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 g aseous 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 b ased sensors respond to H-2 at a temperature of 100 degrees C, while t hick films of alumina display marked changes in both resistance and ca pacitance as a function of relative humidity at room temperature. Nano crystalline SnO2 sensors respond markedly to mixtures of H-2, CO and C H4 in the 100-600 degrees 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 experime nts showed that sensor characteristics were influenced both by pre-tre atment temperature and him thickness.