Electrical properties of BaFe_0.9Sn_0.1O₃–BaCo_0.02^II Co_0.04^III Bi_0.94O₃ composite thick-film thermistors

The BaFe_0.9Sn_0.1O₃–BaCo_0.02^II Co_0.04^III Bi_0.94O₃ composite thick films were prepared by screen printing. X-ray diffraction (XRD) analysis confirms that the composite films are still composed of BaCo_0.02^II Co_0.04^III Bi_0.94O₃ and BaFe_0.9Sn_0.1O₃ phases. For the prepared BaFe_0.9Sn_0.1O₃–BaCo_0.02^II Co_0.04^III Bi_0.94O₃ composite thick films, a linear relationship between the logarithmic resistivity and the reciprocal of the absolute temperature is observed, indicating an excellent NTC thermistor characteristic. The values of resistivity at 25 °C, thermistor constant and activation energy, decreasing with BaCo_0.02^II Co_0.04^III Bi_0.94O₃ content increasing, are in the range of 8.9–92,990 Ω·cm, 1,126–3,777 K and 0.097–0.325 eV, respectively. Impedance analysis shows that at higher BaCo_0.02^II Co_0.04^III Bi_0.94O₃ content, the electrical properties of the composite films are mainly attributed to the contribution of grains and grain boundaries. With the gradual decrease of BaCo_0.02^II Co_0.04^III Bi_0.94O₃ content, the grain boundaries affect strongly the electrical properties of the composite films.