Improving the stability of Fe 0.8 Mn 1.54 Ni 0.66 O 4 NTC thermistor with nano-powders and N 2 annealing

Fe 0.8 Mn 1.54 Ni 0.66 O 4 nano-ceramics have been successfully prepared by sol-gel auto combustion. The microstructure and phase of these samples were observed by using SEM and XRD. The diameters of Fe 0.8 Mn 1.54 Ni 0.66 O 4 ceramic particles pre-fired at 800 °C range from 52 to 83 nm. The powder sintered at above 1050 °C has the compact and uniform spinel structure. We have investigated the electrical characteristics of these thermistors at different sintering temperatures and concluded that the sample sintered at 1200 °C is sufficient to form the appropriate spinel phase. Moreover, the thermistor annealed for 72 h at 450 ∼ 550 °C in N 2 atmosphere has the drift rate of