CuO-modified tin titanate thick film resistors as H2-gas sensors

Thick films of pure and CuO-modified tin titanate—Sn0.8Ti0.2O2 (TT) were prepared by screen printing technique. Unmodified TT showed poor sensitivity while CuO-modified TT showed high sensitivity to H2 gas. The CuO-modified TT films were obtained by dipping them into an aqueous solution of copper chloride for different intervals of time and fired at 500 °C for 30 min. The copper chloride transforms into copper oxide upon firing. A relatively large amount of oxygen would be adsorbed on the CuO-modified TT and resulted in the buildup of potential barriers between the grains. Upon exposure to 1000 ppm H2 gas, the barrier height would decrease markedly due to oxidation leading to a drastic decrease in resistance and giving high sensitivity to H2 gas. High sensitivity was found to H2 gas at 400 °C and no cross response was observed to LPG, NH3, C2H5OH, CO2 and Cl2 gases. The instant response (∼15 s) and fast recovery (∼45 s) are the main features of this sensor. The effects of microstructure and concentration of the CuO additive on the gas response, selectivity, response time and recovery time were studied and discussed.