NTC temperature sensing thermistors have been based upon metal oxide materials such as Mn-Ni oxide. These thermistors are limited in practical application to 250°C. It was desired to extend the useful thermistor range to 500°C. Therefore, the authors investigated various types of non-oxide materials. Non-oxide materials were selected because, despite difficulties in processing, the high temperature per∼ formance of such materials was believed to be stable. It was found that A1203-B4C and A1203-B4C-SiC were acceptable materials for high temperature NTC applications. Using these basic materials, and exercising special process controls, high temperature glass-sealed NTC thermistors were fabricated. After extended environmental and life tests, it was found that the resulting sensors provided repeatable temperature measurements over a long period of time and were suitable for their intended applications.