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Preparation, Thermoelectric Properties and Service Behavior of Barium and Indium Double-filled Skutterudite Based Thermoelectric Materials

Author: DongChunLei
Tutor: ZhaoWenYu
School: Wuhan University of Technology
Course: Composite materials science
Keywords: Skutterudite thermoelectric material nanocomposite microstructure thermoelectric properties service behavior
CLC: TN37
Type: Master's thesis
Year: 2009
Downloads: 128
Quote: 2
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Abstract


Skutterudite is one of the promising thermoelectric materials in the moderate and high temperature range.But many study of skutterudite is focusing on the methods to enhance its thermoelectric properties by filling atoms and lowering its dimensions at present.There is a short of deep and systemic study of its service behavior when the material is used in the moderate and high temperature range.In the present work,a series of n-type Ba0.3In0.2NixCo4-xSb12（x=0.0～0.1,Δx=0.02） filled skutterudite thermoelectric material and SiO2/Ba0.3In0.2Ni0.05Co3.95Sb12（ΔR=1,5,10,20和40 nm） nanocomposite were prepared with a combination methods of vacuum high-temperature melting and spark plasma sintering（SPS） technique and a combination methods of chemical coating method and SPS process respectively.The service behavior of them was investigated based on the systemic study of those microstructure and thermoelectric properties.The thermoelectric properties of Ba0.3In0.2NixCo4-xSb12 were studied,the results indicate that the electrical conductivity decreases and the absolute value of Seebeck coefficient increases while the thermal conductivity first decreases then increases with the increased content of Ni.The ZTmax of 1.14 is obtained for single-phase material of Ba0.3In0.2Ni0.05Co3.95Sb12 at 800 K.The thermoelectric properties of SiO2/ Ba0.3In0.2Ni0.05Co3.95Sb12 were studied,the results indicate that the electric conductivity and thermal conductivity decreases but the absolute value of Seebeck coefficient increases as the thickness of SiO2 coating layers increased.The ZT value of the nanocomposite with 1 nm thickness of nano SiO2 varies hardly.But the ZT value of 0.67 which is obtained for the nanocomposite with the nano SiO2 coating layer of 40 nm is 46.7 percent lower than the ZT value of 1.25 which is is obtained for Ba0.3In0.2Ni0.05Co3.95Sb12 at 800 K。The service behavior of Ba0.3In0.2Ni0.05Co3.95Sb12 indicates that Sb volatilizes slightly and Ba separates from the structure partly and enriches on the boundary of gains,more and more second phase ouccurs and enriches on the boundary of grains then it falls off or volatilizes from the boundary as increasing times of quenching and days of annealing.The electrical conductivity first decreases then increases and the absolute value of Seebeck coefficient increases while the thermal conductivity first decreases then increases as increasing times of quenching.The ZT value of 1.10 which is obtained for the material after 2000 quenching times is 0.09 lower than the ZT value of 1.19 which is is obtained before quenching at 800 K.The electrical conductivity first decreases then increases and decreases again and the absolute value of Seebeck coefficient increases while the thermal conductivity has to be investigated more as the increasing days of annealing.The ZT value of 1.11 which is obtained for the material after 40 annealing days is only 0.11 lower than the ZT value of 1.22 which is is obtained before annealing at 800 K.The service behavior of SiO2/Ba0.3In0.2Ni0.05Co3.95Sb12 nanocomposite with 3 nm thickness of nano SiO2 indicates that the coating of nano SiO2 can enthance the stability of Ba0.3In0.2Ni0.05Co3.95Sb12,there is no evident alteration of its microstructure and distribution of every element afer quenching and annealing。As increasing times of quenching and days of annealing,the electrical conductivity decreases and the absolute value of Seebeck coefficient increases.The thermal conductivity first increases then decreases and increases again after quenching.But it has to be investigated more as the increasing days of annealing.The ZT value of 1.01 which is obtained for the material after 2000 quenching times is only 0.07 lower than the ZT value of 1.08 which is obtained before quenching at 800 K.But the ZT value of 0.87 which is obtained for the material after 40 annealing days is 0.25 lower than the ZT value of 1.12 which is is obtained before annealing at 800 K.

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CLC: > Industrial Technology > Radio electronics, telecommunications technology > Semiconductor technology > Thermoelectric devices,thermistor
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