Achieving white emission by site-selective occupation of Eu2+ in K2BaSr(PO4)2-x(BO3)x:Eu2+

Efficient regulation of activator site occupation is crucial for developing white light phosphors with excellent luminous properties. Herein, we report the synthesis of new borophosphate K2BaSr(PO4)(2-x)(BO3)(x):0,04 Eu2+ phosphors via an anion group substitution strategy. In the pristine sample, there are three different cationic sites (Ba2+ , Sr2+ , and K+) with different coordination environments where Eu2+ can occupy the Ba2+ and/or Sr2+ sites. In the process of (BO3)(3-) partially substituting (PO4)(3-) units, owing to the effect of increased cation disorder generated from the difference in geometric configurations between the two anion groups, a new emission band centering at around 535 nm appears in the emission spectra. The intensity of this band increases as more (PO4)(3- )units are substituted by (BO3)(3-), resulting in the phosphor emission tuned from blue to white by controlling the (BO3)(3-) concentration. This emission band can be attributed to the occupation of Eu2+ at the K+ sites induced by cation disorder through the analysis of structural and photoluminescence properties and first-principles calculations, except for the co-occupation of Eu(2+ )with Ba and Sr sites. A phosphor-converted LED (pc-LED) has been successfully fabricated using the phosphor at optimized compositions, K2BaSr(PO4)(2-x)(BO3)(x):0,04 Eu2++, and a 365 nm near-ultraviolet chip, exhibiting a color rendering index of 81.3 and a correlated color temperature of 7024 K. Our findings demonstrate the effectiveness of the anion group modulation for developing new high-performance LED phosphors.