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本文涉及的材料,是用于制造突变型正温度系数热敏电阻器的掺杂半导体钛酸钡陶瓷。在铁电居里温度以上,这种材料的电阻率急剧地跃升,且在一定温度区域内具有相当大的正温度系数(PTC)。这种材料的电阻率-温度特性,很难象对一般负温度系数(NTC)材料那样,用一个简洁的公式统一地予以表达。图1给出了典型的特性曲线。首先,曲线在低温区呈现一段NTC特性,然后有一个最小电阻率,在稍低于居里温度T。处有一个“膝弯”,在T_c处有一0.1～0.5个数量级的电阻率跃升,接着是3～6个数量级的PTC区域,一个最大电阻率,最后是一段高温区NTC特性。根据这种曲线,可以确定一系列有实用意义的参数。
The material involved in this article is a doped semiconductor barium titanate ceramic used in the manufacture of a mutant positive temperature coefficient thermistor. Above the Ferroelectric Curie temperature, the resistivity of this material has rapidly jumped and has a considerable positive temperature coefficient (PTC) over a certain temperature range. The resistivity-temperature behavior of this material is hardly expressed uniformly by a concise formula like that of a general negative temperature coefficient (NTC) material. Figure 1 shows a typical characteristic curve. First, the curve shows a period of NTC behavior in the low temperature region and then a minimum resistivity, slightly below the Curie temperature. There is a “knee bend” with a 0.1-0.5 magnitude resistivity jump at Tc, followed by a 3-6 order PTC region, a maximum resistivity, and finally a high-temperature NTC profile. Based on this curve, a series of useful parameters can be identified.