Structural, electronic, magnetic and thermoelectric properties of pseudobrookite-type Fe2-xTi1+xO5 (x = 0, 0.5 and 1) compounds: DFT + U approaches

Abstract

The wide band-gap of iron titanium oxide Fe2TiO5 (Pseudobrookite) is very well known as potential thermoelectric compounds for its great Seebeck coefficient. In this article, the thermoelectric, magnetic, electronic, and structural properties of ferrous pseudobrookite Fe2-xTi1+xO5 (x = 0, 0.5, and 1.0) compounds were calculated by first principle calculations. The electronic structures were computed using the plane-wave pseudopotential method within the GGA-PBE approximation considering the Hubbard-U exchange-correlation. The considered electronic structure in the GGA + U scheme displays that two alloys are semiconductors with an indirect energy gap of 1.75 and 0.61 eV, respectively, for Fe2TiO5, and Fe1·5Ti1·5O5 and metallic for FeTi2O5 compounds. The thermoelectric properties were estimated using the semi-classical Boltzmann theory and the rigid band method in the temperature range of 50–800 K. The carrier concentration (n,p), electrical conductivity (σ), Seebeck coefficient (S), electronic thermal conductivity (κ) and the electric figure of merit (ZT) as a function of temperature were obtained for Fe2-xTi1+xO5 (x = 0, 0.5, and 1.0) compounds. Also, the thermoelectric properties versus chemical potential were studied at three constant temperatures. The Seebeck coefficient decreased with increasing temperature. The peak value of S is 1913 μVK−1, 1217 μVK−1, and 616 μVK−1 for Fe2TiO5, Fe1·5Ti1·5O5, and FeTi2O5, respectively. By increasing the chemical potential and moving it to the conduction electrons, the thermal conductivity increased. The results show that n-type Fe2TiO5 and p-type Fe1·5Ti1·5O5 at 300 K can reach the ZT values of 1.21 and 0.98, respectively. These results detected that n-type Fe2TiO5 compounds are potential thermoelectric material at room temperature.