A high-entropy oxygen ion conductor material with a scheelite structure and extremely high interstitial oxygen content and a preparation method thereof

Abstract

The present invention discloses a scheelite-structured high-entropy oxygen ion conductor material with extremely high interstitial oxygen content and a preparation method thereof. (1) Before weighing the raw materials, the lanthanide oxides La2O3, Sm2O3, Nd2O3, and Gd2O3 are sintered at 1000 °C for 12 hours, and CaCO3 is placed in an oven at 180 °C for 12 hours to remove water and CO2 in the raw materials. Weigh according to the designed stoichiometric ratio. Put the weighed raw materials into a mortar, add alcohol and grind for more than 1 hour. After mixing evenly, dry under an infrared lamp to obtain the sample powder. Since MoO3 is prone to volatilization, an excess of 10% needs to be added during weighing to make up for the raw material loss caused during the sintering process. (2) Weigh 0.5 g of the powder sample and put it into a tablet press mold. Press it into a tablet at a pressure of 4 Mpa for 30 seconds, put it into a crucible, pre-sinter at 500 °C for 12 hours, then grind and press the sample again, and finally sinter and hold at 950 °C for 12 hours to obtain the target product. The preparation process of the high-entropy oxygen ion conductor material prepared by the present invention is simple, with good stability and good electrical conductivity.

Description

Technical Field

[0001] The invention belongs to the field of inorganic materials and solid chemistry, and specifically relates to a scheelite structure high-entropy oxygen ion conductor material with extremely high interstitial oxygen content and a preparation method thereof. Background Art

[0002] Solid oxide fuel cells (SOFCs) are a type of clean energy device that efficiently converts chemical energy into electrical energy. They have attracted much attention for their all-solid-state structure and fuel diversity. The electrolyte is a key component of solid oxide fuel cells and determines the operating temperature of the battery. The electrolyte material currently used in practice is 8mol% yttrium-stabilized zirconia (YSZ) that conducts oxygen ions. However, due to the low oxygen ion conductivity of YSZ at medium and low temperatures (400-700°C), its operating temperature usually needs to be maintained above 800°C. High operating temperatures will shorten the service life of various components, cause side reactions between electrodes and electrolytes, and other disadvantages, thereby limiting the application of SOFCs in transportation and portable power. In order to reduce the operating temperature to the medium and low temperature range (400-700°C), it is necessary to develop high conductivity (>10 -3 S / cm) and excellent thermodynamic and chemical stability. However, the main problem of the new electrolyte materials reported so far is that the thermal and chemical stability of the materials are poor, which cannot meet the needs of practical applications. Therefore, in order to be technically feasible, these electrolytes must exhibit high oxygen ion mobility at lower operating temperatures. It is urgent to develop electrolytes with high conductivity and excellent thermodynamic and chemical stability in the medium and low temperature range (400-700 ℃).

[0003] Since Lacorre et al. reported in 2000 that La2Mo2O9 has high oxygen ion conductivity, La2Mo2O9-based oxygen ion conductors have attracted attention due to their excellent performance. The material undergoes a structural transformation at around 580°C, resulting in an increase in conductivity by almost two orders of magnitude. Its conductivity is about 6×10 -2 S cm -1 , which is comparable to the oxygen ion conductivity of the most widely used electrolyte-stabilized ZrO2. Existing research results show that W-substituted La2Mo2O9 has better advantages than pure La2Mo2O9 in terms of chemical stability and DC conductivity, and is expected to be widely used in solid oxide fuel cells and oxygen sensors, with great development potential.

[0004] The present invention adopts the traditional solid phase reaction method, for La2Mo2O9 material, 20% mol of Sm is doped at the La position. 3+ 、Nd 3+ , Gd3+ and Ca 2+ Preparation (La 0.2 Sm 0.2 Nd 0.2 G 0.2 Ca 0.2 )2Mo2O 8.8 High entropy materials, and study the physical phase, structure, electrochemical properties, thermal stability and chemical stability of the materials. Summary of the invention

[0005] The purpose of the present invention is to provide a scheelite structure high entropy oxygen ion conductor material with extremely high interstitial oxygen content and a preparation method thereof. The specific steps for preparing a scheelite structure high entropy oxygen ion conductor material with extremely high interstitial oxygen content are as follows:

[0006] (1) Before weighing the materials, first sinter the lanthanide oxides La2O3, Sm2O3, Nd2O3, and Gd2O3 in a muffle furnace at 1000°C for 12 hours, and place CaCO3 in an oven at 180°C for 12 hours to remove water and CO2 from the raw materials. Weigh according to the designed stoichiometric ratio. Put the weighed raw materials with a purity of more than 99% (mass percentage) into an agate mortar, mix them with alcohol as a dispersant, and use pressure and friction to fully grind them. Generally, grind for more than 1 hour to make them evenly mixed and then dry them under an infrared lamp to obtain sample powder. Since MoO3 material is easy to volatilize, it is necessary to weigh 10% more in the early stage to make up for the loss of raw materials caused by the sintering process.

[0007] (2) Weigh 0.5g of the powder sample and put it into the tableting mold. Use the rotating plunger of the tablet press to provide pressure and friction. Press it into a tablet at a pressure of 4Mpa for 30 seconds to produce a disc with a diameter of 10mm and a thickness of about 1-2mm. Put the tablet into an alumina crucible and pre-sinter it at 500℃ in a muffle furnace for 12 hours. Then continue to grind and tablet the pre-sintered sample, repeat the steps before pre-sintering, and finally sinter and keep it at 950℃ for 12 hours to obtain the target product.

[0008] (3) The ceramic sheet obtained in step (2) was crushed, and then XRD and SEM-EDS tests were performed to determine that the prepared sample was a single phase. From the XRD data, it can be seen that there are two unknown diffraction peaks at 950°C. The SEM-EDS test results show that the elements are evenly distributed, indicating that the sample is a pure phase and is isostructural with AgSmMo2O8 (scheelite structure); the electrochemical impedance spectroscopy was used to study (La 0.2 Sm 0.2 Nd 0.2 G 0.2 Ca 0.2 )2Mo2O 8.8The electrical properties and conductivity type of high entropy material oxygen ion conductor materials. The test results show that the conductivity of the material can reach 1.97×10 at 900°C in air atmosphere. -4 S / cm, and the conductivity in a humid argon atmosphere at the same temperature is 3.71×10 -4 S / cm, and the conductivity did not increase significantly, indicating that there was no proton conduction phenomenon; the stability of the samples was tested by sintering at 800°C in CO2 and humid Ar atmospheres for 48h and 96h respectively. From the XRD diffraction data, it can be seen that the material did not decompose, indicating that the high entropy material has good thermal and chemical stability.

[0009] The high entropy oxygen ion conductor material with extremely high interstitial oxygen content prepared by the present invention has low cost, good thermal stability and chemical stability, good electrical properties, and a nominal composition of (La 0.2 Sm 0.2 Nd 0.2 G 0.2 Ca 0.2 )2Mo2O 8.8 High entropy materials have certain potential as new electrolytes. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 Example Case 1 (La 0.2 Sm 0.2 Nd 0.2 G 0.2 Ca 0.2 )2Mo2O 8.8 XRD spectrum of high entropy material.

[0011] Figure 2 Example Case 1 (La 0.2 Sm 0.2 Nd 0.2 G 0.2 Ca 0.2 )2Mo2O 8.8 SEM-EDS elemental distribution map of high entropy materials.

[0012] Figure 3 Example Case 1 (La 0.2 Sm 0.2 Nd 0.2 G 0.2 Ca 0.2 )2Mo2O 8.8 Arrehnius plot of the electrical conductivity of high entropy materials.

[0013] Figure 4 Example Case 1 (La 0.2 Sm 0.2 Nd 0.2 G0.2 Ca 0.2 )2Mo2O 8.8 Arrehnius plot of the electrical conductivity of a high entropy material after stability testing.

[0014] Figure 5 Example Case 1 (La 0.2 Sm 0.2 Nd 0.2 G 0.2 Ca 0.2 )2Mo2O 8.8 XRD pattern of high entropy material at 800°C in CO2 atmosphere.

[0015] Figure 6 Example Case 1 (La 0.2 Sm 0.2 Nd 0.2 G 0.2 Ca 0.2 )2Mo2O 8.8 XRD patterns of high entropy materials at 800 °C in humid Ar atmosphere. DETAILED DESCRIPTION

[0016] The following is a detailed description in the form of specific embodiments. The embodiments are implemented on the premise of the technical solution of the present invention, and detailed implementation methods and specific operation processes are given, but the protection scope of the present invention is not limited to the following embodiments.

[0017] Implementation Case 1:

[0018] Example 1 Design to generate 1 mol of target product (La 0.2 Sm 0.2 Nd 0.2 G 0.2 Ca 0.2 )2Mo2O 8.8 Materials. Weigh 0.2 mol La2O3, 0.2 mol Sm2O3, 0.2 mol Nd2O3,

[0019] 0.2mol Gd2O3, 0.2mol CaCO3, 2.2mol MoO3. Weigh according to the designed stoichiometric ratio. Since MoO3 material is easy to volatilize, it is necessary to weigh 10% more in the early stage to make up for the loss of raw materials caused by the sintering process. Put the weighed raw materials with a purity of more than 99% (mass percentage) into an agate mortar, mix them with alcohol as a dispersant, and use pressure and friction to fully grind them. Generally, grind them for more than 1 hour to make them evenly mixed and then dry them under an infrared lamp to obtain sample powder. Weigh 0.5g of the powder sample and put it into the tablet pressing mold. Use the rotating plunger of the tablet press to provide pressure and friction. Press it into a tablet at a pressure of 4Mpa for 30 seconds, and press out a disc with a diameter of 10mm and a thickness of about 1-2mm. Put the tablet into an alumina crucible and pre-sinter it at 500℃ in a muffle furnace for 12 hours. Then continue to grind and press the pre-sintered sample, repeat the steps before pre-sintering, and finally sinter and keep warm at 950℃ for 12 hours to obtain the target product. Since MoO3 material is easy to volatilize, it is necessary to weigh 10% more in the early stage to make up for the loss of raw materials caused by the sintering process.

[0020] Figure 1 Given is (La 0.2 Sm 0.2 Nd 0.2 G 0.2 Ca 0.2 )2Mo2O 8.8 XRD spectrum of high entropy material. Figure 2 This is the SEM-EDS element distribution map of the high entropy material. Figure 3 and Figure 4 Arrehnius plot of electrical conductivity before and after stability testing for this high entropy material. Figure 5 and Figure 6 This is the XRD pattern of the high entropy material at 800°C in CO2 and humid Ar atmosphere.

Claims

1. A high-entropy oxygen ion conductor material with a scheelite structure and extremely high interstitial oxygen content (La 0.2 Sm 0.2 Nd 0.2 G 0.2 Ca 0.2 )2Mo2O 8.8 The preparation method is characterized in that The specific preparation steps are: (1) Before weighing the materials, first sinter the lanthanide oxides La2O3, Sm2O3, Nd2O3, and Gd2O3 in a muffle furnace at 1000°C for 12 hours, and dry the CaCO3 in an oven at 180°C for 12 hours to remove water and CO2 from the raw materials; weigh them according to the designed stoichiometric ratio; put the weighed raw materials with a purity of more than 99wt% into an agate mortar, mix them with alcohol as a dispersant, and use pressure and friction to fully grind them for more than 1 hour to make them evenly mixed, and then dry them under an infrared lamp to obtain sample powder; since MoO3 material is easy to volatilize, it is necessary to weigh 10% more in the early stage to compensate for the loss of raw materials caused by the sintering process; (2) Weigh 0.5 g of the powder sample and put it into a tabletting mold. Use the rotating plunger of the tabletting machine to provide pressure and friction, press it into a tablet at a pressure of 4 MPa for 30 seconds, and press out a disc with a diameter of 10 mm and a thickness of 1-2 mm. Put the tablet into an alumina crucible and pre-sinter it at 500 ° C in a muffle furnace for 12 hours. Then continue to grind and tablet the pre-sintered sample, repeat the steps before pre-sintering, and finally sinter and keep it at 950 ° C for 12 hours to obtain the target product. (3) The ceramic sheet obtained in step (2) was crushed, and then XRD and SEM-EDS tests were performed to determine that the prepared sample was a single phase. From the XRD data, it can be seen that there are two unknown diffraction peaks at 950°C. The SEM-EDS test results show that the elements are evenly distributed, indicating that the sample is a pure phase and is isomorphous with the AgSmMo2O8 material with a scheelite structure. Electrochemical impedance spectroscopy was used to study (La 0.2 Sm 0.2 Nd 0.2 G 0.2 Ca 0.2 )2Mo2O 8.8 The electrical properties and conductivity type of high entropy material oxygen ion conductor materials. The test results show that the conductivity of the material can reach 1.97×10 at 900°C in air atmosphere. -4 S / cm, and the conductivity in a humid argon atmosphere at the same temperature is 3.71×10 -4 S / cm, and the conductivity did not increase significantly, indicating that there was no proton conduction phenomenon; the stability of the samples was tested by sintering at 800°C in CO2 and humid Ar atmospheres for 48h and 96h respectively. From the XRD diffraction data, it can be seen that the material did not decompose, indicating that the high entropy material has good thermal and chemical stability.

2. The preparation method according to claim 1, characterized in that For La2Mo2O9 material, 20 mol% Sm is doped at the La position. 3+ 、Nd 3+ , Gd 3+ and Ca 2+ Preparation (La 0.2 Sm 0.2 Nd 0.2 G 0.2 Ca 0.2 )2Mo2O 8.8 The high entropy material forms a single stable scheelite structure phase, and the high entropy material has good electrical properties, thermal stability and chemical stability.

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