Nuclear microprobe local hydrogen measurements in HTPC

Abstract

High-temperature protonic conducting ceramics (HTPC) exhibit promising protonic conductivities at intermediate temperatures (400–600 °C), with a potential for a broad range of practical applications: electrolytes in electrochemical cells, batteries, sensors, etc. A balance still has to be found between high protonic conductivity and chemical stability in a wet environment. In addition to bulk conductivity measurements, local investigations of protonic transport are recommended to evidence limitations induced by their microstructure, such as the role of grain boundaries or intergranular secondary phases. Methods for local hydrogen concentration measurement with spatial resolution at the micrometer level are scarce. The nuclear microanalysis meets this demand. We report here the first application of a nuclear microprobe technique to the study of HTPC perovskites, synthesized according to a melt-process developed at NASA GRC. Elastic Recoil Detection Analysis (ERDA) combined with Rutherford back-scattering (RBS) was first exploited for perovskites containing very low hydrogen contents. A less common method has been developed for thin samples which utilized 1H(p,p) 1H forward scattering with coincidence detection (ERCS). From the broad compositional and structural range of perovskites, we have limited our efforts to SrCe 0.9Y 0.1O 3− δ and Sr 3Ca 1+ x Nb 1.82O 9− δ , compositions which represent simple and complex perovskite structures, respectively.