KBaBP$_2$O$_8$:Tm$^{3+}$: a novel blue-emitting phosphor with high color purity

A series of novel blue emitting K$_{1+x}$Ba$_{1-2x}$Tm$_x$BP$_2$O$_8$ ($0.01\leq x \leq0.08$) phosphors were synthesized by a solid-state reaction at high-temperature for the first time. The phase purity and photoluminescence properties were investigated by $X$-ray diffraction (XRD) and fluorescence spectroscopy (FS) measurements, respectively. The influence of the doping concentration of Tm$^{3+}$ on its relative emission intensity was investigated, and the critical distance was calculated. The as-prepared phosphor can be effectively excited with a $356$ nm light, and exhibit blue emission at $457$ nm with high color purity. The above work indicates this phosphor could be a potential candidate as blue emitting phosphor for application in white light-emitting diodes.