Structural, electronic, optical and thermoelectric properties in the phases of AgTaO3

Abstract Structural phases of silver tantalate (AgTaO3) such as rhombohedral (R3c), monoclinic (P2/m), orthorhombic (Cmcm), tetragonal (P4/mbm) and cubic (Pm-3m) have been investigated using density functional theory (DFT) to verify the previous work. Structural parameters of all these phases are in agreement with the experimental results. Formation enthalpies and cohesive energies of these phases reveal that the monoclinic phase is more stable than the rhombohedral phase. On the basis of electronic properties; direct and indirect band gap transitions are identified as follows, R3c, P2/m and Pm-3m have indirect band gaps (3.086 eV, 2.970 eV and 2.921 eV) whereas Cmcm and P4/mbm have direct band gaps (2.180 eV, 2.762 eV). In view of optical properties AgTaO3, in all phases, is found promising for optoelectronic devices in the visible region. The present compound showed a high dielectric constant in orthorhombic phase. Thermoelectric properties such as Seebeck coefficient 2955 μV/K, electrical conductivity 3.84 × 1020 1/Ωm.s and power factor 1.17 × 1012 W/K2ms showed that AgTaO3 is a potential candidate for thermoelectric devices because of low electrical conductivity and high power factor.