Preparation Of Titanium Oxide Ceramic Thermoelectic Material And Collaborative Optimization Of Electricand Thermal Transportation

As people pay more and more attention to environmental,energy and other issues,thermoelectric materials have gradually attracted the attention of a large number of researchers.Thermoelectric material is a new energy material that can realize the mutual conversion of heat and electric energy.It is mainly used in thermoelectric refrigeration,thermoelectric power generation and other fields.It has the advantages of green source output and no pollution,no noise at work,and can be used to solve waste heat collection,Waste heat power generation,reducing carbon emissions and other issues,has a wide range of application prospects in the market.Titanium oxides such as SrTiO₃ and TiO₂ have a high seebeck coefficient.Only by increasing the electrical conductivity and reducing the thermal conductivity,the overall thermoelectric performance of the material can be optimized.Common methods such as doping,recombination,production of oxygen vacancies,and low-dimensionalization have been proven to be effective and effective methods.The research idea of this thesis is to prepare low-density bulk materials through recombination and reducing atmosphere control,and the production of oxygen vacancies is the main strategy to increase the carrier concentration,increase the electrical conductivity,and reduce the thermal conductivity.The specific research content is as follows:By optimizing the formula and process conditions,the control of the electric heat transmission behavior of oxide thermoelectric materials is realized,the thermoelectric performance of oxide materials is improved,and the mechanism that affects the electric transportation performance of oxide materials is explored.The prepared samples were tested and evaluated for thermoelectric properties under the conditions of 323K-973K.Synthesize and prepare TiO_2-x ceramics sintered in an inert atmosphere.Through solid phase synthesis,the sintering temperature is adjusted to explore the effect of different sintering temperatures on the thermoelectric properties of TiO_2-x ceramics.As the sintering temperature of the sample increases,the electrical conductivity The rate gradually increases,the absolute value of Seebeck coefficient decreases,and the power factor increases.The ceramic sample sintered at 1723K has the highest power factor,which is 84μWm^-1K^-2 at973K.On the basis of the previous work,starch is used as a carbon source to enhance the reducing atmosphere,which greatly improves the thermoelectric performance of TiO_2-x.To explore the influence of different mixed starch concentration on TiO_2-x electrothermal transport performance,the mixing of starch significantly increases the electrical conductivity,and the electrical conductivity gradually increases with the increase of the mixing ratio,while greatly optimizing the electrical transport performance and increasing the power factor.On the other hand,it promotes the conversion of TiO₂ into heterogeneous non-stoichiometric TiO_2-x,reduces the thermal conductivity to 2.082 Wm^-1K^-1,and the final ZT value reaches0.14.On the basis of the work in the previous chapter,graphite is used as the carbon source to further improve the reducing atmosphere,and the influence of the graphite mixing ratio on the TiO_2-x electrothermal transport performance is explored.Compared with mixed starch,mixed graphite can further improve the electrical transport performance.At the test temperature of 973K,the power factor of the sample mixed with 3%graphite can reach400μWm^-1K^-2.However,during the sample preparation process,as the amount of mixed graphite increases,The thermal conductivity of electrons is also significantly increased,and the improvement of the thermal power figure of merit between the mixed graphite and the mixed starch in the preparation process of the two factors is not obvious compared with that of the mixed starch.In order to further improve the thermoelectric merit of the material,the method of preparing composite materials is adopted.By combining SrLa TiO₃ and TiO_2-x,although the power factor is reduced,at the same time the thermal conductivity is reduced more significantly.Combining the two aspects of thermoelectricity The figure of merit has been significantly improved.At the test temperature of 973K,when the composite ratio of TiO_2-x to SrLa TiO₃ is 9:1,the figure of merit is increased to 0.18.