Semi-solid preparation and performance of magnesium based thermoelectric materials

摘要

Ternary Mg-based thermoelectric materials are prepared by Semi-Solid Processing (SSP) and Spark Plasma Sintering (SPS). DTA, XRD and SEM analysis are applied to explore the processing conditions of Mg_2Si_(1-x)Sn_x(x=0, 0.2, 0.4, 0.6, 0.8, 1). The results show that raw-materials should be put into the furnace at 773 K, and kept 60 min in 1123 K. Then stirring 5 min under semi-solid state and air cooled finally. At temperature of 1023 K, pressure of 30 MPa, the sample is sintered by SPS. The XRD shows that the peaks of sample are sharp and complete, and move left with increasing Sn. The thermoelectric properties of Mg_2Si_(1-x)Sn_x(x=0.4, 0.6) are analyzed between 373 K to 673 K. Results indicate that electrical conductivity (σ) increases continually, Seebeck coefficient (α) increases then decreases, and thermal conduction (κ) decreases and increases with increasing temperature. Except that, electrical conductivity and Seebeck of Mg_2Si_(0.6)Sn_(0.4) are better than Mg_2Si_(0.4)Sn_(0.6) made by the same method. The properties of Mg)2Si_(0.4)Sn_(0.6) sintered at 1023 K, is better than the one at 973 K. The maximum zT of Mg_2Si_(0.4)Sn_(0.6) is 0.086 at 573 K.