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.
Fig. 7. GGA + U calculated thermoelectric properties of the double perovskite Ca2ZrTiO6 as a function of temperature (a) ZT at CBM (left) and (b) ZT at VBM (right). The red, green and blue colors represent thermoelectrics properties under ambient, 5(%) tensile strain, and 5(%) compressive strain, respectively. [Display omitted]
•The thermoelectric properties of Ca2ZrTiO6 under 5% compression were improved at CBM, compared to thermoelectric properties under ambient conditions.•The novelty as: direct bandgap semiconductor and improved ZT for the possible applications of Ca2ZrTiO6 in electronic and thermoelectric devices.•t is found that the maximum value ZT of Ca2ZrTiO6 under normal conditions is 4.0, and under 5%-compression is 3.8 at 550 K in case of n-type thermoelectric performance.•To the best of our knowledge, no 3D material is predicted to have such a high value of ZT to date.