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A series of blue phosphors based on Eu2+-activated boracite Zn 3 B 7 O 13 Cl were synthesized by high-temperature solid-state reaction. The phase composition and crystal structure were confirmed by XRD Rietveld refinements, while the optical transitions and band natures were analyzed using absorption spectra. The blue luminescence of Zn 3 B 7 O 13 Cl:Eu2+ shows a narrow band spectrum peaked at 405 nm due to the 4f65 d→4f7(8S 7/2) transitions. Additionally, the sharp line transition of 4f7 (6P 7/2)→4f7 (8S 7/2) was also detected even at 300 K. The experiments confirm that the blue luminescence efficiency of Zn 3 B 7 O 13 (Cl 1-x F x):0.03Eu2+ (x = 0, 0.05, 0.1, 0.2, 0.3) is improved with the increase of the substitution of F− for Cl−. To further improve the luminescence efficiency, the samples were post-annealed at 850 °C in a reducing atmosphere. The results demonstrate that the post-annealing can improve the luminescence efficiency and thermal stability in as-prepared Zn 3 B 7 O 13 (Cl 1-x F x):0.03Eu2+ (x = 0, 0.05, 0.1, 0.2, 0.3) by eliminating the residual Eu3+. The maximum efficiency and thermal activation energy were confirmed in post-annealed Zn 3 B 7 O 13 (Cl 1-x F x):0.03Eu2+ (x = 0.3), which are 65% and 0.31 eV, respectively. The luminescence mechanisms and thermal stability of Eu2+ activators were discussed. • Zn 3 B 7 O 13 Cl:Eu2+ shows an efficient narrowband blue luminescence. • Sharp line transition of 4f7 (6P 7/2).→4f7 (8S 7/2) was also detected even at 300 K. • Luminescence efficiency increases with the substitution of F− for Cl− in the lattice. • Post-annealing eliminates residual Eu3+ resulting in significant improvement of luminescence. [ABSTRACT FROM AUTHOR]

Different B 2 O 3 content was added to Ce3+–doped Gd 2 O 3 –Al 2 O 3 –SiO 2 (xBGAS:1.1Ce3+, x = 0, 5, 10, 15) glasses to improve the photoluminescence (PL) and scintillation properties. The transmittance of 15BGAS:1.1Ce3+ glass is over 80%. The X–ray absorption near edge spectroscopy (XANES) spectra imply that Ce4+ can be effectively reduced to Ce3+ in the glasses by adding Si 3 N 4. The excitation and emission spectra show a blue shift with increase of B 2 O 3 content. The photoluminescence quantum yield (PL QY) increases with the increase of B 2 O 3 content, reached the maximum of 59.55% when x = 15. The PL decay time of the glasses exhibits typical values (44–50 ns) due to 5d→4f transition of Ce3+ ions. The PL thermal activation energy become larger, indicating that xBGAS:1.1Ce3+ glasses have better luminescent thermal stability. The integral X–ray excited luminescence (XEL) intensity of the 15BGAS:1.1Ce3+ glass is 37.38% of Bi 4 Ge 3 O 12 (BGO) crystal, and the light yield is 1267 ph/MeV with an energy resolution of 23.22% at 662 keV when exposed to γ–rays. With the increase of B 2 O 3 content, the fast component of scintillation decay time gradually becomes shorter and the slow component becomes longer. The thermally stimulated luminescence (TSL) curves were measured to investigate the trap depth and density of defects in xBGAS:1.1Ce3+ glasses. [ABSTRACT FROM AUTHOR]