Aluminum-doped TiO 2 nano-powders for gas sensors

Abstract

Nano-powders of pure and Al-doped TiO 2 ceramics were synthesized using a citrate–nitrate auto combustion method. Powders were then used to make thick film gas sensors to measure selectivity and sensitivity in CO and O 2 environment. Titanyl nitrate solution was prepared using commercial TiO 2 powder, hydrofluoric acid (HF) and concentrated nitric acid (HNO 3). An optimized ratio of citrate to nitrate was used to produce TiO 2 nanoparticles. Powder X-ray diffraction data showed that synthesized TiO 2 nano-powders, pure as well as Al-doped, had stable anatase phase up to 800 °C. X-ray fluorescence confirmed the Al concentrations in synthesized nano-powders. BET surface area analysis showed a decrease at 5 wt.% Al addition, followed by an increase at 7.5 wt.% in specific average surface area. Particle size analysis showed particles below 100 nm for both pure and doped TiO 2 even after calcination at 800 °C. The resistance of Al-doped TiO 2 samples was found to be lower than that of pure TiO 2 in O 2 and CO environment. Al-doped TiO 2 gas sensors were more selective and sensitive to CO and O 2 at an operating temperature of 600 °C than pure TiO 2 powders.