Tunable photoluminescence in Eu2+-activated KCaLa(PO4)2 phosphor through structural disorder

Abstract

Cation substitution has emerged as a powerful strategy for both discovering new phosphors and regulating their luminescent properties. However, the incorporation of high concentrations of impurity ions often triggers phase transitions, making it challenging to maintain phase purity while achieving precise luminescent color control. In this study, we present a novel broadband cyan-emitting phosphor KCaLa(PO₄)₂: Eu²⁺, which exhibits multicolor emission capabilities through Sr²⁺ doping-induced site occupancy disorder. By systematically varying the Ca/Sr atomic ratio from 1:0 to 0.7:0.3, we observed significant changes in atomic composition and lattice arrangement, leading to controlled lattice distortion without a phase transition. This structural modification resulted in a progressive red-shift of the Eu²⁺ emission band maximum from 479 nm to 512 nm. Through comprehensive spectroscopic and crystal structure analysis, we elucidated the underlying mechanisms governing photoluminescence intensity variation, emission band shift, and thermal stability, with particular emphasis on the role of local structural modifications. The practical application potential of these synthesized phosphors was demonstrated through the fabrication of full-spectrum white light sources using UV-LED chips, highlighting their promising prospects in solid-state lighting technology.