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Abstract To develop long-afterglow luminescent materials for white LEDs application, a series of Sr 1·97 MgSi 2 O 7-1.5x N x :0.01Eu2+,0.02Dy3+ (0 ≤ x ≤ 0.49) phosphors were designed. The single-phase samples were confirmed and the introduction of N was verified by the XRD patterns and energy-dispersive X-ray spectrum. The average particle size of the phosphors was determined to be about 4.9 μm. When the N is doped, it has been found the Eu2+ emission intensity decreases gradually, which could be owing to the increasing crystal defects by the nonequivalent substitution between N and O. The excitation spectra reveal that the broad and strong excitation bands from 240 to 450 nm can well match the LED chip. It is interesting that the incorporation of N can improve the afterglow time, which has been interpreted by the thermoluminescence curves. The investigation of the temperature-dependent luminescence indicates a beneficial effect on the thermal stability by doping N in the phosphors. Graphical abstract Image 1 Hightlights • A meaningful idea by combining LEDs and afterglow was proposed in lighting field. • The long afterglow time can be increased by introducing N in the phosphors. • The Sr 1·97 MgSi 2 O 7-1.5x N x :0.01Eu2+,0.02Dy3+ shows potential applications in w-LEDs. • The present results could be constructive to the development of similar phosphors. [ABSTRACT FROM AUTHOR]

Abstract A series of Yb3+-Er3+, Yb3+-Ho3+, and Yb3+-Tm3+ doped Ca 2 Gd 8 (SiO 4) 6 O 2 (CGS) phosphors were synthesized by solid-state reaction method, and their upconversion (UC) luminescence properties for temperature sensing were studied. Upon 980 nm excitation, the green and red emissions of Er3+ were observed, and the optimal Er3+ concentration was determined to be 3 mol%. For the CGS:10%Yb3+,yHo3+ phosphors, three emission peaks in the green, red and near-infrared region appear. It was found that the relative intensities of Ho3+ different emissions change with Ho3+ concentration, which has been explained by the cross-relaxation process. The strongest Tm3+ emission appeared at 790 nm, attributed to the 3H 4 -3H 6 transition. The optimal Tm3+ concentration was determined to be 0.5 mol%. The temperature sensing behavior was evaluated by employing the thermally-coupled or non-thermally coupled levels of Er3+, Ho3+ and Tm3+. The maximum sensitivities obtained are 3.71 × 10 − 3 and 1.12 K-1 for CGS:10%Yb3+,3%Er3+, 0.111 K-1 for CGS:10%Yb3+,3%Ho3+ and 3.3 × 10 − 4 K−1 for CGS:10%Yb3+,0.5%Tm3+, respectively. The high sensitivities indicate the present phosphors could have potential application in temperature sensing. Highlights • Different strategies for temperature sensing were introduced in the present phosphors. • The present phosphors show smooth particle surface that benefits the UC luminescence. • High sensor sensitivity has been obtained in the CGS:Yb3+-Er3+/Ho3+/Tm3+. • The present phosphors could have potential application in optical temperature sensors. [ABSTRACT FROM AUTHOR]