Cation distribution investigation of the system Li0.5FexGa2.50-xO4 by X-rays, electrical conductivity and Mossbauer studies

Abstract

Structural, electrical and Mossbauer studies were carried out for the system Li0.5FexGa2.50-xO4. All the compounds with 0 ⩽ x⩽ 2.5 crystallised with cubic spinel structure. Lattice constant values calculated from XRD analysis were found to increase with increasing x. X-ray intensity calculations indicated that Li1+ occupies only the octahedral site and Ga3+ and Fe3+ ions occupy both octahedral and tetrahedral sites. Activation energy and thermoelectric coefficient values decreased with increasing values of x. All the compounds studied were p-type semiconductors and possess low mobility values of 10−7-10−9 cm2V−1 s−1. Mossbauer data show the presence of iron in the Fe3+ state and the isomer shift values for all the compositions of the system are within the range of high spin ferric compounds. The probable ionic configuration for the system is suggested as: $${\text{Ga}}_{{\text{1 - }}\alpha }^{{\text{3 + }}} {\text{Fe}}_\alpha ^{{\text{3 + }}} [Li_{0.5}^1 {\text{Fe}}_{{\text{x - }}\alpha }^{{\text{3 + }}} {\text{Ga}}_{{\text{2}}{\text{.5 - x + }}\alpha }^{\text{3}} ] {\text{O}}_{\text{4}}^{{\text{2 - }}} $$