Blue–Green Emitting Phosphor Ba ₂ LiAlSi ₂ O ₈ :Eu ^{2 +} for Phosphor-Converted Light-Emitting Diodes via Single-Particle Diagnosis in a Quasi-Quaternary System

High Resolution Image Download MS PowerPoint Slide Phosphor-converted light-emitting diodes (PC-LEDs) are widely used in various fields due to their long lifetime and high energy efficiency. In particular, blue–green-emitting phosphors have the potential to fill the cyan gap in white LEDs and to be used in display indicators for autonomous driving. A new blue–green-emitting Ba 2 LiAlSi 2 O 8:Eu 2+ phosphor was discovered through exploratory experiments in the BaO–Li 2 O–Al 2 O 3 –SiO 2 quasi-quaternary system using a single-particle-diagnosis approach. Single-crystal X-ray diffraction analysis revealed that Ba 1.96 Eu 0.04 LiAlSi 2 O 8 crystallizes in a space group of Pna 2 1 (No. 33) with a = 8.04521(11) Å, b = 19.0484(2) Å, c = 5.02228(6) Å, and Z = 4. The crystal structure comprises LiO 4, AlO 4, and SiO 4 tetrahedra, which orderly align and form a framework by sharing apical oxygen atoms. Ba atoms are surrounded by eight and seven oxygen atoms in the framework. Density functional theory calculations corroborated the Al and Si arrangement in the Ba 2 LiAlSi 2 O 8 crystal structure. A single-phase powder of the Ba 2 LiAlSi 2 O 8:Eu 2+ phosphor was successfully obtained via a solid-state reaction. This phosphor exhibited a blue–green luminescence peak at 497 nm with a full width at half-maximum of 85 nm under 372 nm excitation. The internal and external quantum efficiencies were 51.0% and 42.7%, respectively. The peak intensity at 150 °C was 67% of that at room temperature. We fabricated pc-LEDs based on 405 nm LED chips combined with Ba 2 LiAlSi 2 O 8:Eu 2+ phosphor, and the CIE chromaticity coordinates were in the blue–green region. These results indicate that the new Ba 2 LiAlSi 2 O 8:Eu 2+ phosphor is a promising candidate for future LED technologies.