High- Tc superconductors as NO sensor materials: a general investigation

Abstract

The response of several ceramic high- T c superconductors to NO and CO in Taguchi-type gas sensors has been investigated. YBa 2Cu 3O 7-δ decomposes in the presence of NO. Ba 1.5La 1.5Cu 3O x and La 1.85Sr 0.15CuO x do not show any sensitivity or selectivity of interest. Nd 1.85Ce 0.15CuO 4-x exhibits sensitivity to CO, but no sensitivity to NO. These materials are not suitable for NO gas sensors. Bi 2Sr 2CuO su6+x, Bi 2Sr 2CaCu 2O 8+x and Bi 1.8Pb 0.2Sr 2Ca 2Cu 3O 10+x show high selectivity to No against CO. They are promising materials for Taguchi-type NO sensors. Bi 2Sr 2CaCu 2O 8+x exhibits the best properties. The sensitivities of composites of Bi 2Sr 2CaCu 2O 8+x with 0.5, 2 and 10 wt.% A1 2O 3, Bi 2Sr 2CaCu 2O 8+x with 20 wt.% Fe 2O 3, Bi 2Sr 2Ca Cu 2O 8+x with 20 wt.% NiO, Bi 2Sr 2CaCu 2O 8+x with 20 wt% ZrO 2, Bi 2Sr 2CaCu 2O 8+x with 50 wt.% Sb 2O 5 and the lithium-intercalated compound Li 0.11 2Sr 2CaCu 2O 8x to NO and CO at 300 and 350 °C have been studied. While additions of A1 2O 3, ZrO 2 and Sb 2O 5 to Bi 2Sr 2CaCu 2O 8+x do not improve its selectivity to NO CO, additions of Fe 2O 3 and NiO and lithium intercalation do improve the selectivity.