Laser-induced luminescence imaging: Microstructural-chemical analysis for nuclear materials

Modern scanning laser-based Raman spectrometers have allowed for increasingly sophisticated microstructural analysis with high spatial resolution. Fluorescence, long considered a nuisance in these measurements, is now being applied as a direct output signature from these experiments. Rare earth elements (REE) are particularly suited as probe ions for nuclear materials, being important fission products having f–f electronic transitions split by local crystal field, allowing investigation of localized phenomena such as partitioning and atomic environment. Laser excitation wavelength selection combined with limited bandwidth gratings makes certain ions highly sensitive to given experimental conditions (e.g., Pr³⁺: 455 nm excitation; Eu³⁺: 532 nm excitation; Nd³⁺, Yb³⁺: 785 nm excitation). In this paper, several examples of the use of laser-induced luminescence are given, including identification of precursor material impurities, radiation damage in ceramics, and identification of phases in glass–ceramics.