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

TL;DR

This study uses correlative SEM-CL, EBSD, and EPMA techniques to map nanoscale heterogeneities in zirconia oxide, linking chemical, structural, and luminescent features to defect landscapes affecting material performance.

Contribution

It introduces a multi-modal correlative microscopy approach to analyze chemical, structural, and luminescent heterogeneities in ZrO2 at the microscale.

Findings

CL intensity correlates with grain size and boundaries.

Chemical heterogeneities influence luminescence contrast.

Secondary phase precipitates are associated with dark CL regions.

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.