Preferential Neighboring Substitution-Triggered Full Visible Spectrum Emission in Single-Phased Ca10.5- xMg x(PO4)7:Eu2+ Phosphors for High Color-Rendering White LEDs.

Manipulating the distribution of rare-earth activators in multiple cation lattices can achieve versatile color output for single-phased phosphor-converted white light-emitting diodes (LEDs). However, successful cases are barely reported, owing to the uncertain distribution of rare-earth activators and the special combination of three primary colors for white LEDs. Herein, we took whitlockite β-Ca3(PO4)2 as a multiple cation lattice host to manipulate the redistribution of Eu2+ activators, and the surprising Mg2+-guided redistribution of Eu2+ activators among different Ca sites is reported for the first time to regulate the photoluminescence (PL) behavior in series Ca10.5- xMg x(PO4)7:Eu2+ phosphors. The preferential neighboring substitution of smaller Mg2+ cations in Ca(5) and Ca(4) sites triggers a discontinuous evolution of local structure along c axis and induces covalent variable Ca(1), Ca(2), and Ca(3) cation sites for the accommodation of Eu2+ activators. The unique optical feature enables the single-phased Ca9.75Mg0.75(PO4)7:Eu2+ phosphor-converted white LED to exhibit quite high color-rendering index Ra (85) and R9 (91) values. The preferential neighboring-cation substitution reported here can not only manipulate the migration of Eu2+ activators among different cation sites for tunable PL properties, but also carve out a new way for next-generation high-quality solid-state lighting.