In order to obtain the NTC thermistors with small B constant (about 1900 K), applied to wide temperature range, Mn0.43Ni0.9CuFe0.67O4 NTC thermistor materials prepared by Pechini method were microwave-calcined at different temperatures (650°C, 750°C and 850°C). The calcined Mn0.43Ni0.9CuFe0.67O4 powders were pressed and then sintered at 1000°C in a microwave furnace (multimode cavity, 2.45 GHz). The crystal structure, phase compositions, morphology and particle size distribution of the samples were analyzed by FT-IR, X-ray diffraction (XRD), scanning electron microscope (SEM) and a laser particle size analyzer. The experimental results show that the electrical properties of the ceramics are strongly dependent on the calcination and sintering process. The application of microwave leads to a lower calcination temperature (650°C) and densified uniform microstructures. Microwave sintering can obtain the components with well uniformity of B constant and resistivity, of which the Bavg. is 1930 K (deviation of 0.31%) and resistivity ρavg. is 135 Ω·cm (deviation of 4.55%). However, the Bavg. is 1720 K (deviation of 1.47%) and resistivity ρavg. is 78 Ω·cm (deviation of 25.34%) for the conventionally sintered components. From complex impedance analysis, the grain resistance (Rb) and grain boundary resistance (Rgb) are respectively 255 Ω and 305 Ω for the microwave-sintered samples. The Rb and Rgb are respectively 200 Ω and 230 Ω for conventionally sintered samples.
