Study of temperature dependence electrical properties and conduction mechanisms of Co and Ti co-doped hematite (α-Fe2O3) system

The practical limitation of using rhombohedral-structured hematite (α-Fe₂O₃) system in semiconductor industry is its poor electrical conductivity (~ 10^–11 S/m). On the other hand, hematite is a potential candidate for solar cell and hydrogen storage applications. This stimulates a worldwide interest for enhancing electrical conductivity in hematite based materials. The co-doping of divalent Co and tetravalent Ti ions in the hematite structure has remarkably enhanced electrical conductivity up to the order of 10^–2 S/m and promised a wide scope of electronic applications of the materials. The variation of co-doping content (x) and heat treatment environment under air and vacuum played a crucial role for enhancement of electrical conductivity. The material of composition α-Fe_2−xTi_x/2Co_x/2O₃ with x = 0.2, 0.4 and 0.6 has been stabilized in rhombohedral phase by mechanical alloying and post heat treatment at 1000 °C. The current–voltage characteristics of the samples have been measured in the temperature range of 313–723 K. This work has studied the mechanisms of temperature- and applied voltage- dependent electrical properties in Co and Ti co-doped α-Fe₂O₃ system. The experimental results of tuning electrical conductivity and electro-resistance can be useful for applications of hematite based metal oxides in modern spintronic devices, gas sensors, memory devices and thermoelectric devices.