Single-Phase White Phosphor via Energy Transfer from Ce ^{3 <b>+</b>} to Sm ^{3 <b>+</b>} /Tb ^{3 <b>+</b>} in Ca ₃ LuAl ₃ B ₄ O ₁₅ for High-Quality UV LEDs

Single-phase white phosphors are highly desirable for achieving stable white light-emitting diodes (w-LEDs). In this work, a series of Ce 3+ -, Tb 3+ -, and Sm 3+ -doped as well as codoped Ca 3 LuAl 3 B 4 O 15 (CLAB) phosphors were successfully synthesized, and white light was achieved by tuning relative doping concentrations. The phase structure, morphology, and optical properties were systematically investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), and photoluminescence spectroscopy. Energy transfer from the parity-allowed Ce 3+ ions to the parity-forbidden Tb 3+ and Sm 3+ ions was confirmed through spectral analysis and comparison. Under 342 nm excitation, the optimized CLAB:1%Ce 3+,2.5%Sm 3+,10%Tb 3+ phosphor exhibits warm-white-light emission originating from three activators. In addition, the phosphor retains 71% and 42% of its initial emission intensity at 450 and 600 K, respectively, demonstrating the good thermal stability of the phosphor. By combining the optimized CLAB:1%Ce 3+,2.5%Sm 3+,10%Tb 3+ phosphor with a commercial 340 nm ultraviolet (UV) chip, a warm w-LED was fabricated, exhibiting CIE chromaticity coordinates of (0.3631, 0.3625), a correlated color temperature (CCT) of 4419 K, and a color rendering index (CRI) of 93. This study offers a newly designed single-phase white phosphor for high-quality warm w-LEDs.