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Nuclear Microprobe using Elastic Recoil Detection (ERD) for Hydrogen Profiling in High Temperature Protonic Conductors

The interaction between hydrogen and various high temperature protonic conductors (HTPC) has not been clearly understood due to poor densification and unreacted secondary phases. the melt-processing technique is used in producing fully dense simple SrCe(0.9)Y (0.10) O(3-delta) and complex Sr3Ca(1+x)Nb(2+x)O(9-delta) perovskites that can not be achieved by solid-state sintering. the possibilities of ion beam analysis have been investigated to quantify hydrogen distribution in HTPC perovskites subjected to water heat treatment. Nuclear microprobe technique is based on the interactions of a focused ion beam of MeV light ions (H-1, H-2, He-3, He-4,.) with the sample to be analyzed to determine local elemental concentrations at the cubic micrometer scale, the elastic recoil detection analysis technique (ERDA) has been carried out using He-4(+) microbeams and detecting the resulting recoil protons. Mappings of longitudinal sections of water treated SrCeO3 and Sr(Ca(1/3)Nb(2/3))O3 perovskites have been achieved, the water treatment strongly alters the surface of simple SrCe(0.9)Y(0.10)O(3-delta) perovskite. From Rutherford Back Scattering measurements (RBS), both Ce depletion and surface re-deposition is evidenced. the ERDA investigations on water treated Sr3Ca(1+x)Nb(2+x)O(9-delta) perovskite did not exhibit any spatial difference for the hydrogen incorporation from the surface to the centre. the amount of hydrogen incorporation for Sr3Ca(1+x)Nb(2+x)O(9-delta) was low and required further development of two less conventional techniques, ERDA in forward geometry and forward elastic diffusion H-1(p,p) H-1 with coincidence detection.

Berger, Pascal↗

High Temperature Protonic Conductors

High Temperature Protonic Conductors (HTPC) with the perovskite structure are envisioned for electrochemical membrane applications such as H2 separation, H2 sensors and fuel cells. Successive membrane commercialization is dependent upon addressing issues with H2 permeation rate and environmental stability with CO2 and H2O. HTPC membranes are conventionally fabricated by solid-state sintering. Grain boundaries and the presence of intergranular second phases reduce the proton mobility by orders of magnitude than the bulk crystalline grain. To enhanced protonic mobility, alternative processing routes were evaluated. A laser melt modulation (LMM) process was utilized to fabricate bulk samples, while pulsed laser deposition (PLD) was utilized to fabricate thin film membranes . Sr3Ca(1+x)Nb(2-x)O9 and SrCe(1-x)Y(x)O3 bulk samples were fabricated by LMM. Thin film BaCe(0.85)Y(0.15)O3 membranes were fabricated by PLD on porous substrates. Electron microscopy with chemical mapping was done to characterize the resultant microstructures. High temperature protonic conduction was measured by impedance spectroscopy in wet air or H2 environments. The results demonstrate the advantage of thin film membranes to thick membranes but also reveal the negative impact of defects or nanoscale domains on protonic conductivity.

Dynys, Fred↗