填充铌酸锶钡陶瓷的热电性质研究
发布时间：2018-07-14 15:11
【摘要】：热电材料可以实现热能和电能直接转换,在半导体电致冷和温差发电领域有广阔应用前景。其性能由热电优值ZT值来衡量,高的ZT值要求材料具有低电阻率的同时具有高塞贝克系数和低热导率。铌酸锶钡具有特殊的钨青铜结构,本征热导率较低。可以在其未充满的A_2位填充元素,调控电学性能,进而优化热电性能。本论文的工作主要对铌酸锶钡材料进行碱金属元素、稀土金属元素填充,制备致密的Sr_(0.70)Ba_(0.30)M_xNb_2O_6陶瓷,研究不同烧结方法、不同填充元素、不同填充量等因素对材料热电性能的影响。本论文取得的主要结果如下:一、对铌酸锶钡材料填充碱金属元素:(A)采用固相反应法先空气烧结再还原退火制备填充Li的样品,填充量分别为x=0.01、0.03、0.05、0.08、0.10、0.15、0.20,制备得到单相致密的陶瓷。填充Li后,样品电阻率降低,Seebeck系数绝对值也随之降低。其中Sr_(0.70)Ba_(0.30)Li_(0.05)Nb_2O_6样品电阻率最低,在1073K温度时PF值达到486μW/K2m。但是填充Li后,样品的热导率略微升高,所以填充样品ZT值提升不大。(B)直接在还原性气体氛围下烧结制备填充Li的样品,PF值相对于先空气烧结再还原退火制备的样品偏低,热电性能没有得到优化。二、对铌酸锶钡材料填充稀土金属元素:(A)填充Yb后,样品电阻率降低,Sr_(0.70)Ba_(0.30)Yb_(0.10)Nb_2O_6样品的电阻率最低,其PF值达到426 μW/K2m;填充Yb后样品的热导率降低,晶格热导率相对于未填充样品也略低,填充量越大热导率越低,ZT值相对于未填充样品有所提高,Sr_(0.70)Ba_(0.30)Yb_(0.05)Nb_2O_6样品的ZT值在1073 K时达到0.21。(B)填充Y后,样品电阻率降低,并且填充量越大电阻率越低,Sr_(0.70)Ba_(0.30)Y_(0.10)Nb_2O_6 样品 PF 值达到 420μW/K2m,1073 K 时Sr_(0.70)Ba_(0.30)Y_(0.03)Nb_2O_6样品的ZT值达到0.21。(C)填充量相同的情况下,填充Yb、Y稀土元素的样品性能很相近。三、铌酸锶钡材料填充K元素:实验表明,在还原性气体氛围下预烧可以提升最大填充量。在还原性气体氛围下预烧、烧结所得填充K样品的电学性能优于空气烧结再还原退火制备的同填充量的样品。Sr_(0.70)Ba_(0.30)K_(0.10)Nb_2O_6样品PF值在1073 K时达到528 μW/K2m其ZT值达到0.23。本论文系统地研究了元素填充对铌酸锶钡材料热电性质的影响,结果表明A位填充碱金属元素或稀土金属元素后,材料的电阻率和Seebeck系数绝对值降低,功率因子获得提升。填充碱金属元素后,材料功率因子提升较大,PF值可超过500μW/K2m;而填充稀土金属后功率因子提升较低,最大值约为420μW/K2m。填充量较小时,材料的晶格热导率高于未填充样品,随着填充量增大,晶格热导率降低。填充碱金属元素样品的性能优于填充稀土金属元素样品的性能,最高ZT值达到0.23。
[Abstract]:Thermoelectric materials can realize the direct conversion of thermal energy and electric energy, and have a broad application prospect in semiconductor electric cooling and thermoelectric power generation. Its performance is measured by the excellent value of ZT. The high value of ZT requires the material to have low resistivity and high Seebeck coefficient and low thermal conductivity. Barium strontium niobate has a special tungsten bronze structure and low intrinsic thermal conductivity. It is possible to fill the elements at the unfilled As _ 2 position to regulate the electrical properties and thus optimize the thermoelectric properties. The main work of this paper is to prepare dense Sr0.70 Ba0.30 MxNb2O6 ceramics by alkali metal elements and rare earth metal elements filled with strontium barium niobate. The effects of different sintering methods, different filling elements and different filling amount on the thermoelectric properties of the materials are studied. The main results obtained in this paper are as follows: firstly, the basic metal elements are filled with strontium barium niobate: (A) is used to prepare Li filled samples by air sintering and annealing by solid state reaction method. When Li is filled, the resistivity of the sample decreases and the absolute value of Seebeck coefficient decreases. Sr _ (0.70) Ba_ (0.30) Li _ (0.05) NB _ 2O _ 6 samples have the lowest resistivity, and the PF value reaches 486 渭 W / K _ 2 m at 1073K. However, the thermal conductivity of the samples increased slightly after Li was filled, so the ZT value of the filled samples was not much increased. (B) the PF value of the samples sintered directly in the atmosphere of reductive gas was lower than that of the samples prepared by air sintering and then reductive annealing. The thermoelectric performance is not optimized. Second, the rare earth metal elements filled with strontium barium niobate: after Yb was filled with (A), the resistivity of the sample decreased, Sr0.70 Ba0.30 Yb0.10 NbStud2O6 sample had the lowest resistivity, its PF value reached 426 渭 W / K2m.The thermal conductivity of Yb filled sample decreased and the lattice thermal conductivity was slightly lower than that of unfilled sample. The larger the filling amount, the lower the thermal conductivity, the lower the ZT value compared with the unfilled sample, the higher the ZT value of Sr0.70Ba0.30Yb0.05Nb2O6 sample is at 1073 K. (B) after filling Y, the resistivity of the sample decreases. Furthermore, the resistivity of Sr0.70 Ba0.30 Y0.10 Nb2O6 sample is lower than that of Sr0.70 Ba0.30Y0.10 Nb2O6 sample PF value of 420 渭 W / K2mt1073K, the ZT value of Sr0.70 Ba0.30 Y0.03 Nb2O6 sample is 0.21. (C) the properties of the rare-earth element filled with YbCY are very similar. Third, the material of strontium barium niobate is filled with K element: the experiment shows that pre-sintering in the atmosphere of reductive gas can increase the maximum filling amount. The electrical properties of sintered K samples prepared by pre-sintering in reductive gas atmosphere are better than those of the same filling amount samples. Sr0.70 Ba0.30 K0.10 Nb2O6 samples prepared by air sintering and rereduction annealing. The PF value of the sample reached 528 渭 W / K2m ZT value at 1073 K. The effect of element filling on the thermoelectric properties of strontium barium niobate is systematically studied in this paper. The results show that the resistivity and Seebeck coefficient of the material decrease and the power factor increases after filling the alkali or rare earth metal elements at the A site. After filling alkali metal element, the power factor of the material can increase more than 500 渭 W / K _ 2 m, but the power factor of the rare earth metal increases lower, the maximum value is 420 渭 W / K _ 2 m. The lattice thermal conductivity of the material is higher than that of the unfilled sample when the filling amount is small, and the lattice thermal conductivity decreases with the increase of the filling amount. The properties of the samples filled with alkali elements are better than those of the samples filled with rare earth metals, and the highest ZT value is 0.23.
【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ174.1
本文编号：2122049
[Abstract]:Thermoelectric materials can realize the direct conversion of thermal energy and electric energy, and have a broad application prospect in semiconductor electric cooling and thermoelectric power generation. Its performance is measured by the excellent value of ZT. The high value of ZT requires the material to have low resistivity and high Seebeck coefficient and low thermal conductivity. Barium strontium niobate has a special tungsten bronze structure and low intrinsic thermal conductivity. It is possible to fill the elements at the unfilled As _ 2 position to regulate the electrical properties and thus optimize the thermoelectric properties. The main work of this paper is to prepare dense Sr0.70 Ba0.30 MxNb2O6 ceramics by alkali metal elements and rare earth metal elements filled with strontium barium niobate. The effects of different sintering methods, different filling elements and different filling amount on the thermoelectric properties of the materials are studied. The main results obtained in this paper are as follows: firstly, the basic metal elements are filled with strontium barium niobate: (A) is used to prepare Li filled samples by air sintering and annealing by solid state reaction method. When Li is filled, the resistivity of the sample decreases and the absolute value of Seebeck coefficient decreases. Sr _ (0.70) Ba_ (0.30) Li _ (0.05) NB _ 2O _ 6 samples have the lowest resistivity, and the PF value reaches 486 渭 W / K _ 2 m at 1073K. However, the thermal conductivity of the samples increased slightly after Li was filled, so the ZT value of the filled samples was not much increased. (B) the PF value of the samples sintered directly in the atmosphere of reductive gas was lower than that of the samples prepared by air sintering and then reductive annealing. The thermoelectric performance is not optimized. Second, the rare earth metal elements filled with strontium barium niobate: after Yb was filled with (A), the resistivity of the sample decreased, Sr0.70 Ba0.30 Yb0.10 NbStud2O6 sample had the lowest resistivity, its PF value reached 426 渭 W / K2m.The thermal conductivity of Yb filled sample decreased and the lattice thermal conductivity was slightly lower than that of unfilled sample. The larger the filling amount, the lower the thermal conductivity, the lower the ZT value compared with the unfilled sample, the higher the ZT value of Sr0.70Ba0.30Yb0.05Nb2O6 sample is at 1073 K. (B) after filling Y, the resistivity of the sample decreases. Furthermore, the resistivity of Sr0.70 Ba0.30 Y0.10 Nb2O6 sample is lower than that of Sr0.70 Ba0.30Y0.10 Nb2O6 sample PF value of 420 渭 W / K2mt1073K, the ZT value of Sr0.70 Ba0.30 Y0.03 Nb2O6 sample is 0.21. (C) the properties of the rare-earth element filled with YbCY are very similar. Third, the material of strontium barium niobate is filled with K element: the experiment shows that pre-sintering in the atmosphere of reductive gas can increase the maximum filling amount. The electrical properties of sintered K samples prepared by pre-sintering in reductive gas atmosphere are better than those of the same filling amount samples. Sr0.70 Ba0.30 K0.10 Nb2O6 samples prepared by air sintering and rereduction annealing. The PF value of the sample reached 528 渭 W / K2m ZT value at 1073 K. The effect of element filling on the thermoelectric properties of strontium barium niobate is systematically studied in this paper. The results show that the resistivity and Seebeck coefficient of the material decrease and the power factor increases after filling the alkali or rare earth metal elements at the A site. After filling alkali metal element, the power factor of the material can increase more than 500 渭 W / K _ 2 m, but the power factor of the rare earth metal increases lower, the maximum value is 420 渭 W / K _ 2 m. The lattice thermal conductivity of the material is higher than that of the unfilled sample when the filling amount is small, and the lattice thermal conductivity decreases with the increase of the filling amount. The properties of the samples filled with alkali elements are better than those of the samples filled with rare earth metals, and the highest ZT value is 0.23.
【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ174.1
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