Heat capacity and structural transition effect in polycrystalline kesterite

Abstract

As a crucial parameter in the determination of thermal conductivity, the heat capacity of Cu_2+xZn_1−xSnS₄ (CZTS) has been investigated and analyzed in detail from 2 to 773 K. The effects of the Cu–Zn stoichiometric ratio and phase transition have been quantified and correlated with entropy variation. We confirm that the compounds follow the Dulong–Petit approximation above the Debye temperature θ_D and solve literature discrepancies on CZTS. The in-depth low-temperature heat capacity analysis revealed an approximate image of the energy dependence of the phonon density of state in kesterite, which agrees with the results of first-principles calculations.