Effect of Y Substitution on Electrical Properties of Y_n(Ba_(0.8)Bi_(0.2))_(1–n)Fe_(0.9)Sn_(0.1)O_3 Negative Temperature Coefficient Thermistor Ceramics

Negative temperature coefficient thermistor ceramics based on Yn(Ba0.8 Bi0.2)1–n Fe0.9 Sn0.1 O3 were fabricated by conventional solid-state reaction techniques. Phases, microstructures, resistance-temperature curves and impedance characteristics of thermistor ceramics were characterized by X-ray diffraction, scanning electron microscope, resistance-temperature tester and ac impedance analyzer, respectively. Yn(Ba0.8 Bi0.2)1–n Fe0.9 Sn0.1 O3 thermistor ceramics with pseudo-cubic perovskite structure show average grain size of ~1.0 μm and the decreasing lattice parameter a with increase of Y content. Room-temperature resistivity, thermistor constant and activation energy of thermistor ceramics are in the range of 2.17–9.17 M?·cm, 6757–7171 K and 0.583–0.618 eV, respectively. When n = 0.02 and 0.04, the ceramic resistance is mainly attributed to the contribution of grain boundaries, grains and grain shells. Among them, the resistance value of grain is the highest one. However, for the ceramics with n = 0.06 and 0.08, the total resistance of thermistor ceramics is ascribed to the contribution of grain boundaries, domain walls and domains, and the domain regions show the larger resistance value than that of the other two elements. In the limited measured temperature range, all of grain boundaries, grain shells, grains, domain walls and domains show negative temperature coefficient thermistor behavior.