Several spinel compositions, i.e. Mn1+x Cr2-x O-4 (x = 0.7, 0.5, 0), MnFe (x) Cr2-x O-4 (x = 0.1, 1), MgMnCrO4 and Mg1+x Cr2-x O-4 (x = 0, 0.1) were synthesised and studied in terms of phase analysis, density, stability in reducing atmosphere, electrical conductivity and thermal expansion behaviour. The spinel samples were single phase, with cell parameter values in a good correlation with cation sizes. Most of the studied spinels were found to be unstable under reducing conditions of thermal treatment, except MnCr2O4, MgCr2O4 and Mg1.1Cr1.9O4. Electrical properties have been investigated by impedance spectroscopy and DC conductivity measurements at temperatures between 200 and 900 A degrees C.