JP2017034016A - Power generation material, power generation element and power generation system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power generation material capable of fully developing power generation performance even in a high temperature range, and to provide a power generation element composed of that power generation material, and a power generation system obtained using that power generation element.SOLUTION: A power generation element is obtained from a power generation material represented by following general formula (1). A power generation system is obtained using that power generation element. (AB)(MnNb)O... (1) (In the formula, A and B are different from each other, and represent at least one element selected from rare earth elements, alkaline-earth metals, alkaline metals, Cd and Bi, x indicates the atomic ratio of numerical range 0<x≤1, and y indicates the atomic ratio of 0.003≤y≤0.1).SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power generation material, a power generation element, and a power generation system, and more particularly to a power generation material, a power generation element made of the power generation material, and a power generation system obtained using the power generation element.

  Conventionally, in internal combustion engines such as automobile engines, heat exchangers such as boilers and air conditioning equipment, electric engines such as generators and motors, and various energy utilization devices such as light emitting devices such as lighting, for example, as exhaust heat, light, etc. A lot of thermal energy is released and lost.

  In recent years, from the viewpoint of energy saving, it has been required to recover the released thermal energy and reuse it as an energy source.

As such a method, specifically, for example, a heat source whose temperature rises and falls over time, a first device (electric power generation element) that is electrically polarized by a temperature change of the heat source, and a method for extracting electric power from the first device A power generation system including a second device has been proposed, and a power generation element obtained by molding a power generation material having a perovskite crystal structure represented by K _1/2 Na _1/2 NbO ₃ as a power generation element Has been proposed (see, for example, Patent Document 1).

  According to the power generation element described in Patent Literature 1, power generation performance can be sufficiently exhibited in a high temperature range.

JP2015-70203A

  On the other hand, since the power generation element described in Patent Document 1 has a relatively low internal resistance, it may cause a leakage current when used in a power generation system, and may cause a decrease in electromotive force. Therefore, in order to improve the power generation efficiency of the power generation system, a power generation material and a power generation element that can suppress leakage current and suppress a decrease in electromotive force are required.

  An object of the present invention is obtained by using a power generation material capable of suppressing leakage current, suppressing a decrease in electromotive force, and obtaining excellent power generation efficiency, a power generation element made of the power generation material, and the power generation element. It is to provide a power generation system.

The present invention
[1] A power generation material represented by the following general formula (1):
(A _x B _1-x ) NbO ₃ (1)
(In the formula, A and B are different from each other and represent at least one element selected from rare earth elements, alkaline earth metals, alkali metals, Cd and Bi, and x is an atom in a numerical range of 0 <x ≦ 1. Indicates percentage.)
[2] The power generation material according to the above [1], wherein in the general formula (1), A is K, B is Na, and x is 1/2.
[3] A power generation element comprising the power generation material according to [1] or [2] above,
[4] A heat source whose temperature rises and falls over time, a first device that is electrically polarized by a temperature change of the heat source, and a first device for taking out electric power from the first device. A power generation system comprising two devices.

  Since the power generation material of the present invention and the power generation element of the present invention made of the power generation material have a relatively high internal resistance, it is possible to suppress leakage current when used in a power generation system and suppress a decrease in electromotive force. it can. Therefore, the power generation system of the present invention including the power generation element of the present invention is excellent in power generation efficiency.

FIG. 1 is a schematic configuration diagram showing an embodiment of a power generation system of the present invention. FIG. 2 shows XRD data of the power generation elements of Examples 1 to 5. FIG. 3 is a graph showing the dielectric constants of the power generation elements of Examples 5 and 9 and Comparative Example 1. FIG. 4 is a graph showing the dielectric loss of the power generation elements of Examples 5 and 9 and Comparative Example 1. FIG. 5 is a graph showing the internal resistance of the power generation elements of Example 8 and Comparative Example 1.

  The power generation material of the present invention is represented by the following general formula (1).

_{(A x B 1-x)} (Mn y Nb 1-y) O 3 (1)
(In the formula, A and B are different from each other and represent at least one element selected from rare earth elements, alkaline earth metals, alkali metals, Cd and Bi, and x is an atom in a numerical range of 0 <x ≦ 1. And y represents an atomic ratio of 0.003 ≦ y ≦ 0.1.)
In the general formula (1), A and B are different from each other and represent at least one element selected from a rare earth element, an alkaline earth metal, an alkali metal, Cd and Bi.

  In the general formula (1), examples of rare earth elements represented by A and B include La (lanthanum), Ce (cerium), Pr (praseodymium), Yb (ytterbium), and Lu (lutetium). , La (lanthanum), and Ce (cerium).

  Examples of the alkaline earth metal represented by A and B include Be (beryllium), Mg (magnesium), Ca (calcium), Sr (strontium), Ba (barium), and preferably Ca. (Calcium), Sr (strontium), Ba (barium).

  Moreover, as an alkali metal shown by A and B, Li (lithium), Na (sodium), K (potassium), Rb (rubidium), Cs (cesium) etc. are mentioned, for example.

  These may be used alone or in combination of two or more.

  As A and B, preferably both of them are alkali metals, more preferably A is K and B is Na.

  In the general formula (1), x is an atomic ratio of A and represents a numerical range of 0 <x ≦ 1, and preferably represents a numerical range of 1/3 ≦ x ≦ 1. In other words, A is an essential component, and its atomic ratio exceeds 0, preferably 1/3 or more and 1 or less.

  On the other hand, the atomic ratio of B is 1-x, that is, the atomic ratio of the remainder obtained by subtracting the atomic ratio of A from 1 (0 <x ≦ 1). That is, in the general formula (1), B is an optional component and may or may not be included.

  In the general formula (1), y is an atomic ratio of manganese (Mn), and represents a numerical range of 0.003 ≦ y ≦ 0.1. From the viewpoint of improving power generation performance, A numerical range of 0.003 <y <0.1 is shown, and a numerical range of 0.03 ≦ y ≦ 0.05 is more preferable. In other words, manganese (Mn) is an essential component, and the atomic ratio is 0.003 or more, preferably more than 0.003, more preferably 0.03 or more, 0.1 or less, Preferably, it is less than 0.1, more preferably 0.05 or less.

  On the other hand, the atomic ratio of niobium (Nb) is 1-y, that is, the residual atomic ratio obtained by subtracting the atomic ratio of manganese (Mn) (0.003 ≦ y ≦ 0.1) from 1. In other words, niobium (Nb) is an essential component, and its atomic ratio is 0.9 or more, and preferably exceeds 0.9, more preferably 0.95 from the viewpoint of improving power generation performance. Or more, 0.997 or less, preferably less than 0.997, more preferably 0.97 or less.

Specific examples of the power generation material represented by the general formula (1) include La (Nb _97/100 Mn _3/100 ) O ₃ , Li (Nb _97/100 Mn _3/100 ) O ₃ , K (Nb _97/100 Mn _3/100 ) O ₃ , K (Nb _997/1000 Mn _3/1000 ) O ₃ , Mg (Nb _97/100 Mn _3/100 ) O ₃ , Ca (Nb _97/100 Mn _{3 / 100} ) O ₃ , (K _1/2 Na _1/2 ) (Nb _97/100 Mn _3/100 ) O ₃ , (Bi _1/2 K _1/4 Na _1/4 ) (Nb _97/100 Mn _{3 / 100} ) O ₃ , (Sr _1/100 (K _1/2 Na _1/2 ) _99/100 ) (Nb _97/100 Mn _3/100 ) O ₃ , (Ba _1/100 (K _1/2 Na _{1 / 2) 99/100)} Nb _97/100 Mn _{3/100) O 3,} and the like _{(Li 1/10 (K 1/2 Na 1/2} ) 9/10) (Nb 97/100 Mn 3/100) O 3.

As such a power generation material, a power generation material in which both A and B are alkali metals in the general formula (1) is preferable. Particularly preferably, in the above general formula (1), A is K, B is Na, x is 1/2, and y is 3/100 or 3/1000, that is, ( K _1/2 Na _1/2 ) (Nb _97/100 Mn _3/100 ) O ₃ , K (Nb _997/1000 Mn _3/1000 ) O ₃ , more preferably (K _1/2 Na _{1 / 2} ) (Nb _97/100 Mn _3/100 ) O ₃ . According to (K _1/2 Na _1/2 ) (Nb _97/100 Mn _3/100 ) O ₃ , excellent power generation efficiency can be obtained.

  And such an electric power generation material can be manufactured by a well-known method, and an electric power generation element can be manufactured from the obtained electric power generation material.

More specifically, for example, first, so as to obtain the above stoichiometric ratio, carbonates or oxides of each atom (for example, (K _1/2 Na _1/2 ) (Nb _97/100 Mn _{3 / 100} ) O ₃ , K ₂ CO ₃ , Na ₂ CO ₃ , Nb ₂ O ₅ , MnO (or MnO ₂ ), etc.), for example, molar ratio of K, Na, Nb and Mn Are mixed so that K: Na: Nb: Mn = 0.5: 0.5: 0.97: 0.03 to prepare a precursor powder. The mixing method is not particularly limited, and for example, a known wet mixing method can be employed.

  Next, the obtained precursor powder is heat-treated. In the heat treatment, for example, heating is performed from room temperature at a constant rate of temperature rise, and the temperature is maintained at a predetermined temperature for a predetermined time.

  The rate of temperature rise is, for example, 2 ° C./min or more, preferably 4 ° C./min or more, for example, 10 ° C./min or less, preferably 8 ° C./min or less.

  The ultimate temperature is, for example, 700 ° C. or higher, preferably 800 ° C. or higher, more preferably 850 ° C. or higher, and further preferably 870 ° C. or higher, for example, 1100 ° C. or lower, preferably 1000 ° C. or lower, More preferably, it is 900 degrees C or less. Further, the holding time at the reached temperature is, for example, 1 hour or more, preferably 2 hours or more, more preferably 4 hours or more, for example, 24 hours or less, preferably 12 hours or less, more preferably 6 hours or less.

  Thereafter, if necessary, the precursor powder after heat treatment is dry-mixed by a known method and pulverized.

  In this method, if necessary, a binder can be mixed into the heat-treated powder.

  The binder is not particularly limited. For example, polytetrafluoroethylene (PTFE), polyvinyl acetate, polyethylene oxide, polyvinyl ether, polyvinylidene fluoride (PVdF), fluoroolefin copolymer crosslinked polymer, fluoroolefin vinyl ether copolymer crosslinked. A polymer, polyvinyl pyrrolidone, polyvinyl alcohol, polyacrylic acid, polyvinyl butyral (PVB), etc. are mentioned, Preferably, polyvinyl alcohol and polyvinyl butyral (PVB) are mentioned.

  These binders can be used alone or in combination of two or more.

  The blending ratio of the binder is, for example, 0.01 parts by mass or more, preferably 0.04 parts by mass or more, for example, 0.9 parts by mass with respect to 100 parts by mass of the total amount of the powder and the binder after the heat treatment. It is not more than part by mass, preferably not more than 0.1 part by mass.

  Subsequently, the obtained powder (a mixture of a powder and a binder, if necessary) is compression-molded and sintered into an arbitrary shape.

  In the compression molding and sintering, for example, a hot pressing method, a pulse electric current sintering method (PECS) is employed.

  For example, when the hot press method is employed, as the processing conditions, the molding pressure is, for example, 10 MPa or more, preferably 30 MPa or more, for example, 200 MPa or less, preferably 100 MPa or less. The sintering temperature is, for example, 950 ° C. or higher, preferably 1050 ° C. or higher, for example, 1150 ° C. or lower, preferably 1125 ° C. or lower. The holding time at that temperature is, for example, 1 hour or more, preferably 2 hours or more, for example, 12 hours or less, preferably 8 hours or less.

  Further, when the pulse current sintering method is adopted, as the processing conditions, the molding pressure is, for example, 10 MPa or more, preferably 30 MPa or more, for example, 200 MPa or less, preferably 100 MPa or less. The sintering temperature is, for example, 900 ° C. or higher, for example, 1150 ° C. or lower, preferably 1100 ° C. or lower, more preferably 1000 ° C. or lower, and further preferably 950 ° C. or lower. The holding time at that temperature is, for example, 1 minute or more, preferably 3 minutes or more, for example, 1 hour or less, preferably 30 minutes or less.

  By such a method, the precursor powder can be sintered simultaneously with compression molding.

  In addition to the above method, for example, the precursor powder can be first compression molded and then separately sintered.

  The molding conditions in the compression molding are not particularly limited, but the molding pressure is, for example, 10 MPa or more, preferably 30 MPa or more, for example, 200 MPa or less, preferably 100 MPa or less. The molding time is, for example, 1 minute or more, preferably 3 minutes or more, for example, 10 minutes or less, preferably 5 minutes or less.

  In compression molding, for example, a known molding machine such as a uniaxial press molding machine or a CIP molding machine (cold isostatic pressing machine) can be used, and these can be used in combination.

  Preferably, the powder after the heat treatment is first subjected to, for example, 10 MPa or more, preferably 30 MPa or more, such as 100 MPa or less, preferably 50 MPa or less, for example, 1 minute or more, preferably by a single-axis press molding machine. Compression molding is performed for 3 minutes or more, for example, 10 minutes or less, preferably 5 minutes or less. Thereafter, further by a CIP molding machine, for example, 30 MPa or more, preferably 50 MPa or more, for example, 200 MPa or less, preferably 100 MPa or less, for example, 1 minute or more, preferably 3 minutes or more, for example, 10 minutes or less. The compression molding is preferably performed for 5 minutes or less.

  Thereafter, in this method, the obtained molded body is sintered by a known sintering apparatus.

  As sintering conditions, the sintering temperature is, for example, 900 ° C. or higher, for example, 1150 ° C. or lower, preferably 1100 ° C. or lower, more preferably 1000 ° C. or lower, and further preferably 950 ° C. or lower. The holding time at that temperature is, for example, 1 hour or more, preferably 2 hours or more, for example, 48 hours or less, preferably 24 hours or less.

  Also by such a method, the precursor powder can be compression-molded and sintered.

  And thereby, while obtaining the electric power generation material shown by the said General formula (1), the electric power generation element which consists of the electric power generation material can be obtained.

  Further, in this method, the obtained power generation material (power generation element) can be annealed. In the annealing treatment, for example, the power generation material (power generation element) is held at a predetermined temperature for a predetermined time.

  Moreover, the temperature conditions in annealing treatment are 800 degreeC or more, for example, Preferably, it is 900 degreeC or more, for example, is 1100 degrees C or less, Preferably, it is 1000 degrees C or less. The holding time at that temperature is, for example, 1 hour or more, preferably 2 hours or more, for example, 24 hours or less, preferably 12 hours or less.

  By such annealing treatment, the purity of the power generation material (power generation element) can be improved, and the physical stability and chemical stability can be improved.

The power generation element contains other power generation materials represented by the general formula (1), oxides (for example, Nb ₂ O ₅ ), and the like as long as the excellent effects of the present invention are not impaired. be able to.

  Further, the shape of the power generation element is not particularly limited, and various shapes such as a thin film shape (sheet shape) and a disk shape can be selected.

  Further, the size of the power generation element is not particularly limited. For example, when the power generation element is formed in a substantially rectangular thin film, the length of one side is, for example, 0.5 mm or more, preferably 10 mm or more. For example, it is 30 mm or less, preferably 15 mm or less. Moreover, thickness is 0.1 mm or more, for example, Preferably, it is 0.2 mm or more, for example, is 5 mm or less, Preferably, it is 1 mm or less.

  When the power generating element is formed in a disk shape, the diameter length is, for example, 5 mm or more, preferably 10 mm or more, for example, 50 mm or less, preferably 30 mm or less. Moreover, thickness is 0.1 mm or more, for example, Preferably, it is 0.2 mm or more, for example, is 5 mm or less, Preferably, it is 1 mm or less.

The density of such a power generation material is, for example, 3.5 g / cm ³ or more, preferably 4.0 g / cm ³ or more, more preferably 4.3 g / cm ³ or more, for example, 4.8 g / cm ^3. cm ³ or less, preferably 4.6 g / cm ³ or less.

  The relative dielectric constant of such a power generation material is, for example, 500 or more, preferably 1000 or more, for example, 25000 or less, preferably 20000 or less.

  The Curie point (temperature at which the dielectric constant changes rapidly) of the power generation material is, for example, 150 ° C. or higher, preferably 200 ° C. or higher, for example, 500 ° C. or lower, preferably 450 ° C. or lower.

  Moreover, the above-described power generation material may have a plurality (two or more) of Curie points.

  Thus, when there are a plurality of Curie points, the highest Curie point is, for example, 350 ° C. or higher, preferably 400 ° C. or higher, for example, 500 ° C. or lower, preferably 450 ° C. or lower.

  The lowest Curie point is, for example, 150 ° C. or higher, preferably 200 ° C. or higher, for example, 300 ° C. or lower, preferably 250 ° C. or lower.

  And since said electric power generation material and said electric power generation element which consists of the electric power generation material have comparatively high internal resistance, they suppress the leakage current at the time of using it for an electric power generation system, and can suppress the fall of an electromotive force. it can.

  Therefore, the above power generation element can be used in a power generation system as a piezoelectric element, a pyroelectric element, or the like.

  FIG. 1 is a schematic configuration diagram showing an embodiment of a power generation system of the present invention.

  In FIG. 1, a power generation system 1 includes a heat source 2 whose temperature rises and falls over time, a first device 3 whose temperature rises and falls over time due to a temperature change of the heat source 2, and electric power from the first device 3. A second device 4 for taking out, a temperature sensor 8 as a detecting means for detecting the temperature of the first device 3, a voltage applying device 9 as a voltage applying means for applying a voltage to the first device 3, and its voltage application And a control unit 10 for actuating and stopping the device 9.

  The heat source 2 is not particularly limited as long as it is a heat source whose temperature rises and falls over time, specifically, a heat source whose temperature changes periodically over time. For example, various energy utilization devices such as an internal combustion engine and a light emitting device Is mentioned.

  An internal combustion engine is a device that outputs power, for example, for a vehicle. For example, a single cylinder type or a multi-cylinder type is adopted, and a multi-cycle type (for example, a 2-cycle type, a 4-cycle type) is used in each cylinder. System, 6-cycle system, etc.) are employed.

  In such an internal combustion engine, pistons are repeatedly moved up and down in each cylinder. For example, in a 4-cycle system, an intake process, a compression process, an explosion process, an exhaust process, and the like are sequentially performed, and fuel is discharged. It is burned and power is output.

  In such an internal combustion engine, in the exhaust process, high-temperature exhaust gas is exhausted through an exhaust gas pipe, heat energy is transmitted using the exhaust gas as a heat medium, and the internal temperature of the exhaust gas pipe rises.

  On the other hand, in the other steps (steps excluding the exhaust step), the amount of exhaust gas in the exhaust gas pipe is reduced, so that the internal temperature of the exhaust gas pipe decreases compared to the exhaust process.

  As described above, the temperature of the internal combustion engine rises in the exhaust process and falls in the intake process, the compression process, and the explosion process, that is, rises and falls over time.

  In particular, since each of the above steps is periodically and sequentially repeated according to the piston cycle, the inside of the exhaust gas pipe of each cylinder in the internal combustion engine is periodically cycled with the repetition cycle of each of the above steps. A temperature change, more specifically, a high temperature state and a low temperature state are periodically repeated.

  When the light emitting device is turned on (emission light), for example, light such as infrared rays and visible light is used as a heat medium, and the temperature rises due to the heat energy. Therefore, the temperature of the light emitting device increases and decreases over time by turning on (emitting) and turning off over time.

  In particular, for example, when the light-emitting device is a light-emitting device (blinking (flashing) type light-emitting device) in which lighting is turned on and off intermittently over time, the light-emitting device is turned on (light-emitting). Due to the thermal energy of the light, a temperature change periodically, more specifically, a high temperature state and a low temperature state are periodically repeated.

  Moreover, as the heat source 2, for example, a plurality of heat sources can be provided, and a temperature change can be caused by switching between the plurality of heat sources.

  More specifically, for example, two heat sources, a low-temperature heat source (such as a coolant) and a high-temperature heat source (eg, a heating material) having a higher temperature than the low-temperature heat source, are prepared as the heat source. A mode in which a low-temperature heat source and a high-temperature heat source are alternately switched is used.

  Thereby, the temperature as a heat source can be raised or lowered with time, and in particular, the temperature can be periodically changed by periodically switching the low-temperature heat source and the high-temperature heat source.

  Although it does not restrict | limit especially as the heat source 2 provided with the several heat source which can be switched, For example, the high temperature air provided with the low temperature air supply system for combustion, the thermal storage heat exchanger, the high temperature gas exhaust system, and the supply / exhaust switching valve Combustion furnace (for example, a high-temperature gas generator described in Republished No. 96-5474), for example, a seawater exchange device (hydrogen storage alloy actuator-type seawater exchange device) using a high-temperature heat source, a low-temperature heat source, and a hydrogen storage alloy Is mentioned.

  As these heat sources 2, the said heat source can be used individually or in combination with 2 or more types.

  The heat source 2 is preferably an internal combustion engine.

  The first device 3 is a device that is electrically polarized in accordance with a temperature change of the heat source 2.

  The electric polarization referred to here is a phenomenon in which a potential difference occurs due to dielectric polarization due to displacement of positive and negative ions due to crystal distortion, such as a piezo effect and / or a phenomenon in which a dielectric constant changes due to a temperature change and a potential difference occurs, such as pyroelectricity. It is defined as a phenomenon in which an electromotive force is generated in a material, such as an effect.

  More specifically, examples of the first device 3 include a device that is electrically polarized by a piezo effect, a device that is electrically polarized by a pyroelectric effect, and the like.

  The piezo effect is an effect (phenomenon) in which when a stress or strain is applied, it is electrically polarized according to the magnitude of the stress or strain.

  And in this electric power generation system 1, the above-mentioned electric power generation element can be used as the 1st device 3 (henceforth a piezo element (piezoelectric element)) electrically polarized by the piezo effect.

  When a piezo element is used as the first device 3, the piezo element is in contact with the heat source 2 in a state where the periphery is fixed by a fixing member and volume expansion is suppressed, or It arrange | positions so that it may contact (exposure) to the heat medium (exhaust gas mentioned above, light, etc.) which transfers heat.

  It does not restrict | limit especially as a fixing member, For example, the 2nd device 4 (For example, a gold electrode, a silver electrode, etc.) mentioned later can also be used.

  In such a case, the piezo element is heated or cooled (possibly via a heat medium (exhaust gas, light, etc.) as described above) due to a change in temperature of the heat source 2 with time, thereby expanding. Or shrink.

  At this time, since the volume expansion of the piezo element is suppressed by the fixing member, the piezo element is pressed by the fixing member and is electrically polarized by the piezo effect (piezoelectric effect) or phase transformation near the Curie point. . Thereby, as will be described in detail later, power is extracted from the piezo element via the second device 4.

  In addition, such a piezo element is normally maintained in a heated state or a cooled state, and when its temperature becomes constant (that is, a constant volume), the electric polarization is neutralized, and then cooled or heated, Again, it is electrically polarized.

  Therefore, as described above, when the temperature of the heat source 2 periodically changes and the high temperature state and the low temperature state are periodically repeated, the piezo element is periodically heated and cooled. Electrical polarization and its neutralization are repeated periodically.

  As a result, electric power is extracted as a waveform (for example, alternating current, pulsating flow, etc.) that fluctuates periodically by the second device 4 described later.

  The pyroelectric effect is, for example, an effect (phenomenon) in which the insulator is electrically polarized in accordance with a change in temperature when the insulator (dielectric) is heated and cooled, and includes the first effect and the second effect. It is out.

  The first effect is an effect in which, when the insulator is heated and cooled, it spontaneously polarizes due to the temperature change and generates a charge on the surface of the insulator.

  In addition, the second effect is an effect that pressure deformation occurs in the crystal structure due to temperature changes during heating and cooling of the insulator, and piezoelectric polarization occurs due to stress or strain applied to the crystal structure (piezo effect, piezoelectric effect). ).

  And in this electric power generation system 1, the above-mentioned electric power generation element can be used as the 1st device 3 (henceforth a pyroelectric element) electrically polarized by the pyroelectric effect.

  When a pyroelectric element is used as the first device 3, the pyroelectric element is in contact with the heat source 2 or in contact with a heat medium (exhaust gas, light, or the like described above) that transmits the heat of the heat source 2 ( To be exposed).

  In such a case, the pyroelectric element is heated or cooled (possibly via a heat medium (exhaust gas, light, etc.) described above) due to a change in temperature of the heat source 2 with time, and the pyroelectric effect (first The electric polarization is caused by the first effect and the second effect. Thereby, although mentioned later in detail, electric power is taken out from the pyroelectric element via the second device 4.

  Also, such pyroelectric elements are usually maintained in a heated state or a cooled state, and when the temperature becomes constant, the electric polarization is neutralized, and then cooled or heated again to be electrically polarized again. .

  Therefore, when the temperature of the heat source 2 is periodically changed as described above and the high temperature state and the low temperature state are periodically repeated, the pyroelectric element is periodically heated and cooled. The electrical polarization of the element and its neutralization are repeated periodically.

  As a result, electric power is extracted as a waveform (for example, alternating current, pulsating flow, etc.) that varies periodically by the second device 4 described later.

  These first devices 3 can be used alone or in combination of two or more.

  The first device 3 (insulator (dielectric)) is electrically polarized by the temperature change of the heat source 2, and the electrical polarization may be any of electronic polarization, ionic polarization, and orientation polarization.

  For example, it is expected that a material that exhibits polarization by orientation polarization (for example, a liquid crystal material) can improve power generation efficiency by changing its molecular structure.

  In FIG. 1, the second device 4 is provided to extract power from the first device 3.

  More specifically, the second device 4 is not particularly limited, but, for example, two electrodes (for example, a gold electrode, a silver electrode, and the like) disposed to face each other with the first device 3 interposed therebetween, for example, ., And the like, and are electrically connected to the first device 3.

  The temperature sensor 8 is provided close to or in contact with the first device 3 in order to detect the temperature of the first device 3. The temperature sensor 8 directly detects the surface temperature of the first device 3 as the temperature of the first device 3, or detects the ambient temperature around the first device 3, for example, an infrared radiation thermometer, A known temperature sensor such as a thermocouple thermometer is used.

  The voltage application device 9 is provided directly or close to the first device 3 in order to apply a voltage to the first device 3. Specifically, the voltage application device 9 includes, for example, two electrodes (for example, a copper electrode, a silver electrode, and the like) that are arranged to face each other with the first device 3 interposed therebetween, separately from the second device 4 described above. A voltage application power source V and a conductive wire connected thereto are provided, and the first device 3 and the second device 4 are disposed between the electrodes.

  The control unit 10 is a unit (for example, ECU: Electronic Control Unit) that performs electrical control in the power generation system 1, and is configured by a microcomputer including a CPU, a ROM, a RAM, and the like.

  The control unit 10 is electrically connected to the temperature sensor 8 and the voltage application device 9 and operates and stops the voltage application device 9 according to the temperature detected by the temperature sensor 8 as described later.

  In the power generation system 1 shown in FIG. 1, the second device 4 is electrically connected to a booster 5, an AC / DC converter (AC-DC converter) 6, and a battery 7 in order.

  In order to generate electric power using such a power generation system 1, for example, first, the temperature of the heat source 2 is increased and decreased over time, specifically, periodically, and the first device 3 is heated by the heat source 2. And / or cool.

  In such a power generation system 1, the temperature of the heat source 2 is, for example, 100 to 1200 ° C., preferably 700 to 900 ° C. in the high temperature state, and the temperature in the low temperature state is lower than the temperature in the above high temperature state. More specifically, for example, 50 to 800 ° C, preferably 200 to 500 ° C, and the temperature difference between the high temperature state and the low temperature state is, for example, 10 to 600 ° C, preferably 20 to 500 ° C. is there.

  Moreover, the repetition period of these high temperature states and low temperature states is, for example, 10 to 400 cycles / second, preferably 30 to 100 cycles / second.

  And according to such a temperature change, the above-mentioned 1st device 3 is electrically polarized periodically. Thereafter, via the second device 4, the electric power can be taken out as a waveform (for example, alternating current, pulsating current) that periodically varies according to the periodic electrical polarization of the first device 3.

  In the power generation system 1, the extracted power is boosted in a state of a waveform that fluctuates periodically (for example, alternating current, pulsating current) in the booster 5 connected to the second device 4. As the booster 5, a booster capable of boosting AC voltage with excellent efficiency by a simple configuration using, for example, a coil and a capacitor is used. Next, the electric power boosted by the booster 5 is converted into a DC voltage by the AC / DC converter 6 and then stored in the battery 7.

  In this way, the power generation system 1 can extract power from the first device 3.

  In such a power generation system 1, a voltage can be applied to the first device 3 in accordance with the temperature state of the first device 3 in order to generate power more efficiently.

  That is, in the power generation system 1, the temperature of the first device 3 is detected by the temperature sensor 8 as well as the heating and / or cooling by the heat source 2, and the voltage application device 9 is operated based on the detection of the temperature. And stop.

  More specifically, in the power generation system 1, the temperature of the first device 3 is continuously measured by the temperature sensor 8 together with the heating and / or cooling by the heat source 2 described above, and the first device 3 is in a temperature rising state. Or whether the temperature is in the lowered state. For example, when the temperature of the first device 3 detected by the temperature sensor 8 is increased by a predetermined value (for example, 0.2 ° C./s), it is detected that the temperature has risen. Further, when the temperature of the first device 3 is lowered by a predetermined value (for example, 0.2 ° C./s), it is detected that the temperature is in the lowered state.

  In the power generation system 1, when it is detected that the first device 3 is in the temperature rising state, the voltage applying device 9 is operated to apply a predetermined voltage to the first device 3. In addition, the magnitude | size of a voltage is suitably set according to the objective and a use. The time for applying the voltage is until the first device 3 reaches the temperature-decreasing state, and specifically, the temperature-rising state.

  When it is detected that the first device 3 is in the temperature-decreasing state, the control unit 21 switches the control circuit 21 to stop the voltage application device 9 and stops the application of voltage to the first device 3. The time for stopping the application of the voltage is until the first device 3 reaches the temperature rising state, specifically, the temperature falling state.

  As described above, in the power generation system 1 described above, when the temperature rise of the first device 3 is detected, the voltage applying device 9 is activated and a voltage is applied to the first device 3. On the other hand, when the temperature drop of the first device 3 is detected, the voltage application device 9 is stopped and the application of the voltage is stopped.

  Thus, by operating the voltage application device 9 and applying a voltage to the first device 3, it is possible to efficiently extract power from the first device 3.

  And in this electric power generation system 1, as above-mentioned, in the booster 5 connected to the 2nd device 4, the taken-out electric power is in the state of the waveform (for example, alternating current, pulsating flow, etc.) which fluctuates periodically. Boost the pressure. As the booster 5, a booster capable of boosting AC voltage with excellent efficiency by a simple configuration using, for example, a coil and a capacitor is used. Next, the electric power boosted by the booster 5 is converted into a DC voltage by the AC / DC converter 6 and then stored in the battery 7.

  According to such a power generation system 1, since the heat source 2 whose temperature rises and falls with time is used, a fluctuating voltage (for example, an AC voltage) can be extracted, and as a result, a constant voltage (DC voltage) is extracted. Compared to the above, it is possible to store the electric power by boosting with excellent efficiency by a simple configuration. In addition, if the heat source 2 is a heat source that periodically changes in temperature, electric power can be extracted as a waveform that varies periodically. As a result, the electric power can be boosted with higher efficiency and stored with a simple configuration. can do.

  In particular, since such a power generation system 1 includes the power generation element described above, the power generation efficiency is excellent.

  Next, although this invention is demonstrated based on an Example and a comparative example, this invention is not limited by the following Example. “Part” and “%” are based on mass unless otherwise specified. In addition, specific numerical values such as a blending ratio (content ratio), physical property values, and parameters used in the following description are described in the above-mentioned “Mode for Carrying Out the Invention”, and a blending ratio corresponding to them ( Substituting the upper limit value (numerical value defined as “less than” or “less than”) or the lower limit value (number defined as “greater than” or “exceeded”) such as content ratio), physical property values, parameters, etc. be able to.

<Examination of heat treatment conditions>
Examples 1-5
The molar ratio of K, Na, Nb, and Mn in the K ₂ CO ₃ powder, Na ₂ CO ₃ powder, Nb ₂ O ₅ powder, and MnO powder is K: Na: Nb: Mn = 0.5: 0.5: 0.997: 0.003, and the mixture was stirred and mixed for 24 hours by a wet ball mill (made by Nikkato Co., Ltd.) using zirconia balls together with ion-exchanged water and dried.

  Next, the obtained powder was heated in air at a heating rate of 5 ° C./min, heat-treated for the time shown in Table 1 at the temperature shown in Table 1, and then a dry ball mill using zirconia balls (manufactured by Nikkato). For 12 hours and milled.

  Subsequently, polyvinyl alcohol was added as a binder so that it might become 0.04 mass part with respect to 100 mass parts of total of the powder and polyvinyl alcohol after heat processing, and was stirred and mixed by the wet ball mill for 2 hours.

  Next, the obtained mixture is filled into a mold, and a pulse plasma sintering method is employed using a discharge plasma sintering machine (manufactured by SPS Shintex Co., Ltd.) and heated at 900 ° C. for 5 minutes at 50 MPa. A molded body having a diameter of 20 mm was obtained.

Thereafter, the obtained molded body was heated in air at 900 ° C. for 2 hours and annealed. As a result, a power generation material composed of (K _1/2 Na _1/2 ) (Nb _0.997 Mn _0.003 ) O ₃ and a power generation element composed of the power generation material were obtained.

Evaluation (X-ray diffraction)
The electric power generation element obtained by Examples 1-5 was measured using the X-ray diffraction (X-Ray Diffraction: XRD) apparatus. The obtained XRD data is shown in FIG. 2 together with JCPDS card data of (K _0.5 Na _0.5 ) NbO ₃ .

Discussion The power generation element of Example 5 that was heat-treated at 880 ° C. for 6 hours before molding and sintering had a clear peak on the XRD data, and is presumed to have an excellent crystal structure.

<Examination of annealing conditions>
Examples 6-7
(K _1/2 Na _{1) By the} same operation as in Example 5, except that the heat treatment conditions before molding and sintering were 880 ° C. and 6 hours and the annealing conditions were as shown in Table _{1. / 2} ) A power generation material composed of (Nb _0.997 Mn _0.003 ) O ₃ and a power generation element composed of the power generation material were obtained.

Evaluation (appearance)
When the external appearance of the power generation element obtained in Examples 5 to 7 was visually observed, the power generation element of Example 5 that was annealed at 900 ° C. for 2 hours was uniformly annealed, and the material was also deteriorated. It was not confirmed. On the other hand, the power generation elements of Examples 6 to 7 were not uniformly annealed, and the material was slightly deteriorated.

<Examination of Mn content>
Example 8
Instead of MnO powder, MnO ₂ powder was used, and the mixing ratio of each raw material powder was such that the molar ratio of K, Na, Nb and Mn was K: Na: Nb: Mn = 0.5: 0. 5: 0.997: 0.003 (K _1/2 Na _1/2 ) (Nb _0.997 Mn _0.003 ) O ₃ A power generation material and a power generation element made of the power generation material were obtained.

Example 9
The blending amount of the MnO powder was changed, and the blending ratio of each raw material powder was such that the molar ratio of K, Na, Nb and Mn was K: Na: Nb: Mn = 0.5: 0.5: 0.97: A power generation material composed of (K _1/2 Na _1/2 ) (Nb _0.97 Mn _0.03 ) O ₃ by the same operation as in Example 5 except that adjustment was made to be _0.03 , and A power generation element made of the power generation material was obtained.

Comparative Example 1
MnO powder is not blended, and the blending ratio of each raw material powder is such that the molar ratio of K, Na, Nb and Mn is K: Na: Nb: Mn = 0.5: 0.5: 1: 0. In addition, a power generation material composed of (K _1/2 Na _1/2 ) NbO ₃ and a power generation element composed of the power generation material were obtained by the same operation as in Example 1 except for the adjustment.

Evaluation (1) Dielectric constant The dielectric constants of the power generation elements obtained in Examples 5 and 9 and Comparative Example 1 were measured with an impedance analyzer (model number ZGA5920, manufactured by NF Circuit Design Block) from a measurement frequency of 0.1 mHz to 15 MHz. Temperature rising rate 2 ° C./min, measurement temperature range Measurement was performed under conditions from room temperature to 450 ° C.

  The result is shown in FIG.

(2) Dielectric loss The dielectric loss of the power generation elements obtained in Examples 5 and 9 and Comparative Example 1 was increased from a measurement frequency of 0.1 mHz to 15 MHz by an impedance analyzer (model number ZGA5920, manufactured by NF Circuit Design Block). Temperature rate 2 ° C./min, measurement temperature range Measurement was performed under conditions from room temperature to 450 ° C.

  The result is shown in FIG.

(3) Internal resistance The internal resistance of the power generation element obtained in Example 8 and Comparative Example 1 was measured with an electrometer (model number 6517B / J, manufactured by KEITHLEY) at a sampling rate of 0.5 s, 1200 plot, and a measurement temperature of 100. The measurement was performed under the conditions of ° C, 120 ° C, 160 ° C, 200 ° C, 250 ° C, and 300 ° C.

  The result is shown in FIG.

(4) Power generation performance The power generation elements obtained in Examples 8 to 9 and Comparative Example 1 were used as the first device (piezo element), and the thickness was ground to 1.2 mm. Next, gold ions were vapor-deposited on the front and back surfaces for about 10 minutes using gold sputtering to form a gold electrode (second device).

  Then, using the aluminum tape of 20 mm x 20 mm, while sticking one side of two conducting wires (lead wire) on each gold electrode, the other side was connected to the digital multimeter.

  A heat gun was used as a heat source, the spray port was directed to the power generation element, and the heat gun and the power generation element were arranged so that the spray port was 3 cm away from the power generation element.

  By blowing hot air from the heat gun and switching the heat gun on and off over time, the temperature of the heat gun and hot air is raised and lowered over time, and this temperature change raises and lowers the temperature of the power generation element over time and electrically polarizes it. The generated voltage (electric power) was taken out through the electrode and the conductive wire.

  The temperature of the power generation element is measured with an infrared radiation thermometer. It was adjusted. Further, heating and cooling were switched at a cycle of heating / cooling = 10 s / 10 s.

  And the voltage change of the electric power taken out from the electric power generation element was observed with the voltmeter.

  In the five heating / cooling cycles, the average power obtained by the power generation element was 9.22 μW in Example 8, 3.88 μW in Example 9, and 3.12 μW in Comparative Example 1.

  The results are shown in Table 3.

DESCRIPTION OF SYMBOLS 1 Power generation system 2 Heat source 3 1st device 4 2nd device

Claims (4)

It is shown by following General formula (1), The electric power generation material characterized by the above-mentioned.
_{(A x B 1-x)} (Mn y Nb 1-y) O 3 (1)
(In the formula, A and B are different from each other and represent at least one element selected from rare earth elements, alkaline earth metals, alkali metals, Cd and Bi, and x is an atom in a numerical range of 0 <x ≦ 1. And y represents an atomic ratio of 0.003 ≦ y ≦ 0.1.) In the general formula (1),
A is K,
B is Na,
The power generating material according to claim 1, wherein x is ½.   A power generation element comprising the power generation material according to claim 1. A heat source whose temperature rises and falls over time;
A first device comprising the power generating element according to claim 3, wherein the first device is electrically polarized by a temperature change of the heat source,
A power generation system comprising: a second device for extracting power from the first device.

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