The Study Of Ce-Mn-Si-O System High Temperature NTC Materials

High temperature sensors are needed in automobile exhaust temperature control, petroleum and geological drilling and other fields. Negative temperature coefficient thermistor(NTC) are widely used, because of its high sensitivity, high accuracy and low cost. Spinel structure NTC usually applicable for temperature below 300°C because of its ion rearrangement seriously at high temperature. CeO2 is stable work at high temperature with itshigh enthalpy factor, but the resistivity at room temperature is too high, with the temperature change too fast, We get Ce-Mn-Si-O system high temperature NTC thermistor when added MnO2 and SiO2, the research of Ce-Mn-Si-O system high temperature NTC has broad application prospects and far-reaching significance.This paper studied the high temperature NTC characteristics of Ce-Mn-Si-O system by solid state method, we get good NTC characteristics and stable material at high temperature over 25~600°C. The electrical properties and electrical parameters of the materials were studied by changing the system components. To get more wide range use NTC materials and improve the stability of the material in this system, the effect of compound Al2O3, MgO and ZnO on electrical properties and high temperature stability for Ce-Mn-Si-O ceramics was systemically studied. The valence of Mn and Ce elements were detected by XPS analysis, which to coform the valence results of manganese oxides, try to explain the mechanism of what caused the materials to exhibit semiconducting behavior through the XPS result of Ce elements.The main phase of Ce0.84Mn0.7Si0.3O3.68 and 0.8Ce0.64Mn0.8Si0.2O3.28-0.2Al2O3 was fluorite structure CeO2, others includes small number of manganese oxides phase doped, with Si content increases, the SiO2 phase can be detected. The average grain size increased with an increase in Si content, the resistivity and aging coefficient can be adjusted by the content of Si. The resistivity and characteristic parameter increased with enhance of Ce content. The aging factor minimized as the Ce content increased which has high enthalpy factor. At the same sintering temperature, the resistivity increased with an increase in Al2O3, MgO and ZnO content, the characteristic parameter of the thermistor can be controlled by the content of compoudd materials, When the oxide compound amount more than 20%, the characteristic parameter B value is obviously improved.The high temperature stability of these samples was significantly improved by compound with Al2O3, ZnO materials.