<p>This study investigates the evolution of the porous/nanoporous structure of BaGa₂O₄ ceramics upon doping with Eu³⁺ ions. It has been established that the introduction of Eu³⁺ leads to a redistribution of pore sizes, resulting in an overall increase in their average size. Analysis of scanning electron microscopy images using computational algorithms revealed that the average pore radius in undoped BaGa₂O₄ ceramics is 0.79&#xa0;µm, whereas in doped samples, it increases by 11% to 0.88&#xa0;µm. This indicates a modification of pore formation mechanisms under the influence of Eu³⁺ ions, likely associated with grain boundary mobility and densification processes during sintering. Investigation of nanopores using positron annihilation spectroscopy showed that nanopores with a size of 0.3&#xa0;nm initially undergo agglomeration upon the introduction of a small amount of Eu³⁺, followed by fragmentation. However, at a high Eu³⁺ content re-agglomeration occurs. For nanopores with radii of 2–3&#xa0;nm, expansion and agglomeration are observed with increasing Eu³⁺ concentration. The obtained results indicate a significant impact of Eu³⁺ doping on the microstructural characteristics of BaGa₂O₄, which may be crucial for controlling its physicochemical properties.</p> Graphical abstract <p></p>