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Microstructural investigations of chromia-titania system

The chromia-titania system has been successfully employed in gas sensor devices as the active, gas sensitive material. Chromia-rich compositions display the most reliable response to gases in particularly CO in domestic and industrial environments. Conventionally these materials are sintered in air resulting in the formation of porous bodies ideal for the detection of gases which can permeate through open pores, reacting with free surfaces inducing a measurable gas response in terms of changes in electrical conductivity. It has been reported that these materials are surface segregated with Ti (Henshaw et al., 1995) a feature which may be key in the gas response. The sintering regime used for these materials will not promote densification as 0 2 6 3 forms volatile higher oxides leading to condensation-evaporation diffusion mechanisms resulting in grain growth and no shrinkage. By sintering these materials in reducing atmospheres, the formation of volatiles can be suppressed and densifying mechanisms such as bulk and lattice diffusion promoted. This study compares the chemical homogeneity and phase analysis o f materials derived from air and reducing atmosphere sintering regimes.