Metallic conductivity of the oxides of La-Ni-O system

Abstract We have investigated the effect of doping on the electric conductivity of oxides in the systems La3Ni2(1-x)M2x O7 and La4Ni3(1-x)M3x O10, with M = Mo or W, and also in La3(1-x)M'3x Ni2O7 and La4(1-x)M4x Ni3O10 with M' = Sr or Ba. The temperature of the cross-over from semiconductive to metallic conductivity was increased in the case of Mo or W doping, while Sr or Ba had the opposite effect. A similar influence was exercised by heat treatment in reducing or oxidizing treatments, respectively.