Lanthanides (Ln³⁺) doped luminescent materials play critical roles in lighting and display techniques. While increasing experimental and theoretical research have been carried out on aluminate-based phosphors for white light-emitting diodes (WLEDs) over the past decades, most investigation was mainly focused on their luminescent properties; therefore, the local structure of the light emission center remains unclear. Especially, doping-induced local composition and structure modification around the luminescent centers have yet to be unveiled. In this study, we use advanced electron microscopy techniques including electron diffraction (ED), high-resolution transmission electron microscopy (HRTEM), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), in combination with energy dispersive X-ray spectroscopy (EDX) and electron energy loss spectroscopy (EELS), to reveal atomically resolved crystalline and chemical structure of Ce³⁺ doped CaYAlO₄. The microscopic results prove substantial microstructural and compositional inhomogeneities in Ce³⁺ doped CaYAlO₄, especially the appearance of Ce dopant clustering and Ce³⁺/Ce⁴⁺ valence variation. Our research provides a new understanding the structure of Ln³⁺ doped luminescent materials and will facilitate the materials design for next-generation WLEDs luminescent materials.

Ferroelectric barium titanate nanoparticles (BTO NPs) may play critical roles in miniaturized passive electronic devices such as multi-layered ceramic capacitors. While increasing experimental and theoretical understandings on the structure of BTO and doped BTO have been developed over the past decade, the majority of the investigation was carried out in thin-film materials; therefore, the doping effect on nanoparticles remains unclear. Especially, doping-induced local composition and structure fluctuation across single nanoparticles have yet to be unveiled. In this work, we use electron microscopy-based techniques including high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), integrated differential phase contrast (iDPC)-STEM, and energy dispersive X-ray spectroscopy (EDX) mapping to reveal atomically resolved chemical and crystal structure of BTO and strontium doped BTO nanoparticles. Powder X-ray diffraction (PXRD) results indicate that the increasing strontium doping causes a structural transition from tetragonal to cubic phase, but the microscopic data validate substantial compositional and microstructural inhomogeneities in strontium doped BTO nanoparticles. Our work provides new insights into the structure of doped BTO NPs and will facilitate the materials design for next-generation high-density nano-dielectric devices.