Study of the enhanced electronic and thermoelectric (TE) properties of ZrxHf1-x-yTayNiSn: a first principles study

A density functional theory (DFT) approach employing generalized gradient approximation (GGA) and the modified Becke Johnson (TB-mBJ) potential has been used to study the electronic and thermoelectric (TE) properties of ZrxHf1-x-yTayNiSn. The presence of an indirect band gap at E-F in the parent compound predicts this material to be a small band gap insulator. The substitution of Ta atoms at the Hf site increases the density of states (DOS) at E-F which facilitates charge carrier mobility. The influence of Ta content increases the Seebeck coefficient and electrical conductivity, and suppresses the thermal conductivity; as a result the figure of merit ZT is enhanced. We report an increment in ZT value of 36% over the undoped system. The theoretical data were compared with the experimental results.