characteristics of the capacitance.

  The dielectric ceramic composition contains a compound other than the complex oxide having the composition represented by the chemical formula (A) as an impurity or a trace amount of additive as long as the effect of the present invention is not impaired. Also good. Examples of such compounds include oxides of Na, Al, Si, P, K, Ca, Fe, Cu, Zn, Hf, Ta, or W.

  The method for manufacturing a dielectric ceramic composition according to the present embodiment described above mainly includes a step of granulating a raw material powder of the dielectric ceramic composition, a step of pressing the raw material powder to form a formed body, And firing the formed body to form a sintered body. Hereinafter, each step will be specifically described.

First, a starting material for preparing a dielectric ceramic composition is prepared. As starting materials, oxides of each element constituting the composite oxide having the composition represented by the above chemical formula (A) and / or compounds that become these oxides after firing (carbonate, hydroxide, oxalic acid) Salt, nitrate, etc.). As specific starting materials, PbO, ZnO, Nb ₂ O ₅ , TiO _2, ZrO ₂ or the like may be used. Each of these starting materials is blended at a mass ratio such that a composite oxide having a composition represented by the above chemical formula (A) is formed after firing. Further, NiO is added to the blended starting material, and Co ₃ O ₄ is also added as necessary. The amount of NiO added is adjusted so that the content of Ni element converted to NiO is 0.01 to 0.3 parts by mass with respect to 100 parts by mass of the composite oxide in the dielectric ceramic composition obtained after firing. To do. The amount of Co ₃ O ₄ added is such that in the dielectric ceramic composition obtained after firing, the content of Co element converted to Co ₃ O ₄ is 0 part by mass or more and 0.1 part by mass with respect to 100 parts by mass of the composite oxide. Adjust to be less than part.

  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 firing, a temporary fired body containing the dielectric ceramic composition of the present embodiment described 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 molded body is fired to obtain a sintered body made of the dielectric ceramic composition according to the present embodiment. 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.

In the present embodiment, the dielectric ceramic composition included in the load capacitance elements C _L1 and C _L2 has a composition represented by the above chemical formula (A), and therefore, compared with a load capacitance element including a conventional dielectric ceramic composition. The temperature characteristic of the capacitance of the load capacitor element can be improved and the dielectric loss can be reduced. Therefore, in the oscillator according to the present embodiment, fluctuations in the oscillation frequency F ₀ due to the temperature characteristics of the capacitance of the load capacitive element and the dielectric loss are suppressed as compared with the oscillator including the conventional load capacitive element. . That is, in this embodiment, the temperature characteristics of the oscillation frequency F ₀ of the oscillator can be improved as compared with the conventional oscillator.

In the present embodiment, it is preferable that the piezoelectric element P and the load capacitance elements C _L1 and C _L2 are integrated in the oscillator. That is, the resonator according to the present embodiment is preferably a load capacitor built-in type oscillator including the piezoelectric element P and the load capacitor elements C _L1 and C _L2 integrated with the piezoelectric element P. In the present embodiment, not only can the temperature characteristics of the capacitance be improved and the dielectric loss can be reduced, but also the relative dielectric constant of the dielectric ceramic composition can be lowered, so that the piezoelectric element A miniaturized oscillator in which P and load capacitance elements C _L1 and C _L2 are integrated can be realized. Specifically, in this embodiment, a small oscillator having a size of 2520 or 2016 can be realized.

  Hereinafter, an example of a built-in load capacitor type oscillator according to the present embodiment will be described.

  As shown in FIGS. 2 and 3, the load capacitor built-in type resonator 200 according to the present embodiment includes a piezoelectric element 1, a sealing unit 2, a top plate 3, a base substrate 4, and external electrodes 51 and 52. And 53. The vertical, horizontal, and height dimensions of the load capacitor built-in type resonator 200 are about 2.5 mm in length, 2 mm in width, and about 1 mm in height. The vibration mode of the piezoelectric element 1 may be thickness longitudinal vibration or thickness shear vibration.

The piezoelectric element 1 includes a piezoelectric substrate 10, a pair of vibrating electrodes 11 and 12 sandwiching the piezoelectric substrate 10, and lead electrodes 14 and 15 connected to the vibrating electrodes 11 and 12. The piezoelectric substrate 10 is composed of a piezoelectric ceramic composition such as lead zirconate titanate (PZT) or lead titanate (PbTiO ₃ ). The piezoelectric substrate 10 is formed in a rectangular plate shape and is polarized in the thickness direction. The vibrating electrodes 11 and 12 and the extraction electrodes 14 and 15 are formed on the front and back surfaces (main surfaces 101 and 102) of the piezoelectric substrate 10 by a film forming method such as sputtering or vapor deposition. A vibration region 110 is formed above the vibration electrode 11. A vibration region 120 is formed below the vibration electrode 12. The vibrating electrodes 11 and 12 are opposed to each other, and are electrically connected to the external electrodes 51 and 52 provided on the side surface of the oscillator 200 via the extraction electrodes 14 and 15, respectively. The external electrode 53 is a ground electrode.

  The base substrate 4 is composed of a dielectric ceramic composition according to this embodiment. A portion formed by the external electrodes 51, 52 and 53 and the base substrate 4 located on the first side surface of the oscillator 200 functions as a load capacitor element. In addition, a portion constituted by the external electrodes 51, 52 and 53 and the base substrate 4 located on the second side opposite to the first side of the oscillator 200 functions as another load capacitance element.

  The pair of sealing portions 2 are formed on both main surfaces 101 and 102 of the front and back surfaces of the piezoelectric substrate 10, and each include a vibration space forming layer 21 and an adhesive layer 22. The thickness of the sealing portion 2 may be a thickness that can secure a space in which the piezoelectric element 1 vibrates, and may be adjusted according to the vibration frequency of the piezoelectric element 1. The thickness of the sealing part 2 is usually about 15 to 50 μm. Of the thickness of the sealing portion 2, about 10 μm corresponds to the thickness of the adhesive layer 22, and the remaining about 5 to 40 μm corresponds to the thickness of the vibration space forming layer 21.

  The vibration space forming layer 21 is formed by printing means so as to surround the vibration regions 110 and 120 and to be in close contact with both the front and back main surfaces 101 and 102 of the piezoelectric element 1. The vibration space forming layer 21 is made of a thermosetting resin such as epoxy.

  The adhesive layer 22 is laminated on the vibration space forming layer 21 and adheres the top plate 3 and the base substrate 4 to the vibration space forming layer 21. An insulator or the like is used as the material of the top plate 3.

  The adhesive layer 22 is formed, for example, by applying a thermosetting resin such as epoxy or a B-stage resin to the vibration space forming layer 21 by printing means. Alternatively, the adhesive layer 22 may be formed by laminating a B-stage resin sheet with punched portions corresponding to the vibration regions 110 and 120 on the vibration space forming layer 21. When the top plate 3 and the base substrate 4 are bonded to the vibration space forming layer 21 with the adhesive layer 22, the top plate 3, the sealing portion 2, the piezoelectric element 1, the sealing portion 2 and the base substrate 4 are overlapped, May be heated while pressing in the laminating direction.

  The preferred embodiment of the dielectric ceramic composition and the oscillator according to the present invention has been described above, but the present invention is not necessarily limited to the above-described embodiment.

For example, the dielectric ceramic composition according to the present invention may further contain SiO ₂ . Also in this case, the effects of the present invention can be achieved. Further, by the dielectric ceramic composition contains SiO _2, it is possible to improve the mechanical strength of the sintered body made of a dielectric ceramic composition. In order to obtain such an effect, the content of SiO ₂ in the dielectric ceramic composition is 0 to 0.1 mass with respect to 100 mass parts of the composite oxide having the composition represented by the chemical formula (A). Part.

  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 1)
Starting materials include lead oxide (PbO), zinc oxide (ZnO), niobium oxide (Nb ₂ O ₅ ), titanium oxide (TiO ₂ ), zirconium oxide (ZrO ₂ ), nickel oxide (NiO) and cobalt tetroxide (Co ₃ O ₄ ) powder raw materials were prepared. Each powder raw material was weighed and blended so that the composition of the dielectric ceramic composition constituting the sintered body obtained after the main firing described later has the composition shown in Table 1. Note that x (unit: part by mass) in Table 1 indicates the content of Ni element in the dielectric ceramic composition, and the composite oxide Pb _a [Zn _b Nb _c Ti _{{1- (B + c + d)}} It is the content of Ni element converted to NiO when the content of Zr _d ] O ₃ is 100 parts by mass. Moreover, y (unit: mass part) in Table 1 indicates the content of Co element in the dielectric ceramic composition, and is a composite oxide Pb _a [Zn _b Nb _c Ti _{{1- (b + c + d)}} Zr _d ]. This is the content of Co element converted to Co ₃ O ₄ when the content of O ₃ is 100 parts by mass.

  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 900 ° C. to obtain a temporarily fired body. Next, the calcined product was finely pulverized with a ball mill, and then dried, and an appropriate amount of PVA (polyvinyl alcohol) solution (PVA concentration: 10% by mass) as a binder was added and granulated. About 1 g of the obtained granulated powder was put into a 12φ mm mold and molded under a load of 245 MPa using a uniaxial press molding machine. The molded sample was heat treated at 700 ° C. for 1 hour to remove the binder, and then subjected to main firing at 1100 to 1200 ° C. for 2 hours. By such a method, a disk-shaped sintered body composed of the dielectric ceramic composition was obtained.

  Next, the obtained sintered body was planarized to a thickness of 0.35 mm with a double-sided lapping machine, and then a Ag paste having a size of 8 mm was applied to both surfaces of the sintered body. Formed. By such a method, a sample 1 (load capacitance element) including a disk-shaped sintered body made of a dielectric ceramic composition and a pair of disk-shaped Ag electrodes sandwiching the sintered body was obtained.

[Measurement of relative permittivity and dielectric loss]
The capacitance C _p (unit: F) and dielectric loss tan δ (unit:%) of sample 1 at room temperature were measured. For the measurement, an impedance analyzer (4294A manufactured by Agilent Technologies) was used. In the measurement, a voltage of 0.22 V was applied between the Ag electrodes of Sample 1 at a frequency of 1 MHz. Moreover, based on the following formula (2), the relative dielectric constant ε _r of the sintered body included in the sample 1 was obtained.
ε _r = (C _p × d) / (ε ₀ × S) (2)
In the above formula (2), d is the thickness of the sintered body included in the sample 1. ε ₀ is the vacuum dielectric constant. S is the area of the portion where the sintered body and Ag electrode overlap in sample 1 (Ag electrode area).

[Measurement of temperature characteristics of capacitance]
After measuring the relative dielectric constant and dielectric loss, the temperature characteristics of the electrostatic capacity of Sample 1 were evaluated by the following method.

Sample 1 was placed in a constant temperature bath at 25 ° C., and the capacitance of sample 1 (hereinafter referred to as C _p (25 ° C.)) when the temperature in the bath was stabilized at 25 ° C. was measured. Further, the temperature of the thermostatic chamber containing the sample 1 is set to −40 ° C., and the capacitance of the sample 1 when the temperature in the bath is stabilized at −40 ° C. (hereinafter, referred to as C _p (−40 ° C.)). ) Was measured. Further, the temperature of the constant temperature bath containing the sample 1 is set to 125 ° C., and the capacitance of the sample 1 when the temperature in the bath is stabilized at 125 ° C. (hereinafter referred to as C _p (125 ° C.)). It was measured. For measurement of C _p (25 ° C.), C _p (−40 ° C.), and C _p (125 ° C.), an impedance analyzer (4294A manufactured by Agilent Technologies) was used. In the measurement, a voltage of 0.22 V was applied between the Ag electrodes of Sample 1 at a frequency of 1 MHz.

From the values of C _p (25 ° C.), C _p (−40 ° C.), and C _p (125 ° C.), the temperature characteristic value CTC (unit: ppm / ° C.) of capacitance is calculated using the following mathematical formula (3). Asked. In addition, the smaller the CTC, the less the capacitance is changed with respect to the temperature change, and the better the temperature characteristics of the capacitance. Therefore, the smaller the CTC, the better.
CTC (ppm / ° C.) = 10 ⁶ × {C _p (125 ° C.) − C _p (−40 ° C.)} / [{125 ° C .− (− 40 ° C.)} × C _p (25 ° C.)] (3)

(Samples 2 to 26)
The same as sample 1 except that the above powder raw materials were weighed and blended so that the composition of the dielectric ceramic composition constituting the sintered body obtained after the main firing was the composition shown in Table 1. Samples 2 to 26 were prepared by the method described above. Further, in the same manner as in the case of Sample 1, C _p , ε _r , tan δ, C _p (25 ° C.), C _p (−40 ° C.), C _p (125 ° C.) at room temperature of Samples 2 to 26 and CTC was determined. Table 1 shows CTC, ε _r and tan δ of Samples 1 to 26. The CTC is preferably 3000 ppm / ° C. or less. ε _r is preferably 800 to 1300. It is preferable that tan δ is 2.5% or less.

The sintered bodies included in Samples 1, 2, 5-7, 10-12, 16-20, and 22-25 include a perovskite-type composite oxide having a composition represented by the following chemical formula (A), Ni element, . Further, the content of Ni element in terms of NiO in the sintered body is 0.01 to 0.3 parts by mass with respect to 100 parts by mass of the composite oxide, and the content of Co element in terms of Co ₃ O ₄ However, it was 0 mass part or more and less than 0.1 mass part with respect to 100 mass parts of complex oxide.
Pb _a [Zn _b Nb _c Ti _{{1- (b + c + d)}} Zr _d ] O ₃ (A)
In the above chemical formula (A),
0.98 ≦ a ≦ 1.01,
0.01 ≦ b ≦ 0.02,
0.02 ≦ c ≦ 0.04,
0.48 ≦ d ≦ 0.51.

In samples 1, 2, 5-7, 10-12, 16-20, and 22-25, CTC was 3000 ppm / ° C. or less, ε _r was 800 to 1300, and tan δ was 2.5% or less. .

In a 0.98 less than the sample 4, ε _r was higher than 1300. In sample 8 where a was greater than 1.01, tan δ was greater than 2.5%.

In sample 21, where b was smaller than 0.01, c was smaller than 0.02, and d was larger than 0.51, CTC was larger than 3000 ppm / ° C. and tan δ was larger than 2.5%. b is greater than 0.02, c is greater than 0.04, d is the 0.48 less than the sample 26, epsilon _r was higher than 1300.

In Sample 2 where x was greater than 0.3 parts by mass, CTC was greater than 3000 ppm / ° C. and tan δ was greater than 2.5%. In x 0.01 parts by mass than smaller samples 9, epsilon _r was higher than 1300.

  In sample 15 where y was 0.1 part by mass, CTC was greater than 3000 ppm / ° C.

DESCRIPTION OF SYMBOLS 1, P ... Piezoelectric element, 20 ... Colpitts oscillation circuit, C _L1 , C _L2 ... Load capacity element, E ... Equivalent circuit of piezoelectric element, 200 ... Oscillator.

Claims (4)

A dielectric ceramic composition of the load capacitive element in an oscillator including a piezoelectric element and a load capacitive element,
Pb _a [Zn _b Nb _c Ti _{{1- (b + c + d)}} Zr _d ] O ₃ ,
0.98 ≦ a ≦ 1.01,
0.01 ≦ b ≦ 0.02,
0.02 ≦ c ≦ 0.04, and 0.48 ≦ d ≦ 0.51,
A perovskite-type composite oxide satisfying
Ni element,
The content of the Ni element converted to NiO is 0.01 to 0.3 parts by mass with respect to 100 parts by mass of the composite oxide,
The content of Co element converted to Co ₃ O ₄ is 0 part by mass or more and less than 0.1 part by mass with respect to 100 parts by mass of the composite oxide.
Dielectric ceramic composition. The content of the Co element in terms of Co ₃ O ₄ is 0 to 0.05 parts by mass with respect to 100 parts by mass of the composite oxide.
The dielectric ceramic composition according to claim 1. Comprising a piezoelectric element and a load capacitive element;
The load capacitor element has the dielectric ceramic composition according to claim 1 or 2.
Oscillator. The piezoelectric element and the load capacitance element are integrated,
The resonator according to claim 3.

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