Fu Ming, Agrawal Dinesh, Fang Yi
Department of Electronic Science and Technology, Huazhong University of Science and Technology, China.
J Microw Power Electromagn Energy. 2007;40(3):133-9. doi: 10.1080/08327823.2005.11688534.
BaTiO3-based positive temperature coefficient (PTC) thermistors have been prepared by microwave sintering. The sintering process was carried out in a 2.45 GHz multimode microwave tube furnace without any susceptor The heating behavior of the PTC material, influence of processing conditions on microstructure, and electrical properties of the sintered samples were investigated. The sintering temperature range varied from 1275 degrees C to 1350 degrees C. The optimum density and microstructure were achieved between 1300 degrees C to 1325 degrees C. Samples were also microwave sintered at 1300 degrees C for various soaking times from 10 min to 90 min. It was found that soaking between 30 min to 60 min generated a uniform microstructure. Cooling rate varied from 7.5 degrees C/min to 2 degrees C/min. The study showed that the cooling rate has an influence on PTC effect but not on microstructure. Slower cooling rate is essential for achieving better PTC effect. Compared to conventional method, the microwave-processed samples exhibited higher density and better PTC effect. The relative density of microwave sample was 93.5%, compared to 90.2% of the conventional sample. The R25, alphaT, Beta, Tc and Rmax, of the microwave sintered samples are 17.6 2, 15.8, 6.7 x 10(5), 88.0 degrees C, and 11.5 M omega, respectively, compared to 12.1 omega, 14.6, 1.1 x 10(5), 88.1 degrees C, and 1.3 M omega, respectively, for the conventional sample.
基于钛酸钡的正温度系数（PTC）热敏电阻已通过微波烧结制备而成。烧结过程在一台2.45 GHz多模微波管式炉中进行，未使用任何基座。研究了PTC材料的加热行为、加工条件对微观结构的影响以及烧结样品的电学性能。烧结温度范围为1275摄氏度至1350摄氏度。在1300摄氏度至1325摄氏度之间可实现最佳密度和微观结构。样品还在1300摄氏度下进行微波烧结，保温时间从10分钟到90分钟不等。结果发现，保温30分钟至60分钟可产生均匀的微观结构。冷却速率从7.5摄氏度/分钟变化到2摄氏度/分钟。研究表明，冷却速率对PTC效应有影响，但对微观结构没有影响。较慢的冷却速率对于实现更好的PTC效应至关重要。与传统方法相比，微波处理的样品具有更高的密度和更好的PTC效应。微波样品的相对密度为93.5%，而传统样品为90.2%。微波烧结样品的R25、αT、β、Tc和Rmax分别为17.6Ω、15.8、6.7×10⁵、88.0摄氏度和11.5 MΩ，而传统样品的相应值分别为12.1Ω、14.6、1.1×10⁵、88.1摄氏度和1.3 MΩ。
