Negative temperature coefficient thermistor based on BaFe x Sn1−x O3−ε solid solutions

Abstract

A negative temperature coefficient (NTC) thermistors based on BaFe x Sn1−x O3−e were fabricated by conventional solid-state reaction method. The microstructure and electrical properties of the NTC thermistors were characterized by X-ray diffraction (XRD), electric (R(T)), and impedance measurements. The XRD analysis shows that the BaFe x Sn1−x O3−e still remains cubic perovskite structure and the crystal growth orientation changes at higher Fe content. Similarly, the electric measurements indicates that all the samples show typical NTCR behavior; with increasing Fe content, the room temperature resistivity, activation energy, and thermistor constant decrease, are in the range of 2.52–217 KΩ cm, 0.343–0.43 eV, and 3900–4896 K, respectively. The impedance spectroscopy confirms that the observed ac resistance, consisting of the grain bulks, grain boundaries, and electrode–ceramic interface, mainly attributes to the grain boundaries and grain bulks; with the rise in temperature the grain boundary resistance shows more rapid change than the grain resistance; moreover, the Fe concentration can greatly affect the grain and grain boundary resistance.