JP2009234904A - Piezoceramic composition, piezoelectric element using the same and non-resonance knock sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoceramic composition with excellent piezoelectric and temperature characteristics, to provide a piezoelectric element using the piezoceramic composition and to provide a non-resonance knock sensor. <P>SOLUTION: The piezoceramic composition has a composition represented by Pb<SB>m</SB>äZr<SB>1-x-y-z</SB>Ti<SB>x</SB>Sn<SB>y</SB>(Sb<SB>1-n</SB>Nb<SB>n</SB>)<SB>z</SB>}O<SB>3</SB>, wherein 1.000≤m≤1.075, 0.470≤x<0.490, 0.020≤y≤0.040, 0<n<1.000 and 0<z≤0.025, and the crystallite size is 30 to 39 nm. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention includes, for example, a piezoelectric ceramic composition that can be used for a piezoelectric sensor such as a pressure sensor, an acceleration sensor, a knock sensor, a yaw rate sensor, a gyro sensor, and a shock sensor using a piezoelectric effect, a piezoelectric element using the same, and The present invention relates to a non-resonant knock sensor.

Piezoelectric sensors that convert mechanical energy into electrical energy using the piezoelectric effect of piezoelectric ceramic compositions are widely applied in the fields of electronics and mechatronics. The piezoelectric sensor generally has a piezoelectric element in which at least one pair of electrodes is provided on a sintered body (bulk) made of piezoelectric ceramic, and the piezoelectric element is held via a pressure contact member such as an adhesive member or a spring. The structure is such that it is held by a component and an electric signal is taken out from the piezoelectric element by a lead terminal. Further, since the piezoelectric element is pressed by adhesion, a mold, a spring or the like, a mechanical restraining force (preset load) is applied in the assembled state.
When the piezoelectric element receives stress to be detected, it generates a charge or voltage, and the charge or voltage is sent to a circuit connected to the sensor or a circuit integrated with the sensor, thereby converting the stress into a voltage signal. can do.

  In the piezoelectric sensor, when the temperature of the usage environment changes, the piezoelectric characteristics and the like of the piezoelectric ceramic change, so the sensitivity (output voltage) of the piezoelectric sensor changes. Also, if the temperature of the piezoelectric sensor changes due to temperature changes in the operating environment or temperature rise due to driving, thermal stress is generated due to the difference in thermal expansion between the piezoelectric ceramics and the electrodes and holding members that are in contact with them. There has been a problem that noise is generated in the piezoelectric sensor, resulting in variations in sensitivity. Further, when the temperature of the piezoelectric sensor changes, a voltage is generated in the piezoelectric sensor due to the pyroelectric effect, noise is generated in the piezoelectric sensor, and there is a problem that sensitivity variation occurs. Further, there is a problem that the piezoelectric characteristics are lowered due to the weight applied to the piezoelectric element, and the output of the piezoelectric sensor is lowered.

For this reason, the operating temperature range of the piezoelectric sensor is usually about -40 ° C to 170 ° C. However, since the piezoelectric sensor is used for severe applications such as automobile parts, the temperature characteristics in a wider temperature range. There is a demand for a piezoelectric element that does not vary.
Therefore, Sn is added to PZT (lead zirconate titanate) to improve the thermal stability, and Nb and Sb are added to soften it (to increase the crystal distortion and improve the piezoelectric characteristics) and to lower the temperature. Piezoelectric ceramic compositions that enable sintering are disclosed (Patent Documents 1 to 3).

Japanese Patent No. 2789374 Japanese Patent No. 2964265 Japanese Patent No. 2957002

However, the prior art is insufficient in terms of improving the piezoelectric characteristics and temperature characteristics. For example, a piezoelectric constant d33 that is an indicator of piezoelectric characteristics (sensitivity) is required to be 340 or more, but no composition having such a high piezoelectric constant has been reported. Further, the maximum temperature of the pressure sensor used in the vicinity of the automobile engine part may reach about 170 ° C., and it is desirable that the Curie temperature which is an index of heat resistance is 340 ° C. or higher, but such a high Curie temperature is high. The resulting composition has not been reported.
That is, an object of the present invention is to provide a piezoelectric ceramic composition excellent in piezoelectric characteristics and temperature characteristics, a piezoelectric element using the same, and a non-resonant knock sensor.

The present inventors have found a piezoelectric ceramic composition having high heat resistance and high piezoelectric characteristics by controlling the composition of the Pb-Zr-Ti-Sn-Sb-Nb-based oxide and its crystal state. .
That is, the piezoelectric ceramic composition of the present invention comprises Pb _m {Zr _1-xyz Ti _x Sn _y (Sb _1-n Nb _n ) _z } O ₃ (wherein 1.000 ≦ m ≦ 1.075, 0.470 ≦ x <0.490, 0.020 ≦ y ≦ 0.040, 0 <n <1.000, 0 <z ≦ 0.025), and the crystallite diameter is 30 to 39 nm.

In addition, the piezoelectric ceramic composition of the present invention has Pb _m {Zr _1-xyz Ti _x Sn _y (Sb _1-n Nb _n ) _z } O ₃ (wherein 1.000 ≦ m ≦ 1.075, 0.470 ≦ x <0.490, 0.020 ≦ y ≦ 0.040, 0 <n <1.000, 0 <z ≦ 0.025 is satisfied), and the piezoelectric constant d33 is 340 pC / N or more.

The piezoelectric element of the present invention uses the piezoelectric ceramic composition.
The non-resonant type knocking sensor of the present invention is disposed on the piezoelectric element, the piezoelectric element comprising the piezoelectric ceramic composition and the element electrode, a support member having a support main body for supporting the piezoelectric element, and the piezoelectric element. A weight member that presses the weight toward the support main body, and at least part of the element electrode is formed by projecting the weight member and the piezoelectric element along the thickness direction of the piezoelectric element. The member faces the bottom surface facing the piezoelectric element side, and the ratio of the surface area of the element electrode facing the bottom surface to the bottom surface area of the weight member is 45% or more.

  According to the present invention, a piezoelectric ceramic composition excellent in piezoelectric characteristics and temperature characteristics, a piezoelectric element using the same, and a non-resonant knock sensor can be obtained.

Hereinafter, embodiments of the present invention will be described.
The piezoelectric ceramic composition of the present invention is based on a PbTiO ₃ -PbZrO ₃ system (PZT (lead zirconate titanate)). PbTiO ₃ is a ferroelectric substance belonging to the tetragonal system, and when Ti in the crystal structure is substituted with Zr, the amount of Zr solid solution is about 53 mol% and changes to a rhombohedral phase. Such a phase boundary in which the crystal system changes depending on the composition is called a morphotropic phase boundary (MPB), and it is known that the piezoelectricity shows a maximum in this vicinity. On the other hand, in the vicinity of the morphotropic phase boundary, the stability of the crystal decreases, and the variation of the capacitance Cp with respect to temperature increases.
Therefore, the piezoelectric ceramic composition of the present invention shifts the composition from the morphotropic phase boundary region, and further has a substitution effect including (added) Sn, Sb, and Nb, so that the piezoelectricity and the capacitance Cp are stable with respect to temperature. Pb _m {Zr _1-xyz Ti _x Sn _y (Sb _1-n Nb _n ) _z } O ₃ (where 1.000 ≦ m ≦ 1.075, 0.470 ≦ x <0.490, 0.020 ≦ y ≦ 0.040, 0 <n <1.000, 0 <z ≦ 0.025).

  By setting the composition of the piezoelectric ceramic composition within the above range, the piezoelectric constant d33 can be set to 340 pC / N or more. The piezoelectric constant d33 [pC / N] is represented by the amount of charge generated by applying stress due to the positive effect of piezoelectricity (pressure → electricity). The larger the piezoelectric constant d33, the larger the amount of charge generated by the load (the sensor output becomes larger).

When m <1, it deviates from the composition of PZT and the piezoelectric constant d33 becomes small. When m> 1.075, as shown in FIG. 1, PbO is generated inside the piezoelectric ceramic composition, and the piezoelectric constant d33 becomes small.
In the case of x <0.470, there is a possibility that ΔCp> 2500 ppm / K due to low Ti content. When 0.490 ≦ x, the piezoelectric constant d33 tends to decrease, and the d33 deterioration rate with respect to heat increases.
In the case of y <0.020, the Curie temperature Tc may decrease due to the small Sn content.
When n = 0, the stability of the crystal is lowered because Nb is not included. In the case of n = 1.000, the stability of the crystal is lowered because Sb is not included.
When z = 0, since both Nb and Sb are not included, the sintering temperature becomes high, and the crystallite diameter described later cannot be defined within a predetermined range. Moreover, the d33 deterioration rate with respect to heat also falls. In the case of 0.025 ≦ z, the contents of Nb and Sb are excessively increased, and ΔCp> 2500 ppm / K, or the Curie temperature Tc may be lowered.

The piezoelectric ceramic composition of the present invention has a crystallite diameter of 30 to 39 nm.
The crystallite diameter is the maximum region that can be regarded as a single crystal and is an index of crystal perfection. A normal substance is composed of a plurality of crystallites.
When the crystallite diameter is less than 30 nm, domains (regions) in which crystals are aligned in the same direction are reduced, and it is difficult to improve piezoelectric characteristics. Theoretically, by increasing the firing temperature, the crystallite diameter can be increased and the piezoelectric characteristics are improved, but in reality the volatile elements (Pb, Sn, Sb) in the composition are evaporated and the composition is increased. Collapses, and on the contrary, the piezoelectric characteristics deteriorate. For this reason, when the crystallite diameter exceeds 39 nm, the piezoelectric characteristics deteriorate.
On the other hand, the crystal grain size of the composition does not necessarily reflect the size of the domain, and it is difficult to improve the piezoelectric characteristics even if the crystal grain size of the composition is defined. However, if the crystal grain size is too large, the gap between grains tends to increase, and the amount of charge (sensor output) generated by the load tends to decrease.
For this reason, in the present invention, the crystallite size was experimentally determined to be 30 to 39 nm, not controlled by the crystal grain size.

The crystallite diameter can be controlled by changing the firing temperature, calcination conditions, the pulverized diameter of the raw material, and the like.
The crystallite diameter can be measured by performing XRD (X-ray diffraction) on the sample and substituting the half-value width (or integral width) representing the spread of incident X-rays into Scherrer's equation. According to Scherrer's equation, D = Kλ / (βcosθ) (D: crystallite diameter, K: Scherrer constant, λ: X-ray wavelength, β: half-width of reflected X-ray, θ: diffraction angle) .

In the piezoelectric ceramic composition of the present invention, the Curie temperature (Tc) is preferably 340 ° C. or higher. The higher the Tc, the better the heat resistance, and it is suitable for high temperature environment applications such as automobile engine parts.
The piezoelectric ceramic composition of the present invention preferably has a capacitance change rate (ΔCp) at 20 ° C. to 150 ° C. of 2500 ppm / K or less. As ΔCp is smaller, the temperature change of the capacitance is smaller and variation in sensor sensitivity is reduced.
Furthermore, in the piezoelectric ceramic composition of the present invention, it is preferable that the deterioration rate of the piezoelectric constant d33 after a heat resistance test at 250 ° C. for 10 hours is within −10%. The smaller the d33 deterioration rate, the better the heat resistance. The d33 deterioration rate is represented by {(piezoelectric constant d33 after heat test) − (initial piezoelectric constant d33)} / (initial piezoelectric constant d33).

The piezoelectric ceramic composition of the present invention is excellent in stability, heat resistance and durability. For example, a pressure sensor, a resonator, a piezoelectric vibrator, an actuator, a combustion pressure sensor, a knocking sensor, an ultrasonic motor, a piezoelectric gyro sensor, and a fingerprint. It can be suitably used for a piezoelectric element such as an authentication device.
The piezoelectric element of the present invention is a piezoelectric ceramic composition provided with a pair of electrodes having at least positive and negative polarities.

The piezoelectric ceramic composition of the present invention can be produced, for example, as follows. First, a raw material powder made of oxide, carbonate or hydrogencarbonate is blended so as to have the above composition formula, added to a dispersion medium such as ethanol, water, etc., and then wet-mixed and pulverized by a ball mill or the like. To do. The obtained slurry is dried to obtain a raw material mixed powder.
Next, for example, the raw material mixed powder is calcined at 600 ° C. to 1100 ° C. for 10 minutes to 300 minutes in an air atmosphere to obtain a calcined powder. Further, for example, an organic binder such as polyvinyl alcohol and polyvinyl butyral, a water-soluble binder, and a dispersion medium such as alcohols, ethers, and water are added to the calcined powder, and wet milling is performed by a ball mill or the like to obtain a slurry. The obtained slurry is dried to obtain a granulated powder.
Further, the granulated powder is molded into a predetermined shape to obtain a molded body. The shape of the molded body is not particularly limited, and a ring shape, a disk shape, or the like can be appropriately selected as necessary. In addition, for example, it is preferable to perform uniaxial molding at about 30 MPa and then cold isostatic press (CIP) treatment at about 150 MPa. The molded body thus obtained is fired, for example, in the range of 900 ° C. to 1250 ° C. for 1 hour to 10 hours to obtain a sintered body.

Next, element electrodes are formed on two opposing surfaces of the obtained sintered body. If the sintered body is, for example, a disk shape, both surfaces of the sintered body may be polished to form electrode forming surfaces. The element electrode can be formed by applying a conductive paste to the element electrode formation surface by screen printing or the like and baking it appropriately.
Examples of the conductive paste include those made of a conductive component, glass frit, and an organic medium. As the conductive component, for example, a noble metal powder composed of a noble metal such as silver, gold, palladium or platinum, an alloy powder composed of an alloy of these noble metals, or a mixed powder composed of two or more of these noble metal powders may be used. it can. In addition to such noble metals, powders made of metals such as copper and nickel, alloy powders, mixed powders, and the like can also be used. As the glass frit, for example, one containing SiO ₂ , Al ₂ O ₃ , ZnO and TiO ₂ can be used. Moreover, what is used for this kind of pastes, such as alcohol and ethers, can be used as an organic medium.

A DC voltage of about 3 kV / mm to 20 kV / mm is applied for about 10 to 100 minutes in an insulating oil such as a silicone oil of about room temperature to about 200 ° C., for example, to the sintered body on which the element electrode is formed. Then, a polarization treatment is performed to obtain a piezoelectric ceramic composition. The polarization treatment may be performed by applying a high voltage in the air to the overheated element instead of in silicone oil. Thus, the piezoelectric ceramic composition in which the element electrode is formed may be used in a state in which the element electrode is formed, or may be used after removing the element electrode formed on the surface.
The piezoelectric ceramic composition which has been polarized in this way and has a predetermined shape can be used as a piezoelectric element.

A non-resonant type knocking sensor can be configured using the piezoelectric element described above.
FIG. 5 is a cross-sectional view of the non-resonant knock sensor 10 according to the embodiment of the present invention. In FIG. 5, a knocking sensor 10 is a so-called center hole type non-resonant knocking sensor having a mounting hole 12f for mounting on a cylinder block or the like of an internal combustion engine at the center. The knocking sensor 10 is configured by covering a sensor main body 20 with a resin molded body 11, and is formed into a short cylindrical shape as a whole, and a connector portion 11b protrudes radially outward from the outer periphery of the cylinder.
The sensor body 20 is disposed on the piezoelectric element 15, the support member (metal shell) 12 having the support body portion 12 b that supports the piezoelectric element 15, and presses the piezoelectric element toward the support body portion 12 b. The weight member 17 is provided.
Further, a first terminal 14a and a second terminal 16a extending from the lower electrode 14 and the upper electrode 16 respectively project from the inner side of the connector portion 11b (only the first terminal 14a is shown in FIG. 5) and are connected to an external connector (not shown). It has become so.

As shown in the exploded perspective view of FIG. 6, the support member 12 has a cylindrical portion 12a and a support main body portion 12b formed in a bowl shape at the lower end of the cylindrical portion 12a. A male screw portion 12x is formed on the upper outer peripheral surface of 12a. And on the outer periphery of the cylindrical part 12a, the annular first insulating plate 13, the lower electrode 14, the piezoelectric element 15, the upper electrode 16, the second insulating plate 13t, and the weight member 17 are sequentially arranged from the support main body part 12b side. And the disc spring 18 is engage | inserted and the 1st insulating board 13 is mounted on the support main-body part 12b.
Further, by screwing a nut 19 having an internal thread portion 19 y formed on the inner surface thereof to the external thread portion 12 x, the laminated body extending from the first insulating plate 13 to the disc spring 18 is formed between the support main body portion 12 b and the nut 19. The sensor body 20 is configured by being sandwiched and fixed therebetween. Thereby, the weight member 17 presses the piezoelectric element 15 toward the support main body 12b.

  A cylindrical insulating sleeve 13s is fitted on the outer peripheral surface of the cylindrical portion 12a to prevent the lower electrode 14, the piezoelectric element 15 and the upper electrode 16 from being in electrical contact with the cylindrical portion 12a. In addition, first and second terminals 14a and 16a for taking out voltages extend in the form of pieces on the radially outer sides of the lower electrode 14 and the upper electrode 16, respectively.

In the non-resonant type knocking sensor 10, at least a part (all in this embodiment) of the element electrodes 15 a constituting the piezoelectric element 15 causes the weight member 17 and the piezoelectric element 15 to extend along the thickness direction of the piezoelectric element 15. Are projected to the bottom surface SA of the weight member 17 facing the piezoelectric element 15 side. The ratio of the area S2 of the surface SB of the element electrode 15a to the area S1 of the bottom surface SA of the weight member 17 is 45% or more. The surface SB faces the bottom surface SA.
Here, if the area S2 can be made smaller than the area S1, the usage amount of the electrode material of the element electrode 15a constituting the piezoelectric element 15, and further the usage amount of the electrode material of the element electrode 15b paired with the element electrode 15a. The cost of the non-resonant knock sensor 10 can be reduced. Further, since the degree of freedom of changing the ratio of the area S2 to the area S1 is increased, the capacitance of the piezoelectric element 15 can be adjusted to an optimum value. However, if the area S2 is made smaller than the area S1, the output of the knocking sensor is reduced and the sensitivity may be lowered. Therefore, the ratio of the area S2 to the area S1 is specified to be 45% or more.

FIG. 7 is a partial cross-sectional view showing the vicinity of the piezoelectric element 15 and the weight member 17. In FIG. 7, the components other than the piezoelectric element 15 and the weight member 17 are appropriately omitted for easy understanding.
In the present embodiment, the end of the bottom surface SA of the weight member 17 facing the piezoelectric element 15 is chamfered to form a chamfered portion 17f. Therefore, the flat surface facing the piezoelectric element 15 excluding the chamfered portion 17f described above among the bottom surface SA of the weight member 17 is defined as the bottom surface SA, and the area S1 is calculated.
Similarly, in this embodiment, the end of the upper surface (that is, the surface facing the bottom surface SA of the weight member 17) of the piezoelectric element 15 on the weight member side (specifically, the sintered body as the piezoelectric ceramic composition) is chamfered. Thus, a chamfered portion 15f is formed. And the element electrode 15a is formed in the upper surface of the sintered compact as a piezoelectric ceramic composition except this chamfer part. Then, the area of the surface SB facing the bottom surface SA of the weight member 17 in the element electrode 15a is calculated as the area S2 of the element electrode 15a.

  It goes without saying that the present invention is not limited to the above-described embodiments, and extends to various modifications and equivalents included in the spirit and scope of the present invention.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated concretely, this invention is not limited to these examples of course.

Each raw material powder of lead oxide, zirconium oxide, titanium oxide, tin oxide, antimony oxide, niobium oxide is prepared, and the composition after sintering is a ratio shown in each of inventive examples 1-9 and comparative examples 1-15 in Table 2. Then, the mixed powder was added to ethanol, then wet mixed and pulverized by a ball mill, and dried to obtain a raw material mixed powder.
The raw material mixed powder was calcined at 800 ° C. for 2 to 3 hours in an air atmosphere to obtain a calcined powder having a calcined and pulverized particle size of about 0.6 to 1 μm. An organic binder, a water-soluble binder, and alcohols were added to the calcined powder, wet pulverized by a ball mill, and dried to obtain a granulated powder.
Further, this granulated powder was pressure-molded into a disk shape having a diameter of 19 mm and a thickness of 1.4 mm. The molding was uniaxially molded at about 30 MPa and then cold isostatically pressed (CIP) at about 150 MPa. The obtained molded body was fired in an air atmosphere at 1100 ° C. or 1300 ° C. for 2 to 4 hours to obtain a sintered body.
Both surfaces of the sintered body were flat-polished, and then a silver paste was screened on this surface and baked to form an electrode. Next, the sintered body on which the electrodes were formed was subjected to a polarization treatment by applying a direct current voltage of 3 to 5 kV / mm in a silicone oil at 100 to 150 ° C. to obtain a piezoelectric ceramic composition.

The following items were evaluated about the obtained piezoelectric ceramic composition.
(1) ΔCp (Capacitance (Cp) change rate from 20 ℃ to 150 ℃)
Using an impedance analyzer (model HP4194A, manufactured by Hewlett-Packard Company), the capacitance Cp (20) at 20 ° C. and the capacitance Cp (150) at 150 ° C. were measured (unit: pF). Next formula
Δ [Cp was calculated from [[(Cp (150) -Cp (20)) / Cp (20)] / [150-20]] * 1000000. If ΔCp is 2500 ppm / K or less, there is no practical problem.
(2) Curie temperature (Tc)
Tc was measured using an impedance analyzer (model HP4194A, manufactured by Hewlett Packard) and an electric furnace.
(3) Piezoelectric constant d33
The piezoelectric constant d33 was measured according to the resonance anti-resonance method described in EMAS-6100, and was also used in combination with a d33 meter (model ZJ-4B, manufactured by China Academy of Sciences).
(4) d33 deterioration rate After measuring the initial d33, each sample was subjected to a heat resistance test at 250 ° C. for 10 hours in an air atmosphere, and d33 was measured in the same manner. The d33 deterioration rate was determined by the following formula {(piezoelectric constant d33 after heat test) − (initial piezoelectric constant d33)} / (initial piezoelectric constant d33).

The obtained results are shown in Table 1.

As apparent from Table 1, Pb _m {Zr _1-xyz Ti _x Sn _y (Sb _1-n Nb _n ) _z } O ₃ , wherein 1.000 ≦ m ≦ 1.075, 0.470 ≦ x <0.490, In the case of Invention Examples 1 to 9 having compositions satisfying 0.020 ≦ y ≦ 0.040, 0 <n <1.000, 0 <z ≦ 0.025, ΔCp is 2500 ppm / K or less, d33 is 340 pC / N or more, Tc is 340 ° C., d33 The deterioration rate was -10% or less, and the piezoelectric characteristics and temperature characteristics were excellent.

On the other hand, in the case of Comparative Example 10 where 0.490 ≦ x in the above formula, d33 was less than 340 pC / N, the d33 deterioration rate exceeded −10%, and the piezoelectric characteristics were significantly inferior.
In the case of Comparative Example 11 in which z = 0 in the above formula, the d33 deterioration rate exceeded -10%, the piezoelectric characteristics were significantly inferior, the sintering temperature was as high as 1300 ° C., and the crystal grains became coarse. When the sintering temperature is 1300 ° C. or higher, d33 is not improved as shown in Example 2 below, which is not preferable.
In Comparative Examples 12 and 13 where n = 0 and 1 in the above formula, ΔCp exceeded 2500 ppm / K. This is presumably because the stability of the crystal was lowered because only one of Nb and Sb was contained.
In the case of Comparative Example 14 where m> 1.075 in the above formula, PbO is generated inside the piezoelectric ceramic composition as shown in FIG. 1 (white streaks in FIG. 1), and the piezoelectric constant d33 is less than 340 pC / N. As a result, the piezoelectric characteristics were greatly inferior.
In the case of Comparative Example 15 where m <1 in the above formula, the piezoelectric constant d33 was less than 340 pC / N, and the piezoelectric characteristics were significantly inferior.

  For the composition of Invention Example 1 of Example 1, a piezoelectric ceramic composition was produced by changing the sintering temperature. D33 of the obtained piezoelectric ceramic composition was measured in the same manner as in Example 1. Further, XRD (X-ray diffraction) measurement of the disk surface (surface from which the electrode was removed) of the sintered sample was performed, and the crystallite diameter was determined by Scherrer's equation.

The obtained results are shown in Table 2 and FIG.

As is apparent from Table 2 and FIG. 2, when the sintering temperature was between 1050 ° C. and 1250 ° C., d33 was 340 pC / N or more, and the crystallite size at this time was 30 to 39 nm. On the other hand, when the sintering temperature was 1050 ° C. and when it exceeded 1250 ° C., d33 was less than 340 pC / N, and the crystallite size at this time was less than 30 nm or more than 39 nm.
For this reason, it is necessary to control the crystallite diameter to 30 to 39 nm.

3 and 4 show scanning micrographs showing the crystal grains of the sample when the sintering temperatures are 1250 ° C. and 1300 ° C., respectively.
It can be seen that when the sintering temperature reaches 1300 ° C., the crystal grains grow rapidly and become coarse grains.

Using the piezoelectric ceramic composition of Invention Example 1 of Example 1 as the piezoelectric element 15, the area S1 of the bottom surface SA of the weight member 17 and the area S2 of the surface SB of the element electrode 15a facing the bottom surface SA are variously changed. A non-resonant knock sensor shown in FIGS.
The element electrode 15a was formed by printing a silver paste on the surface of the chamfered piezoelectric element 15 and firing it. Polyamide was used as the resin for the resin molded body 11, and brass was used as the lower electrode 14 and the upper electrode 16. Further, PET was used as the first insulating plate 13, the second insulating plate 13t, and the insulating sleeve 13s. Further, as shown in Table 3, the knocking sensor of the sample number 5 uses an iron material as the weight member 17. The knocking sensors of other sample numbers used brass as the weight member 17. However, the mass of the weight member 17 was unified to 10.0 g in the knocking sensors of all the sample numbers. In Example 3, when all of the element electrodes 15a constituting the piezoelectric element 15 project the weight member 17 and the piezoelectric element 15 along the thickness direction of the piezoelectric element 15, the weight member 17 Under the condition of facing the bottom surface SA facing the piezoelectric element 15 side, knocking sensors in which the areas S1 and S2 were variously changed were manufactured.

For the obtained knocking sensor, the capacitance Cp (20) at 20 ° C. was measured in the same manner as in Example 1. Further, the sensor output between the first and second terminals 14a and 16a was measured under a condition where a 3G impact was applied by a vibrator.
The obtained results are shown in Table 3 and FIG.

  As is apparent from Table 3 and FIG. 8, the ratio of the area S2 of the surface SB facing the bottom surface SA of the element electrode 15a of the piezoelectric element 15 to the area S1 of the bottom surface SA of the weight member 17 is 45% or more. In the case of 3 to 9 non-resonant knocking sensors, the sensor output exceeded 75 mV, and practically good sensitivity was exhibited.

It is a figure which shows the scanning electron microscope image of the surface of the piezoelectric ceramic composition of the comparative example 14. It is a figure which shows the relationship between the crystallite diameter of a piezoelectric ceramic composition, and d33. It is a figure which shows the scanning micrograph of the sample whose sintering temperature is 1250 degreeC. It is a figure which shows the scanning micrograph of the sample whose sintering temperature is 1300 degreeC. It is sectional drawing in alignment with the axial direction of the non-resonance type knocking sensor which concerns on embodiment of this invention. 1 is an exploded perspective view of a non-resonant knock sensor according to an embodiment of the present invention. It is a fragmentary sectional view showing the neighborhood of a piezoelectric element and a weight member of a non-resonance type knocking sensor according to an embodiment of the present invention. It is a figure which shows a sensor output when changing the ratio of the area of the element electrode of a piezoelectric element with respect to the bottom area of a weight member.

Explanation of symbols

DESCRIPTION OF SYMBOLS 15 Piezoelectric element 15a Element electrode 10 Non-resonance type knocking sensor 12 Support member 12a Support main-body part 17 Weight member SA Bottom surface which faces the piezoelectric element side of a weight member SB Surface of element electrode S1 Area of bottom surface of weight member S2 Surface of element electrode area

Claims (4)

Pb _m {Zr _1-xyz Ti _x Sn _y (Sb _1-n Nb _n ) _z } O ₃ (where 1.000 ≦ m ≦ 1.075, 0.470 ≦ x <0.490, 0.020 ≦ y ≦ 0.040, 0 <n <1.000 0 <z ≦ 0.025), and the piezoelectric ceramic composition has a crystallite diameter of 30 to 39 nm. Pb _m {Zr _1-xyz Ti _x Sn _y (Sb _1-n Nb _n ) _z } O ₃ (where 1.000 ≦ m ≦ 1.075, 0.470 ≦ x <0.490, 0.020 ≦ y ≦ 0.040, 0 <n <1.000 And a piezoelectric constant d33 having a piezoelectric constant d33 of 340 pC / N or more. A piezoelectric element using the piezoelectric ceramic composition according to claim 1. A piezoelectric element comprising the piezoelectric ceramic composition according to claim 1 or 2 and an element electrode;
A support member having a support main body for supporting the piezoelectric element;
A weight member disposed on the piezoelectric element and pressing the piezoelectric element toward the support main body,
At least a part of the element electrode faces the bottom surface of the weight member facing the piezoelectric element when the weight member and the piezoelectric element are projected along the thickness direction of the piezoelectric element. A non-resonant knock sensor in which a ratio of an area of a surface of the element electrode facing the bottom surface is 45% or more with respect to an area of the bottom surface of the member.