JP2016069206A - Piezoelectric ceramic composition and piezoelectric resonator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric ceramic composition and a piezoelectric resonator capable suppressing variation of resonance frequency of a piezoelectric element and making stable frequency.SOLUTION: A piezoelectric ceramic composition contains a composite perovskite type compound represented by (PbBaSrCa)(NbSbMn)(TiZr)O, where a, b, c, d, e and f satisfy 0.97≤a+d+e+f≤1.03, 0.02≤b≤0.25, 0.51≤c≤0.61 and 0≤d+e+f≤0.2 as a main component and Al of 0.001 to 0.3 pts.mass, Fe of 0.001 to 0.5 pts.mass and Si of 0.005 to 0.058 pts.mass based on 100 pts.mass of the main component.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a piezoelectric ceramic composition used as a piezoelectric resonator and a piezoelectric resonator.

  Conventionally, piezoelectric resonators using piezoelectric elements are known. The piezoelectric material constituting the piezoelectric element has a large piezoelectric characteristic (for example, an electromechanical coupling coefficient k and a mechanical quality factor Qm) for ensuring oscillation stability, and changes in the resonance frequency with respect to temperature changes. Because of its small size, lead zirconate titanate and lead titanate are mainly used (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 2002-60269

  In piezoelectric resonators that use general lead zirconate titanate materials and lead titanate materials as piezoelectric elements that make up piezoelectric elements, fluctuations in resonance frequency and temperature changes under high temperature and high humidity (cooling cycle) In addition, there is a problem that the resonance frequency varies greatly due to mechanical impact (drop impact).

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a piezoelectric ceramic composition and a piezoelectric resonator that can suppress fluctuations in the resonance frequency of the piezoelectric element and achieve a stable frequency.

The piezoelectric ceramic composition of the present _{invention, (Pb a-d-e} -f Ba d Sr e Ca f) (Nb 19/30 Sb 1/10 Mn 4/15) b (Ti c Zr 1-c) 1- _b O ₃ and a, b, c, d, e, f are 0.97 ≦ a + d + e + f ≦ 1.03, 0.02 ≦ b ≦ 0.25, 0.51 ≦ c ≦ 0.61 , 0 ≦ d + e + f ≦ 0.2 as a main component, and 0.001 to 0.3 parts by mass of Al and 0.001 to 0% of Fe with respect to 100 parts by mass of the main component. .5 parts by mass and Si are contained in an amount of 0.005 to 0.058 parts by mass.

  The piezoelectric resonator of the present invention includes a support substrate and vibration electrodes mounted on the main surface of the support substrate and facing each other on one main surface and the other main surface of the piezoelectric body made of the piezoelectric ceramic composition. The piezoelectric element is provided.

  According to the piezoelectric ceramic composition of the present invention, it is possible to suppress fluctuations in the resonance frequency due to changes in the resonance frequency under high temperature and high humidity, temperature changes (cooling cycle), and mechanical shocks (dropping shock). In addition, according to the piezoelectric resonator of the present invention, it is possible to suppress the fluctuation of the resonance frequency of the piezoelectric element using the piezoelectric body made of the piezoelectric ceramic composition and to obtain a stable frequency.

It is a schematic sectional drawing which shows an example of embodiment of the piezoelectric resonator of this invention.

  Hereinafter, an example of an embodiment of the piezoelectric ceramic composition of the present invention will be described.

The piezoelectric ceramic composition of the present _{embodiment, (Pb a-d-e} -f Ba d Sr e Ca f) (Nb 19/30 Sb 1/10 Mn 4/15) b (Ti c Zr 1-c) 1 represented by _-b O _3, wherein a, b, c, d, e, f are 0.97 ≦ a + d + e + f ≦ 1.03,0.02 ≦ b ≦ 0.25,0.51 ≦ c ≦ 0. 61, a composite perovskite compound that satisfies 0 ≦ d + e + f ≦ 0.2 as a main component, 0.001 to 0.3 parts by mass of Al, and 0.001 to Fe for 100 parts by mass of the main component 0.5 part by mass and 0.005 to 0.058 part by mass of Si are included.

The composite perovskite type compound as the main component in the piezoelectric ceramic composition of the present embodiment is a lead zirconate titanate-based material containing at least Pb, Ti, Nb, Sb, Mn, and Zr as a metal element, depending on the molar ratio. The composition formula can be _expressed as Pb _a (Nb _19/30 Sb _1/10 Mn _4/15 ) _b (Ti _c Zr _1-c ) _1-b O ₃ .

  Here, except for the case of partial replacement described later, when the amount of Pb at the A site of the composite perovskite compound decreases, there is a tendency that resonance does not occur due to a drop impact, and when the amount of Pb increases, the resonance after the thermal cycle The frequency change rate tends to increase.

  Moreover, a part of Pb may be substituted with at least one of Ba, Sr, and Ca, and this substitution can give strain to the crystal lattice and induce polarization inversion of the lead zirconate titanate-based material. This has the effect of improving the piezoelectric characteristics such as the electromechanical coupling coefficient. In addition, when the substitution amount (Molar ratio of Ba, Sr, Ca) when a part of Pb is substituted with one or all of Ba, Sr, and Ca increases the resonance frequency after high temperature and high humidity. The rate of change and the rate of change of the resonance frequency of the temperature cycle tend to increase.

From the above, the composite perovskite compound is the main component in this embodiment, as the composition formula by molar _{ratio, (Pb a-d-e} -f Ba d Sr e Ca f) (Nb 19/30 Sb 1 / ₁₀ Mn _4/15 ) _b (Ti _c Zr _1-c ) _1-b O ₃ , and a, d, e, f at the A site of this composite perovskite compound are 0.97 ≦ a + d + e + f ≦ 1.03, 0 ≦ d + e + f ≦ 0.2 is satisfied.

  When Pb is not substituted with at least one of Ba, Sr, and Ca (when d + e + f = 0), 0.97 ≦ a ≦ 1.03, and Pb is at least one of Ba, Sr, and Ca. Thus, for example, when the molar ratio is 0.2 (d + e + f = 0.2), 0.77 ≦ a ≦ 1.03.

  On the other hand, when B is less than 0.02 at the B site of this composite perovskite type compound, the rate of change in resonance frequency after the thermal cycle tends to increase. On the other hand, if b exceeds 0.25, the rate of change in resonance frequency after high temperature and high humidity tends to increase. Moreover, when c is less than 0.51, the change rate of the resonance frequency after the cooling / heating cycle tends to increase. On the other hand, if c exceeds 0.61, the rate of change in resonance frequency after high temperature and high humidity tends to increase. Therefore, it is necessary to satisfy 0.02 ≦ b ≦ 0.25 and 0.51 ≦ c ≦ 0.61.

  Furthermore, the piezoelectric ceramic composition of the present embodiment has 0.001 to 0.3 parts by mass of Al and 0.001 to 0.5 parts by mass of Fe with respect to 100 parts by mass of the main component composed of the composite perovskite compound. And 0.005 to 0.058 parts by mass of Si.

  When the Fe content is less than 0.001 part by mass with respect to 100 parts by mass of the main component, the rate of change of the resonance frequency in the cooling cycle tends to increase after high temperature and high humidity, exceeding 0.5 part by mass. In the same manner, the rate of change of the resonance frequency in the temperature cycle tends to increase after high temperature and high humidity.

  Further, when the amount of Al is less than 0.001 part by mass with respect to 100 parts by mass of the main component, the rate of change of the resonance frequency in the cooling cycle tends to increase after high temperature and high humidity, 0.3 parts by mass Similarly, when the temperature exceeds 50%, the rate of change of the resonance frequency in the cooling / heating cycle tends to increase after high temperature and high humidity.

  Further, when the amount of Si is less than 0.005 parts by mass with respect to 100 parts by mass of the main component, the change rate of the resonance frequency tends to increase after high temperature and high humidity, and when it exceeds 0.058 parts by mass, There is a tendency for the rate of change of the resonance frequency in the cycle to increase, and there is also a tendency for resonance not to occur.

  Note that at least a part of the Fe and Al may be dissolved in the composite perovskite compound. For example, when Fe is dissolved as a divalent or trivalent ion at the B site of the composite perovskite compound, oxygen vacancies are generated and sintering is promoted. Further, Al is dissolved as a trivalent ion at the B site of the composite perovskite compound, whereby oxygen vacancies are generated and sintering is promoted.

  In addition, when Fe is dissolved as divalent or trivalent ions, or Al is dissolved as trivalent ions, oxygen vacancies are generated, and a pinning effect acts on the domain wall (domain wall). (Domain wall) fluctuations can be suppressed. Therefore, it seems that the fluctuation | variation of the resonant frequency by a thermal cycle and a drop impact can be suppressed.

In addition, Si becomes a liquid phase at the grain boundary as SiO ₂ , so that the diffusion rate is improved and sintering is promoted. Therefore, since the sinterability of the piezoelectric ceramic produced by the piezoelectric ceramic composition of the present embodiment is improved and moisture can be prevented from entering from the grain boundary, the fluctuation of the resonance frequency under high temperature and high humidity is suppressed. Seems to be able to. Furthermore, Si is preferably present as SiO _{2 at the} grain boundary. Since the thermal conductivity of SiO ₂ is lower than the thermal conductivity of lead zirconate titanate-based materials, such a configuration makes it possible to conduct heat to crystal particles composed of lead zirconate titanate-based materials. Therefore, the fluctuation of the resonance frequency due to the cooling / heating cycle can be further reduced.

The fact that Si is present at the grain boundary as SiO ₂ is an element that uses a transmission electron microscope (TEM), structural analysis using an electron beam diffraction pattern, and characteristic X-rays generated by electron beam irradiation. It can be measured by analysis.

  According to the piezoelectric ceramic composition of the present embodiment, fluctuations in the resonance frequency of a piezoelectric element using a piezoelectric body made of the piezoelectric ceramic composition can be suppressed and a stable frequency can be obtained.

  The above-described piezoelectric ceramic composition can be used as a piezoelectric resonator (resonator).

  The piezoelectric resonator according to the present embodiment is mounted on the main surface of the support substrate 2 and the support substrate 2, and the vibrating electrode is opposed to the one main surface and the other main surface of the piezoelectric body 11 made of the piezoelectric ceramic composition. And a piezoelectric element 1 provided with 12.

The support substrate 2 is, for example, both main surfaces of a dielectric formed as a rectangular flat plate having a length of 2.5 mm to 7.5 mm, a width of 1.0 mm to 3.0 mm, and a thickness of 0.1 mm to 1 mm. Are provided with electrodes such as terminal electrodes and capacitance forming electrodes. Examples of electrode materials include conductive resins in which metal powders such as gold, silver, copper, aluminum, and tungsten are dispersed in resins, and thick film conductors that are baked by adding additives such as glass to these metal powders. Can be used. If necessary, Ni / Au or Ni / Sn plating may be formed.

  On the support substrate 2, the piezoelectric element 1 is mounted. Specifically, both end portions of the piezoelectric element 1 are fixed on the support substrate 2 by the support portion 3 and the conductive bonding material 4 so as to vibrate.

  In the piezoelectric element 1, the vibration electrode 12 provided on the upper main surface of the piezoelectric body 11 is provided so as to extend from one end portion in the longitudinal direction toward the other end portion. The vibration electrode 12 provided on the main surface is provided so as to extend from the other end portion in the longitudinal direction toward the one end portion, and has regions facing each other. The vibrating electrode 12 can be made of metal such as gold, silver, copper, or aluminum, and is attached to the surface of the piezoelectric body 11 to a thickness of, for example, 0.1 μm to 3 μm.

  The vibration electrode 12 of the piezoelectric element 1 is electrically connected to the electrode on the support substrate 1 through the support portion 3 and the conductive bonding material 4. The support portion 3 and the conductive bonding material 4 also have a function of ensuring a predetermined space (gap) between the support substrate 2 and the piezoelectric element 1.

  The support part 3 is formed of, for example, a conductive paste. Moreover, as the conductive bonding material 4, for example, solder, a conductive adhesive, or the like is used. If it is a solder, for example, a lead-free material such as copper, tin, or silver can be used. If it is a conductive adhesive, it contains 75 to 95% by mass of conductive particles such as silver, copper, and nickel. Epoxy conductive resin or silicone resin can be used.

  When the piezoelectric element 1 mounted on the support substrate 2 in this way is applied with a voltage between the upper vibrating electrode 12 and the lower vibrating electrode 12, the piezoelectric element 1 has a specific frequency in a region where they face each other. A piezoelectric vibration of thickness longitudinal vibration or thickness shear vibration is generated.

  A lid 5 is provided on the support substrate 2 so as to cover the piezoelectric element 1. The lid 5 is bonded to the peripheral edge of the upper surface of the support substrate 2 with an adhesive or the like, thereby causing the piezoelectric element 1 accommodated in the space formed together with the support substrate 2 to physically influence from the outside. And a function of protecting from chemical influences, and a hermetic sealing function for preventing entry of foreign matters such as water into the space formed together with the support substrate 2. In addition, as a material of the lid 5, for example, a metal such as SUS, ceramics such as alumina, resin, glass, or the like can be used. In addition, an insulating resin material such as an epoxy resin may contain an inorganic filler in a proportion of 25 to 80% by mass so as to reduce the difference in thermal expansion coefficient from the capacitive substrate 1.

  With such a configuration, a piezoelectric resonator having a stable frequency can be obtained.

  Next, a method for manufacturing the piezoelectric resonator of this embodiment will be described.

First, a piezoelectric body 11 made of the piezoelectric ceramic composition constituting the piezoelectric element 1 is produced.
Predetermined amounts of high-purity PbO, ZrO ₂ , TiO ₂ , Nb ₂ O ₅ , Sb ₂ O ₅ , MnO ₂ , Fe ₂ O ₃ , Al ₂ O ₃ and SiO ₂ are used as raw material powders, and ZrO For example, wet mixing is performed for 10 hours in a ball mill using _two balls, then the mixture is dehydrated and dried, calcined, and the calcined product is wet pulverized again by the ball mill.

  Thereafter, an organic binder is mixed into the pulverized product and granulated.

The obtained powder is press-molded so as to have a predetermined shape at a pressure of 1.5 ton / cm ² and fired. Then, the sintered body is polished, for example, silver electrodes are baked on both end faces, and a polarization process is performed by applying a direct current electric field between the electrodes. The sample subjected to the polarization treatment is subjected to a heat treatment at 100 ° C. for 1 hour in an oven, and then left for 24 hours to produce the piezoelectric body 11.

  Next, the vibrating electrodes 12 are provided on the upper and lower main surfaces of the piezoelectric body 11. The vibrating electrodes 12 formed on the upper and lower main surfaces of the piezoelectric body 11 are coated with a metal film by using a vacuum deposition method, a PVD method, a sputtering method, or the like, and a photoresist film having a thickness of, for example, 1 μm to 10 μm is used. It can be formed by patterning by photoetching after it is formed on the metal film by screen printing or the like. The piezoelectric element 1 is manufactured by cutting the patterned piezoelectric body 11 of the vibration electrode 12 into a predetermined size by dicing or the like.

  Next, a multi-piece substrate for producing the support substrate 2 is produced. For example, raw powders such as lead titanate, lead zirconate titanate, and barium titanate are mixed together with water and a dispersant using a ball mill, and then a binder, a plasticizer, and the like are added, followed by drying and sizing. The raw material thus obtained is press-molded and, if necessary, subjected to hole processing, degreased at a predetermined temperature, fired at a peak temperature of, for example, 900 ° C. to 1600 ° C., and polished to a predetermined thickness . Thereafter, for example, a conductive paste containing a metal powder such as silver or nickel and glass is printed and baked at a predetermined temperature to form an electrode or the like to obtain the support substrate 2.

  A support portion 3 made of a conductive paste is formed on the obtained support substrate 2 with a thickness of 1 μm to 100 μm, for example, using screen printing or the like.

  Then, the piezoelectric element 1 is mounted on the support portion 3 of the support substrate 2 and fixed using the conductive bonding material 4. Here, in the case where the conductive bonding material 4 is a conductive adhesive in which metal powder is dispersed in a resin, the conductive adhesive is applied on the support portion 3 using a dispenser or the like, The piezoelectric element 1 may be placed on the support portion 3 and the conductive adhesive resin may be cured by heating or ultraviolet irradiation.

  Then, the opening peripheral surface of the lid 5 is joined to the peripheral portion of the upper surface of the support substrate 2 so as to cover the piezoelectric element 1. As the lid 5, a multi-piece collective cover sheet having a plurality of concave portions is used, and the multi-piece collective cover sheet is placed on the pick-up substrate so that the concave portions cover the piezoelectric elements 1. The convex portion of the collective cover sheet serving as the opening peripheral surface is joined to the peripheral portion of the upper surface of the support substrate 2. For example, a thermosetting insulating adhesive is applied to the convex portion of the collective lid sheet that is the peripheral edge of the opening of the prepared lid 5, and the lid 5 is placed on the upper surface of the support substrate. Thereafter, the lid 5 or the support substrate 2 is heated to raise the temperature of the insulating adhesive to 100 to 150 ° C., and the lid 5 is bonded to the upper surface of the support substrate 2.

  Finally, it cut | disconnects by dicing etc. along the boundary of each piezoelectric resonator (piece | piece). The piezoelectric resonator of this example is manufactured by the above method.

  Examples of the piezoelectric resonator will be described.

  A piezoelectric resonator equipped with a piezoelectric element including a piezoelectric body made of the piezoelectric ceramic composition of the present embodiment was manufactured as follows.

Specifically, high-purity PbO, ZrO ₂ , TiO ₂ , Nb ₂ O ₅ , Sb ₂ O ₅ , MnO ₂ , Fe ₂ O ₃ , Al ₂ O ₃ and SiO ₂ are used as raw material powders. A predetermined amount was weighed so that the ratio of each component of the sintered body would be the ratio shown in Table 1, and a piezoelectric material constituting the piezoelectric element was produced.

  Granules were produced using this raw material, and depressurized and fired after press molding to produce a piezoelectric body.

  The piezoelectric body was processed, polarized, and the thickness was adjusted by lapping, and then metal films were formed on both main surfaces. Thereafter, pattern etching was performed to form a vibrating electrode, which was cut into a length of 2.5 mm and a width of 0.5 mm to produce a rectangular piezoelectric element having a thickness of 0.15 mm.

  In addition, a support substrate having a thickness of 0.3 mm on which predetermined capacitance electrodes and terminal electrodes were formed was prepared, the above-described piezoelectric element was mounted, and after joining, the lid was joined with an adhesive. This substrate was cut into a length of 3.2 mm and a width of 1.3 mm to produce a piezoelectric resonator having a product thickness of 1.0 mm.

  The piezoelectric resonator thus fabricated was applied to a high-temperature and high-humidity test at 85 ° C., 85% and a durability time of 1000 h, a thermal cycle test of 1000 cycles at −55 ° C. for 30 min, 105 ° C. for 30 min, and a test substrate. An impact test was performed in which the piezoelectric resonator was soldered and dropped 18 times from a height of 1.8 m. These results are shown in Table 1. In addition, a numerical value shows the change rate of the resonant frequency before and behind a test.

  According to Table 1, the piezoelectric resonator equipped with the piezoelectric element including the piezoelectric body of the piezoelectric ceramic composition of the present embodiment has a stable frequency even under high temperature and high humidity, under a cooling cycle, and with respect to a drop impact. It can be seen that it can be maintained.

DESCRIPTION OF SYMBOLS 1 ... Piezoelectric element 11 ... Piezoelectric body 12 ... Vibration electrode 2 ... Support substrate 3 ... Support part 4 ... Conductive joining material 5 ... Cover

Claims (3)

Represented by _{(Pb a-d-e-} f Ba d Sr e Ca f) (Nb 19/30 Sb 1/10 Mn 4/15) b (Ti c Zr 1-c) 1-b O 3, wherein a, b, c, d, e, f are 0.97 ≦ a + d + e + f ≦ 1.03, 0.02 ≦ b ≦ 0.25, 0.51 ≦ c ≦ 0.61, 0 ≦ d + e + f ≦ 0.2 Containing a satisfactory composite perovskite compound as the main component,
0.001 to 0.3 parts by mass of Al, 0.001 to 0.5 parts by mass of Fe, and 0.005 to 0.058 parts by mass of Si with respect to 100 parts by mass of the main component Piezoelectric ceramic composition. _2. The piezoelectric ceramic composition according to claim 1, wherein SiO ₂ exists in a crystal grain boundary of the composite perovskite compound. A supporting substrate and vibration electrodes mounted on the main surface of the supporting substrate and facing each other on one main surface and the other main surface of the piezoelectric body made of the piezoelectric ceramic composition according to claim 1 or 2 are provided. And a piezoelectric element.

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