ceramics

Abstract

The present disclosure provides a ceramic represented by formula (1): (1-m) PbSc0.5-xTa0.5+xO3-mPbMg0.5-yW0.5+yO3 (1) [In formula (1), m satisfies 0.60≤m≤0.95, x,y≤0.1 and 0≤x+y≤0.13 are satisfied if 0≤x, y, -0.1≤x<0 and 0≤y≤ 0.1 are satisfied if 0>x and 0≤y, -0.1≤x,y and -0.13≤x+y<0 are satisfied if 0≥x and 0>y, and 0<x≤0.1 and -0.1≤y<0 are satisfied if 0<x and 0>y].

Description

[Technical Field]

[0001] The present disclosure relates to ceramics. [Background technology]

[0002] In recent years, new solid-state cooling elements and systems that utilize the electrocaloric effect have attracted attention as cooling elements, and research and development into them is being actively conducted. Compared to existing cooling systems that use refrigerants that are greenhouse gases, these have the advantages of high efficiency and low power consumption because they do not require refrigerants, and they are also quiet because they do not use compressors. In order to obtain an excellent electrocaloric effect, a material is required that has a transition temperature in the desired temperature range and that can be subjected to a large electric field. Such a material is PbSc 0.5 Ta 0.5 O3 (hereinafter, ceramics containing Pb, Sc, and Ta are also referred to as "PST") (Patent Document 1, Non-Patent Documents 1-2), and PbMg 0.5 W 0.5 O3 (hereinafter, ceramics containing Pb, Mg, and W are also referred to as "PMW") is known as a promising material. 0.5 W 0.5 It has been reported that O3 exhibits large positive and negative electrocaloric effects. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2021 / 131142 [Non-patent literature]

[0004] [Non-Patent Document 1] Nature volume 575, pages468-472(2019) [Non-patent document 2] Ferroelectrics, 184, 239 (1996) [Non-patent document 3] Adv. Funct. Mater. 31, 2101176 (2021).

Summary of the Invention

Problems to be Solved by the Invention

[0005] PMW is an antiferroelectric material and has the characteristic of transforming into a ferroelectric material by applying a voltage above the threshold voltage. Below this threshold voltage, the electrocaloric effect of PMW is very small, and when the threshold voltage is exceeded, the electrocaloric effect is shown according to the magnitude of the applied voltage. That is, when using PMW as a solid cooling element, it is necessary to apply a large voltage exceeding the threshold voltage of PMW, and the electric field strength required to show the electrocaloric effect also increases.

[0006] The object of the present disclosure is to provide a ceramic that exhibits a large electrocaloric effect at a lower electric field than before. More specifically, it is an object to provide a ceramic that exhibits a large electrocaloric effect at a lower electric field than conventional PMW.

Means for Solving the Problems

[0007] The present disclosure relates to a ceramic represented by the formula (1): (1 - m)PbSc 0.5-x Ta 0.5+x O3 - mPbMg 0.5-y W 0.5+y O3(1) [In formula (1), m satisfies 0.60 ≤ m ≤ 0.95, when 0 ≤ x, y, x, y ≤ 0.1 and 0 ≤ x + y ≤ 0.13 are satisfied, when 0 > x, 0 ≤ y, -0.1 ≤ x < 0 and 0 ≤ y ≤ 0.1 are satisfied, when 0 ≥ x, 0 > y, -0.1 ≤ x, y and -0.13 ≤ x + y < 0 are satisfied, when 0 < x, 0 > y, 0 < x ≤ 0.1 and -0.1 ≤ y < 0 are satisfied.] and relates to the ceramic represented thereby.

[0008] The present disclosure includes the following aspects. [1] Formula (1): (1 - m)PbSc 0.5-x Ta 0.5+x O3 - mPbMg 0.5-y W 0.5+y O3(1) [In formula (1), m satisfies 0.60 ≤ m ≤ 0.95, When 0 ≤ x, y, x, y satisfy 0 ≤ x, y ≤ 0.1 and 0 ≤ x + y ≤ 0.13, When 0 > x, 0 ≤ y, x satisfies -0.1 ≤ x < 0 and y satisfies 0 ≤ y ≤ 0.1, When 0 ≥ x, 0 > y, x, y satisfy -0.1 ≤ x, y and -0.13 ≤ x + y < 0, When 0 < x, 0 > y, x satisfies 0 < x ≤ 0.1 and y satisfies -0.1 ≤ y < 0.] Ceramics represented by this. [2] In the above formula, When 0 ≤ x, y, x + y satisfies 0 ≤ x + y ≤ 0.1, When 0 ≥ x, 0 > y, x + y satisfies -0.1 ≤ x + y < 0, the ceramics according to [1] above. [3] In the above formula, x is 0 and y is 0, the ceramics according to [1] or [2] above. [4] In the above formula, m satisfies 0.6 ≤ m ≤ 0.9, the ceramics according to any one of [1] to [3] above. [5] The ceramics according to any one of [1] to [4] above, wherein the crystal structure of the ceramics has a perovskite structure. [6] An electrocaloric effect element in which a noble metal electrode and the ceramics according to any one of [1] to [5] above are alternately laminated. [7] The electrocaloric effect element according to [6] above, wherein the noble metal electrode is formed of Pt. [8] An electronic component having the electrocaloric effect element according to [6] or [7] above. [9] An electronic device having the electrocaloric effect element according to [6] or [7] above or the electronic component according to [8] above. [Effects of the Invention]

[0009] According to the present disclosure, it is possible to provide ceramics that exhibit a large electrocaloric effect in a low electric field, more specifically, ceramics that exhibit a large electrocaloric effect in a lower electric field than conventional PWM. [Brief explanation of the drawings]

[0010] [Figure 1] Figure 1 shows the electric polarization-electric field strength curve of the PMW at 15°C. [Figure 2] FIG. 2 shows the electric polarization-field strength curves at −18° C. for samples within the scope of the present invention. [Figure 3] FIG. 3 is a schematic cross-sectional view of an electrocaloric effect element according to one embodiment of the present disclosure. [Figure 4] FIG. 4 is a diagram for explaining the measurement sequence of the electrocaloric effect. [Figure 5] FIG. 5 shows the electric polarization-electric field strength curve of the PMW of sample number 1 at 15°C. [Figure 6] FIG. 6 shows the relationship between the electrocaloric effect and the electric field strength at 15° C. for the PMW of sample number 1. [Figure 7] FIG. 7 shows the relationship between the electrocaloric effect and temperature for sample number 1 at a PMW field strength of 20 MV / m. [Figure 8] FIG. 8 shows the relationship between the electrocaloric effect and temperature for the PST of sample number 2 at an electric field strength of 15 MV / m. [Figure 9] FIG. 9 shows the relationship between the electrocaloric effect and temperature for the PST of sample No. 2 and sample No. 6 at an electric field strength of 15 MV / m. [Figure 10] FIG. 10 shows the results of characteristic tests for various compositions of x and y. DETAILED DESCRIPTION OF THE INVENTION

[0011] The ceramics and electrocaloric effect elements using the ceramics of the present disclosure will be described in detail below with reference to the drawings. However, the shapes and arrangements of the electrocaloric effect elements and components of the present embodiments are not limited to the examples shown in the drawings.

[0012] [Ceramics] The ceramics according to an embodiment of the present disclosure contain Pb, Sc, Ta, Mg, and W as main components. The above ceramics are complex oxides containing Pb, Sc, Ta, Mg, and W, The content ratio of Pb is substantially equal to the total content ratio of Sc, Ta, Mg, and W, When the content ratio of Sc is set to "0.5 - x", the content ratio of Ta is "0.5 + x", and when the content ratio of Mg is set to "0.5 - y", the content ratio of W is "0.5 + y", The ranges of x and y are When 0 ≤ x, y, 0 ≤ x, y ≤ 0.1 and 0 ≤ x + y ≤ 0.13 are satisfied, When 0 > x, 0 ≤ y, -0.1 ≤ x < 0 and 0 ≤ y ≤ 0.1 are satisfied, When 0 ≥ x, 0 > y, -0.1 ≤ x, y and -0.13 ≤ x + y < 0 are satisfied, When 0 < x, 0 > y, 0 < x ≤ 0.1 and -0.1 ≤ y < 0 are satisfied, When the total content ratio of Mg and W is set to "m", the total content ratio of Sc and Ta is "1 - m", and the range of m is 0.60 ≤ m ≤ 0.95. Note that all the above ratios are molar ratios. By setting the composition within the above range, a large electrocaloric effect can be obtained at a low electric field.

[0013] Note that the above "the content ratio of Pb is substantially equal to the total content ratio of Sc, Ta, Mg, and W" is not limited to the case where the content ratio of Pb is exactly equal to the total content ratio of Sc, Ta, Mg, and W. That is, "the content ratio of Pb is substantially equal to the total content ratio of Sc, Ta, Mg, and W" includes the case where the difference between the content ratio of Pb and the total content ratio of Sc, Ta, Mg, and W is, for example, within 3% in terms of molar ratio.

[0014] The composition of the ceramics of the present disclosure can be analyzed and measured by performing composition analysis using, for example, high-frequency inductively coupled plasma optical emission spectrometry, fluorescent X-ray analysis, etc.

[0015] The electrocaloric effect is a heat absorption / heat generation phenomenon caused by a change in entropy when the electric dipole moments in a material are aligned or disrupted by a change in electric field. The performance index of the electrocaloric effect in the present invention may be the adiabatic temperature change (ΔT). In other words, "a large electrocaloric effect" may mean a large adiabatic temperature change (ΔT). In the present invention, a larger adiabatic temperature change (ΔT) is preferable.

[0016] The adiabatic temperature change ΔT refers to the temperature change of a ceramic caused by the application of an electric field to the ceramic and / or the removal of the applied electric field. Specifically, it may be the difference between the temperature of the ceramic before the application of an electric field and the temperature of the ceramic immediately after the application of the electric field, or the difference between the temperature of the ceramic before the removal of the electric field and the temperature of the ceramic immediately after the removal of the electric field.

[0017] Generally, the adiabatic temperature change ΔT increases as the electric field strength applied to the ceramic increases. Furthermore, the adiabatic temperature change ΔT tends to increase as the temperature of the ceramic approaches the antiferroelectric transition temperature (or ferroelectric transition temperature) when the electric field is applied. For example, the electrocaloric effect decreases rapidly as the temperature of the ceramic drops below the transition temperature. Specifically, in conventional PMWs with a transition temperature of approximately 20 to 30°C, the electrocaloric effect tends to decrease significantly when the temperature of the ceramic drops below 0°C.

[0018] In another embodiment, the ceramic has the formula (1): (1-m)PbSc 0.5-x Ta 0.5+x O3-mPbMg 0.5-y W 0.5+y O3(1) [In formula (1), m satisfies 0.60≦m≦0.95, If 0≦x, y, then x, y≦0.1 and 0≦x+y≦0.13 are satisfied; If 0>x, 0≦y, -0.1≦x<0 and 0≦y≦0.1 are satisfied, If 0≧x, 0>y, -0.1≦x, y and -0.13≦x+y<0 are satisfied; When 0 < x, 0 > y, it satisfies 0 < x ≤ 0.1 and -0.1 ≤ y < 0. It may be a ceramic represented by. By setting x, y, and m within the above ranges, a large electrocaloric effect at a low electric field (for example, 0.8 K or more when an electric field strength of 8 MV / m is applied) can be obtained.

[0019] Although the present disclosure is not bound by any theory, the mechanism by which the above effects are obtained is considered as follows.

[0020] Substances showing a large electrocaloric effect include PMW showing antiferroelectricity and PbSc showing ferroelectricity 0.5 Ta 0.5 O3 (hereinafter, the ceramic containing Pb, Sc, and Ta is also referred to as "PST"). PMW and PST each show antiferroelectricity and ferroelectricity with a large latent heat during transition due to the alignment of cations at the B site (Mg and W in PMW, Sc and Ta in PST).

[0021] In the case of PMW, it shows a negative electrocaloric effect (heat absorption during electric field application, heat generation during removal) due to its antiferroelectricity below the phase transition temperature, and a large positive electrocaloric effect (heat generation during electric field application, heat absorption during removal) near the transition temperature. That is, the positive and negative of the electrocaloric effect are reversed by temperature. As the electrocaloric effect used in practical applications, either the positive electrocaloric effect or the negative electrocaloric effect may be used. In the case of PMW, a large electric field strength of 10 MV / m or more is required to obtain a large negative electrocaloric effect, and below 10 MV / m, only a very small electrocaloric effect is shown.

[0022] It is generally known that the greater the difference in ionic radius between the two B-site cations, the easier they are to align. PMW has a larger difference in ionic radius between Mg and W than PST, making it easier for the B-site to align. Unlike PST, PMW has the advantage of aligning the B-site ions without requiring prolonged heat treatment. In this study, we successfully lowered the threshold voltage of the antiferroelectric by adding PST to PMW. This is believed to be due to a moderate decrease in the alignment of the PMW B-site.

[0023] The threshold voltage refers to the voltage (approximately 18 MV / m) at which electric polarization increases suddenly, as shown in Figure 1. Below the threshold voltage, the electric polarizations are aligned so that they cancel each other out, but above the threshold voltage, the electric polarizations begin to align in the direction of the electric field. At stronger electric fields, the polarizations all align in one direction, similar to a typical ferroelectric. In other words, by applying a voltage above the threshold voltage, antiferroelectrics are induced to a state with electric polarization similar to that of a ferroelectric. Below the threshold voltage, antiferroelectrics do not exhibit an electrocaloric effect because the electric polarizations are aligned so that they cancel each other out (state A in Figure 1). However, above the threshold voltage, the electric polarizations align (state B in Figure 1), and they exhibit a positive or negative electrocaloric effect depending on the magnitude of the voltage.

[0024] As shown in Figure 2, the ceramics of the present disclosure have a lower threshold voltage. This allows the ceramics of the present disclosure to exhibit an electrocaloric effect even in a low electric field. Note that, once an electric field is applied to a ferroelectric, a partial polarization remains (called remanent polarization), which reduces the entropy change when the electric field is applied and removed, resulting in a loss in the electrocaloric effect. On the other hand, in an antiferroelectric, the electric polarization returns to zero completely when the electric field is removed, so no loss in the electrocaloric effect occurs.

[0025] Furthermore, in this invention, by adding PST to the PMW, not only is the threshold voltage of the antiferroelectric material lowered, but the transition temperature of the PMW is also successfully lowered below room temperature. In other words, compared to conventional PMW, the ceramics disclosed in this disclosure can achieve an excellent electrocaloric effect even at temperatures below 0°C (e.g., -15°C).

[0026] In addition, in the present invention, it is further possible to prevent the positive / negative inversion of the electrothermal quantity effect from occurring at a relatively low electric field strength of 8 MV / m or more within the actual use temperature range (for example, -20 to 0 °C). Therefore, compared with the conventional PMW, the ceramics of the present disclosure have improved controllability of the electrothermal quantity effect, and no complicated control is required when the ceramics of the present disclosure are used as a cooling system.

[0027] In one aspect, the ranges of x and y are when 0 ≤ x, y, x, y ≤ 0.1 and 0 ≤ x + y ≤ 0.12 are satisfied, when 0 > x, 0 ≤ y, -0.1 ≤ x < 0 and 0 ≤ y ≤ 0.1 are satisfied, when 0 ≥ x, 0 > y, -0.1 ≤ x, y and -0.12 ≤ x + y < 0 are satisfied, when 0 < x, 0 > y, 0 < x ≤ 0.1 and -0.1 ≤ y < 0 are satisfied.

[0028] In one aspect, the ranges of x and y are when 0 ≤ x, y, x, y ≤ 0.1 and 0 ≤ x + y ≤ 0.11 are satisfied, when 0 > x, 0 ≤ y, -0.1 ≤ x < 0 and 0 ≤ y ≤ 0.1 are satisfied, when 0 ≥ x, 0 > y, -0.1 ≤ x, y and -0.11 ≤ x + y < 0 are satisfied, when 0 < x, 0 > y, 0 < x ≤ 0.1 and -0.1 ≤ y < 0 are satisfied.

[0029] In one aspect, the ranges of x and y are when 0 ≤ x, y, 0 ≤ x + y ≤ 0.1 is satisfied, when 0 > x, 0 ≤ y, -0.1 ≤ x < 0 and 0 ≤ y ≤ 0.1 are satisfied, when 0 ≥ x, 0 > y, -0.1 ≤ x + y < 0 is satisfied, when 0 < x, 0 > y, 0 < x ≤ 0.1 and -0.1 ≤ y < 0 are satisfied.

[0030] In one aspect, the ranges of x and y are when 0 ≤ x, y, 0 ≤ x + y ≤ 0.08 is satisfied, When 0 > x and 0 ≤ y, it satisfies -0.08 ≤ x < 0 and 0 ≤ y ≤ 0.08. When 0 ≤ x and 0 > y, it satisfies -0.08 ≤ x + y < 0. When 0 < x and 0 > y, it satisfies 0 < x ≤ 0.08 and -0.08 ≤ y < 0.

[0031] In one aspect, the ranges of x and y are When 0 ≤ x and 0 ≤ y, it satisfies 0 ≤ x ≤ 0.05 and 0 ≤ y ≤ 0.05. When 0 > x and 0 ≤ y, it satisfies -0.05 ≤ x < 0 and 0 ≤ y ≤ 0.05. When 0 ≤ x and 0 > y, it satisfies -0.05 ≤ x < 0 and -0.05 ≤ y < 0. When 0 < x and 0 > y, it satisfies 0 < x ≤ 0.05 and -0.05 ≤ y < 0.

[0032] In another aspect, the ranges of x and y are When 0 ≤ x and 0 ≤ y, it satisfies 0 ≤ x + y ≤ 0.05. When 0 > x and 0 ≤ y, it satisfies -0.05 ≤ x < 0 and 0 ≤ y ≤ 0.05. When 0 ≤ x and 0 > y, it satisfies -0.05 ≤ x + y < 0. When 0 < x and 0 > y, it satisfies 0 < x ≤ 0.05 and -0.05 ≤ y < 0.

[0033] In one aspect, the ranges of x and y may be a range determined by arbitrarily combining the ranges of x and y in the "when 0 ≤ x and 0 ≤ y", "when 0 > x and 0 ≤ y", "when 0 ≤ x and 0 > y", and "when 0 < x and 0 > y" listed above.

[0034] In a preferred aspect, x and y above are 0. That is, (1 - m)PbSc 0.5-x Ta 0.5+x O3 - mPbMg 0.5-y W 0.5+z O3 represented by the formula becomes (1 - m)PbSc 0.5 Ta 0.5 O3 - mPbMg 0.5 W 0.5 O3.

[0035] In one embodiment, m is 0.60 <m≦0.95であってよい。

[0036] From the viewpoint of improving the electrocaloric effect in a low electric field, the range of m is preferably 0.60≦m≦0.90, more preferably 0.70≦m≦0.90, and even more preferably 0.70≦m≦0.80.

[0037] From the viewpoint of improving the electrocaloric effect at low temperatures, the range of m is preferably 0.60≦m≦0.90, more preferably 0.65≦m≦0.90, and even more preferably 0.65≦m≦0.85.

[0038] From the viewpoint of obtaining a negative electrocaloric effect, the range of m may be 0.90≦m≦0.95.

[0039] From the viewpoint of obtaining a positive electrocaloric effect, the range of m may be 0.60≦m≦0.80.

[0040] The crystal structure of the ceramic according to one embodiment of the present invention may be a perovskite structure. Ceramics having a perovskite structure include not only ceramics having a "perovskite-type crystal structure" but also ceramics having a "perovskite-like crystal structure." For example, ceramics having a perovskite structure may have a crystal structure that can be recognized as a perovskite crystal structure by those skilled in the art of ceramics in X-ray diffraction.

[0041] [Electrocaloric effect element] The electrocaloric effect element of the present disclosure has a laminate in which electrode layers and ceramic layers containing the ceramic of the present disclosure as a main component are alternately stacked.

[0042] As shown in FIG. 3 , an electrocaloric effect element 1 according to one embodiment of the present disclosure includes a laminate 6 in which electrode layers 2a and 2b (hereinafter collectively referred to as “electrode layers 2”) and ceramic layers 4 are alternately stacked, and external electrodes 8a and 8b (hereinafter collectively referred to as “external electrodes 8”) connected to the electrode layer 2. The electrode layers 2a and 2b are electrically connected to external electrodes 8a and 8b, respectively, which are disposed on end faces of the laminate 6. When a voltage is applied to the external electrodes 8a and 8b, an electric field is formed between the electrode layers 2a and 2b. This electric field causes the ceramic layer 4 to generate heat due to the electrocaloric effect. When the voltage is removed, the electric field disappears, and as a result, the ceramic layer 4 absorbs heat due to the electrocaloric effect.

[0043] The electrode layer 2 is a so-called internal electrode. The electrode layer 2 has a function of applying an electric field to the ceramic layer 4, and can also have a function of transporting heat between the ceramic layer 4 and the outside.

[0044] The electrode layer may be an electrode layer whose main component is a precious metal. Here, the term "main component" in the electrode layer means that the electrode layer is composed of 80% by mass or more of the precious metal, and for example, means that the electrode layer is composed of 95% by mass or more, more preferably 98% by mass or more, even more preferably 99% by mass or more, still more preferably 99.5% by mass or more, and particularly preferably 99.9% by mass or more of the precious metal.

[0045] In this specification, the term "noble metal" may be, for example, Au, Ag, Pt, or Pd. From the viewpoint of improving the electrocaloric effect at low temperatures, the main component of the electrode layer used in the present disclosure may be Pt or Pd. That is, it may be a Pt or Pd electrode layer. However, from the viewpoint of improving chemical durability and / or cost, the noble metal electrode layer may be an alloy (e.g., Ag-Pd alloy) or mixture of Pt and / or Pd with other elements (e.g., Ag, Pd, Rh, Au, etc.). The same effect can be obtained even if the Pt or Pd electrode layer is composed of these alloys or mixtures. Furthermore, it may contain other elements that may be mixed in as impurities, particularly unavoidable elements (e.g., Fe, Al2O3, etc.). In this case, the same effect can be obtained.

[0046] The thickness of the electrode layer 2 is 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. By making the thickness of the electrode layer 0.5 μm or more, the resistance of the electrode layer can be reduced and the heat transport efficiency can be increased. Furthermore, by making the thickness of the electrode layer 10 μm or less, the thickness (and therefore the volume) of the ceramic layer can be increased, and the amount of heat that can be handled by the electrocaloric effect of the entire element can be increased. Furthermore, the element can be made smaller.

[0047] The ceramic layer 4 may contain one type of ceramic as the main component, or two or more types of ceramic as the main components.

[0048] Here, the term "main component" in the ceramic layer means that the ceramic layer is substantially composed of the target ceramic, and for example, means that 90% by mass or more of the ceramic layer is the target ceramic, more preferably 95% by mass or more, even more preferably 98% by mass or more, still more preferably 99% by mass or more, and particularly preferably 99.5% by mass or more. Other components may include a crystalline phase having a pyrochlore structure, which is different from the perovskite structure, other elements mixed in as impurities, and particularly unavoidable elements (e.g., Zr, C, etc.).

[0049] The composition of the ceramic layer 4 can be determined by high-frequency inductively coupled plasma emission spectroscopy, fluorescent X-ray analysis, etc. The structure of the ceramic layer 4 can be determined by powder X-ray diffraction.

[0050] The thickness of the ceramic layer 4 is preferably 5 μm to 100 μm, more preferably 5 μm to 50 μm, even more preferably 10 μm to 50 μm, even more preferably 20 μm to 50 μm, and particularly preferably 20 μm to 40 μm. By increasing the thickness of the ceramic layer, the heat capacity of the element can be increased. By decreasing the thickness of the ceramic layer, a higher ΔT can be obtained and the withstand voltage can also be improved.

[0051] The withstand voltage of the ceramic layer 4 may be preferably 15 MV / m or more, more preferably 20 MV / m or more, and even more preferably 25 MV / m or more. By increasing the withstand voltage of the ceramic layer, a larger voltage (electric field) can be applied, and a larger ΔT can be obtained.

[0052] The material for the pair of external electrodes 8a, 8b is not particularly limited, but examples thereof include Ag, Cu, Pt, Ni, Al, Pd, Au, and alloys thereof (e.g., Ag-Pd, etc.), and the electrodes may be made of these metals and glass, or may be made of metal and resin. Of these metals, Ag is preferred.

[0053] The electrocaloric effect element 1 has electrode layers 2 and ceramic layers 4 stacked alternately, but the number of stacked electrode layers and ceramic layers is not particularly limited in the electrocaloric effect element of the present disclosure. Furthermore, all of the internal electrodes do not need to be connected to external electrodes, and internal electrodes that are not connected to external electrodes may be included as necessary for heat transport or stress relief due to piezoelectricity or electrostriction.

[0054] In the electrocaloric effect element 1, the internal electrodes and the ceramic layer are in contact with each other over substantially the entire surface. However, the electrocaloric effect element of the present disclosure is not limited to this structure and is not particularly limited as long as it has a structure that allows a voltage (electric field) to be applied to the ceramic layer. Furthermore, while 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 and may be, for example, cylindrical or sheet-like, and may further have irregularities or through holes. Furthermore, the internal electrodes may be exposed on the surface for heat transport and heat exchange with the outside.

[0055] The ceramic and electrocaloric effect element of the present embodiment described above are manufactured, for example, as follows. High-purity lead oxide (Pb3O4), tantalum oxide (Ta2O5), scandium oxide (Sc2O3), magnesium carbonate (MgCO3), and tungsten oxide (WO3) are weighed as raw materials to achieve the desired composition ratio after firing. The raw materials are pulverized and mixed with partially stabilized zirconia (PSZ) balls, pure water, a dispersant, and other ingredients in a ball mill. The pulverized and mixed slurry is then dried and sized, and calcined, for example, at 800-900°C in air. The resulting calcined powder is mixed with PSZ balls, ethanol, toluene, a dispersant, and other ingredients and pulverized. A dissolved binder solution is then added to the pulverized powder and mixed to produce a slurry for sheet molding. The resulting slurry is molded into a sheet on a support, and a Pt electrode paste is printed on it. Printed and unprinted sheets are stacked to form the desired structure, then compressed at a pressure of 100 MPa to 200 MPa and cut to produce a green chip. The green chip is then heat-treated in air at 500°C to 600°C to remove the binder. The debindered chip is then fired at 800°C to 1400°C in a sealed alumina sheath, along with PbZrO powder to create a Pb atmosphere. The chip end faces are then polished with sandpaper, external electrode paste is applied, and the chip is baked at a specified temperature to produce an electrocaloric effect element as shown in Figure 3.

[0056] The electrocaloric effect element of the present disclosure exhibits an excellent electrocaloric effect and can therefore be used as a thermal management element, particularly a cooling element (including cooling / heat pump elements for air conditioners and other air conditioning devices, refrigerators, and freezers).

[0057] The present disclosure also provides an electronic component comprising the electrocaloric effect element of the present disclosure, as well as an electronic device comprising the electrocaloric effect element or electronic component of the present disclosure.

[0058] Examples of electronic components include, but are not limited to, electronic components used in air conditioners, refrigerators, or freezers; or electronic components (e.g., batteries) used in air conditioners for electric vehicles and hybrid cars; central processing units (CPUs), hard disks (HDDs), power management ICs (PMICs), power amplifiers (PAs), transceiver ICs, voltage regulators (VRs), and other integrated circuits (ICs); light-emitting diodes (LEDs), incandescent bulbs, semiconductor lasers, and other light-emitting elements; and field-effect transistors (FETs), which can serve as heat sources; and other components commonly used in electronic devices, such as lithium-ion batteries, circuit boards, heat sinks, and housings.

[0059] Examples of electronic devices include, but are not limited to, air conditioners, refrigerators or freezers; air conditioners used as heat pumps, air conditioners for electric vehicles or hybrid cars, mobile phones, smartphones, personal computers (PCs), tablet devices, hard disk drives, data servers, and other small electronic devices.

[0060] The electrocaloric element of the present disclosure can be used as a thermal management system (or temperature management system) that manages the heat (temperature) of the electronic components and electronic devices. Examples of the thermal management system include a cooling system that cools the electronic components and electronic devices. [Example]

[0061] <Fabrication of electrocaloric effect element> High-purity lead oxide (Pb3O4), tantalum oxide (Ta2O5), scandium oxide (Sc2O3), magnesium carbonate (MgCO3), and tungsten oxide (WO3) were prepared as raw materials. These raw materials were weighed to achieve the desired composition ratios shown in Tables 1-4 after firing. They were then milled and mixed in a ball mill with 2 mm diameter partially stabilized zirconia (PSZ) balls, pure water, and a dispersant for 16 hours. The milled and mixed slurry was then dried on a hot plate, sized, and calcined in air at 850°C for 2 hours.

[0062] The calcined powder was mixed with 5 mm diameter PSZ balls, ethanol, toluene, and a dispersant for 16 hours and pulverized. The dissolved binder solution was then added to the pulverized powder and mixed for 4 hours to produce a slurry for sheet molding. The prepared slurry was formed into a sheet on a PET film using a doctor blade method to a thickness corresponding to the desired ceramic layer thickness, cut into strips, and then screen-printed with a platinum internal electrode paste. The sheet thickness of the multilayer element to be produced was controlled by changing the gap of the doctor blade used during sheet molding.

[0063] A predetermined number of sheets printed with platinum internal electrode paste and unprinted sheets were stacked, then compressed at a pressure of 150 MPa and cut to produce green chips. The green chips were debindered by heat treatment in air at 550°C for 24 hours. The green chips were then sealed in a sealed alumina sheath together with PbZrO powder for creating a Pb atmosphere and fired at 900-1300°C for 4 hours. Samples within the scope of the present invention could be sufficiently fired at temperatures between 900 and 1250°C. Sample No. 1 shown in Table 1, a comparative example, was fired at a high temperature of 1400°C and then heat treated at 1000°C for 1000 hours.

[0064] Thereafter, the end faces of the chip were polished with sandpaper, Ag external electrode paste was applied, and baking was performed at a temperature of 750°C to obtain the electrocaloric effect element shown in Figure 3.

[0065] The dimensions of the obtained element were approximately L 10.2 mm × W 7.2 mm × T 0.88 mm for an element with a ceramic layer thickness of 40 μm. There were 19 ceramic layers sandwiched between the internal electrode layers, and the electrode area was 49 mm 2 / layer, total electrode area is 49mm 2 The thickness of the ceramic layer of the element obtained above was confirmed using a scanning electron microscope after polishing the cross section of the element.

[0066] <Evaluation> (composition) The ceramic composition of the obtained element was confirmed by high frequency inductively coupled plasma emission spectroscopy and X-ray fluorescence analysis.

[0067] (crystal structure) Powder X-ray diffraction measurements were performed to evaluate the crystalline structure of the obtained elements. One element was randomly selected from each lot, crushed in a mortar, and an X-ray diffraction profile was obtained. From the obtained X-ray diffraction profile, it was confirmed whether the crystalline structure of the ceramic was perovskite, and the presence and abundance ratio of impurity phases (mainly pyrochlore phase) were estimated from the intensity ratio. When the abundance ratio of the perovskite structure was 0.95 or higher, it was determined that the main component had a perovskite structure, and when it was less than 0.95, it was determined that a different phase was present.

[0068] (electrocaloric effect) A 50 μm diameter ultra-fine K thermocouple was attached to the center of the element surface with Kapton tape to constantly monitor the temperature, and wires for applying voltage were attached to both ends of the external electrodes with Ag paste, and voltage was applied using a high-voltage generator.

[0069] The electrocaloric effect was evaluated by applying a voltage to the sample in the sequence shown in Figure 4(a). Specifically, first, a voltage was applied to the sample, the voltage was maintained, and then the applied voltage was removed and maintained. This cycle was repeated to measure the change in the electrocaloric effect. When a voltage was applied to a ferroelectric material in this sequence, the sample temperature rose immediately upon application of the voltage. During the voltage application process, the sample temperature gradually decreased to the same temperature as before the voltage was applied due to the gradual diffusion of heat during the voltage application process. During the voltage removal process, the sample temperature also decreased immediately upon removal. During the voltage removal process, the sample temperature gradually increased to the original temperature (see Figure 4(b)). This is due to the alignment and disordering of the ferroelectric domains upon application and removal of the voltage. This change in entropy results in the heat absorption and heat absorption effect (electrocaloric effect).

[0070] On the other hand, when a voltage is applied to an antiferroelectric in the sequence shown in the graph of Figure 4(a), in a specific temperature range, as shown in Figure 4(c), it exhibits an electrocaloric effect opposite to that of a ferroelectric, that is, a negative caloric effect in which the temperature decreases (endothermic) when a voltage is applied and increases (heat generation) when the voltage is removed.

[0071] In this example, the adiabatic temperature change ΔT was measured by applying a predetermined voltage, maintaining the application for 50 seconds, and then removing the voltage and maintaining the application for 50 seconds. This sequence was repeated three times. The temperature of the element was constantly measured during the voltage application and voltage removal sequence, and the adiabatic temperature change ΔT was calculated from the temperature change. Furthermore, when electric fields of 8 MV / m and 15 MV / m were applied at -15°C, absolute values of the adiabatic temperature change ΔT of 0.8 K or greater and 1.5 K or greater, respectively, were judged as "Go." The results are shown in Tables 1 to 4.

[0072] The evaluation results are shown below. In the table, samples marked with "*" are comparative examples, and the other samples are examples.

[0073] [Table 1]

[0074] [Table 2]

[0075] [Table 3]

[0076] [Table 4]

[0077] The ferroelectric properties of the conventional PMW shown in sample number 1 are shown in Figure 5, and the electrocaloric effect is shown in Figures 6 and 7. As shown in Figure 5, the conventional PMW exhibits double hysteresis, which is characteristic of antiferroelectrics, in that as the electric field strength increases, the electric polarization increases rapidly from a threshold voltage (approximately 15 MV / m) and then saturates at even higher electric field strengths. The threshold voltage is approximately 15 MV / m at 15°C, but as the temperature decreases, the threshold voltage increases and a larger electric field is required.

[0078] Figure 6 shows the adiabatic temperature change ΔT measured at 15°C while varying the electric field strength. Figure 7 shows the adiabatic temperature change ΔT measured at a fixed electric field strength of 20 MV / m while varying the temperature. As shown in Figure 6, a negative caloric effect was observed at 15°C, where heat was absorbed when the electric field was applied and generated when the electric field was removed. However, when we focus on the relationship between the adiabatic temperature change ΔT and the electric field strength, we confirm that there is almost no electrocaloric effect at low electric fields, and that the adiabatic temperature change ΔT gradually increases near the threshold voltage. In other words, although a negative caloric effect can be obtained with PMW, a large electric field of 12 MV / m or more is required to obtain a sufficient electrocaloric effect. Therefore, not only is a high electric field strength required for PMW, but it is also difficult to control the caloric effect by varying the electric field strength.

[0079] As shown in Figure 7, focusing on the temperature dependence of the adiabatic temperature change ΔT, it was confirmed that the calorific effect obtained even with an electric field strength of 20 MV / m is very small at temperatures below 0°C. Because the transition temperature of PMW is near 20°C, the sign of the adiabatic temperature change ΔT changes at 20°C, which is close to the transition temperature, and above 20°C, a positive calorific effect is obtained, with heat generated when voltage is applied and heat absorbed when voltage is removed. As such, with antiferroelectrics, the sign of the calorific effect reverses in the temperature range across the transition temperature, making it extremely difficult to control. Therefore, simply lowering the transition temperature of an antiferroelectric can lead to the problem of the sign of the calorific effect reversing in the expected temperature range.

[0080] Figure 8 shows the electrocaloric effect of PST shown in the conventionally known sample number 2. Unlike PMW, PST obtained a positive electrocaloric effect in all temperature ranges. The adiabatic temperature change ΔT was maximized near the transition temperature of 20 °C, and an excellent electrocaloric effect was obtained. However, below 0 °C, the effect decreased rapidly, and a sufficient effect could not be obtained at low temperatures.

[0081] Table 1 shows the characteristic test results of the samples prepared above. Specifically, Table 1 shows the electrocaloric effect of samples in which the values of x and y in formula (1) were fixed at 0 and m was changed to various values. The samples having the compositions shown in Table 1 all had a desired perovskite structure as the main component and few heterogeneous phases as a result of XRD measurement.

[0082] For PMW shown in the conventionally known sample number 1 and PST shown in sample number 2, the electrocaloric effect at -15 °C was low and the adiabatic temperature change was less than 1.5 K. On the other hand, in the samples of the composition within the scope of the present invention, the absolute values of the adiabatic temperature change were 0.8 K and 1.5 K or more, respectively, when an electric field of 8 MV / m and 15 MV / m was applied. In addition, in the samples within the range of 0.6 ≦ m ≦ 0.8, a positive electrocaloric effect was shown in the range of -20 °C to 0 °C when an electric field strength of 15 MV / m was applied, and there was no sign inversion in that temperature range. In the samples within the range of 0.8 < m ≦ 0.95, a negative electrocaloric effect was shown in that temperature range and electric field strength, but there was no sign inversion.

[0083] Figure 9 shows the temperature dependence of the adiabatic temperature change when an electric field of 15 MV / m is applied to sample number 2 and sample number 6. (As shown in Figure 7, since the sample of sample number 1 had a small electrocaloric effect in the temperature range below 0 °C as a result of measuring the adiabatic temperature change at a larger electric field strength (20 MV / m), the comparison here was omitted.)

[0084] As shown in Figure 9, in the sample of sample number 6 within the scope of the present invention, an excellent adiabatic temperature change was obtained in a wide temperature range from 0 °C to -50 °C and below room temperature. Therefore, it can be seen that the ceramics of the present disclosure are suitable for applications that require driving at low temperatures, such as refrigerators and freezers.

[0085] When the value of m is smaller than 0.6, the ferroelectric transition temperature cannot be sufficiently lowered, and when m is larger than 0.95, the transition temperature cannot be sufficiently lowered and the antiferroelectric threshold voltage cannot be lowered either, which is thought to result in a small adiabatic temperature change at low temperatures and low electric fields.

[0086] Tables 2, 3, and 4 show the results of measuring the electrocaloric effect of the ceramics represented by formula (1) when m=0.6, m=0.8, and m=0.95, respectively. In samples where m was within the range of the present invention, both x and y were most stable when they were near 0, and the proportion of material with the desired crystal structure was close to 100%. Even when x and y were not near 0, no heterogeneous phases were formed, but when x and y deviated significantly from 0, the proportion of heterogeneous phases increased, or the insulating properties deteriorated, resulting in device breakdown when an electric field was applied (see the crystal structure columns in Tables 2 to 4). However, when the composition was within the range of the present invention, the main components had the desired structure, and the absolute values of the adiabatic temperature changes were 0.8 K and 1.5 K or more, respectively, when electric fields of 8 MV / m and 15 MV / m were applied at -15°C.

[0087] Figure 10 shows the composition ranges of x and y in Table 2 that resulted in a Go rating in the characteristic test. As shown in Figure 10, it was confirmed that ceramics within the range of the present invention were rated as Go in the characteristic test. Tables 3 and 4 also show results similar to those in Figure 10. [Industrial Applicability]

[0088] The electrocaloric effect element of the present disclosure can exhibit a high electrocaloric effect, and therefore can be used, for example, as a thermal management element in electric vehicles or hybrid cars, air conditioners (e.g., air conditioners used in electric vehicles or hybrid cars, air conditioners used as heat pumps, etc.), refrigerators or freezers, etc., and can also be used as a cooling device for various electronic devices, for example, small electronic devices such as mobile phones, smartphones, tablet terminals, hard disk drives, or data servers, where heat countermeasure issues are becoming more prominent, or personal computers (PCs). [Explanation of symbols]

[0089] 1...Electrocaloric effect element 2a, 2b...electrode layer 4...Ceramic layer 6...Laminate 8a, 8b…External electrode

Claims

1. Formula (1): (1-m)PbSc ０．５－ｘ Ta ０．５＋ｘ O ３ -mPbMg ０．５－ｙ W ０．５＋ｙ O ３ (1) [In formula (1), m satisfies 0.60≦m≦0.95, In the case where 0≦x, y, x, y≦0.1 and 0≦x+y≦0.13 are satisfied; When 0>x and 0≦y, −0.1≦x<0 and 0≦y≦0.1 are satisfied; When 0≧x, 0>y, −0.1≦x, y and −0.13≦x+y<0 are satisfied; In the case of 0<x, 0>y, 0<x≦0.1 and −0.1≦y<0 are satisfied.] Ceramics represented by.

2. In the above formula, When 0≦x, y, 0≦x+y≦0.1 is satisfied; The ceramic according to claim 1, wherein, when 0≧x, 0>y, −0.1≦x + y<0 is satisfied.

3. 3. The ceramic according to claim 1, wherein in the formula, x is 0 and y is 0.

4. The ceramic according to claim 1, wherein, in the formula, m satisfies 0.6≦m≦0.

9.

5. The ceramic according to claim 1 , wherein the crystalline structure of the ceramic has a perovskite structure.

6. 10. An electrocaloric effect element in which noble metal electrodes and the ceramic material according to claim 1 are alternately stacked.

7. 7. The electrocaloric effect element according to claim 6, wherein the noble metal electrode is made of Pt.

8. An electronic component comprising the electrocaloric effect element according to claim 6 or 7.

9. 8. An electronic device comprising the electrocaloric effect element according to claim 6 or 7.

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