Gas sensors based on oxides of early transition metals

Abstract The conductivities of semiconducting oxides are generally influenced by the chemical reactions of any gas molecules that have access to their surfaces. This phenomenon is exploited in the development of gas sensitive resistors that offer a simple route to the monitoring of atmospheric composition. Material properties may be optimized for this application by adjustment of the stoichiometry of the semiconducting oxide. Oxides of early transition metals are particularly useful in this “tuning” process. Examples are given of the development of two oxides with useful gas response characteristics—one for the monitoring of oxygen, the other for ammonia.