Environment-Dependent Eu<sup>2+</sup>-Activated Ba<sub>3</sub>CaK(PO<sub>4</sub>)<sub>3</sub> toward White-Light Emission by Chemical Cosubstitution of the (BO<sub>3</sub>)<sup>3–</sup> Anion Group
Guodong Xie, Jiayong Si, Guihua Li, Gemei Cai
Abstract
Investigating the phosphors doped with single activators in a single component to realize white-light emission is urgently desired for phosphor-converted white-light-emitting diodes. In this work, on the basis of the chemical unit cosubstitution strategy, the new borophosphate phosphors Ba3CaK(PO4)3–x(BO3)x:0.02Eu2+ with a mixed anion group were prepared. Coupling structure refinement and photoluminescence analyses, Ba3CaK(PO4)3–x(BO3)x consists of five different cationic sites with different coordination environments, with Eu2+ occupying the three sites for Ba2+. In the process of partial substituting (BO3)3– for (PO4)3–, because of the greatly distorted coordination field generated from the difference in the geometric configurations between the two anion groups, a red shift and broadening of the emission bands occurs, resulting in a color-adjustable emission from blue to white. A phosphor-converted light-emitting diode has been successfully fabricated with the incorporation of an as-prepared Ba3CaK(PO4)2.6(BO3)0.4:0.02Eu2+ phosphor and a 405 nm near-ultraviolet chip, which exhibits Commission International de I’Eclairage chromaticity coordinates of (0.31, 0.37) and a correlated color temperature of 6295 K. As demonstrated in the present work, an approach adopted from phosphate to borophosphate is conducted to develop high-quality phosphors.