JP5305263B2 - Piezoelectric material for power generation - Google Patents

Description

The present invention relates to a piezoelectric body for power generation using piezoelectric ceramics (porcelain).

  In recent years, small portable electronic devices have come to be used on a daily basis, and accordingly, development of various self-supporting power generation methods that do not require charging has been promoted. For example, a rotating power generation mechanism (Automatic Generating System, AGS) as a power source for watches and a power generation technology using thermoelectric power generation have reached a practical stage. There is also a growing demand for development of low-environmental load generation methods such as power generation using natural vibration and wave power generation.

  As a method for obtaining electrical energy from mechanical energy, a method using a piezo (piezoelectric) element has been known for a long time in addition to the above-described power generation method. This method was originally developed as an ignition source for internal combustion engines because of the high level of generated voltage. After that, it was used as an ignition source for gas ranges, water heaters, rice cookers, etc., and for lighters. Used as a power source. The principle of these ignition power sources is to generate a high voltage by applying a mechanical stress to the piezoelectric ignition element and to perform a spark discharge in the gas. Since the power generation method using a piezoelectric element is small and simple, it has recently begun to be used for power generation applications for relatively small and small power as a self-supporting mouse, a self-power generation mechanism (shoe sole), and a light emitting element.

Patent Document 1 describes a structure in which power is generated by striking one or both sides as a layered ceramic plate in which two plate-shaped piezoelectric ceramic elements are joined with their polarizations reversed.
Patent Document 2, Patent Document 3, and Patent Document 4 describe power generation structures using stacked piezoelectric elements.

  In recent years, sensor network technology using small and integrated sensor terminals in a network has progressed, and power source development suitable for this field has become a new technological development element. Here, although it does not necessarily require the output of an existing battery, simple and continuous power supply is required, and it is required to generate power from vibrations such as external vibration and self-excitation, for example, Patent Document 5, Patent Document 6, and Patent Document 7 disclose inventions related to animal health management technology using a small sensor terminal, and development of a power development mechanism with low power consumption is also required for these devices. ing.

Patent Document 8 describes an experimental apparatus for measuring various characteristics of a piezoelectric element.
JP 2001-145375 A JP-A-8-321642 Japanese Patent Laid-Open No. 11-146663 JP 2006-32935 A JP 2008-151555 A JP 2008-151562 A JP 2008-152432 A JP 2003-65913 A

As described above, as a power generation mechanism for small electronic devices, by adopting a basic structure that maximizes the output performance of the power generation unit element or improves the output performance per unit volume, It is necessary to optimize the production and preparation conditions to improve the characteristics.
However, the one described in Patent Document 1 can achieve high output by laminating the basic structure of power generation in the vertical direction or expanding it in the horizontal direction, but the volume or area increases, and the small structure In applications that are assumed to be embedded in the power generation, it is necessary to develop a basic element for a new power generation structure.

In addition, the materials described in Patent Documents 2 to 4 do not mention the optimization of Young's modulus and the optimization of the polarization electric field with respect to the element material of the piezoelectric element, in order to optimize the improvement of characteristics as a power generator. The conditions necessary for manufacturing the piezoelectric element are not described.
An object of the present invention is to provide a power generation piezoelectric body in which the power generation amount per unit volume is improved by adding an appropriate amount of an appropriate additive.

  In order to solve the above-mentioned problems, the present inventors have conducted intensive investigations. As a result, when a certain amount of mechanical energy is applied, the amount of electrical energy can be efficiently output with a low elastic modulus and high It has been found that it is effective to use a piezoelectric body made of an element having a dielectric constant. Here, the piezoelectric effect exhibited by the piezoelectric body (piezoelectric material) generally includes a piezoelectric inverse effect that converts electrical input into mechanical output and a piezoelectric positive effect that converts mechanical input into electrical output. The latter is power generation characteristics. Hereinafter, a piezoelectric body that exhibits a piezoelectric positive effect is referred to as a piezoelectric power generation body.

Regarding the power generation characteristics of the piezoelectric power generator, the elastic modulus and dielectric constant of the piezoelectric power generator itself are considered to be parameters. In the mechanism that develops the characteristics related to the piezoelectric power generator, electrical energy is temporarily accumulated in the piezoelectric body due to strain corresponding to the elastic modulus with respect to mechanical input. At this time, the amount of energy stored is determined according to the dielectric constant of the piezoelectric body.
Therefore, by adding a small amount of additives to the base piezoelectric material (hereinafter sometimes referred to as a piezoelectric element) to produce a homogeneous solid solution with controlled elastic modulus and dielectric constant, its output characteristics Can be controlled.

This invention is based on the said knowledge by the present inventors, and the piezoelectric substance for electric power generation concerning Claim 1 of this invention for solving the said subject is lead oxide, a zircon oxide, and a titanium oxide by PZT (52 / 48) 1 mol% of niobium is added as an additive to the base material having a phase boundary composition , fired at 1150 ° C. to 1300 ° C., and polarized with a polarization electric field of 1.5 kV / cm, The dielectric constant is 1000 F / m or more, the elastic modulus is 40 Pa or less, the piezoelectric modulus is 200 m / V, the initial load is 4 to 5 MPa, the load fluctuation amplitude is 3 to 4 Mpa, and the number of vibrations is 3.0 × 10 ⁶ times. A plurality of piezoelectric elements that maintain ± 15% of the initial voltage when stacked are stacked via electrodes with the same polarity of each piezoelectric element facing each other,
Among the electrodes provided at both ends of the outermost piezoelectric element and the electrodes provided between the piezoelectric elements, there are output terminals that connect electrodes of the same polarity.
As the base material, piezoelectric zirconate titanate (PZT) is preferable. Hereinafter, the base material may be referred to as “PZT”.

The additive is preferably an element that is introduced into the B site of the perovskite crystal structure and can supply a donor to the base material as a low elastic modulus element. Examples of such elements include niobium, tungsten, tantalum, lanthanum, antimony, bismuth, and thorium oxides .

According to the first aspect of the present invention, the Young's modulus is reduced by about 10% and the amount of elastic energy that can be stored is increased. Accordingly, the output of electrical energy is greatly increased with respect to applied mechanical energy. Can be improved.
In particular, by adding 1 mol% of niobium as an additive to the base material, it is possible to provide a power generation piezoelectric body in which the output of electrical energy with respect to the applied mechanical energy is particularly improved.

  First, the manufacture of the piezoelectric element according to the present invention will be described. First, a powdery raw material as a raw material is prepared. Using lead oxide, zircon oxide, and titanium oxide, which are powdery raw materials, having a phase boundary composition of PZT (52/48), and further adding 1 mol% of niobium to the niobium oxide using an electronic balance. Weigh. Next, these raw materials are put into a monopot for mixing together with alcohol and zirconia balls, and are mixed using a ball mill for about one day. The powder after mixing is subjected to evaporation of the alcohol component using a hot stirrer, and then the moisture is evaporated in an oven at 80 ° C. or higher for a whole day and night. After the dried powder is classified using a # 100 mesh, it is weighed to about 10 to 20 grams using a balance and temporarily molded using a molding jig.

  The compacted green compact is heat treated in an electric furnace. The heat treatment is first performed at 600 ° C. for 2 hours to burn off the bakelite adhering during the temporary molding. Thereafter, preliminary sintering is performed at 800 ° C. for 2 hours. The molded body that has been pre-sintered is pulverized again. For grinding, alcohol and zirconia balls are placed in a monopot and ground for about 1 day. The ground powder and alcohol are evaporated with a hot stirrer, and the dried powder is dried for about one day in an oven at 80 ° C. or higher. The dried powder is classified by # 100 mesh, and thereafter, a 3% solution of polyvinyl alcohol (PVA) is added and granulated. Granulated powder is classified by # 40 mesh. The classified powder is molded, the molded body is placed in a baking furnace, and heat treatment is performed at 600 ° C. for 2 hours to bake off the bakelite adhering to the molding. Thereafter, main baking is performed at 1200 ° C. for 2 hours to complete the sintering of the bulk molded body.

Subsequently, the sample is electrically polarized and molded using the bulk molded body. The molded sample is polished and smoothed so that the parallelism of the upper and lower surfaces is about 10 microns or less, and then electrodes are formed on the upper and lower surfaces. For electrode formation, a platinum film of 50 nm is formed by film formation for 120 seconds using a platinum coater.
Next, a polarization process is performed on the element on which the electrode is formed. This element is placed in a dedicated polarization holder and immersed in an oil bath containing silicon oil. The temperature of the oil bath is controlled by a heater and kept at 150 ° C. for about 1 hour. In an oil bath at 150 ° C., a polarization electric field of 1.5 kV or more per 1 mm thickness is applied to the element for 30 minutes. The piezoelectric element taken out after the temperature of the oil bath returns to room temperature is placed in an oven at 80 ° C. for one day to stabilize the polarization, and finally the piezoelectric element is obtained.

  Various measurements are performed on the piezoelectric element manufactured by the above manufacturing method using an experimental apparatus. As the experimental apparatus, a known apparatus as described in Patent Document 8 is used. Using such an apparatus, a static force is applied to the piezoelectric element, and various electric quantities generated at that time are measured. More specifically, a static force is applied to the piezoelectric element via the load cell, and mechanical energy is output as electrical energy to an external circuit via the electrode of the piezoelectric element. The output is amplified by a DC amplifier, and the output voltage is recorded by a digital multimeter. The output power is calculated using an external resistance provided in the external circuit.

The experimental results will be described below.
FIG. 1 is a graph showing the relationship between the load applied to the piezoelectric element and the output power obtained when the load is applied and abruptly unloaded. The horizontal axis represents the load (kN), and the vertical axis represents the output power (W ). FIG. 1A is a graph showing a comparison of output power between a PZT having an element thickness of 10 mm added with 1 mol% of niobium and a PZT having an element thickness of 10 mm without addition, and FIG. 1B shows 1 mol% of niobium. is a graph showing the output power comparison with the added element thickness 5mm of PZT and the element thickness 5mm with no additive PZT, FIGS. 2 (a) element has been added 1 mol% of niobium thickness 2.5mm of PZT FIG. 2 ( b ) is a graph showing a comparison of output power between PZT having a thickness of 2.5 mm and an additive-free element having a thickness of 2.5 mm, and FIG. FIG. 3 is a graph showing a comparison of output power with PZT, and FIG. 3 shows a comparison of output power between PZT with an element thickness of 0.5 mm added with 1 mol% of niobium and PZT with an additive thickness of 0.5 mm. It is a graph. As shown in these graphs, the addition of 1 mol% of niobium improves the output power by about an order of magnitude compared to the case where the output power is not added. This is considered to have contributed greatly to the improvement of electric power. In addition, almost the same results were obtained when the element thickness was 10 mm and 5 mm. Although not shown, tantalum, tungsten, lanthanum, antimony, bismuth, and thorium are also effective as additives in addition to niobium, and the addition amount is preferably 0.01 to 10 mol%, 4 mol% is more preferable, 0.02 to 3 mol% is further preferable, and 1 mol% is particularly preferable.

FIG. 4 is a graph showing the relationship between the polarization electric field applied and the output power in the polarization process performed in the process of manufacturing the piezoelectric element. The horizontal axis represents the polarization electric field (kV / mm), and the vertical axis represents the output power (W).
As shown in the figure, the output power gradually increases as the applied force (2 kN, 6 kN, 10 kN) increases and the polarization electric field increases, and reaches a substantially constant maximum at a polarization electric field of 1.5 kV / mm or more. It can be seen that the output voltage is obtained.

FIG. 5 is a diagram showing a configuration of a piezoelectric element structure (piezoelectric body) in which piezoelectric elements and piezoelectric elements are stacked.
FIG. 5A shows a piezoelectric element having a thickness of 10 mm, FIG. 5B shows a piezoelectric element structure having two piezoelectric elements stacked and a thickness of 10 mm as a whole, and FIG. 5C shows a piezoelectric element. FIG. 5D is a cross-sectional view showing a piezoelectric element structure in which three piezoelectric elements are stacked and have a thickness of 10 mm, and FIG. 5D is a piezoelectric element structure in which four piezoelectric elements are stacked and has a thickness of 10 mm as a whole.

In these figures, 1 is a piezoelectric body prepared by adding 1 mol% of niobium as an additive, and a polarization electric field is applied at 1.5 kV / mm during the polarization process, 2 is an electrode, 3 and 4 are output terminals. It is. Electrodes 2 are formed on the upper and lower surfaces of the piezoelectric body 1 to constitute a piezoelectric element, and the electrodes 2 of the stacked piezoelectric elements are connected with the same polarity to form output terminals 3 and 4.
FIG. 6A is a graph showing the relationship between the number of stacked piezoelectric elements and the output voltage in the piezoelectric element or piezoelectric element structure shown in FIG. 5, the horizontal axis is the number of stacked layers, and the vertical axis is the output voltage (V). It is. FIG. 6B is a graph showing the relationship between the number of stacked piezoelectric elements in the piezoelectric element or piezoelectric element structure shown in FIG. 5 and the output power. The horizontal axis represents the number of stacked layers, and the vertical axis represents the output power (W · s).

  As shown in these drawings, when the thickness (10 mm) of the piezoelectric element and the piezoelectric element structure is constant, the applied force (1 kN, 4 kN, 7 kN, 10 kN) is larger and the number of piezoelectric bodies (electrodes) is larger. It can be seen that a large output voltage and output power can be obtained. That is, as shown in FIG. 5, the entire thickness of the piezoelectric element and the piezoelectric element structure is constant (10 mm), and a larger output voltage and output power can be obtained as the piezoelectric element is divided. In other words, in a piezoelectric element or piezoelectric element structure having the same volume, a larger output voltage and output power can be obtained as the number of piezoelectric bodies (or electrodes) is increased.

FIG. 7 is a graph showing the relationship between the thickness of the piezoelectric element or the output power constituting the piezoelectric element or the piezoelectric element structure shown in FIG. 5 and the output power. The horizontal axis is the thickness (mm) of the piezoelectric element, and the vertical axis is the output. Electric power (W · s).
As is clear from these figures, when the applied force (1 kN, 4 kN, 7 kN, 10 kN) is large and the thickness of the piezoelectric element is 4 to 8 mm, preferably 5 mm, a large output voltage and output power can be obtained. I understand.

As described above, the output power and output power of the piezoelectric element and the piezoelectric element structure according to the present invention depend on the additive and the polarization electric field of the piezoelectric element, and in order to make maximum use of the output characteristics, niobium It is necessary to add an element that serves as an acceptor such as a piezoelectric body that has been subjected to a polarization treatment with a polarization electric field of 1.5 kV / mm or more.
It can also be seen that the output power and output power of the piezoelectric element and the piezoelectric element structure do not depend on the volume of the piezoelectric element, but on the number of piezoelectric bodies (electrodes) per unit volume. As a result, it can be seen that it is effective to have a plurality of stacked piezoelectric elements per unit volume as a structure for improving the amount of power generation per unit volume. The conventional knowledge suggests the possibility of improving the output by stacking the basic units, but this invention shows the effectiveness of the electrode division, and it will be introduced in this field as a new basic structure in the future. It becomes possible to apply.

In the above description, an experiment in which a static force is applied to the piezoelectric element has been described. However, a vibration test was performed in consideration of the fact that the piezoelectric element is often used in a situation where a vibration force is applied. Below, a vibration test and its result are demonstrated.
FIG. 8 is a diagram showing the PZT structure used in the vibration test.
FIG. 8A is a diagram illustrating a 10 mm single-layer type PZT having a diameter of 16 mm and a thickness. FIG. 8B is a diagram illustrating a two-layer type PZT in which two 5 mm layers are stacked. FIG. 8 (c) shows a total of four types of PZT (A-1, A-2, B-1, B-2), which is obtained by adding Nb to PZT (◯) and not adding (×). It is a table.

In these PZTs, brass having a diameter of 16 mm and a thickness of 2 mm is attached as an electrode between both ends and between each PZT, and a positive electrode treatment and a negative electrode treatment are applied to the end faces of the PZT.
FIG. 9 is a diagram illustrating the entire structure of the vibration test apparatus, FIG. 9A is a plan view of the vibration test apparatus, and FIG. 9B is a schematic side view of the vibration test apparatus.
As shown in the figure, the vibration test apparatus is installed on a horizontal vibration table. A structure in which PZT 11 is sandwiched in a jig having a load meter 12 attached to the side surface of a 66.4 kg weight 13, an initial load is applied to the opposite side surface via a vibration isolating rubber 17, and the weight 13 is vibrated in the horizontal direction. It is. Accelerometers 6 to 9 for measuring the axial direction and the orthogonal direction of the axis are attached to the four sides of the weight 13, and accelerometers 5 and 10 for the excitation direction are attached to the horizontal vibration table.

In this test, a force was applied in the vibration direction using the jack 14, an initial load was applied, and then a single sine wave vibration was performed in the vibration direction by the weight 13. The initial load conditions are 0.5KN (2.49MPa), 1KN (4.97MPa), 1.5KN (7.46MPa), and the excitation frequency is 3Hz, 4Hz, 5Hz, 10Hz, 15Hz, Nine cases of 20 Hz, 25 Hz, 30 Hz, and 35 Hz were used. In addition, the excitation amplitude was ² to 5 m / s ² in 4 cases. The load acting on the PZT 11 at this time, the generated voltage, and the acceleration of the weight 13 were measured as time history data.

FIG. 10 shows, as an example of a vibration test, a single layer PZT (+ Nb) with an initial load of 1.5 KN, an excitation acceleration of 5 m / s ² , an acceleration of the weight 13 in the case of an excitation frequency of 35 Hz, a variable load, and PZT. It is a figure which shows the time history of the generated voltage.
FIG. 11 and FIG. 12 are diagrams showing the influence of the initial load, the vibration frequency, and the presence or absence of Nb on the generated voltage and the generated electric energy for the single layer PZT.

  In the figure, the generated power amount is obtained by calculating the power per cycle from the time history of the generated voltage and converting it per hour. In this vibration test, since the natural frequency of the vibration test specimen is about 70 Hz, the response of the weight gradually amplifies as the vibration frequency is increased. Therefore, here, the load amplitude of PZT at each excitation frequency was normalized by the load amplitude (F (N)) at the time of 3 Hz excitation, and the generated voltage in each excitation test was converted. From these figures, it can be seen that the generated voltage increases in proportion to the vibration frequency, and the electric power increases in proportion to the square.

FIGS. 13 and 14 are diagrams showing the influence of the initial load, the frequency, and the presence or absence of Nb on the generated voltage and the generated power amount of the two-layer PZT.
As shown in the figure, it can be seen that, even in the case of stacking, the generated voltage is proportional to the vibration frequency and the generated power amount is approximately proportional to the square, as in the case of the single layer. In addition, the generated voltage increases by approximately the number of stacked layers with respect to the single layer PZT.

FIG. 15 is a diagram showing the influence of the load speed on the generated voltage in each PZT.
As shown in the figure, it can be seen that the generated voltage is substantially proportional to the increase in the load speed. The generated voltage of PZT is considered to be proportional to the change in load rather than the frequency, that is, the compressive strain rate of the PZT laminate. In this test range, the maximum voltage and maximum power are generated at the time of 35 Hz excitation for each condition. At this time, PZT with Nb added is approximately 7 times the generated voltage and PwT generated with respect to PZT without Nb added. It was found to be about 15 times higher. In each vibration test, it was found that the initial load had little effect on the generated voltage and the generated electric energy. The vibration power generation test was repeated under each initial load condition, but the PZT was not damaged.

Next, FIG. 16 shows the relationship between the thickness of the piezoelectric body in which no additive is added to the base material and the effect of the load variation per unit area defined as the stress rate on the generated voltage. As the thickness of the piezoelectric body, three examples of 10 mm, 3.3 mm, and 2.5 mm were tried. Also, the horizontal axis “Pω / A ₀ ” in FIG. 16 indicates the stress rate, the load fluctuation amplitude P (KN), the angular frequency ω (1 / s) of vibration, and the cross-sectional area A ₀ (m ² ) of the element. ).

In addition, the same test was performed on thicknesses of 10 mm, 3.3 mm, and 2.5 mm in a piezoelectric body in which 1 mol% of Nb was added to the base material. The result is shown in FIG.
As shown in FIGS. 16 and 17, the generated voltage increased in proportion to the increase in the stress rate of the piezoelectric body, and it was confirmed that the power generation characteristics were significantly improved by adding Nb.
It was also found that the thickness dependence of the piezoelectric body was relatively small in both cases of the piezoelectric body with the additive added to the base material and the piezoelectric body without the additive added to the base material.

FIG. 18 is a graph showing the relationship between the influence of the concentration of Nb added to the base material on the generated voltage and the stress rate for a test piece (piezoelectric body) having a thickness of 10 mm.
As shown in FIG. 18, the power generation characteristics are improved with the Nb addition concentration peaking at 1 mol%. When this addition concentration exceeds 4 mol%, the power generation characteristics are reduced to the same level as those of the piezoelectric body to which no additive is added.

That is, in the piezoelectric body in which the additive was added to the base material in an addition amount of about 0.1 mol% to 4 mol%, an improvement in power generation characteristics was observed compared to the piezoelectric body in which the additive was not added to the base material. On the other hand, when the addition amount is larger than this, the characteristics are inferior compared to the piezoelectric body in which no additive is added to the base material.
Thus, there is an optimum value that exhibits a peak of the output voltage in the Nb addition concentration, and in this example, the addition concentration of 1 mol% was the optimum value. It was confirmed that the piezoelectric body having an Nb addition concentration of 1 mol% has a remarkable effect of generating a voltage about 9.8 times that of the piezoelectric body to which no additive is added. This is considered to be caused by the difference in how Nb is dissolved in PZT depending on the concentration of Nb added.

FIG. 19 shows a piezoelectric material in which PZT having a thickness of 10 mm is used as a base material, a piezoelectric body in which no additive is added to the base material, and 1 mol% of various additives (Nb, Fe, Ta, W) are added to the base material. It is a graph which shows the influence which the stress rate has on the generated electric energy about a body. The generated electric energy is obtained by calculating electric power from the time history of the generated voltage and integrating it over time.
From the results shown in FIG. 19, it can be confirmed that the piezoelectric body having the Nb addition concentration of 1 mol% has a remarkable effect of generating about 136 times the amount of electric power compared to the piezoelectric body to which no additive is added. It was. Further, it has been found that when Ta is added to PZT as an additive other than Nb, a relatively large amount of generated electric power can be obtained as compared with the case where Fe or W is added to PZT. It was also confirmed that in any of the piezoelectric bodies in which various additives were added to the base material, the amount of generated power increased as the stress rate increased, and was proportional to the square of the generated voltage.

  FIG. 20 is a stress-strain diagram as a result of measuring the Young's modulus of a piezoelectric body in which PZT having a thickness of 10 mm and a diameter of 16 mm is used as a base material, and no additive is added to the base material. FIG. 5 is a stress-strain diagram as a result of measuring Young's modulus for a piezoelectric body in which 1 mol% of Nb is added to a base material. This result was obtained by using a strain gauge attached to the side surface of the element and measuring the strain generated with respect to the applied force.

20 and 21, the Young's modulus of the piezoelectric body in which 1 mol% of Nb is added to the base material is 32.8 kN, which is about 20% as compared with the Young's modulus of 44.3 kN of the piezoelectric body in which no additive is added to the base material. It can be seen that it has been reduced.
22-24 is a figure which shows the electric power generation characteristic of the piezoelectric material which added additives other than Nb to the base material. Specifically, FIG. 22 is a diagram showing the power generation characteristics of a piezoelectric body in which iron is added to the base material as an additive, and FIG. 23 is a power generation characteristic of the piezoelectric body in which tantalum is added to the base material as an additive. FIG. 24 is a diagram showing power generation characteristics of a piezoelectric body in which tungsten is added to a base material as an additive.

  Here, the measurement of the power generation characteristics was performed using the apparatus shown in FIG. Specifically, a force from a press is applied to the sample via a load cell. The voltage taken out from the upper and lower electrodes of the element is recorded by a voltage recorder having a resistance of 1 MΩ, and then taken into a personal computer. The applied force is taken into the personal computer via the amplifier. Here, the load cell used LU-10KSB34D made by Kyowa Denki, and the recorder used Omniace RA2300 made by NEC.

  In addition, FIG. 22 shows the results of three trials (Fe-1, Fe-2, Fe-3) using the same iron sample as the additive, and FIG. 23 shows the same tantalum sample as the additive. FIG. 24 shows the results of four trials (Ta-1, Ta-2, Ta-3, Ta-4), and FIG. 24 shows the results of four trials (W-1, W-2, W-3, W-4) The results of trials are shown. This trial was conducted to confirm the variation in the same additive.

As shown in FIG. 22, when iron was added to the base material as an additive, the power generation characteristics were significantly reduced. This is considered to be because iron is an element that can supply an acceptor as a high elastic modulus element. As with iron, examples of the element that becomes a donor source when introduced into the B site include chromium, manganese, cobalt, and the like.
As shown in FIG. 23, when tantalum was added to the base material as an additive, the power generation characteristics increased to the same extent as when niobium was added to the base material.

Further, as shown in FIG. 24, when tungsten was added as an additive to the base material, the same power generation characteristics as when no additive was added to the base material were shown.
26 to 28 are graphs showing the relationship between the additive amount in a piezoelectric body in which Nb, Fe, Ta, and W are added as additives to the base material (PZT), and the dielectric constant, elastic modulus, and piezoelectric constant. . The piezoelectric body has a firing temperature of 1260 ° C., a diameter of 15.96 ± 0.02 (mm), a thickness of 10.023 ± 0.031 (mm), and a mass of 15.3409 ± 0.3345 (g). The polarization condition was 2 kV / mm.

FIG. 26 shows that an element having a large power generation characteristic has a large dielectric constant and can store generated charges. Further, FIG. 27 shows that an element having a large power generation characteristic is an element having a small elastic modulus, and therefore, an element strain caused by a unit applied force increases. These facts also appear in the piezoelectricity shown in FIG. That is, the piezoelectric constant (piezoelectric constant d ₃₃ ) is proportional to the square root of the product of the dielectric constant and the reciprocal of the elastic modulus, and the piezoelectric body having a so-called high piezoelectric power generation characteristic with a small elastic modulus and a large dielectric constant is the piezoelectric. The rate is increasing.

FIG. 29 is a diagram showing a change with time of vibration amplitude when a power generation test is performed under each initial load condition using the vibration test apparatus of FIG. 9, and FIG. 29 (a) is not excited. FIG. 29B is a diagram showing a change over time in vibration amplitude when the number of vibrations is 10 ⁷ [cycle]. FIG.
FIG. 30 is a diagram showing a change over time in servo acceleration when the power generation test is performed under each initial load condition. FIG. 30 (a) shows a change over time in servo acceleration when no vibration is applied. FIG. 30B is a diagram showing a change in servo acceleration with time when the number of vibrations is 10 ⁷ [cycle].

FIG. 31 is a diagram showing a change over time in the acceleration of the weight when the power generation test is performed under each initial load condition, and FIG. 31 (a) shows the acceleration of the weight in a state where no vibration is applied. FIG. 31B is a diagram showing a change with time, and FIG. 31B is a diagram showing a change with time of the acceleration of the weight when the number of times of vibration is 10 ⁷ [cycle].
FIG. 32 is a diagram showing the change over time in the voltage output from the piezoelectric body when the power generation test is carried out under each initial load condition. FIG. 32 (a) shows a state in which no vibration is applied. FIG. 32B is a diagram showing the change with time of the voltage output from the piezoelectric body, and FIG. 32B is a diagram showing the change with time of the voltage output from the piezoelectric body when the number of excitations is 10 ⁷ [cycle]. is there.

FIG. 33 shows the test results of the durability of the voltage output from the piezoelectric body to which Nb was added and the piezoelectric body to which no additive was added when the power generation test was performed under each initial load condition. FIG. Note that the power generation test was repeatedly performed under each initial load condition, but the PZT was not damaged. The experimental conditions of the power generation test are shown below.
From the results shown in FIGS. 29 to 33, it can be seen that during the power generation test in which the number of times of vibration is set to 10 ⁷ [cycle], the output is hardly decreased and stable output is shown.

-Experimental conditions-
-Initial load: 1 [kN] 4.97 [MPa]
・ Base material: PZT (no additives)
-Base material thickness: 10 [mm]
・ Excitation frequency: 30 [Hz]
・ Excitation acceleration (setting value): 3 [m / s ² ]
Excitation acceleration (weight part): 3.54 [m / s ² ]
-Load fluctuation amplitude (calculated value): 235 [N] 3.67 [MPa]
・ Load fluctuation amplitude (measured value): 183.8 [N] 2.87 [MPa]

  The piezoelectric element structure of the present invention includes: electricity, machinery, mechatronics, electronics, MEMS (Micro Electro Mechanical Systems), MST (Micro System Technology), micromachines, nanotechnology, electrical and electronic equipment, and information communication equipment. In such a field, it is extremely useful for a functional transducer (energy conversion) or a basic element of a power generation element that uses a mechanical input energy converted into an electrical output.

It is a graph which shows the relationship with the output electric power obtained when a load is applied to a piezoelectric element. It is a graph which shows the relationship with the output electric power obtained when a load is applied to a piezoelectric element. It is a graph which shows the relationship with the output electric power obtained when a load is applied to a piezoelectric element. It is a graph which shows the relationship between the polarization electric field applied at the time of the polarization process performed in the process of producing a piezoelectric element, and output electric power. It is a figure which shows the structure of the piezoelectric element structure which laminated | stacked the piezoelectric element and the piezoelectric element. 6 is a graph showing the relationship between the number of stacked piezoelectric elements and the output voltage in the piezoelectric element or piezoelectric element structure shown in FIG. 5 and the relationship between the number of stacked piezoelectric elements and the output power. It is a graph which shows the relationship between the thickness of the piezoelectric element which comprises the piezoelectric element or piezoelectric element structure shown in FIG. 5, and output electric power. It is a figure which shows the PZT structure used for the experiment used for the vibration test. It is a figure which shows the whole structure of a vibration test apparatus. As an example of a vibration test, for a single layer PZT (+ Nb), the initial load is 1.5 KN, the excitation acceleration is 5 m / s ² , the acceleration of the weight when the excitation frequency is 35 Hz, the time of the fluctuating load and the generated voltage of PZT. It is a figure which shows a history. It is a figure which shows the influence which the initial load, the vibration frequency, and the presence or absence of Nb exert on the generated voltage and the generated electric energy for the single layer PZT. It is a figure which shows the influence which the initial load, the vibration frequency, and the presence or absence of Nb exert on the generated voltage and the generated electric energy for the single layer PZT. It is a figure which shows the influence which the initial stage load of 2 layer PZT, the frequency, and the presence or absence of Nb have on the generated voltage and generated electric energy. It is a figure which shows the influence which the initial stage load of 2 layer PZT, the frequency, and the presence or absence of Nb have on the generated voltage and generated electric energy. It is a figure which shows the influence which the load speed has on the generated voltage in each PZT. It is the graph which showed about the influence which the voltage output of the base material (PZT) which does not contain an additive, and what defined the load fluctuation per unit area as a stress rate has on the generated voltage. It is the graph which showed about the influence which the voltage output of the preform | base_material (PZT) with which niobium (Nb) was added as an additive, and what defined the load fluctuation per unit area as a stress rate has on generated voltage. It is a graph which shows the relationship between the density | concentration of the additive added to the base material (PZT), and a voltage output. It is a graph which shows the relationship between a stress rate and generated electric energy about the piezoelectric material which added 1 mol% of various additives (Nb, Fe, Ta, W) to the base material. It is a graph which shows the result of having measured the Young's modulus about the piezoelectric material which does not add an additive to a base material. It is a graph which shows the result of having measured Young's modulus about the piezoelectric material which added 1 mol% of Nb as an additive to a base material. It is a graph which shows the electric power generation characteristic of the piezoelectric material by which iron (Fe) was added to the base material (PZT) as an additive. It is a graph which shows the electric power generation characteristic of the piezoelectric material with which tantalum (Ta) was added to the base material (PZT) as an additive. It is a graph which shows the electric power generation characteristic of the piezoelectric material with which tungsten (W) was added to the base material (PZT) as an additive. It is a figure which shows the structure of the apparatus for measuring a power generation characteristic. It is a graph which shows the relationship between the density | concentration of an additive, and a dielectric constant. It is a graph which shows the relationship between the density | concentration of an additive, and an elasticity modulus. It is a graph which shows the relationship between the density | concentration of an additive, and a piezoelectric constant. It is a graph which shows the time-dependent fluctuation | variation of the load amplitude during a durability experiment. It is a graph which shows the time-dependent fluctuation of the servo acceleration during the durability experiment. It is a graph which shows the time-dependent fluctuation | variation of the acceleration of the weight in durability experiment. It is a graph which shows the time-dependent fluctuation | variation of the voltage output from PZT in a durability experiment. It is a graph which shows the durability test result of the voltage output from a base material (PZT).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Piezoelectric body 2 Electrode 3,4 Output terminal 5,10 Accelerometer (Excitation direction)
6, 7, 8, 9 Accelerometer (excitation vertical direction)
11 PZT
12 Load meter 13 Weight 14 Jack 15 Support 16 Support frame 17 Anti-vibration rubber

Claims (1)

1 mol% of niobium is added as an additive to a base material in which lead oxide, zircon oxide, and titanium oxide are made to have a phase boundary composition of PZT (52/48) , fired at 1150 ° C. to 1300 ° C., and 1 Polarized with a polarization electric field of 0.5 kV / cm, dielectric constant is 1000 F / m or more, elastic modulus is 40 Pa or less, piezoelectric constant is 200 m / V, initial load is 4 to 5 MPa, load fluctuation amplitude is 3 to 4 MPa. A plurality of piezoelectric elements that maintain ± 15% of the initial voltage when the number of times of vibration is performed 3.0 × 10 ⁶ times are stacked via electrodes with the same polarity of each piezoelectric element facing each other,
A power generating piezoelectric body comprising: an electrode provided at both ends of the outermost piezoelectric element; and an output terminal connecting electrodes of the same polarity among electrodes provided between the piezoelectric elements.

Images