Valence‐induced effects on the electrical properties of NiMn ₂ O ₄ ceramics with different Ni sources

Spinel-structured NiMn2O4 ceramics, with different valence Ni sources, were originally prepared using Ni2O3 and NiO as raw materials, the effects of sources on their electrical properties first investigated. XRD patterns show that both Ni2O3-based NiO-based ceramics are single cubic spinel structures. SEM/EDS images indicate exhibited high density at experiment-determined sintering temperatures. XPS results Raman drifts prove valence-induced changes in Mn ions B sites played a significant role thermal stability ceramics. Compared NiMn2O4, resistivity 25°C (ρ25°C) increased dramatically from 3109 to 106958 Ω cm, constant (B25/50) 3264 4473 K, resistance shifts after annealing for 1000 h 150°C decreased 0.80% 0.74%. The investigation relationship between material has provided new effective way designing spinel-structured negative temperature coefficient (NTC) materials by modulating A materials.