Poisoning of Temperature Independent Resistive Oxygen Sensors by Sulfur Dioxide

Sulfur dioxide strongly affects temperature independent resistive oxygen sensors of SrTi_1-xFe_xO_3-. Time dependent sensor deterioration was investigated for lanthanum doped SrTi_0.65Fe_0.35O_3- (STF35). Parameters were sulfur dioxide concentration, oxygen partial pressure, temperature, and sensor morphology. The sensor poisoning consists of two steps. At lower temperatures sulfur dioxide adsorption and sulfate ion formation at the grain surface is suggested. At higher temperatures the material decomposes into SrSO₄, iron depleted STF35, and Fe₂TiO₅.