Accurate in situ measurements of thermoelectric transport properties at high pressure and high temperature

Regulating electron structure and electron-phonon coupling by means of pressure and temperature is an effective way to optimize thermoelectric properties. However, in situ testing of thermoelectric transport performance under pressure and temperature is hindered by technical constraints that obscure the intrinsic effects of pressure and temperature on thermoelectric properties. In the present study, a new reliable assembly was developed for testing the in situ thermoelectric transport performance of materials at high pressure and high temperature (HPHT). This reduces the influence of thermal effects on the test results and improves the success rate of in situ experiments at HPHT. The Seebeck coefficient and electrical resistivity of α-Cu2Se were measured under HPHT, and the former was found to increase with increasing pressure and temperature; for the latter, although an increase in the pressure acted to lower the electrical resistivity, an increase in the temperature acted to increase it. On increasing pressure from 0.8 to 3 GPa at 333 K, the optimal power factor of α-Cu2Se was increased by ∼76% from 2.36 × 10-4-4.15 × 10-4 W m-1 K-2, and the higher pressure meant that α-Cu2Se had its maximum power factor at lower temperature. The present work is particularly important for understanding the thermoelectric mechanism under HPHT.