X-ray, electrical conductivity, and infrared studies of oxide spinels containing cobalt, titanium and manganese

Abstract

X-ray, electrical conductivity and infrared studies of the system Co_2−x Ti_1−x Mn_2x O₄ were carried out with a view to investigate the cation distribution. Compounds 0 ⩽ x ⩽ 0.6 showed cubic symmetry, compounds 0.8 ⩽ x ⩽ 1 are tetragonal. X-ray intensity calculation indicated the presence Of Co²⁺ and Mn³⁺ at both octahedral and tetrahedral sites. A plot of activation energy against composition shows a break where crystal symmetry changes. The electrical conductivity-temperature behaviour obeys the Raschhinrichsen law. The mobility of holes calculated from infrared and conductivity data is of the order Of 10⁻⁹ cm² V⁻¹ sec⁻¹. X-ray intensity calculations and conductivity measurements suggest the ionic configuration of the system to be Co ²⁺_1−x Mn ³⁺ _x [Co ²⁺_2−2x Mn ³⁺ _x Ti ⁴⁺ _x ]O ²⁻₄ .