| compound is a promising new thermoelectric material for its high performance at temperature field from 400 K to 700 K. In4Se3 compound was synthesizd by many pursuers using various methods such as melting, solid-state reaction, Bridgman crystal, ball milling etc. Generally, these methods demand large duration of heat process or complicated instruments. Therefore, looking for a simple synthesis route will be of great important, which just needs cheap raw materials, simple equipments and easy controllable process.In this paper, we explored a synthesis process of In4Se3 powders by sonochemical method, and acquired dense bulk materials by Spark Plasma Sintering (SPS). The impacts of synthesis process of powders, SPS process of bulk materials and samples doping on the phase, microstructure and thermoelectric properties were systematically studied. The following results have been obtained in this thesis:(1)Preparation of single phased In4Se3 thermoelectric powders by Sonochemical method conbining heat treatment process was feasible. The optimum Sonochemical reaction conditions were:hydrazine hydrate (N2H4.H2O) as reducing agent, deionized water as solvent,3 h sonochemical reaction at temperature of 50℃. Acquired precursors were rods Se and small grains In(OH)3. The length of rods was 200 nm to 1 u m and diameter was about 100 nm. The size of samall grains was 10-50 nm. The optimum heat treatment conditions were:1 h heat treatment at 450℃at atmosphere of H2. In4Se3 powders acquired were grains of average 200 nm large. The grains were uniform and some grains reunited.(2)A high density of In4Se3 bulk material could be acquired by SPS technology. The following were the optimized SPS process conditions:470℃as sintering temperature,5 min as sintering time,30 MPa as sintering pressure and 10 Pa as the largest vacuum. Sintering temperature had a significant impact on thermoelectric transport properties of the samples. As it increased, electricity conductivity rised and Seebeck coefficient showed a downward trend. Power factor of the sample did not change significantly. Due to thermal conductivity increased with increasing sintering temperature, thermoelectric transport properties decreased. By using the optimal sintering temperature, sintering time has little effect on the thermoelectric properties. The largest ZT value reached 0.55 at 700 K at the optimum SPS process conditions.(3)The influences of Sn doping in In-bit on bulk phase composition, microstructure and thermoelectric properties were investigated. XRD tests showed that all the doped samples were good single-phase, and Sn has replaced In into the crystal lattice. All samples showed n-type conduction characteristics. With Sn content increasing, the conductivity increased monotonically, while the Seebeck coefficient first increased and then decreased slightly. Because electrical conductivity increased significantly, electrical transport properties of the Sn doping samples effectively optimized. With increasing Sn content, the thermal conducticity decreased first and then increased. ZT values of all samples increased as the temperature increasing monotonically. With the increasing of Sn amount, ZT values increased first and then decreased. When x= 0.02, ZT value of the sample In3.9gSn0.02Se3 (the actual composition was In3.988Sn0.012Se2.472) approached 0.64 at 700 K. Compared to undoped samples and similar composition sample prepared by solid-state reaction, ZT value increased nearly 20% and 60%.
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