Effects of Cu and Zn co-doping on the electrical properties of Ni0.5Mn2.5O4 NTC ceramics

The effects of Cu and Zn co-doping on Ni–Mn–O spinel-structured NTC ceramics were investigated. Dense Cu and Zn co-doped Ni0.5Mn2.5O4 spinel-structured ceramics were prepared from mixed oxalate-derived powders. XPS analysis revealed that in the co-doped material CuxZn1.0Ni0.5Mn1.5−xO4, the majority of Cu ions resided at the B-sites due to the almost exclusive occupation of Zn ions at the A-sites, but in the material doped with Cu alone, Cu ions were situated at both A- and B-sites. The co-doped material exhibited a significant decrease in electrical resistivity without much decrease in the thermal constant. In comparison with the material doped with Cu alone, the co-doped material also showed much improved electrical stability upon annealing at 150 °C in air, which is attributed to its stable distribution of cations in the spinel.