Mapping optical, chemical, structural features in ZrO2 via cross-sectional SEM-Cathodoluminescence correlation microscopy

Abstract

Understanding how nanoscale heterogeneities influence charge transport and mass transfer in oxides is critical for developing advanced materials for energy and electronic uses. In high-temperature applications, the formation of thermal oxides with complex chemical and structural features plays a central role in material lifetime. While thermally grown zirconia (ZrO2) on zirconium alloys exhibits strong chemical and microstructural gradients across the oxide thickness, linking these heterogeneities to electronic-defect landscapes remains challenging. We demonstrate cross-sectional scanning electron microscope-cathodoluminescence (SEM-CL) as a mesoscale probe of spatial variations in luminescence in zirconia and establish correlations with co-registered electron backscatter diffraction (EBSD) and electron probe micro-analysis (EPMA) on the same region. The SEM-CL signal is dominated by the ~2.7 eV defect band, but its intensity varies strongly across the oxide cross section. Correlative EBSD-CL analysis reveals that CL intensity increases with grain area and decreases at the grain boundaries, consistent with enhanced non-radiative recombination associated with microstructural disorder. EPMA mapping shows that a substantial fraction of CL-dark features co-localize with secondary phase precipitates enriched in iron. These results show that SEM-CL contrast in corrosion-grown ZrO2 is controlled by both chemical heterogeneity and microstructural disorder, underscoring the need for correlative registration to interpret CL images. This multi-modal approach provides an efficient route to connect electronic properties and luminescence signatures across complex oxide cross sections to underlying chemistry and microstructure, thereby providing a pathway to relate local defect landscapes to regions likely to bias electronic/ionic transport during oxidation.