High-Resolution Synchrotron µXRD and µXRF for Local Phase and Elemental Analysis in Suspension Plasma Sprayed Environmental Barrier Coatings

Abstract Suspension plasma spraying (SPS) enables the fabrication of environmental barrier coatings (EBCs) with complex multilayer architectures; however, degradation in such systems often initiates locally at buried interfaces, making it difficult to resolve using conventional laboratory-scale characterization techniques. In this work, the applicability of synchrotron-based micro-x-ray diffraction (µXRD), combined with micro-x-ray fluorescence (µXRF), is evaluated for the characterization of SPS-deposited ytterbium disilicate (YbDS) EBCs. An as-sprayed YbDS coating was investigated as a baseline case to examine differences between conventional XRD and spatially resolved µXRD, while an annealed and CMAS-exposed YbDS coating was studied as a service-relevant case to probe localized phase evolution. The samples were selected from previously optimized SPS process conditions and are not intended for direct comparison. Laboratory-scale XRD provided global phase information, whereas µXRD enabled layer-specific phase identification and resolved localized interfacial features. In the as-sprayed condition, µXRD confirmed phase-pure YbDS, resolved the crystallinity of individual coating layers, and verified the absence of unintended interfacial reaction phases that are not accessible by conventional XRD. In the annealed + CMAS-exposed coating, µXRD and µXRF revealed the formation of a calcium–ytterbium–silicate oxyapatite phase confined to the YbDS/Si interface, highlighting the localized nature of CMAS-induced degradation. These results demonstrate that synchrotron microanalysis provides valuable complementary insight for probing localized phase evolution in thermally sprayed EBC systems.