Gel-combustion assisted synthesis of eulytite-type Sr3Y(PO4)3 as a single host for narrow-band Eu3+ and broad-band Eu2+ emissions

A series of eulytite-type Sr3Y1-x(PO4)3:xEu3+ (x = 0-0.13) and Sr3-yY(PO4)3:yEu2+ (y = 0-0.10) phosphors were successfully synthesized via gel-combustion and subsequent calcination in O2 and Ar/H2 atmospheres at 1250 °C, respectively. Detailed crystal structure analysis via Rietveld refinement showed that the phosphors were crystallized in the cubic system (space group I-43d, No. 220), in which the Eu3+ and Eu2+ activators reside at the Y3+ and Sr2+ sites, respectively. The trivalent Eu3+ ions (CN = 6) exhibited typical narrow-band luminescence via intra-4f6 transitions, with the red emission at ~ 615 nm being dominant (5D0 → 7F2 transition, FWHM = 15.9 ± 0.2 nm). The divalent Eu2+ ions (CN = 6 and 9) showed broad-band luminescence ranging from light-blue to blue via 4f65d1 → 4f7 transitions (FWHM = 115 ± 2 nm). The optimal Eu3+ and Eu2+ concentrations were determined to be 10 at% (x = 0.10) and 7 at% (y = 0.07), respectively, and the mechanisms of concentration quenching were discussed. The excitation/emission properties, fluorescence decay kinetics, CIE chromaticity, and particularly the rarely addressed thermal stability of the phosphors were investigated in detail.