Crystal structure refinement and luminescence properties of Ce3+ singly doped and Ce3+/Mn2+ co-doped KBaY(BO3)2 for n-UV pumped white-light-emitting diodes

Abstract

A series of novel Ce³⁺ singly doped and Ce³⁺/Mn²⁺ co-doped color-tunable KBaY(BO₃)₂ phosphors were synthesized by a high-temperature solid-state reaction, and the crystal structures and luminescence properties were investigated in detail. The crystallographic cation sites occupancy of the doping Ce³⁺ and Mn²⁺ ions for KBaY(BO₃)₂: Ce³⁺, Mn²⁺ samples were analyzed by the Rietveld refinement method. It was demonstrated that Ce³⁺ and Mn²⁺ ions can both enter into the two types of cation sites in the KBaY(BO₃)₂ crystal lattice, with a slight tendency of occupancy for Ce³⁺ on Y³⁺ ion sites and Mn²⁺ on the Ba²⁺/K⁺ ion sites. By controlling Mn²⁺ ions content with a fixed Ce³⁺ concentration, the emission color of the phosphor varied from blue (0.160, 0.150) to pink-white (0.348, 0.272) and eventually to orange (0.490, 0.372). The critical energy transfer distance calculated by the concentration quenching theory was 16.52 Å and the energy transfer from Ce³⁺ to Mn²⁺ took place via a resonance-type dipole–dipole mechanism. By combining the single-phase KBa_0.97Y_0.97(BO₃)₂: 0.01Ce³⁺, 0.05Mn²⁺ phosphor with an n-UV 370 nm InGaN chip, a phosphor-converted white LED lamp was successfully fabricated, producing a white light with a warm correlated color temperature of 4710 K and color coordinates of (0.347, 0.307).