al2o3掺杂cacetiwo系高温ntc热敏材料分析word格式论文.docxVIP

优秀毕业论文 精品参考文献资料 ABSTRACT With the growing popularity of the vehicle exhaust catalytic converters in recent years, high temperature thermistors are becoming increasingly important. Negative temperature coefficient thermistors (NTCR) are widely used, because they afford the best sensitivity and accuracy at the lowest price. NTC materials that have been put into use are mostly spinel structure formed by solid solutions of transition metal oxides, such as Mn3O4, Co3O4 and NiO, but this type of NTC thermistors is usually applicable for temperature measurement below 300°C. Scheelite structure NTC materials are found to be expected for high temperature thermometry recently. Therefore, this paper studied the NTC characteristics in Ca-Ce-Ti-W-O system at high temperature carefully, and got stable NTC ceramic materials. CaWO4-CeTi2O6 ceramics were prepared by high temperature solid state method, the effect of the CeTi2O6 content on the phase composition, microstructure, electrical properties and high temperature stability was systemically investigated. The samples showed good NTC characteristics over 25－800°C after sintering at 1300°C and the main crystalline phase was scheelite CaWO4 phase. With an increase in CeTi2O6 content the average grain size increased, however the resistivity and aging coefficient decreased. The existence of electron hopping between Ce3+/Ce4+, which caused the materials to exhibit semiconducting behavior, has been confirmed by XPS analysis. The effect of the high resistance phase Al2O3 on the phase composition, microstructure, electrical properties and high temperature stability for CaCe0.5TiWO10 ceramics was systemically studied for the first time. All the samples sintered over 1300－1360°C have NTC characteristics. At the same sintering temperature, the resistivity increased with an increase in Al2O3 content, whereas the aging coefficient decreased. The aging coefficient of these samples which have same Al2O3 content decreased to minimal