Spectral broadening of blue (Sr, Ba)5(PO4)3Cl:Eu2+ phosphors by changing Ba2+/Sr2+ composition ratio for high color rendering index

A single-phase Sr5-x-yBay(PO4)3Cl:xEu2+ blue phosphors were synthesized through a solid-state reaction. By increasing Ba2+/Sr2+ ratio, their emission spectra are redshifted (449 nm→460 nm in main peak) and broadened (34→90 nm in half width). Their excitation spectra are in the near ultraviolet region ascribed to be the allowed transition of Eu2+ from the 4f ground state to the 5d excited state. The phosphors show a similar thermal stability with Y3Al5O12:Ce3+ commercial phosphor. A white-light-emitting diode was fabricated using 400 nm chip with blue Sr2.45Ba2.45(PO4)3Cl:0.1Eu2+ and orange Sr3SiO5:Eu2+ phosphors. The white-light-emitting diode shows the color coordinates (0.3118, 0.3039) at a white light (correlated color temperature=6810 K) and excellent color rendering index of 86. These results suggest that Sr2.45Ba2.45(PO4)3Cl: 0.1Eu2+ is a promising blue phosphor for high color-rendering ultraviolet-based white-light-emitting diode.