Effect of Phase Transition on the Thermoelectric Properties of Ag₂Te

Abstract

Ag₂Te is well-known as a silver ion conductor. In this compound, a phase transition occurs at around 420 K and silver ions jump to interstitial sites repeatedly at the point of starting the phase transition. We consider that the active movement of silver ions would have influence on the scatterings of both charge carriers and heat carrying phonons in Ag₂Te. In order to evaluate the effect of the silver ion conduction on the thermoelectric properties of Ag₂Te, the Seebeck coefficient, electrical resistivity, thermal conductivity and Hall coefficient of polycrystalline bulk samples of Ag₂Te were examined in the temperature range from room temperature to 650 K. The electrical resistivity and the Seebeck coefficient dramatically changed at around 420 K due to the change of the carrier concentration before and after the phase transition. However, the carrier mobility and the lattice thermal conductivity showed no remarkable change at around the phase transition temperature. These results imply that the thermoelectric transport properties of Ag₂Te were affected by the change of the crystal structure rather than the presence or absence of the movement of silver ions.