Electrical properties of lead-free thick film NTC thermistors based on perovskite-type BaCoIIxCoIII2xBi1 − 3xO3

Lead-free thick film negative temperature coefficient (NTC) thermistors based on perovskite-type BaCoIIxCoIII2xBi1 − 3xO3 (x ≤ 0.1) were prepared by mature screen-printing technology. The microstructures of the thick films sintered at 720 °C were examined by X-ray diffraction and scanning electron microscopy. The electrical properties were analyzed by measuring the resistance-temperature characteristics. For the BaBiO3 thick films, the room-temperature resistivity is 0.22 MΩ cm, while the room-temperature resistivity is sharply decreased to about 3 Ω cm by replacing of Bi with a small amount of Co. For compositions 0.02 ≤ x ≤ 0.1, the values of room-temperature resistivity (ρ23), thermistor constant (B25/85) and activation energy are in the range of 1.995–2.975 Ω cm, 1140–1234 K and 0.102–0.111 eV, respectively.

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► The BaCoIIxCoIII2xBi1 − 3xO3 (x = 0.02–0.1) thick films can be sintered at temperature 720 °C.
► The resistivity values of the BaCoIIxCoIII2xBi1 − 3xO3 thick films decrease to about 3 Ω cm.
► The novel material has the potential for the substitution of toxic PbO and high-cost RuO2.