微结构调控提高NTC材料热敏性能研究

Negative temperature coefficient (NTC) thermistors have been widely used for temperature measurement and control, temperature compensation, current surge suppression and infrared detecting bolometers, due to their high sensitivity to temperature change and low price. However, the crucial problems of NTC thermistor are low thermal constant (B) and low electrical stability. This proposal aims at developing a material with high B constant and electrical stability by controlling microstructure based on nickel manganese spinel materials.They are fabricated by improving two-step sintering approach. An innovation method for preparation of nano NTC thermistor material with high performance will be established based on investigating the effect of sintering process, microstructure, functional phase, grain and grain boundary effects on the electrical properties. Meanwhile， the relationship between microstructure and B constant, as well as cation/cation vacancy migration and aging will be illustrated. Finally, we will explore a new way to fabricate NTC thermistor with high thermal sensitivity and high electrical stability, and also provide theoretical base and scientific foundation for development of high performance NTC thermistor.

NTC热敏陶瓷因具有灵敏度高，造价低等优点，被广泛应用于温度测量与控制、温度补偿、抑制浪涌电流和红外探测等领域。针对目前NTC热敏材料的热敏材料常数（B值）较小，且老化率较大缺点，本项目拟以镍锰尖晶石系为研究对象，采用改进的两步烧结法制备纳米NTC热敏材料，通过微结构调控以实现大的B值和高的电学稳定性，研究烧结工艺、微观结构、功能相、晶粒及晶界效应等因素对NTC热敏材料的热敏性能影响规律，阐明纳米材料微观结构对B值影响、阳离子/阳离子空位迁移与老化关系的科学问题，建立一种制备高性能NTC热敏材料的方法。本项目为制备高灵敏度、高稳定的NTC热敏电阻提供了新的思路，为开发高性能的NTC热敏材料提供理论基础和科学依据。

负温度系数热敏电阻（NTC）作为温度传感器的一种，具有电阻随温度的升高而减小的特性。NTC热敏电阻作为温度检测、控制以及抑制浪涌电流的关键元件，在汽车、医疗、家用电器、航空航天等领域有着广泛的应用。针对目前NTC热敏材料的热敏材料常数（B值）较小，且其老化率较大缺点，本项目以镍锰尖晶石系为研究对象，先采用溶胶-凝胶法得到粒径小于50nm的粉体，并采用改进的两步烧结和等离子活化烧结（SPS）法制备纳米NTC热敏材料，研究了烧结工艺、微观结构、功能相、晶粒及晶界效应等因素对NTC热敏材料的热敏性能影响规律，得到了晶粒尺寸小于200nm、且致密度大于90%的NTC热敏电阻，其B值大于5000 K,且老化率低于2%；研究表明纳米级比微米级的热敏材料表现出更高的B值和更低的室温电阻率，主要原因是纳米级陶瓷晶粒尺寸小，晶界数量多使得的晶界势垒增大，进而提高了B值；同时，纳米陶瓷的晶粒和晶界均为近邻跳跃导电模型，电子跃迁易于发生且稳定，从而降低了电阻率。通过本项目的实施，建立一种制备高性能纳米NTC热敏材料的新方法，并阐明了纳米NTC热敏材料的导电机制，也为制备高灵敏度、高稳定的NTC热敏电阻提供了新的思路，为开发高性能的NTC热敏材料提供理论基础和科学依据。