Preparation and Microwave Sinterability of Mn0.43Ni0.9CuFe0.67O4 NTC Thermistor Materials by Pechini Method

In order to obtain the NTC thermistors with small B constant (about 1900K), applied to wide temperature range, Mn0.43Ni0.9CuFe0.67O4 NTC thermistor materials prepared by Pechini method were microwave-calcined at different temperatures (650 750 nd 850 The calcined Mn0.43Ni0.9CuFe0.67O4 powders were pressed and then sintered at 1000 n a microwave furnace (multimode cavity, 2.45GHz).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 and densified uniform microstructures. Microwave sintering can obtain the components with well uniformity of B constant and resistivity, of which the Bavg. is 1930K (deviation of 0.31%) and resistivity | SUB>avg. is 135| ¤cm (deviation of 4.55%). However, the Bavg. is 1720K (deviation of 1.47%) and resistivity |Сvg. is 78| ¤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| and 305| for the microwavea2sintered samples. The Rb and Rgb are respectively 200| and 230| for conventionally sintered samples.