Novel potassium niobate thermoelectric oxide material and preparation method thereof

Abstract

The invention relates to a novel potassium niobate thermoelectric oxide material and a preparation method thereof, the raw materials comprise potassium carbonate and niobium oxide, and the molar ratio of potassium carbonate to niobium oxide is (1-1.02): 1; the preparation method comprises the following steps: firstly, preparing potassium niobate ceramic powder through a solid phase method, and then, carrying out vacuum hot pressed sintering on the obtained potassium niobate ceramic powder material to obtain the potassium niobate thermoelectric oxide material. According to the invention, the intrinsic behavior of the potassium niobate type material is directly modified and excited by utilizing vacuum hot pressed sintering, and a vacuum environment is introduced; the potassium niobate type ferroelectric material can show the thermoelectric performance which the material does not have, deep development of intrinsic performance of the material is greatly facilitated, particularly, no other components are introduced, experimental errors and industrial efficiency cost are directly and greatly reduced, and the potassium niobate type ferroelectric material has the advantages of being easy and efficient to operate and good in product performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of the preparation of potassium niobate powder, and particularly relates to a novel potassium niobate thermoelectric oxide material and a preparation method thereof. Background Art

[0002] Thermoelectric materials are materials that can convert thermal energy and electrical energy into each other, and are widely used in industrial waste heat recovery, aerospace, deep sea exploration and other fields due to their unique energy conversion performance. Thermoelectric materials have the Seebeck effect, the Peltier effect, and the Thomson effect, and these three effects are the theoretical basis of thermoelectric materials. A good thermoelectric material must have a large Seebeck coefficient S to ensure an obvious thermoelectric effect; have a high electrical conductivity σ to ensure that less Joule heat is generated; and should have a low thermal conductivity κ to keep the heat near the joint. The comprehensive thermoelectric performance reflected by these values can be represented by a unified thermoelectric figure of merit (ZT):

[0003] ZT = (S^2 * σ) / (κ * T)

[0004] At present, the mainstream thermoelectric materials are group-IV-VI semiconductor materials, such as SnSe (tin selenide), PbTe (lead telluride), etc. They have high thermoelectric conversion capabilities and high thermoelectric figure of merit (ZT>1). However, due to limitations such as the melting point, cost, and environmental safety of the materials themselves, the widespread application of group-IV-VI semiconductor thermoelectric materials has certain limitations [Herring C. Theory of the Thermoelectric Power of Semiconductors [J]. Phys Rev, 1954, 96(5): 1163-1187. DOI: 10.1103 / PhysRev.96.1163.]. Correspondingly, thermoelectric oxide materials have been widely studied by scholars. Currently, a variety of thermoelectric oxide materials have been discovered, such as SrTiO3 (strontium titanate), ZnO (zinc oxide), BiCuSeO (bismuth copper selenium oxide), etc. They have low costs and good chemical stability, but there is still a certain gap in their thermoelectric performance compared to semiconductors [WU T, GAO P. Development of Perovskite-Type Materials for Thermoelectric Application. [J / OL]. Materials, 2018: 999. http: / / dx.doi.org / 10.3390 / ma11060999. DOI: 10.3390 / ma11060999.]. Nevertheless, the outstanding advantages of oxides still fascinate scholars. Compared with traditional group-IV-VI semiconductor thermoelectric materials, the types of thermoelectric oxide materials are fewer and the research scope is narrower. Many new thermoelectric oxide materials are urgently needed to be developed. Among them, materials with a perovskite structure (ABO3), due to their unique composition structure, especially the discovery of oxide thermoelectric materials such as strontium titanate and calcium manganate, have proved that ABO3-type materials have the potential to be applied in the thermoelectric field.

[0005] Potassium niobate (KNbO3) has a typical perovskite structure. Potassium niobate and BaTiO3 have the same phase transition process. From high temperature to low temperature, they undergo the following phase transition processes: cubic → tetragonal (435 °C) → orthorhombic (225 °C) → trigonal (-10 °C). Except for the cubic phase, the other three structures are ferroelectric phases. Potassium niobate has excellent thermoelectric properties and optical characteristics and is widely used in many fields such as light conduction, frequency doubling and amplification technology of lasers, and information storage. Moreover, potassium niobate has low cost, high stability at high temperatures, is non-toxic and pollution-free, and has low intrinsic thermal conductivity [Delorme F, Chen C, Schoenstein F, et al. Low intrinsic thermal conductivity of Spark Plasma Sintered dense KNbO3 and NaNbO3 perovskite ceramics [J]. Thermochimica Acta, 2020, 695: 178807. DOI: 10.1016 / j.tca.2020.178807.], which expands its applications in various fields. However, there are some problems with existing KNbO3 materials. The large band gap exhibits insulating properties, and the activity of potassium elements makes it difficult to obtain high-quality impurity-free potassium niobate powder and single crystal samples, which limits its application in the thermoelectric direction. As a result, the current research on potassium niobate mainly focuses on the preparation of powders and their photocatalysis, ceramic sintering, and growth of thin film materials [Chen Jishi. Research on the wet chemical preparation of KNbO3 powders [D]. Dalian: Master's thesis of Dalian Jiaotong University, 2007: 2-4.], and reports on using it as a thermoelectric material are extremely rare. Summary of the Invention

[0006] In order to overcome the problems existing in the above-mentioned prior art, the purpose of the present invention is to propose a new type of potassium niobate thermoelectric oxide material and its preparation method. By directly modifying and activating the intrinsic behavior of potassium niobate-based materials through vacuum hot pressing sintering, a vacuum environment is introduced, which can enable ferroelectric materials of the potassium niobate type to exhibit thermoelectric properties that they do not have themselves. The modification process is simple and efficient, and the product performance is good.

[0007] In order to achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0008] A new type of potassium niobate thermoelectric oxide material, the raw materials include potassium carbonate and niobium oxide, and the molar ratio of potassium carbonate to niobium oxide is (1 - 1.02):1.

[0009] A preparation method of a new type of potassium niobate thermoelectric oxide material, specifically including the following steps:

[0010] Step 1: Prepare potassium niobate ceramic powder by solid-phase method:

[0011] Step 2: Vacuum hot-press sinter the potassium niobate ceramic powder material obtained in Step 1 to obtain potassium niobate thermoelectric oxide material.

[0012] The specific method of Step 1 is as follows:

[0013] Weigh and mix potassium carbonate and niobium oxide according to the molar ratio of (1 - 1.02):1, ball mill for 20h - 24h, and then dry at 80℃ - 95℃; pre-sinter the dried powder at 820℃ - 850℃ for 3h - 6h to obtain potassium niobate powder; ball mill the potassium niobate powder for 4h - 6h, dry it, and store it in vacuum.

[0014] The specific method of Step 2 is as follows:

[0015] Place the potassium niobate powder prepared in Step 1 in a hot-press mold for vacuum hot-press sintering, with a pressure of 20Mpa - 50Mpa, a pressing thickness of 2mm - 3.5mm, a sintering vacuum degree < 0.05pa, a sintering temperature of 1000℃ - 1050℃, and a holding time of 2h - 6h; obtain potassium niobate thermoelectric oxide material.

[0016] A novel potassium niobate thermoelectric oxide material is prepared from the above-mentioned raw materials or according to the preparation method described in Step 1 and Step 2.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] The present invention innovatively uses the means of vacuum hot-press sintering. Compared with traditional sintering means such as hot pressing, this method introduces a vacuum environment, enabling ferroelectric materials of the potassium niobate type to exhibit thermoelectric properties that they do not possess themselves, and the modification process is simple and efficient.

[0019] The present invention directly modifies and stimulates the intrinsic behavior of potassium niobate-type materials by vacuum hot-press sintering, without relying on doping modification, solid solution component modification and other methods. This greatly facilitates the in-depth development of the intrinsic properties of materials. In particular, the introduction of no other components directly greatly reduces experimental errors and industrial efficiency costs, and it is an effective modification means.

[0020] For the sintering method used in the present invention, only by selecting appropriate sintering parameters and controlling the sintering process conditions, a novel potassium niobate thermoelectric oxide material can be obtained. The operation is simple, and the performance of the sample is good.

[0021] In summary, through the modification method of vacuum hot pressing sintering, the potassium niobate material of the present invention can exhibit good thermoelectric performance, with the advantages of simplicity, high efficiency, and good product performance. In the research of the present invention, the perovskite-structured potassium niobate material was innovatively modified, and the potassium niobate (KNbO3) material with thermoelectric performance was successfully prepared, adding a new type of applicable material to the oxide thermoelectric materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is the flow chart of the solid-phase process of potassium niobate of the present invention.

[0023] Figure 2 is the schematic diagram of the hot pressing sintering principle for the preparation of the potassium niobate thermoelectric oxide material of the present invention.

[0024] Figure 3 is the flow chart of the thermoelectric performance test of the potassium niobate thermoelectric oxide material of the present invention.

[0025] Figure 4 is the thermoelectric performance of the potassium niobate thermoelectric oxide material of the present invention under different vacuums; wherein Figure 4 (a) is the sample and conductivity under the vacuum condition > 0.05 pa; Figure 4 (b) is the sample and conductivity under the vacuum condition < 0.05 pa. Figure 4 (c) is the thermoelectric figure of merit of the material under the vacuum condition < 0.05 pa.

[0026] Figure 5 is the thermoelectric performance diagram of the potassium niobate thermoelectric oxide material of the present invention sintered under different pressures; Figure 5 (a) is the conductivity of sintering under different pressures; Figure 5 (b) is the thermal conductivity of sintering under different pressures; Figure 5 (c) is the thermoelectric figure of merit of sintering under different pressures.

[0027] Figure 6 is the thermoelectric performance diagram of the potassium niobate thermoelectric oxide material of the present invention at different sintering temperatures; Figure 6 (a) is the conductivity at different sintering temperatures; Figure 6 (b) is the thermal conductivity at different sintering temperatures; Figure 6 (c) is the thermoelectric figure of merit at different sintering temperatures.

[0028] Figure 7 is the thermoelectric performance diagram of the potassium niobate thermoelectric oxide material of the present invention at different sintering times; Figure 7 (a) is the conductivity at different sintering times; Figure 7 (b) is the thermal conductivity at different sintering times; Figure 7 (c) is the thermoelectric figure of merit at different sintering times. DETAILED DESCRIPTION OF THE INVENTION

[0029] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments.

[0030] A novel potassium niobate thermoelectric oxide material, the raw materials include potassium carbonate and niobium oxide, and the molar ratio of potassium carbonate to niobium oxide is (1 - 1.02):1.

[0031] The specific method of step 1 is as follows:

[0032] Weigh and mix potassium carbonate and niobium oxide according to the molar ratio of (1 - 1.02):1, ball mill for 20h - 24h, and then dry at 80°C - 95°C; pre - sinter the dried powder at 820°C - 850°C for 3h - 6h to obtain potassium niobate powder; ball mill the potassium niobate powder for 4h - 6h, dry it, and store it in vacuum.

[0033] Step 2: Place the potassium niobate powder prepared in step 1 in a hot - pressing mold, perform vacuum hot - pressing sintering, with a pressure of 20Mpa - 50Mpa, a pressing thickness of 2mm - 3.5mm, a sintering vacuum degree <0.05pa, a sintering temperature of 1000°C - 1050°C, and a holding time of 2h - 6h; thus obtaining the potassium niobate thermoelectric oxide material.

[0034] Cut out a thermal conductivity test sample with dimensions of length * width * height of 7.7mm - 8.02mm * 7.7mm - 8.02mm * 0.8mm - 1.2mm and an electrical conductivity test sample with dimensions of length * width * height of 2.5mm - 3.5mm * 2.5mm - 3.5mm * 9mm - 12.5mm from the obtained potassium niobate thermoelectric oxide material; then use a laser thermal conductivity system (CLA) and a thermoelectric material test system (CTA) to test the thermal conductivity and electrical conductivity of the samples respectively, and finally obtain the ZT value (0.11 - 0.16, 973K) of the potassium niobate thermoelectric oxide material.

[0035] Example 1

[0036] A preparation method of a novel potassium niobate thermoelectric oxide material, the technological process is as Figure 1 shown; the specific steps are as follows:

[0037] Step 1: Prepare potassium niobate ceramic powder by the solid - state method: First, uniformly mix potassium carbonate and niobium oxide according to the molar ratio of 1:1, ball mill for 20h, and then dry in an 80°C oven; place the dried powder in a muffle furnace for pre - sintering, and the pre - sintering parameters are: hold at 850°C for 3h to obtain potassium niobate powder; finally, ball mill the powder for 4h, dry it, and store it in a vacuum tank.

[0038] Step 2. Vacuum hot-press sinter the potassium niobate ceramic powder material obtained in Step 1: Place the potassium niobate powder in a hot-press mold, and conduct vacuum hot-press sintering in a vacuum hot-press sintering furnace. The pressure is 40 Mpa, the pressing thickness is 3 mm, the sintering vacuum degree is 0.01 pa, the sintering temperature is 1030 °C, and the heat preservation time is 4 h to obtain a potassium niobate thermoelectric oxide material; the hot-press principle is as Figure 2 shown.

[0039] Conduct cutting tests on the potassium niobate thermoelectric oxide material obtained in Step 2. The test process is as Figure 3 shown: First, cut out a thermal conductivity test sample with dimensions of 8.00 mm * 8.00 mm * 1 mm and an electrical conductivity test sample with dimensions of 3 mm * 3 mm * 10 mm. Then, use a laser thermal conductivity system (CLA) and a thermoelectric material test system (CTA) to test the above samples respectively. Finally, obtain the ZT value of the potassium niobate thermoelectric oxide material (when the vacuum degree is 0.01 pa < 0.05 pa, ZT = 0.13, 973 K). The results are as Figure 4 shown.

[0040] Example 2

[0041] A preparation method of a novel potassium niobate thermoelectric oxide material is as follows:

[0042] Step 1. Prepare potassium niobate ceramic powder by the solid-phase method: First, mix potassium carbonate and niobium oxide evenly according to a molar ratio of 1.01:1, ball mill for 22 h, then dry in an oven at 85 °C. Place the dried powder in a muffle furnace for pre-sintering. The pre-sintering parameters are: heat preservation at 840 °C for 6 h to obtain potassium niobate powder; finally, ball mill the powder for 6 h, dry it, and store it in a vacuum tank;

[0043] Step 2. Vacuum hot-press sinter the potassium niobate ceramic powder material obtained in Step 1: Place the potassium niobate powder in a hot-press mold, and conduct vacuum hot-press sintering in a vacuum hot-press sintering furnace. The pressure is 30 Mpa, the pressing thickness is 2.5 mm, the vacuum degree during sintering is 0.01 pa, the sintering temperature is 1050 °C, and the heat preservation time during sintering is 5 h to obtain a potassium niobate thermoelectric oxide material.

[0044] Conduct cutting tests on the potassium niobate thermoelectric oxide material obtained in Step 2. First, cut out a thermal conductivity test sample with dimensions of 7.9 * 7.9 mm * 0.9 mm and an electrical conductivity test sample with dimensions of 2.5 mm * 2.5 mm * 11 mm. Then, use CLA and CTA to test the above samples respectively. Finally, obtain the ZT value of the potassium niobate thermoelectric oxide material (0.15, 973 K). The results are as Figure 5 shown.

[0045] Example 3

[0046] A preparation method of a novel potassium niobate thermoelectric oxide material is as follows:

[0047] Step 1: Prepare potassium niobate ceramic powder by the solid-phase method: First, mix potassium carbonate and niobium oxide evenly according to a molar ratio of 1.02:1, ball mill for 23 h, and then dry in an oven at 90 °C. Place the dried powder in a muffle furnace for pre-sintering, and the pre-sintering parameters are: keep the temperature at 830 °C for 6 h to obtain potassium niobate powder; finally, ball mill the powder for 4 h, dry it, and store it in a vacuum tank;

[0048] Step 2: Perform vacuum hot pressing sintering on the potassium niobate ceramic powder material obtained in Step 1: Place the potassium niobate powder in a hot pressing mold, and perform vacuum hot pressing sintering in a vacuum hot pressing sintering furnace. The pressure is 50 Mpa, the pressing thickness is 3.5 mm, the sintering vacuum degree is 0.02 pa, the sintering temperature is 1030 °C, and the heat preservation time is 5 h; to obtain the potassium niobate thermoelectric oxide material.

[0049] Cut and test the potassium niobate thermoelectric oxide material obtained in Step 2. First, cut out a thermal conductivity test sample with dimensions of 8.01 mm - 8.01 mm * 0.8 mm and an electrical conductivity test sample with dimensions of 3.5 mm * 3.5 mm * 9 mm, and then use CLA and CTA to test the above samples respectively. Finally, obtain the ZT value (0.14, 973 K) of the material. The results are as Figure 6 shown.

[0050] Example 4

[0051] A preparation method of a novel potassium niobate thermoelectric oxide material is as follows:

[0052] Step 1: Prepare potassium niobate ceramic powder by the solid-phase method: First, mix potassium carbonate and niobium oxide evenly according to a molar ratio of 1:1, ball mill for 24 h, and then dry in an oven at 95 °C. Place the dried powder in a muffle furnace for pre-sintering, and the pre-sintering parameters are: keep the temperature at 820 °C for 6 h to obtain potassium niobate powder; finally, ball mill the powder for 6 h, dry it, and store it in a vacuum tank for supplementation;

[0053] Step 2: Perform vacuum hot pressing sintering on the potassium niobate ceramic powder material obtained in Step 1: Place the potassium niobate powder in a hot pressing mold, and perform vacuum hot pressing sintering in a vacuum hot pressing sintering furnace. The pressure is 50 Mpa, the pressing thickness is 2.9 mm, the sintering vacuum degree is 0.03 pa, the sintering temperature is 1050 °C, and the heat preservation time is 4 h; to obtain the potassium niobate thermoelectric oxide material.

[0054] The potassium niobate thermoelectric oxide material obtained in Step 2 was subjected to cutting tests. First, a thermal conductivity test sample with dimensions of 7.9 mm * 7.9 mm * 1.1 mm and an electrical conductivity test sample with dimensions of 2.9 mm * 2.9 mm * 12.5 mm were cut out. Then, the above samples were tested using CLA and CTA respectively, and finally the ZT value (0.14, 973K) of the material was obtained. The results are as Figure 7 shown.

[0055] Analysis:

[0056] Figure 1 is the preparation process diagram of potassium niobate ceramic powder. In the present invention, traditional solid-phase sintering method is used to prepare active potassium niobate ceramic powder, and then vacuum hot pressing sintering is used to modify the thermoelectric behavior of potassium niobate material. Its schematic diagram is as Figure 2 shown. Sintering under vacuum conditions can induce the appearance of freely moving electrons in potassium niobate material, thus showing conductive behavior. Pressure can directly control its forming process, and then adjust properties such as density, conductivity, and defect structure. The time and temperature of vacuum hot pressing sintering also have a certain influence on the modification of potassium niobate material. Therefore, through the joint control of vacuum, pressure, sintering time and temperature, potassium niobate thermoelectric oxide material can be obtained.

[0057] Figure 3 is the test process of the novel thermoelectric oxide potassium niobate material in the present invention. The sintered material was cut into a thermal conductivity test sample with dimensions of 7.7 mm - 8.02 mm * 7.7 mm - 8.02 mm * 0.8 mm - 1.2 mm and an electrical conductivity test sample with dimensions of 2.5 mm - 3.5 mm * 2.5 mm - 3.5 mm * 9 mm - 12.5 mm. Then, the above samples were tested using a laser thermal conductivity system (CLA) and a thermoelectric material test system (CTA) respectively, and finally the ZT value of the potassium niobate thermoelectric oxide material was obtained.

[0058] Vacuum is an important condition for the modification of the thermoelectric behavior of potassium niobate material. The degree of vacuum directly affects whether potassium niobate can exhibit thermoelectric properties. The fundamental reason for the thermoelectric behavior of potassium niobate material is the appearance of free electrons caused by K and O vacancies. Figure 4 is the exploration of the vacuum condition in the vacuum hot pressing sintering method used for the modification of the thermoelectric behavior of potassium niobate material in Example 1 of the present invention, and gives the lowest vacuum condition for the appearance of thermoelectric behavior. The figure intuitively shows that when sintering at a relatively high vacuum (<0.05 Pa), the potassium niobate thermoelectric oxide material exhibits conductive properties and shows thermoelectric properties (ZT = 0.16, 973K); when sintering at a relatively low vacuum (>0.05 Pa), the potassium niobate thermoelectric oxide material is white and does not show conductive behavior. This directly proves that the necessary condition for the modification of the thermoelectric behavior of potassium niobate thermoelectric oxide material is a relatively high degree of vacuum (<0.05 Pa).

[0059] Figure 5 This is the exploration of the pressure conditions in the vacuum hot pressing sintering method used for modifying the thermoelectric behavior of the potassium niobate material in Example 2 of the present invention, and the pressure range in which the thermoelectric performance appears is given. The results in the figure show that the thermoelectric performance appears at pressures of 20 Mpa - 50 Mpa, and the electrical conductivity of the sample first increases and then decreases with the increase in pressure, but the degree of decrease is not large. The thermal conductivity of the sample decreases with the increase in pressure, which ultimately leads to an increase in the thermoelectric figure of merit (ZT) of the sample with the increase in pressure. This is because pressure is one of the important factors in the vacuum hot pressing sintering of the potassium niobate thermoelectric oxide material. For the potassium niobate thermoelectric oxide material, both K and O have certain escape behaviors, and the escape of K is more serious. Therefore, the greater the pressure during sintering, the better the thermoelectric performance after sintering.

[0060] Figure 6 This is the exploration of the temperature conditions in the vacuum hot pressing sintering method used for modifying the thermoelectric behavior of the potassium niobate material in Example 3 of the present invention, and the temperature range in which the thermoelectric performance appears is given. The potassium niobate material is relatively sensitive to temperature. The results in the figure show that the material sintered at 990 °C cannot successfully complete the thermoelectric modification process, and the material melts when sintered at 1060 °C. In the sintering temperature range of 1000 °C - 1050 °C, the potassium niobate thermoelectric oxide material sample successfully exhibits thermoelectric performance. And with the increase in temperature, the electrical conductivity of the sample increases, and the thermal conductivity also increases accordingly. Ultimately, it leads to an increase in the thermoelectric figure of merit (ZT) of the sample with the increase in the sintering temperature.

[0061] Figure 7 This is the exploration of the sintering time conditions in the vacuum hot pressing sintering method used for modifying the thermoelectric behavior of the potassium niobate material in Example 4 of the present invention, and the sintering time range in which the thermoelectric performance appears is given. The sintering time also has a certain influence on the thermoelectric performance of the potassium niobate material. The results in the figure show that the potassium niobate does not successfully exhibit thermoelectric performance when sintered for 1 h, while the potassium niobate exhibits thermoelectric performance when sintered for 2 h - 6 h. And with the increase in sintering time, the electrical conductivity first increases and then decreases, and the thermal conductivity also has a certain trend of first increasing and then decreasing, but the overall change is not large. Ultimately, it leads to the thermoelectric performance of the potassium niobate thermoelectric oxide material first increasing and then decreasing with the increase in sintering time (2 h - 6 h).

[0062] In summary, the vacuum hot pressing sintering parameters for the potassium niobate thermoelectric oxide material to achieve thermoelectric behavior modification are as follows: the vacuum degree during sintering < 0.05 Pa, the pressure during sintering is 20 Mpa - 50 Mpa, the sintering temperature is 1000 °C - 1050 °C, and the heat preservation time during sintering is 2 h - 6 h. Eventually, a new type of potassium niobate thermoelectric oxide material can be obtained. The present invention provides a simple and feasible method for the development of new thermoelectric oxide materials. Perovskite structures similar to potassium niobate materials can all be attempted to be made thermoelectric in this way to make them exhibit unique properties. This provides technical guidance for the development of new types of thermoelectric oxide materials.

Claims

1. A new type of potassium niobate thermoelectric oxide material, characterized in that: The raw materials include potassium carbonate and niobium oxide, and the molar ratio of potassium carbonate to niobium oxide is (1-1.02):

1.

2. A method for preparing a novel potassium niobate thermoelectric oxide material according to claim 1, characterized in that: The specific steps include: Step 1: Prepare potassium niobate ceramic powder by solid phase method: Step 2: vacuum hot pressing and sintering the potassium niobate ceramic powder material obtained in step 1 to obtain a potassium niobate thermoelectric oxide material.

3. The method for preparing a novel potassium niobate thermoelectric oxide material according to claim 2, characterized in that: The specific method of step 1 is: Potassium carbonate and niobium oxide are weighed and mixed in a molar ratio of (1-1.02):1, ball-milled for 20h-24h, and then dried at 80°C-95°C; the dried powder is pre-calcined at 820°C-850°C and kept warm for 3h-6h to obtain potassium niobate powder; the potassium niobate powder is ball-milled for 4h-6h, dried, and stored in a vacuum.

4. The method for preparing a novel potassium niobate thermoelectric oxide material according to claim 2, characterized in that: The specific method of step 2 is: The potassium niobate powder prepared in step 1 is placed in a hot pressing mold for vacuum hot pressing sintering, with a pressure of 20Mpa-50Mpa, a pressing thickness of 2mm-3.5mm, a sintering vacuum degree of <0.05pa, a sintering temperature of 1000°C-1050°C, and a holding time of 2h-6h; and a potassium niobate thermoelectric oxide material is obtained.

5. A method for preparing a novel potassium niobate thermoelectric oxide material according to claim 2, characterized in that: The specific steps are as follows: Step 1, preparing potassium niobate ceramic powder by a solid phase method: first, potassium carbonate and niobium oxide are mixed evenly in a molar ratio of 1:1, ball milled for 20 hours, and then dried in an oven at 80°C; the dried powder is placed in a muffle furnace for pre-calcination, and the pre-calcination parameters are: 850°C for 3 hours to obtain potassium niobate powder; finally, the powder is ball milled for 4 hours, dried, and stored in a vacuum tank; Step 2, vacuum hot pressing and sintering the potassium niobate ceramic powder material obtained in step 1: placing the potassium niobate powder in a hot pressing mold, vacuum hot pressing and sintering in a vacuum hot pressing sintering furnace, with a pressure of 40 MPa, a pressing thickness of 3 mm, a sintering vacuum degree of 0.05 Pa, a sintering temperature of 1030° C., and a holding time of 4 hours to obtain a potassium niobate thermoelectric oxide material.

6. A method for preparing a novel potassium niobate thermoelectric oxide material according to claim 2, characterized in that: The specific steps are as follows: Step 1, preparing potassium niobate ceramic powder by a solid phase method: first, potassium carbonate and niobium oxide are mixed evenly in a molar ratio of 1.01:1, ball milled for 22 hours, and then dried in an oven at 85°C, and the dried powder is placed in a muffle furnace for pre-calcination, and the pre-calcination parameters are: 840°C for 6 hours to obtain potassium niobate powder; finally, the powder is ball milled for 6 hours, dried, and stored in a vacuum tank; Step 2, vacuum hot pressing and sintering the potassium niobate ceramic powder material obtained in step 1: placing the potassium niobate powder in a hot pressing mold, vacuum hot pressing and sintering in a vacuum hot pressing sintering furnace, with a pressure of 30 MPa, a pressing thickness of 2.5 mm, a vacuum degree of 0.01 Pa during sintering, a sintering temperature of 1050° C., and a holding time of 5 h during sintering to obtain a potassium niobate thermoelectric oxide material.

7. A method for preparing a novel potassium niobate thermoelectric oxide material according to claim 2, characterized in that: The specific steps are as follows: Step 1: Prepare potassium niobate ceramic powder by solid phase method: first, mix potassium carbonate and niobium oxide in a molar ratio of 1.02:1, ball mill for 23 hours, and then dry in an oven at 90°C. Pre-sinter the dried powder in a muffle furnace, and the pre-sintering parameters are: 830°C for 6 hours to obtain potassium niobate powder; finally, ball mill the powder for 4 hours, dry it, and store it in a vacuum tank; Step 2, vacuum hot pressing and sintering the potassium niobate ceramic powder material obtained in step 1: placing the potassium niobate powder in a hot pressing mold, vacuum hot pressing and sintering in a vacuum hot pressing sintering furnace, with a pressure of 50 MPa, a pressing thickness of 3.5 mm, a sintering vacuum degree of 0.02 Pa, a sintering temperature of 1030° C., and a holding time of 5 h; obtaining a potassium niobate thermoelectric oxide material.

8. A method for preparing a novel potassium niobate thermoelectric oxide material according to claim 2, characterized in that: The specific steps are as follows: Step 1, preparing potassium niobate ceramic powder by a solid phase method: first, potassium carbonate and niobium oxide are mixed evenly in a molar ratio of 1:1, ball milled for 24 hours, and then dried in an oven at 95°C, and the dried powder is placed in a muffle furnace for pre-calcination, and the pre-calcination parameters are: 820°C for 6 hours to obtain potassium niobate powder; finally, the powder is ball milled for 6 hours, dried, and stored in a vacuum tank; Step 2, vacuum hot pressing and sintering the potassium niobate ceramic powder material obtained in step 1: placing the potassium niobate powder in a hot pressing mold, vacuum hot pressing and sintering in a vacuum hot pressing sintering furnace, with a pressure of 50 MPa, a pressing thickness of 2.9 mm, a sintering vacuum degree of 0.03 Pa, a sintering temperature of 1050° C., and a holding time of 4 hours; obtaining a potassium niobate thermoelectric oxide material.

9. A novel potassium niobate thermoelectric oxide material, prepared from the raw material according to claim 1 or prepared according to any one of the preparation methods of claims 1 to 8.

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