Synthesis and luminescence properties of Ba3Y2B6O15: Ce3 +, Eu3+/Eu2+ phosphors with Ca2+-induced auto-reduction for high-performance pc-wLEDs

Borate-based phosphors have emerged as ideal host materials for near-ultraviolet ( n UV) pumped phosphor-converted white light-emitting diodes (pc- w LEDs) owing to their mild synthesis conditions, broad transparency window, and excellent chemical and thermal stability. Cubic Ba 3 Y 2 B 6 O 15 (BYB) features a highly symmetric lattice structure, providing stable binding sites for rare-earth ions. Its [YO 6 ] octahedral structure allows for controllable lattice distortion, making it an ideal host for multivalent rare-earth luminescent systems. In this study, Ce 3+ , Eu 3+ , Eu 2+ , and Ca 2+ co-doped BYB nanophosphors were prepared in an Ar atmosphere. The partial substitution of Ba 2+ by Ca 2+ promotes the generation of more oxygen vacancies, which in turn induces the self-reduction of Eu 3+ to Eu 2+ . The phosphor exhibits strong absorption characteristics at 365 nm. Acting as an efficient sensitizer, Ce 3+ can simultaneously transfer energy to Eu 2+ and Eu 3+ . By tuning the Ca 2+ content, the Eu 3+ /Eu 2+ ratio and the emission color can be continuously adjusted, achieving a smooth transition from blue-green to orange-red. This Ca 2+ mediated strategy stabilizes the coexistence of Eu 2+ and Eu 3+ , addressing the key limitations of traditional single-phase phosphors. It provides a novel approach for developing high-performance n UV-excited warm white phosphors and demonstrates potential for widespread application in highly efficient pc- w LED devices.