Low lattice thermal conductivity suppressed by Sr-deficiency in Sr0.9Ca0.1Si2

We present a study of the temperature-dependent electrical resistivity, Seebeck coefficient, and thermal conductivity in Sr0.9-δCa0.1Si2 alloys to shed light on Sr-deficient effect on the thermoelectric performance, as characterized by the dimensionless thermoelectric figure-of-merit, ZT. It is found that the thermal conductivity is considerably reduced upon introducing Sr deficiency in Sr0.9Ca0.1Si2. In particular, a marked low lattice thermal conductivity of about 1.1 W/m-K at room temperature is achieved for Sr0.77Ca0.1Si2. Such a promising result leads to a relatively high ZT of 0.27 at room temperature for this material. Furthermore, with the extrapolation of thermoelectric parameters to high temperatures, a possible maximum ZT of about 0.52 at 850 K can be realistically estimated for Sr0.77Ca0.1Si2.