Patent Application
20240376013
The present disclosure relates to a ceramic.
In recent years, as a cooling element, a new solid cooling element and a new cooling system using an electrocaloric effect have attracted attention, and research and development thereof have been actively conducted. Compared with an existing cooling system using a refrigerant which is a greenhouse gas, there are advantages of high efficiency and low power consumption without requiring a refrigerant, and there is also an advantage of being quiet because no compressor is used. In order to obtain an excellent electrocaloric effect, a material that has a transition temperature in a desired temperature range and enables application of a large electric field is required. As such a material, PbSc0.5Ta0.5O3 (hereinafter, a ceramic containing Pb, Sc, and Ta is also referred to as “PST”) (Patent Document 1, Non-Patent Documents 1 and 2) and PbMg0.5W0.5O3 (hereinafter, a ceramic containing Pb, Mg, and W is also referred to as “PMW”) are known as promising materials. Non-Patent Document 3 reports that PbMg0.5W0.5O3 exhibits large positive and negative electrocaloric effects.
The PMW is an antiferroelectric and has a feature of being transferred to a ferroelectric by applying a voltage equal to or higher than a threshold voltage. The electrocaloric effect of the PMW is very small at a voltage equal to or lower than this threshold voltage, and when the voltage exceeds the threshold voltage, the PMW exhibits an electrocaloric effect according to the magnitude of the applied voltage. That is, when the PMW is used as a solid cooling element, it is necessary to apply a large voltage exceeding the threshold voltage of the PMW, and thus the electric field intensity required for exhibiting the electrocaloric effect also increases.
An object of the present disclosure is to provide a ceramic that exhibits a larger electrocaloric effect at a lower electric field than before. More specifically, an object of the present disclosure is to provide a ceramic that exhibits a larger electrocaloric effect at a lower electric field than that of a conventional PMW.
The present disclosure relates to a ceramic represented by Formula (1):
(1−m)PbSc0.5−xTa0.5+xO3−mPbMg0.5−yW0.5+yO3 (1)
wherein
The present disclosure includes the following aspects.
[1] A ceramic represented by Formula (1):
(1−m)PbSc0.5−xTa0.5+xO3−mPbMg0.5−yW0.5+yO3 (1)
wherein
[2] The ceramic according to [1], wherein
[3] The ceramic according to [1] or [2], wherein x is 0 and y is 0.
[4] The ceramic according to any one of [1] to [3], wherein 0.6≤m≤0.9.
[5] The ceramic according to any one of [1] to [4], wherein a crystal structure of the ceramic has a perovskite structure.
[6] An electrocaloric effect element, wherein a noble metal electrode and the ceramic according to any one of [1] to [5] are alternately stacked.
[7] The electrocaloric effect element according to [6], wherein the noble metal electrode comprises Pt.
[8] An electronic component including the electrocaloric effect element according to [6] or [7].
[9] An electronic device including the electrocaloric effect element according to [6] or [7] or the electronic component according to [8].
According to the present disclosure, it is possible to provide a ceramic that exhibits a large electrocaloric effect at a low electric field. More specifically, it is possible to provide a ceramic that exhibits a larger electrocaloric effect at a lower electric field than a conventional PMW.
Hereinafter, a ceramic of the present disclosure and an electrocaloric effect element using the ceramic will be described in detail with reference to the drawings. Note that, the shapes and arrangements of the electrocaloric effect element and respective constituent elements according to the present embodiment are not limited to those in the illustrated examples.
The ceramic according to an embodiment of the present disclosure contains Pb, Sc, Ta, Mg, and W as main components. The ceramic is a composite oxide containing Pb, Sc, Ta, Mg, and W.
A content of Pb is substantially equal to a total content of Sc, Ta, Mg, and W.
When a content of Sc is “0.5−x”, a content of Ta is “0.5+x”, and when a content of Mg is “0.5−y”, a content of W is “0.5+y”.
The ranges of x and y are set such that
0<x≤0.1 and −0.1≤y<0 when 0<x and 0>y.
When a total content of Mg and W is denoted by “m”, a total content of Sc and Ta is “1−m”, and the range of m is 0.60≤m≤0.95. All of the above contents are molar ratios. When the composition in the above ranges is employed, a large electrocaloric effect can be obtained at a low electric field.
The expression “the content of Pb is substantially equal to the total content of Sc, Ta, Mg, and W” is not limited to a case where the content of Pb is exactly equal to the total content of Sc, Ta, Mg, and W. That is, the expression “the content of Pb is substantially equal to the total content of Sc, Ta, Mg, and W” includes a case where the difference between the content of Pb and the total content of Sc, Ta, Mg, and W is, for example, 3% or less in terms of molar ratio.
The composition of the ceramic of the present disclosure can be analyzed and measured by performing composition analysis using, for example, high-frequency inductively coupled plasma emission spectroscopy, or X-ray fluorescence spectroscopy.
The electrocaloric effect is an endothermic and exothermic phenomenon caused by a change in entropy when electric dipole moments in a substance are aligned or disordered by a change in the electric field. A performance indicator of the electrocaloric effect in the present disclosure may be an adiabatic temperature change (ΔT). That is, the expression “the electrocaloric effect is large” may mean that the adiabatic temperature change (ΔT) is large. In the present disclosure, a larger adiabatic temperature change (ΔT) is more preferable.
The adiabatic temperature change ΔT means a temperature change of the ceramic caused by application of the electric field to the ceramic and/or removal of the electric field applied to the ceramic. Specifically, the adiabatic temperature change ΔT may be a difference between a temperature of the ceramic before application of the electric field and a temperature of the ceramic immediately after application of the electric field, or may be a difference between a temperature of the ceramic before removal of the electric field and a temperature of the ceramic immediately after removal of the electric field.
In general, the adiabatic temperature change ΔT increases as the electric field intensity to be applied to the ceramic increases. The adiabatic temperature change ΔT tends to increase as the temperature of the ceramic at the time of application of the electric field approaches the antiferroelectric transition temperature (or ferroelectric transition temperature). For example, the electrocaloric effect rapidly decreases as the temperature of the ceramic becomes lower than the transition temperature. Specifically, in the conventional PMW having a transition temperature of about 20 to 30° C., the electrocaloric effect tends to decrease significantly when the temperature of the ceramic is 0° C. or lower.
In another aspect, the ceramic may be a ceramic represented by Formula (1):
(1−m)PbSc0.5−xTa0.5+xO3−mPbMg0.5−yW0.5+yO3 (1)
wherein
When x, y, and m are set within the above ranges, a large electrocaloric effect (for example, 0.8 K or more when an electric field intensity of 8 MV/m is applied) at a low electric field can be obtained.
Although the present disclosure is not bound by any theory, a mechanism for obtaining the above effect is considered as follows.
Examples of the substance exhibiting a large electrocaloric effect include PMW exhibiting antiferroelectricity and PbSc0.5Ta0.5O3 (hereinafter, a ceramic containing Pb, Sc, and Ta is also referred to as “PST”) exhibiting ferroelectricity. The PMW and PST show antiferroelectricity and ferroelectricity, respectively, which have a large latent heat at the time of transition due to alignment of cations at the B site (Mg and W for PMW, Sc, and Ta for PST).
In the case of the PMW, the PMW exhibits a negative electrocaloric effect (heat absorption at the time of application of the electric field and heat generation at the time of removal of the electric field) derived from its antiferroelectricity at a temperature equal to or lower than the phase transition temperature, and exhibits a large positive electrocaloric effect (heat generation at the time of application of the electric field, and heat absorption at the time of removal of the electric field) in the vicinity of the transition temperature. That is, the positive and negative of the electrocaloric effect are inverted depending on the temperature. As the electrocaloric effect for practical use, both a positive electrocaloric effect and a negative electrocaloric effect may be used. In the case of the PMW, a large electric field intensity of 10 MV/m or more is required to obtain a large negative electrocaloric effect, and when the electric field intensity is less than 10 MV/m, the PMW exhibits only a very small electrocaloric effect.
In general, it is known that cations at the B site are easily aligned as the difference in ionic radius between two cations at the B site is larger. In the PMW, the difference in ionic radius between Mg and W is larger than that in the PST, so that ions at the B site is easily aligned. Accordingly, unlike the PST, the PMW has a feature that ions at the B site are aligned without performing a heat treatment for a long time. In the present disclosure, the threshold voltage of the antiferroelectric has been successfully lowered by adding the PST to the PMW. This is considered to be because the alignment of ions at the B site of the PMW is moderately decreased.
The threshold voltage means a voltage (about 18 MV/m) at which electric polarization rapidly increases as shown in
As shown in
In the present disclosure, when the PST is added to the PMW, not only the threshold voltage of the antiferroelectric is lowered, but also the transition temperature of the PMW is successfully lowered to room temperature or lower. That is, as compared with the conventional PMW, the ceramic of the present disclosure can provide an excellent electrocaloric effect at 0° C. or lower (for example, −15° C.).
Further, in the present disclosure, it is also possible to prevent inversion of the positive and negative of the electrocaloric effect from occurring in the temperature range of actual use (for example,−20 to 0° C.), at a relatively low electric field intensity, and 8 MV/m or more. Therefore, as compared with the conventional PMW, the ceramic of the present disclosure has improved controllability of the electrocaloric effect, and does not require complicated control when used as a cooling system.
In one aspect, the ranges of x and y are set such that
In one aspect, the ranges of x and y are set such that
In one aspect, the ranges of x and y are set such that
In one aspect, the ranges of x and y are set such that
In one aspect, the ranges of x and y are set such that
In another aspect, the ranges of x and y are set such that
In one aspect, the ranges of x and y may be determined by optionally combining the ranges of x and y in the cases of “0≤x, y”, “0>x, 0≤y”, “0≥x, 0>y”, and “0<x, 0>y” described above.
In a preferred aspect, x and y are 0. That is, the formula represented by (1−m) PbSc0.5−xTa0.5+xO3−mPbMg0.5−yW0.5+zO3 is (1−m) PbSc0.5Ta0.5O3−mPbMg0.5W0.5O3.
In one aspect, m may be 0.60<m 0.95.
The range of m is preferably 0.60 m 0.90, more preferably 0.70≤m≤0.90, and still more preferably 0.70≤m≤0.80 from the viewpoint of improving the electrocaloric effect at a low electric field.
The range of m is preferably 0.60≤m≤0.90, more preferably 0.65≤m≤0.90, and still more preferably 0.65≤m≤0.85 from the viewpoint of improving the electrocaloric effect at a low temperature.
The range of m may be 0.90≤m≤0.95 from the viewpoint of obtaining a negative electrocaloric effect.
The range of m may be 0.60≤m≤0.80 from the viewpoint of obtaining a positive electrocaloric effect.
The crystal structure of the ceramic according to an embodiment of the present disclosure may be a perovskite structure. The ceramic having a perovskite structure means not only a ceramic having a “perovskite crystal structure”, but also a ceramic having a “crystal structure similar to the perovskite crystal structure”. For example, the ceramic having a perovskite structure may have a crystal structure that can be recognized as the crystal structure of perovskite by those skilled in the art of ceramic in X-ray diffraction.
An electrocaloric effect element of the present disclosure has a laminate in which an electrode layer and a ceramic layer containing the ceramic of the present disclosure as a main component are alternately stacked.
As shown in
The electrode layer 2 is a so-called internal electrode. The electrode layer 2 can have a function of transferring a heat quantity between the ceramic layer 4 and the outside in addition to a function of applying the electric field to the ceramic layer 4.
The electrode layer 2 may be an electrode layer containing a noble metal as a main component. Here, the “main component” in the electrode layer 2 means that the electrode layer 2 is formed from 80 mass % or more of noble metal, and for example, means that 95 mass % or more, more preferably 98 mass % or more, further preferably 99 mass % or more, still more preferably 99.5 mass % or more, and particularly preferably 99.9 mass % or more of the electrode layer 2 is noble metal.
In the present specification, the “noble metal” may be, for example, Au, Ag, Pt, or Pd. From the viewpoint of improving the electrocaloric effect at a low temperature, the main component of the electrode layer 2 used in the present disclosure may be Pt or Pd. That is, the electrode layer 2 may be a Pt or Pd electrode layer. However, from the viewpoint of improving chemical durability and/or cost, the electrode layer 2 of the noble metal may be an alloy (for example, an Ag—Pd alloy, and the like) or a mixture of Pt and/or Pd and another element (for example, Ag, Pd, Rh, Au, and the like). When the Pt or Pd electrode layer is formed of an alloy or a mixture thereof, a similar effect can be obtained. Other elements that can be mixed as impurities, particularly inevitable elements (for example, Fe, Al2O3, and the like) may be contained. In this case, similar effects are achievable.
The thickness of the electrode layer 2 can be preferably 0.2 μm to 10 μm, more preferably 1.0 μm to 5.0 μm, for example, 2.0 μm to 5.0 μm, or 2.0 μm to 4.0 μm. When the thickness of the electrode layer 2 is 0.5 μm or more, resistance of the electrode layer 2 can be reduced, and heat transport efficiency can be increased. When the thickness of the electrode layer 2 is 10 μm or less, the thickness (thus, volume) of the ceramic layer can be increased, and the heat quantity that can be handled by the electrocaloric effect of the entire element can be further increased. In addition, the element can be made smaller.
The ceramic layer 4 may contain one type of ceramic as a main component, or two or more types of ceramics as main components.
Here, the “main component” in the ceramic layer means that the ceramic layer is substantially formed from a target ceramic, and for example, means that 90 mass % or more, more preferably 95 mass % or more, further preferably 98 mass % or more, still more preferably 99 mass % or more, and particularly preferably 99.5 mass % or more of the ceramic layer is the target ceramic. The other component may be a crystal phase having a structure different from the perovskite structure, which is a pyrochlore structure, other elements mixed as impurities, and particularly inevitable elements (for example, Zr, C, and the like).
The composition of the ceramic layer 4 can be determined by, for example, high-frequency inductively coupled plasma emission spectroscopy, X-ray fluorescence spectroscopy, or another method. The structure of the ceramic layer 4 can be determined by powder X-ray diffraction.
The thickness of the ceramic layer 4 can be preferably 5 μm to 100 μm, more preferably 5 μm to 50 μm, further preferably 10 μm to 50 μm, still more preferably 20 μm to 50 μm, and particularly preferably 20 μm to 40 μm. When the thickness of the ceramic layer 4 is further increased, the heat quantity that can be handled by the element can be increased. When the thickness of the ceramic layer 4 is further reduced, a higher ΔT can be obtained, and the withstand voltage can also be improved.
The withstand voltage of the ceramic layer 4 can be preferably 15 MV/m or more, more preferably 20 MV/m or more, and still more preferably 25 MV/m or more. When the withstand voltage of the ceramic layer 4 is further increased, a larger voltage (electric field) can be applied, and a larger ΔT can be obtained.
A material constituting a pair of the external electrodes 8a and 8b is not particularly limited, examples thereof include Ag, Cu, Pt, Ni, Al, Pd, Au, and alloys thereof (for example, Ag—Pd and the like), and an electrode composed of these metals and glass or an electrode composed of metal and resin may be used. Among the metals, Ag is preferable.
In the electrocaloric effect element 1, the electrode layer 2 and the ceramic layer 4 are alternately stacked. In the electrocaloric effect element of the present disclosure, the number of stacked electrode layers 2 and ceramic layers 4 is not particularly limited. All the internal electrodes may not be connected to the external electrodes, and may include internal electrodes that are not connected to the external electrodes as necessary for heat transfer, stress relaxation due to piezoelectricity and electrostriction, and the like.
In the electrocaloric effect element 1, the internal electrode and the ceramic layer are in contact with each other on substantially the entire surface. However, the electrocaloric effect element of the present disclosure is not limited to such a structure, and is not particularly limited as long as it has a structure capable of applying a voltage (electric field) to the ceramic layer. Although the electrocaloric effect element 1 has a rectangular parallelepiped block shape, the shape of the electrocaloric effect element of the present disclosure is not limited thereto. For example, the electrocaloric effect element 1 may have a cylindrical shape or a sheet shape, and may further have unevenness, a through hole, or the like. The internal electrode may be exposed on a surface for heat transfer or heat exchange with the outside.
The ceramic and electrocaloric effect element of the present embodiment described above is manufactured, for example, as follows.
As raw materials, high purity lead oxide (Pb3O4), tantalum oxide (Ta2O5), scandium oxide (Sc2O3), magnesium carbonate (MgCO3), and tungsten oxide (WO3) are weighed so as to have a desired composition ratio after firing. The above raw materials are pulverized and mixed with partially stabilized zirconia (PSZ) balls, pure water, a dispersant, and the like by a ball mill. Thereafter, a slurry obtained by pulverization and mixing is dried and sized, and then calcined under the conditions of, for example, 800° C. to 900° C. in an air atmosphere. A calcined powder obtained is mixed with PSZ balls, ethanol, toluene, a dispersant, and the like and pulverized. Next, a dissolved binder solution is added to the pulverized powder obtained, and mixed to prepare a slurry for sheet forming. The prepared slurry is formed into a sheet shape on a support, and a Pt electrode paste is applied thereon. A sheet to which the Pt electrode paste has been applied and a sheet to which the Pt electrode paste has not been applied are stacked so as to have a desired structure, and then the stack is pressure-bonded at a pressure of 100 MPa to 200 MPa, and cut to prepare a green chip. The green chip is heat-treated at 500° C. to 600° C. in an air atmosphere to perform a binder removal treatment. Next, the chip subjected to binder removal is fired at 800° C. to 1,400° C. together with a PbZrO3 powder for creating a Pb atmosphere using, for example, an alumina sealed sagger. Thereafter, the end surfaces of the chip are polished with sandpaper, an external electrode paste is applied, and baking treatment is performed at a predetermined temperature, so that an electrocaloric effect element as shown in
The electrocaloric effect element of the present disclosure exhibits an excellent electrocaloric effect, and thus can be used as a heat management element, particularly as a cooling element (including cooling/heat pump elements of an air conditioning apparatus such as an air conditioner, a refrigerator, and a freezer).
The present disclosure also provides an electronic component including the electrocaloric effect element of the present disclosure, and an electronic device including the electrocaloric effect element of the present disclosure or the electronic component.
The electronic component is not particularly limited, and examples thereof include electronic components used for an air conditioner, a refrigerator or a freezer, or electronic components (for example, batteries) used for an air conditioner of electric vehicles and hybrid cars; and components commonly used for electronic devices such as integrated circuits (ICs) such as a central processing unit (CPU), a hard disk (HDD), a power management IC (PMIC), a power amplifier (PA), a transceiver IC, and a voltage regulator (VR); light-emitting elements such as a light emitting diode (LED), an incandescent light bulb, and a semiconductor laser; components which can be a heat sources such as a field-effect transistors (FET); and other components, for example, a lithium ion battery, a substrate, a heat sink, a housing, and the like.
The electronic device is not particularly limited, and examples thereof include an air conditioner, a refrigerator, and a freezer; an air conditioner used as a heat pump, an air conditioner of electric vehicles or hybrid cars, and small electronic devices such as a cellular phone, a smartphone, a personal computer (PC), a tablet terminal, a hard disk drive, and a data server.
The electrocaloric effect element of the present disclosure can be used as a heat management system (or a temperature management system) that manages heat (temperature) of the electronic component and the electronic device. Examples of the heat management system include a cooling system that cools the electronic component and the electronic device.
As raw materials, high purity lead oxide (Pb3O4), tantalum oxide (Ta2O5), scandium oxide (Sc2O3), magnesium carbonate (MgCO3), and tungsten oxide (WO3) were prepared. These raw materials were weighed so as to have a predetermined composition ratio as shown in Tables 1 to 4 after firing, and pulverized and mixed with partially stabilized zirconia (PSZ) balls having a diameter of 2 mm, pure water, and a dispersant by a ball mill for 16 hours. Thereafter, a slurry obtained by pulverization and mixing was dried on a hot plate and sized, and then calcined for 2 hours under the condition of 850° C. in an air atmosphere.
A calcined powder obtained was mixed with PSZ balls having a diameter of 5 mm, ethanol, toluene, and a dispersant for 16 hours, and pulverized. Next, a dissolved binder solution was added to a pulverized powder obtained, and mixed for 4 hours to prepare a slurry for sheet forming. The prepared slurry was formed into a sheet shape on a PET film by a doctor blade method in a thickness corresponding to a thickness of a predetermined ceramic layer, cut into strips, and then a platinum internal electrode paste was applied to the cut strips by screen printing. The thickness of a sheet of the stacked element to be produced was controlled by changing a gap of a doctor blade used at the time of sheet formation.
A predetermined number of sheets to which the platinum internal electrode paste had been applied and sheets to which the platinum internal electrode paste had not been applied were stacked, and then the stack was pressure-bonded at a pressure of 150 MPa, and cut to prepare a green chip. The green chip was heat-treated at 550° C. for 24 hours in an air atmosphere to perform the binder removal treatment. Next, the green chip was sealed in an alumina sealed sagger together with a PbZrO3 powder for creating a Pb atmosphere, and fired at 900 to 1,300° C. for 4 hours. Samples within the scope of the present disclosure were sufficiently fired at a temperature of 900 to 1,250° C. A sample of sample No. 1 as Comparative Example shown in Table 1 was fired at a high temperature of 1,400° C. and then heat-treated at 1,000° C. for 1,000 hours.
Thereafter, the end surfaces of the chip were polished with sandpaper, an Ag external electrode paste was applied, and baking treatment was performed at a temperature of 750° C., so that an electrocaloric effect element as shown in
The size of the obtained element was about L 10.2 mm×W 7.2 mm×T 0.88 mm for the element in which the thickness of the ceramic layer was 40 μm. The number of ceramic layers sandwiched between the internal electrode layers was 19, the electrode area was 49 mm2/layer, and the total electrode area was 49 mm2×19 layers. The thickness of the ceramic layer of the element obtained above was confirmed using a scanning electron microscope after polishing a section of the element.
The ceramic composition of the obtained element was confirmed using high-frequency inductively coupled plasma emission spectroscopy and X-ray fluorescence spectroscopy.
In order to evaluate the crystal structure of the obtained element, powder X-ray diffraction measurement was performed. One element was randomly selected from each lot and ground in a mortar, and then an X-ray diffraction profile was obtained. From the obtained X-ray diffraction profile, it was confirmed whether the crystal structure of the ceramic was the perovskite structure, and the presence or absence and abundance of an impurity phase (mainly a pyrochlore phase) were estimated from the intensity ratio. When the abundance of the perovskite structure was 0.95 or more, it was determined that the main component had the perovskite structure, and when the abundance was less than 0.95, it was determined that there was a heterophase.
An ultrafine K thermocouple having a diameter of 50 μm was attached to a central portion of the surface of an element with a Kapton tape. The temperature was constantly monitored, a wire for voltage application was bonded to both ends of the external electrode with an Ag paste, and a voltage was applied to the element using a high voltage generator.
The electrocaloric effect was evaluated by applying a voltage to the sample in a sequence as shown in the graph of
On the other hand, when a voltage is applied to an antiferroelectric in a sequence as shown in the graph of
In this example, for the adiabatic temperature change ΔT, after applying a predetermined voltage, the temperature was measured with the voltage kept applied for 50 seconds, and then after removing the voltage, the temperature was measured without any voltage applied for 50 seconds. This sequence was repeated three times. During the sequence of voltage application and voltage removal, the temperature of the element was constantly measured, and the adiabatic temperature change ΔT was obtained from the temperature change. Samples in which the absolute value of the adiabatic temperature change ΔT when electric fields of 8 MV/m and 15 MV/m were applied at −15° C. were 0.8 K to 1.5 K or more, respectively, were rated as “Go”. The results are shown in Tables 1 to 4.
Hereinafter, the above evaluation results are shown. Samples marked with “*” in the tables are Comparative Examples, and other samples are Examples.
The ferroelectric characteristics of the conventional PMW shown in sample No. 1 are shown in
As shown in
Table 1 shows the characteristic test results of the samples prepared above. Specifically, Table 1 shows the electrocaloric effects of samples in which the values of x and y in Formula (1) are fixed to 0 and m is changed to various values. As a result of XRD measurement, in all the samples having the compositions shown in Table 1, the main component had a desired perovskite structure, and the number of heterophases was small.
The PMW shown in the conventionally known sample No. 1 and the PST shown in sample No. 2 had a low electrocaloric effect at −15° C., and the adiabatic temperature change was smaller than 1.5 K. On the other hand, in the samples having the compositions within the scope of the present disclosure, the absolute values of the adiabatic temperature change when electric fields of 8 MV/m and 15 MV/m were applied were 0.8 K and 1.5 K or more, respectively.
Samples in which m was in the range of 0.6 m 0.8 exhibited a positive caloric effect in the range of −20° C. to 0° C. when an electric field intensity of 15 MV/m was applied, and there was no inversion of the sign in this temperature range. Samples in which m was in the range of 0.8<m 0.95 exhibited a negative caloric effect in the above-described temperature range and electric field intensity, but there was no inversion of the sign.
As shown in
It is considered that when the value of m was less than 0.6, the ferroelectric transition temperature was not sufficiently lowered, and when the value of m was more than 0.95, not only the transition temperature was not sufficiently lowered, but also the threshold voltage of antiferroelectric was not lowered, so that the adiabatic temperature change at a low temperature and a low electric field was reduced.
Tables 2, 3, and 4 show the measurement results of the electrocaloric effects of the ceramics represented by Formula (1) in the cases where m is 0.6, m is 0.8, and m is 0.95, respectively.
Among the samples in which m is within the scope of the present disclosure, the proportion of the substance having a desired crystal structure was most stably close to 100% in the samples where both x and y are near 0. Even when both x and y are not in the vicinity of 0, no heterophase was generated, but when x and y are greatly deviated from 0, the proportion of the heterophase increased or the insulation property decreased, and element breakdown occurred when an electric field was applied (see the columns of crystal structure in Tables 2 to 4). However, in the compositions within the scope of the present disclosure, the main component had a desired structure, and the absolute values of the adiabatic temperature change when electric fields of 8 MV/m and 15 MV/m were applied at −15° C. were 0.8 K and 1.5 K or more, respectively.
The electrocaloric effect element of the present disclosure can exhibit a high electrocaloric effect, and thus can be used as heat management elements in, for example, an electric vehicle or a hybrid car, an air conditioner (for example, an air conditioner used for an electric vehicle or a hybrid car, an air conditioner used as a heat pump, and the like), a refrigerator, a freezer, and the like. The electrocaloric effect element of the present disclosure can also be used as cooling devices of various electronic devices, for example, small electronic devices such as a cellular phone, a smartphone, a tablet terminal, a hard disk drive, a data server, and the like in which a heat countermeasure problem is remarkable, or a personal computer (PC) and the like.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022-059401 | Mar 2022 | JP | national |
The present application is a continuation of International application No. PCT/JP2023/012593, filed Mar. 28, 2023, which claims priority to Japanese Patent Application No. 2022-059401, filed Mar. 31, 2022, the entire contents of each of which are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2023/012593 | Mar 2023 | WO |
| Child | 18780740 | US |
