Microspheres of the gas sensor material Cr2 − xTixO3 prepared by the sol–emulsion–gel route

Chromium titanium oxide (CTO) Cr2 − xTixO3 (x = 0.05 to 0.4) is the first gas-sensitive resistor material successfully to be commercialised since tin dioxide in the 1960s. Microspheres were synthesised by the sol–emulsion–gel method and characterised by X-ray diffraction, scanning electron microscopy (SEM/EDAX) and X-ray photoelectron spectroscopy (XPS). Three differently sized microspheres of size 10, 2 and 0.7 µm were synthesised. The microspheres showed minimal variation in size and good compositional homogeneity. The CTO powders fired at 1000 °C crystallised as single phases for Cr1.95Ti0.05O3, Cr1.9Ti0.1O3 and Cr1.8Ti0.2O3. For x > 0.2 the formation of a secondary CrTiO3 phase was noted. EDAX and XPS measurements revealed the absence of impurities and a surface segregation of the Ti atoms.