Preparation and characterization of LaNiO3 A/F ratio-sensitive thin film by sol–gel process based on amorphous citrate precursors

Thin film of lanthanum nickelate (LaNiO3) has been prepared by the sol–gel process based on the amorphous citrate precursors. The sheet resistance of LaNiO3 thin film greatly decreases and trends towards a stable value with increasing the repeated dipping–calcining cycles. The sheet resistance of about 1.2 μm thick LaNiO3 thin film produced by the dipping–calcining 10 cycles is about 22.4 Ω at room temperature and less sensitive to temperature in the PO2 range from 103.3 to 105 Pa or in the lean-burn region (λ=1.15). The sensitivity and response characteristics of the LaNiO3 thin film sensor have been investigated in the exhaust gas of air–propane combustion. It has been shown that thin film sensor has high sensitivity, fairly good response and reproducibility from λ=1.15 to 0.85 and vice versa, and no temperature compensation is needed for stoichiometric air/fuel control over a 300–800°C range. The thin film sensor is a promising A/F sensitive sensor that needs no temperature compensation.