Barium titanate materials displaying a positive temperature coefficient of resistivity are ubiquitously employed as thermistors in electrical current and voltage control systems, as well as in gas and thermal sensing applications. The positive temperature coefficient of resistivity effect is widely accepted to be a grain boundary-based phenomenon, although detailed studies on grain boundary structure and chemistry, and their influence on the resulting electrical properties, are seriously lacking. Tailoring of the positive temperature coefficient of resistivity electrical characteristics, for specific high-value applications, will require improved understanding and control over grain boundary phenomenon. A comprehensive overview of the development of barium titanate-based positive temperature coefficient of resistivity ceramics is initially presented. We then advance to a discussion on emerging grain boundary characterization techniques, specifically, a stereographic analysis of electron backscatter diffraction data that could assist in enhancing control over BaTiO₃ defect chemistry and microstructure, through characterization and subsequent manipulation of the population of grain boundary types. These techniques have great potential for increasing the understanding of the delicate interplay between processing conditions, chemistry, microstructure, and functional electrical properties, and are relevant to the development of advanced, high-performance ceramics and electroceramics in general. Contemporary advancements in the field, such as lead-free positive temperature coefficient of resistivity effect materials and multilayer miniaturized systems based on hypostoichiometric barium compositions, are reviewed. Finally, perspectives on future lines of thermistor research, with a focus on the energy sector, are presented including applications in gas separation and chemical sensing.

中文翻译：

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基于钛酸钡的热敏电阻：过去的成就、最先进的技术和未来的前景

显示正电阻温度系数的钛酸钡材料普遍用作电流和电压控制系统以及气体和热传感应用中的热敏电阻。电阻率效应的正温度系数被广泛接受为基于晶界的现象，尽管严重缺乏对晶界结构和化学及其对所得电性能的影响的详细研究。为特定的高价值应用定制电阻率电特性的正温度系数，需要更好地理解和控制晶界现象。初步介绍了钛酸钡基电阻陶瓷正温度系数的发展概况。然后我们继续讨论新兴的晶界表征技术，特别是电子背散射衍射数据的立体分析，可以帮助增强对 BaTiO 的控制₃缺陷化学和微观结构，通过晶界类型的表征和随后的操作。这些技术在增进对加工条件、化学、微观结构和功能电学特性之间微妙相互作用的理解方面具有巨大潜力，并且与先进的高性能陶瓷和电陶瓷的开发有关。回顾了该领域的当代进步，例如电阻率效应材料的无铅正温度系数和基于亚化学计量钡成分的多层小型化系统。最后，提出了对未来热敏电阻研究路线的展望，重点是能源领域，包括在气体分离和化学传感方面的应用。