Gas sensing properties of nanocrystalline metal oxide powders produced by a laser evaporation technique

Nanosized powders of Al2O3 , ZrO2 and SnO2 have been produced by laser ablation of ceramic samples followed by condensation in a controlled gaseous atmosphere. X-Ray powder diffraction, transmission and scanning electron microscopy have been used to investigate the morphology and structure of the materials. A study of the gas sensing characteristics of thick films prepared from these materials revealed that zirconia based sensors respond to H2 at a temperature of 100 °C, while thick films of alumina display marked changes in both resistance and capacitance as a function of relative humidity at room temperature. Nanocrystalline SnO2 sensors respond markedly to mixtures of H2 , CO and CH4 in the 100–600 °C temperature range and display sensitivity values which are higher than those obtained using SnO2 powder samples prepared via a conventional wet chemistry route. Optimisation experiments showed that sensor characteristics were influenced both by pre-treatment temperature and film thickness.