Temperature Dependence of Responses in Metal Oxide Gas Sensors

Selecting an optimum operating temperature for metal oxide gas sensors is of prime technical importance. Here, the temperature behavior of various kinds of metal oxide gas sensors in response to different levels of reducing contaminants in air is reported. The examined gas sensor samples include a Tin oxide-based resistive gas sensor and home-made diode-type Ag-TiO2-Ti gas sensors. Recorded response vs. temperature curves of all samples represent two different typical features: The responses related to the resistive gas sensor exhibit distinct maximum response at a well defined operating temperature regardless of the target gas concentration level, but the diode type samples demonstrated a continuously rising response as the operating temperature decreased to highly contaminated atmospheres. At low contaminant levels, diode type gas sensors change their behaviour and act similar to resistive gas sensors. Reported results were described by a model based on the gas diffusion theory.