ceramics

Abstract

The present disclosure provides a ceramic represented by formula 1. [Formula 1]: (1 - m)PbSc0.5 - xTa0.5 + xO3 - mPbMg0.5 - yW0.5 + yO3 [where: m satisfies 0.03 ≤ m ≤ 0.60; if 0 ≤ x, y, then x, y ≤ 0.1 and 0 ≤ x + y ≤ 0.13 are satisfied; if 0 > x and 0 ≤ y, then -0.1 ≤ x < 0 and 0 ≤ y ≤ 0.1 are satisfied; if 0 ≥ x and 0 > y, then -0.1 ≤ x, y and -0.13 ≤ x + y < 0 are satisfied; and if 0 < x and 0 > y, then 0 < x ≤ 0.1 and -0.1 ≤ y < 0 are satisfied].

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 a good electrocaloric effect, a ferroelectric material must exhibit a first-order phase transition in the desired temperature range and be able to be subjected to a large electric field. PbSc 0.5 Ta 0.5 O3 (hereinafter, ceramics containing Pb, Sc, and Ta are also referred to as "PST") is known as the most promising material. For example, Non-Patent Documents 1 to 3 describe PbSc 0.5 Ta 0.5 It has been reported that O3 exhibits a large electrocaloric effect. [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] J. Am. Ceram. Soc, 78

[71] 1947-52 (1995) Summary of the Invention [Problem to be solved by the invention]

[0005] Solid-state cooling elements are required to exhibit a large electrocaloric effect at temperatures appropriate for their intended use. For example, when used in a refrigerator, a solid-state cooling element may be required to exhibit a large electrocaloric effect at temperatures below 4°C.

[0006] However, although conventional PSTs exhibit a large electrocaloric effect at temperatures above 20°C, the electrocaloric effect drops significantly at low temperatures, making them unsuitable for use as solid-state cooling elements at low temperatures.

[0007] Improving the voltage resistance of PST allows for the application of higher voltages, improving the electrocaloric effect. Furthermore, the higher the degree of ordering of the Sc and Ta cations at the B site of PST, the better the ferroelectric properties and the better the electrocaloric effect. PST with partial substitution of Na for some of the Pb improves the voltage resistance, allowing for the application of higher voltages. It also makes it possible to control the ferroelectric transition temperature below 20°C. Furthermore, the degree of ordering at the B site can be easily increased, improving the electrocaloric effect at low temperatures. However, the effect is limited, and further improvement is desired.

[0008] An object of the present disclosure is to provide ceramics that exhibit a greater electrocaloric effect at lower temperatures than previously possible. [Means for solving the problem]

[0009] The present disclosure provides a compound of formula (1): (1-m)PbSc 0.5-x Ta 0.5+x O3-mPbMg 0.5-y W 0.5+y O3(1) [Formula (1): medium, m satisfies 0.03≦m≦0.60, 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, When 0≧x and 0>y, it satisfies -0.1≦x,y and -0.13≦x + y < 0, When 0<x and 0>y, it satisfies 0<x≦0.1 and -0.1≦y < 0.] Relates to the ceramics represented by

[0010] This 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 0.03≦m≦0.60, When 0≦x,y, it satisfies x,y≦0.1 and 0≦x + y≦0.13, When 0>x and 0≦y, it satisfies -0.1≦x < 0 and 0≦y≦0.1, When 0≧x and 0>y, it satisfies -0.1≦x,y and -0.13≦x + y < 0, When 0<x and 0>y, it satisfies 0<x≦0.1 and -0.1≦y < 0.] The ceramics represented by [2] In the above formula, When 0≦x,y, it satisfies 0≦x + y≦0.1, When 0≧x and 0>y, it 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 0.05≦m≦0.5, 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 comprising the electrocaloric effect element according to [6] or [7] above. [9] An electronic device comprising the electrocaloric effect element according to [6] or [7] above or the electronic component according to [8] above. [Effects of the Invention]

[0011] According to the present disclosure, it is possible to provide ceramics that exhibit a large electrocaloric effect at low temperatures, more specifically, ceramics that exhibit a large electrocaloric effect even at temperatures below 0°C. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic cross-sectional view of an electrocaloric effect element according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a diagram for explaining the measurement sequence of the electrocaloric effect. [Figure 3] FIG. 3 is a diagram showing the measurement results of the electrocaloric effect of samples Nos. 1 and 6 in the example. [Figure 4] FIG. 4 shows the results of property tests for various compositions of x and y. DETAILED DESCRIPTION OF THE INVENTION

[0013] 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.

[0014] [Ceramics] A ceramic according to an embodiment of the present disclosure is mainly composed of Pb, Sc, Ta, Mg, and W. The ceramic is a composite oxide 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 "0.5 - x", the content ratio of Ta is "0.5 + x", and when the content ratio of Mg is "0.5 - y", the content ratio of W is "0.5 + y". The ranges of x and y are When 0 ≤ x, y, it satisfies 0 ≤ x, y ≤ 0.1 and 0 ≤ x + y ≤ 0.13. When 0 > x, 0 ≤ y, it satisfies -0.1 ≤ x < 0 and 0 ≤ y ≤ 0.1. When 0 ≥ x, 0 > y, it satisfies -0.1 ≤ x, y and -0.13 ≤ x + y < 0. When 0 < x, 0 > y, it satisfies 0 < x ≤ 0.1 and -0.1 ≤ y < 0. When the total content ratio of Mg and W is "m", the total content ratio of Sc and Ta is "1 - m", and the range of m is 0.03 ≤ m ≤ 0.60. Note that all the above ratios are molar ratios. By setting the composition within the above range, a large electrocaloric effect at low temperatures can be obtained.

[0015] The statement that "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 cases 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.

[0016] 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, X-ray fluorescence spectrometry, etc.

[0017] The electrocaloric effect is an endothermic and exothermic phenomenon caused by the change in entropy when the electric dipole moments in a substance are aligned or disrupted due to a change in the electric field. The performance index of the electrocaloric effect in the present invention may be the adiabatic temperature change (ΔT). That is, "a large electrocaloric effect" may mean a large adiabatic temperature change (ΔT). In the present invention, the larger the adiabatic temperature change (ΔT), the more preferable.

[0018] The adiabatic temperature change (ΔT) means the temperature change of the ceramics caused by applying an electric field to the ceramics and / or removing the electric field applied to the ceramics. Specifically, it may be the difference between the temperature of the ceramics before applying the electric field and the temperature of the ceramics immediately after applying the electric field, or it may be the difference between the temperature of the ceramics before removing the electric field and the temperature of the ceramics immediately after removing the electric field.

[0019] The adiabatic temperature change ΔT increases as the electric field strength applied to the ceramics increases. Also, the adiabatic temperature change ΔT increases as the temperature of the ceramics at the time of applying the electric field approaches the ferroelectric phase transition temperature (hereinafter, also referred to as the "phase transition temperature"). For example, as the temperature of the ceramics becomes lower than the transition temperature, the electrocaloric effect rapidly decreases. Specifically, in the conventional PST with a transition temperature of about 15 to 25 °C, the electrocaloric effect at a temperature of 0 °C or lower of the ceramics is significantly reduced.

[0020] In another aspect, the above-mentioned ceramics have 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 0.03 ≤ m ≤ 0.60, 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.] It may be the ceramics represented by. By setting x, y, and m within the above ranges, a large electrocaloric effect at low temperatures (for example, ΔT of 1.5 K or more when an electric field strength of 15 MV / m is applied) can be obtained.

[0021] Although the present disclosure is not bound by any theory, the mechanism by which the above-described effects are obtained is thought to be as follows. For example, by adding Na to PST or a paraelectric substance (e.g., SrTiO3), it is possible to lower the phase transition temperature, and the electrocaloric effect can be obtained even at temperatures below 0°C. However, at the same time, the ferroelectricity is reduced, so there is room for improvement in the electrocaloric effect obtained. In this invention, we have developed PbMg, which has a perovskite structure similar to PST and is characterized by the ordering of cations at the B site. 0.5 W 0.5 We focused on O3 (hereinafter, ceramics containing Pb, Mn, and W are also referred to as "PMW") and discovered that adding such PMW to PST can achieve a better electrocaloric effect even at temperatures below 0°C.

[0022] PbMg 0.5 W 0.5 O3 is an antiferroelectric material that transitions to a ferroelectric state when a voltage above the threshold voltage is applied. It is generally known that the greater the difference in ionic radius between the two cations at the B site, the easier they become to align, and PMW is more likely to align the B site than PST. Since ferroelectricity is significantly affected by the degree of alignment at the B site, adding PMW, which facilitates alignment at the B site, to PST can lower the ferroelectric transition temperature without significantly reducing ferroelectricity, resulting in an excellent electrocaloric effect below 0°C.

[0023] The production of PST requires firing at a high temperature of 1400°C, and in addition, after firing, a long-term heat treatment at a high temperature of, for example, 1000°C for 1000 hours is essential. On the other hand, the ceramics within the scope of the present invention do not require long-term heat treatment, which significantly improves productivity. Furthermore, since they can be fired at 1250°C or less, it is possible to significantly reduce wear on the furnace body, setter, sheath, etc. during production.

[0024] In one embodiment, the ranges for x and y are: If 0≦x, y, then x, y≦0.1 and 0≦x+y≦0.12 are satisfied; When 0 > x and 0 ≤ y, it satisfies -0.1 ≤ x < 0 and 0 ≤ y ≤ 0.1. When 0 ≥ x and 0 > y, it satisfies -0.1 ≤ x, y and -0.12 ≤ x + y < 0. When 0 < x and 0 > y, it satisfies 0 < x ≤ 0.1 and -0.1 ≤ y < 0.

[0025] In one aspect, the ranges of x and y are When 0 ≤ x, y, it satisfies x, y ≤ 0.1 and 0 ≤ x + y ≤ 0.11. When 0 > x and 0 ≤ y, it satisfies -0.1 ≤ x < 0 and 0 ≤ y ≤ 0.1. When 0 ≥ x and 0 > y, it satisfies -0.1 ≤ x, y and -0.11 ≤ x + y < 0. When 0 < x and 0 > y, it satisfies 0 < x ≤ 0.1 and -0.1 ≤ y < 0.

[0026] In one aspect, the ranges of x and y are When 0 ≤ x, y, it satisfies 0 ≤ x + y ≤ 0.1. When 0 > x and 0 ≤ y, it satisfies -0.1 ≤ x < 0 and 0 ≤ y ≤ 0.1. When 0 ≥ x and 0 > y, it satisfies -0.1 ≤ x + y < 0. When 0 < x and 0 > y, it satisfies 0 < x ≤ 0.1 and -0.1 ≤ y < 0.

[0027] In one aspect, the ranges of x and y are When 0 ≤ x, y, it satisfies 0 ≤ x + y ≤ 0.08. 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.

[0028] In one aspect, the ranges of x and y are When 0 ≤ x, 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.

[0029] In one 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.

[0030] In one aspect, the ranges of x and y may be ranges 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.

[0031] In a preferred aspect, x and y are 0. That is, (1 - m)PbSc 0.5-x Ta 0.5+x O3 - mPbMg 0.5-y W 0.5+y The formula represented by O3 becomes (1 - m)PbSc 0.5 Ta 0.5 O3 - mPbMg 0.5 W 0.5 O3.

[0032] From the viewpoint of improving the electrocaloric effect at low temperatures, the range of m is preferably 0.05≦m≦0.5, more preferably 0.05≦m≦0.4, and even more preferably 0.05≦m≦0.3.

[0033] 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.

[0034] [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.

[0035] As shown in FIG. 1 , 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 the 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.

[0036] 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.

[0037] 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.

[0038] 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 electrode layer used in the present disclosure may be mainly composed of 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 or mixture of Pt and / or Pd with other elements (e.g., Ag, Pd, Rh, Au, etc.). For example, the alloy may be an Ag-Pd alloy. 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.

[0039] 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.

[0040] 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.

[0041] 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.).

[0042] 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.

[0043] The thickness of the ceramic layer 4 may be preferably 5 μm or more and 100 μm or less, more preferably 5 μm or more and 50 μm or less, even more preferably 10 μm or more and 50 μm or less, even more preferably 20 μm or more and 50 μm or less, and particularly preferably 20 μm or more and 40 μm or less. By increasing the thickness of the ceramic layer, the amount of heat that the element can handle can be increased. By decreasing the thickness of the ceramic layer, a higher ΔT can be obtained. Furthermore, the withstand voltage can also be improved.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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 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.

[0048] 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 1000°C to 1500°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 1.

[0049] 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).

[0050] 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.

[0051] 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; integrated circuits (ICs) such as central processing units (CPUs), hard disks (HDDs), power management ICs (PMICs), power amplifiers (PAs), transceiver ICs, and voltage regulators (VRs); light-emitting elements such as light-emitting diodes (LEDs), incandescent bulbs, and semiconductor lasers; and components that can serve as heat sources, such as field-effect transistors (FETs); and other components commonly used in electronic devices, such as lithium-ion batteries, circuit boards, heat sinks, and housings.

[0052] 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.

[0053] 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]

[0054] <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.

[0055] 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.

[0056] 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 PbZrO3 powder for creating a Pb atmosphere and fired at 1150-1400°C for 4 hours. 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.

[0057] 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 1.

[0058] 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.

[0059] <Evaluation> (composition) The ceramic composition of the obtained element was confirmed by high frequency inductively coupled plasma emission spectroscopy and X-ray fluorescence analysis.

[0060] (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.

[0061] (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.

[0062] The electrocaloric effect was evaluated by applying a voltage to the sample in the sequence shown in the upper graph of Figure 2. 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 applying a voltage in this sequence, the sample temperature rose immediately upon application of the voltage. During the voltage-maintaining step, heat was gradually diffused, and the sample temperature decreased to the same temperature as before the voltage was applied. During the voltage-removing step, the sample temperature decreased immediately upon removal of the applied voltage. During the voltage-removing step, the sample temperature gradually increased to the original temperature. 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). The adiabatic temperature change ΔT was calculated from the temperature change upon application and removal of the voltage. Specifically, in this example, a voltage of 15 MV / m was applied, and the temperature was measured while the voltage was maintained for 50 seconds. Then, the voltage was removed, and the temperature was measured while the voltage was not maintained for 50 seconds. This sequence was repeated three times. The temperature of the element was constantly measured during the voltage application and voltage removal sequences, and the adiabatic temperature change ΔT was calculated from the temperature change. A Go rating was given to elements whose absolute values of the adiabatic temperature change ΔT at -10°C and 0°C were 1.5 K or greater. The results are shown in Tables 1 to 4.

[0063] The evaluation results are shown below. In the table, samples marked with "*" are comparative examples, and the other samples are examples.

[0064] [Table 1]

[0065] [Table 2]

[0066] [Table 3]

[0067] [Table 4]

[0068] Tables 1 to 4 show the electrocaloric effect results for the prepared samples. Specifically, Table 1 shows the electrocaloric effect of samples in which the values of x and y in formula (1) are fixed at 0 and m is varied. Tables 2 to 4 show the electrocaloric effect of samples in which x and y are varied when m = 0.03, m = 0.2, and m = 0.6 in formula (1), respectively. Tables 1 to 4 show the electrocaloric effect when the sample temperatures are 0°C and -10°C. Furthermore, Figure 3 shows the temperature dependence of the electrocaloric effect for representative samples, sample number 1 (conventionally known) and sample number 6 of the present invention. XRD analysis of the samples with the compositions shown in Table 1 revealed that all of the main components had the desired perovskite structure and contained few heterophases.

[0069] As shown in Figure 3, the conventional PST ceramics, PbSc 0.5 Ta 0.5 Sample No. 1, which has a composition of O3, exhibited an adiabatic temperature change of 1.5 K or more in a temperature range above 20°C, demonstrating an excellent electrocaloric effect. Sample No. 1 is suitable for operation at room temperature or above. However, as shown in Table 1, the adiabatic temperature change of Sample No. 1 at 0°C and -10°C was less than 1.5 K, confirming that the electrocaloric effect significantly decreased at low temperatures.

[0070] As shown in Table 1, samples 3 to 8, which have compositions within the range of the present invention, exhibited adiabatic temperature changes of more than 1.5 K at 0°C and −10°C. In particular, as shown in FIG. 3, sample 6 exhibited an excellent adiabatic temperature change of more than 2 K over a wide temperature range from 20°C to −40°C. Sample 2, which has an m value outside the range of the present invention, exhibited an excellent electrocaloric effect above 0°C, but the electrocaloric effects at 0°C and −10°C were small, at 0.9 K and 0.3 K, respectively. This is thought to be due to the small m value and an insufficient decrease in the ferroelectric transition temperature of the ceramic. Sample 9, which has an m value outside the range of the present invention, exhibited a small electrocaloric effect at 0°C, at 0.8 K. This is thought to be due to the large m value, which caused the ferroelectric transition temperature of the ceramic to drop too low and reduced ferroelectricity.

[0071] Tables 2, 3, and 4 show the results of measuring the electrocaloric effect of ceramics represented by formula (1) when m = 0.03, m = 0.2, and m = 0.6, respectively. For samples with m within the range of the present invention, both x and y were most stable near 0, and materials with the desired crystal structure were obtained at a rate close to 100%. Even when x and y were not near 0, no heterogeneous phases were formed, but the rate of heterogeneous phases increased when x and y deviated significantly from 0 (see the crystal structure columns in Tables 2 to 4). For compositions within the range of the present invention, the adiabatic heat change at 0°C and -10°C was 1.5 K or more.

[0072] Figure 4 shows the composition ranges of x and y for which the results of the characteristic tests in Table 2 were judged as "Go." From Figure 4, it can be seen that ceramics within the range of the present invention were judged as "Go" in the characteristic tests. Tables 3 and 4 also show results similar to those in Figure 4. [Industrial Applicability]

[0073] 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]

[0074] 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 0.03≦m≦0.60, 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 0.05≦m≦0.

5.

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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