Thermoelectric Performance of p-Type Mg2Si0.25Sn0.75 with Li and Ag Double Doping

The single-phase of p-type Mg2Si0.25Sn0.75 with Li and Ag double doping were prepared by the liquid-solid reaction and hot-pressing methods. All samples thus obtained were identified by XRD as single-phase solid solutions with an anti-fluorite structure. The effects of Li and Ag double doping on thermoelectric performance were investigated at temperature differences (Delta T) of 0 to 500 K. The thermoelectromotive force (E) of the Li-25000 ppm single-doped sample was determined to be 88 mV at Delta T = 500 K. For the Li-20000 ppm and Ag-5000 ppm double-doped sample, the E value became larger (92 mV) after Ag substitution. A maximum E value of 97 mV was obtained for the Ag-25000 ppm single-doped sample and the Li-5000 ppm and Ag-20000 ppm double-doped sample. Mean resistivity (r(m)) at Delta T = 500 K decreased by double doping and showed a minimum value of 2.94 x 10(-5) Omega m for the Li-5000 ppm and Ag-20000 ppm double-doped sample. The maximum effective power (P = E-2/4r(m)) increased with Delta T. The P values of single-doped samples at Delta T = 500 K were 38 Wm(-1) for Li single-doped and 72 Wm(-1) for Ag single-doped samples. P for the Li-20000 ppm and Ag-5000 ppm double-doped sample was 64 Wm(-1) which was an improvement of about 90% compared with the Li single-doped sample. The maximum value of P at Delta T = 500 K was 80 Wm(-1) for the Li-5000 ppm and Ag-20000 ppm double-doped sample. which was an improvement of about 10% compared with the Ag single-doped sample. [doi: 10.2320/matertrans.MH200906]