Preparation of Sr8Mg1−mZnmY(PO4)7:Eu2+ solid solutions and their luminescence properties

Abstract

A series of orthophosphate solid solutions with a general formula of Sr₈Mg_1−mZn_mY(PO₄)₇: Eu²⁺ (0 ≤ m ≤ 1) were synthesized by the combustion-assisted synthesis technique. The XRD patterns confirm the formation of a solid solution of Sr₈Mg_1−mZn_mY(PO₄)₇ and lattice parameters of the solid solutions are linearly dependent on m. The excitation spectra of these phosphors show broad band excitation and absorption in the 250–470 nm near ultraviolet (UV) region, which is ascribed to the 4f⁷–4f⁶5d¹ transitions of Eu²⁺. With an increase in m, the emission color shifts from yellow to green under near-UV excitation, which is rationalized in terms of two competing factors of the crystal filed strength and bond covalence. All the results indicate that the solid solution Sr₈Mg_1−mZn_mY(PO₄)₇: Eu²⁺ can be a good candidate of phosphor applicable to near-UV LEDs for solid-state lighting.