Predicted double perovskite material Ca2ZrTiO6 with enhanced n-type thermoelectric performance

Abstract

Herein, using first-principles calculations, we studied the electronic and thermoelectric properties of isolated perovskites CaTiO3, CaZrO3 and double perovskite Ca2ZrTiO6 crystal structure under ambient conditions, biaxial compression, and biaxial tensile strain. We used generalized gradient approximation and the Hubbard parameter (GGA ​+ ​U) to calculate exchange and correlation interactions. The isolated perovskite CaTiO3 and CaZrO3 are indirect bandgap (Γ ​− ​R) semiconductors of values 1.90 ​eV, 3.2 ​eV, respectively. The construction of a double perovskite Ca2ZrTiO6 results in a direct (Γ ​− ​Γ) bandgap semiconductor material. The bandgap values under 2% & 5% biaxial tensile strain and compressive strain are in the range of 2.3 ​eV and 2.2 ​eV. We studied the thermoelectric properties by taking the two chemical potential values (μ) equal to CBM and VBM, respectively. The thermoelectric properties of Ca2ZrTiO6 under 2% & 5% biaxial tensile strain were improved at CBM, while thermoelectric properties under 2% & 5% biaxial compression strain were enhanced at VBM as compared to thermoelectric properties under ambient conditions. At CBM, the maximum value of the figure of merit (ZT) is about 4.4 ​at 500 ​K, required for the next generation of the thermoelectric device. The ZT value shows that the novel double perovskite is a very suitable candidate for thermoelectric devices.