The NTC thermistor fabricated by boundary-layer technology

A thermistor with a negative temperature coefficient of resistance (NTCR), based on the semiconducting (Ba_0.8Sr_0.2) (Ti_0.9Zr_0.1)O₃ ceramics, is fabricated by boundary-layer (BL) technology. By adding a suitable amount of V₂O₅ as additive, a semiconducting boundary layer is segregated at the grain boundaries after sintering in a reducing atmosphere. This layer dominates the temperature-dependent property and shows an NTCR effect with a thermistor constant of about 4200 K. Based on the microstructural and electrical properties, an n⁺-n-n⁺ energy band model is proposed for this boundary-layer thermistor.