Electrical properties of lead-free thick film NTC thermistors based on BaFe0.9Sn0.1O3 ceramic

Lead free thick film NTC (negative temperature coefficient) thermistors based on perovskite-type semiconducting materials of different compositions BaFe_0.9Sn_0.1O₃ + BaBiO₃, and BaFe_0.9Sn_0.1O₃ + BaBiO₃ + CuO were fabricated on alumina substrate by screen printing technology. The evolution of microstructure, electrical performance of these resistors and the influence of thickness of thermistor layer on the thermistor constant and initial resistivity were studied. The thick film samples adhere very well to alumina substrate and show homogeneous microstructure. The electrical resistivity at 22 °C (ρ₂₂), thermistor constant (B_25/85), and activation energy (E_a) of the NTC thermistors decreases with increasing CuO content. At the almost same thickness, the values of ρ₂₂, B_25/85, and E_a of the thick film NTC thermistors are 3.197-19.25 kΩ·cm, 3318-4322 K, 0.289-0.376 eV, respectively. As thickness of the films increases, the thermistor constant and the initial resistivity of the thick film NTC thermistors decrease.