High-temperature And High-pressure Synthesis And Properties Of Strontium Titanate Thermoelectric Materials

Thermoelectric conversion technology is currently a new type of technology that researchers are paying more attention to.In order to reduce dependence on fossil fuels,reduce environmental pollution and prevent global warming and other key issues,it is necessary to find suitable new functional materials.Thermoelectric materials have been applied in many scenarios due to their environmental friendliness and pollution-free properties.In order to obtain performance that can be applied to actual thermoelectric materials,researchers have tried techniques such as structural modification and doping to improve the performance of thermoelectric materials.With the deepening of research,materials with excellent properties such as bismuth telluride and lead telluride have entered people's field of vision.However,their service temperature is limited to medium and low temperature.Considering the practical application,it is necessary to explore and study suitable materials in the high temperature zone.SrTiO3 is an oxygen-containing compound,which has broad prospects for application in high-temperature environments,and its low cost is suitable for large-scale use,and it is worthy of in-depth research by researchers.The synthesis and performance optimization of materials are the main issues in the research.The high temperature and high pressure method can provide temperature and synthesis pressure at the same time,and adjust the performance of synthetic materials from two dimensions.From the perspective of sample synthesis,the high temperature and high pressure method not only provides the synthesis temperature,but also the synthesis pressure.From the energy point of view,it can reduce the difficulty of material synthesis.In terms of material properties,the material can be coordinated and optimized by adjusting the temperature or pressure.In this thesis,the synthesis of strontium titanate materials and the effect of different pressures on the properties of non-stoichiometric strontium titanate thermoelectric materials synthesized under different pressures were studied by solid-phase reaction method and high-temperature and high-pressure synthesis methods.The details are as follows:1.SrTiO₃ materials were prepared by solid-phase reaction using high temperature and high pressure method,and strontium titanate blocks were prepared by sintering at the same temperature and different pressure conditions.The test results show that the SrTiO3 samples synthesized in the synthesis pressure range of 3.0 GPa?5.0 GPa have obvious differences in grain size under different synthesis pressure conditions,and the pressure has a certain influence on the microstructure of the material.Due to the nature of the SrTiO3 material,the synthesized sample has poor electrical properties at room temperature.2.SrTiO_2.8 was synthesized by solid-phase reaction using high temperature and high pressure method.SrTiO2.8 samples were prepared by adding a certain proportion ofTipowder into the synthesis raw materials,and the non-stoichiometric ratio of titanic acid synthesized under different synthesis pressures was prepared.Strontium was studied.The SrTiO2.8 sample synthesized under high temperature and high pressure has an effect on the crystal grain size and synthesis pressure through scanning electron microscopy.At the same time,the test results of transmission electron microscopy show that the sample synthesized under high pressure has changed from a microscopic point of view.These changes from the microscopic morphology The change in angle helps to reduce the lattice thermal conductivity of the SrTiO2.8 sample,and it is found through UV spectroscopy that high voltage can reduce the band gap of the sample,which helps to reduce its electrical conductivity.Through the selection and optimization of experimental conditions,the maximum zT value of the material was finally obtained at 0.20.