Characterization of functional materials for liquid blanket systems by cathodoluminescence measurement

Highlights: • Cathodoluminescence (CL) of ceramics for liquid blanket systems was examined. • Lower crystallinities made CL peaks broader and shifted to longer wavelengths. • Irradiation damages also changed CL spectra significantly. • CL measurement using SEM is effective in material development for blanket systems. • CL could be used in inspection and monitoring of materials in fusion reactors. - Abstract: Applicability of cathodouminescence (CL) measurements in development of functional materials for advanced liquid blanket systems was investigated by using a conventional scanning microprobe and CCD spectrometer. Firstly, CL spectra of lithium compounds for tritium fuel breeding, oxide, nitride and carbide functional materials for advanced blanket systems, fluoride materials for coolants, etc. were obtained to construct a database. Relations between changes in the spectra and the crystallinities of specimens were examined for ZrO₂, Y₂O₃ and TiO₂ coatings baked at different temperatures. The specimens with lower crystallinities showed broader luminescence peak at longer wavelengths. Changes in CL spectra by irradiation damages were also examined for Y₂O₃ and SiC by ion beam irradiations. Since luminescence intensity decreased significantly for the specimens with low crystallinities, an SEM system which can control the electron beam current more than 2 orders while keeping the spatial resolution of <1 μm is suitable for quick acquisition of CL spectra in the development of the functional materials. Once a database of CL spectra for candidate materials and their changes by crystallinities and irradiation damages is constructed, the CL measurement would be a reliable tool also in inspection and monitoring of materials during reactor construction and operation.