Bismuth trioxide-tailored sintering temperature, microstructure and NTCR characteristics of MnCoFeO ceramics.

MnCoFeO ceramics with tailored sintering temperature, microstructure, and NTCR characteristics were prepared using BiO sintering additive by a solid-state reaction route. Densification and morphological characterization indicate that bismuth trioxide can play a critical role in the sintering process. The results reveal that the sintering temperature can be decreased significantly from 1200 °C to 1050 °C by using the appropriate content of BiO additive. The resistivity decreases first and then increases with increasing BiO content. The obtained value and ranges were 3647-3697 K, and 800-1075 Ω cm, respectively. Oxygen sorption theory can be used to illustrate the optimal thermal stability (Δ/ = 0.10%). Complex impedance analysis further elucidates that grain boundaries make a dominant contribution to the total resistance. The mechanisms of grain boundary conduction and relaxation behavior are systematically analyzed. These findings open up a window for the further advancement of NTC ceramics at lower sintering temperature.