<p>Single- or multi-phase ceramics and glass–ceramic composite materials are widely recognised as candidate wasteforms for the immobilisation of intermediate- and high-level radioactive wastes (ILW and HLWs). The long-term performance of these materials is governed by their microstructural features which may include grain size, crystallographic orientation, and phase distribution. These attributes influence dissolution rates, material response to radiation damage, and mechanical integrity, making them essential parameters in predictive models of wasteform durability over extended timescales. However, quantitative determination of grain-size and phase composition in ceramic and glass–ceramic wasteforms remains scarcely reported due to the inherent limitations of conventional methods. Here we present a novel methodology to produce reliable Electron Backscatter Diffraction (EBSD) maps of complex multi-phase systems to address this challenge. The approach enables precise grain-size measurement, phase quantification, texture analysis, and interphase boundary characterisation, in single- and multi-phase ceramics and glass–ceramic materials, significantly advancing microstructural assessment in nuclear wasteform research.</p> Graphical Abstract <p></p>