Development of oxygen-permeable ceramic membranes for NOx-sensors

Several mixed ionic–electronic conductors such as Gd1–xCaxCoO3–d (GCC) and La1–xSrxCo1–yCuyO3–d as well as composite materials like Gd1–xCaxCoO3–d / Ce1–xGdxO2–d (GCCCGO) have been investigated with respect to their use as highly selective membranes within a new amperometric sensor system. Materials characterisation was carried out concerning surface reactions of the membranes, thermal expansion, and electronic as well as oxygen permeation properties. Taking advantage of the effective medium theory, the optimum component-ratio for the composit ceramic GCCCGO with respect to permeation behaviour has been predicted. Based on experimental and modelling data, the overall performance of a system using a GCCCGO membrane has been determined.