Synthesis, crystal structure, and characterization of DyMgB5O10: thermal behavior, band gap calculation, and luminescence

Abstract

Abstract A new member of the rare-earth magnesium pentaborate family, DyMgB5O10, was synthesized via solid-state reaction followed by flux growth in a K2Mo3O10 melt. Single crystals up to 0.5 mm were obtained and characterized by SEM, EDX, DSC, and XRD techniques. The crystal structure was refined in the monoclinic space group P21/n, confirming that it belongs to the same structural family as other RMgB5O10 compounds. The structure consists of alternating anionic borate layers built from [B5O12]3− clusters and cationic Dy–O–Mg layers. Dy3+ ions are coordinated by ten oxygen atoms in distorted polyhedra, while Mg2+ occupy edge-sharing octahedral dimers. Thermal analysis revealed incongruent melting with T onset ∼ 1,072 °C. DFT calculations gave an indirect band gap of ∼6.06 eV, indicating a wide-bandgap dielectric. Photoluminescence and X-ray induced luminescence spectra exhibit characteristic Dy3+ intra-4f transitions, with dominant blue (4F9/2 → 6H15/2) and yellow (4F9/2 → 6H13/2) emissions. The intense yellow emission reflects the low symmetry of the DyO10 polyhedra. Characteristic luminescence under X-ray excitation confirms effective energy transfer from the borate matrix to Dy3+. The combination of high thermal stability, wide band gap, and favorable optical properties makes DyMgB5O10 a promising candidate for phosphors and X-ray scintillators.