Impact of impurities and time on thermoelectric performance of MgAgSb

Abstract

In this work the thermoelectric performance of MgAgSb was improved by enhancing electrical conductivity, Seebeck coefficient and reducing thermal conductivity simultaneously. We synthesized MgAgSb at various sintering temperatures and researched its thermoelectric properties in detail. The effect of impurities associated with MgAgSb on the thermoelectric properties shows that their presence can deteriorate the performance. The resultant samples were tested after 2, 3 and 8 months from its preparation for thermoelectric performance and a significant enhancement in thermoelectric properties are observed. The resultant power factor improved from 8.5 μWcm-1K-2to 15.8 μWcm-1K-2 and the thermal conductivity is reduced from 1.12 Wm-1K-1 to 0.86Wm-1K-1 and we find an improved ZT~0.91. The internal mechanism for the reducing thermal conductivity is presented which plays an important role in improving ZT value of MgAgSb.Furthermore, we discussed that the strength of the chemical bonding among the atoms may also be reduced with the passage of time in thermoelectric materials and resulting in decrease in localized frequency of vibration, which has an ultimate effect in reducing the thermal conductivity of the material.