Experimental and computational study on the influence of cobalt substitution on the structural, impedance, electronic, magnetic, and optical properties of pseudobrookite-structured Fe2TiO5

Abstract

We report on how Co substitution of the Fe sites of pseudobrookite (Fe₂TiO₅) influences the crystal structure, high-temperature electric permittivity, impedance, electronic structure, magnetic, and optical properties via experimental and theoretical investigations. The pseudobrookite phase contains two types of octahedral sites, Fe atoms reside on type of the sites while Ti on the others and replacing Fe with Co can have a huge influence on one or more physical properties that can render the material more useful for solar energy applications. X-ray diffraction and high-temperature electric permittivity/impedance were the experimental tools used. A temperature range of 20–300 °C and a frequency range of 100 Hz to 1 MHz were used for studying various types of relaxation mechanism via impedance analysis, including grains, grain boundaries, and interfacial effects. To explore the electronic structure, magnetic, and optical properties from first principles, dispersion-corrected density functional theory (PBE-D2/U) was employed. The structure as well as the electric impedance properties are impacted slightly by the Co substitution of Fe in Fe₂TiO₅ whereas the electronic structure and magnetic properties are influenced significantly. The bandgap is reduced slightly and the average magnetic moment per Fe ion is reduced upon Co substitution of Fe in Fe₂TiO₅.