A new silicate phosphor MgGd4Si3O13:Ce3+,Tb3+ was successfully synthesized with the objective of application in ultraviolet-excited light emitting diodes (LEDs) and field emission displays (FEDs). The structural and photoluminescence (PL) properties of un-doped MgGd4Si3O13 were studied. The PL properties and the energy transfer from Gd3+ to Tb3+ and Ce3+ to Tb3+ in Ce3+ and Tb3+ singly- and co-doped MgGd4Si3O13 were discussed. Ce3+ occupying two different crystalline sites show diverse PL properties and distinct energy transfer efficiencies to Tb3+. The cathodoluminescence (CL) spectra, depending on the accelerating voltage and probe current, were also studied. Excellent degradation resistance properties with good colour stability were obtained with continuous low-voltage electron-beam excitation.

•The blue long lasting phosphorescence of Sr5(PO4)3Cl:Eu2+ is first reported.•Filling and fading experiments are carried out for revealing natures of traps.•The afterglow mechanism for independent traps of Sr5(PO4)3Cl:Eu2+ is proposed.A novel blue emitting long lasting phosphorescence phosphor Sr5(PO4)3Cl:Eu2+ is synthesized by solid state method at 1223 K in reducing atmosphere. The afterglow emission spectrum shows one broad band centered at 441 nm due to the 5d–4f transition of Eu2+ at six coordinated Sr(II) sites and the color coordinates are calculated to be (0.149, 0.095) which is close to the light blue region. The excitation band is in 240–430 nm and partly overlaps the solar irradiation on Earth's surface. The long lasting phosphorescence of the optimal sample doping by 0.1 mol%Eu2+ can be recorded for about 1040 s (0.32 mcd/m2). Thermoluminescence shows that there are at least three types of traps corresponding to peaks at 340 K, 382 K, 500 K, respectively. The filling and fading experiments reveal that the traps in Sr5(PO4)3Cl:Eu2+ are independent. The shallow traps (340 K) essentially contribute to the visible long lasting phosphorescence, while the deep traps (382 K and 500 K) are proved to be very stable. Thus, the Sr5(PO4)3Cl:Eu2+ material shows potential applications as not only a long lasting phosphorescence phosphor, but also an optical storage material.

Undoped and Eu3+-doped Sr2Mg1−xZnxSi2O7 (0 ⩽ x ⩽ 1) powder crystals were obtained by conventional solid-state reaction. X-ray diffraction, inductively coupled plasma analysis, and Fourier transform infrared spectroscopy results implied that a complete solid-solution formed between Sr2MgSi2O7 and Sr2ZnSi2O7 as well as local structural adjustment. Excitation spectra exhibited O2−-Eu3+ charge transfer (CT) bands centered at 250 nm for Sr2MgSi2O7:Eu3+ and 258 nm for Sr2ZnSi2O7:Eu3+. Emission spectra exhibited a major band around 616 nm, which showed the environment around Eu3+ was non-centrosymmetric in both Sr2MgSi2O7:Eu3+ and Sr2ZnSi2O7:Eu3+. In addition, first principles calculations within the local density approximation (LDA) of density functional theory (DFT) were used to calculate the electronic structure of Sr2MgSi2O7 and Sr2ZnSi2O7. Calculated results were correlated with experimental UV-vis reflection spectra and the observed shift of the O2−-Eu3+ CT band.

The electronic structures and linear optical properties of Y2Si2O7 (YSO) and La2Si2O7 (LSO) are calculated by LDA method based on the theory of DFT. Both YSO and LSO are direct-gap materials with the direct band gap of 5.89 and 6.06 eV, respectively. The calculated total and partial density of states indicate that in both YSO and LSO the valence band (VB) is mainly constructed from O 2p and the conduction band (CB) is mostly formed from Y 4d or La 5d. Both the calculated VB and CB of YSO exhibit relatively wider dispersion than that of LSO. In addition, the CB of YSO presents more electronic states. Meanwhile, the VB of LSO shows narrower energy distribution with higher electronic states density. The theoretical absorption of YSO shows larger bandwidth and higher intensity than that of LSO. The results are compared with the experimental host excitations and impurity photoluminescence in Eu3+-doped YSO and LSO.Research highlights► Host excitation near the band gap of Y2Si2O7 and La2Si2O7 is analyzed. ► The calculated result well explains Eu3+ PL behaviors in Y2Si2O7 and La2Si2O7. ► The electronic structure and Eu3+ VUV PL in La2Si2O7 are first estimated.

The blue phosphor Ba0.9 Mg0.98Al10O17:0.1Eu2+, 0.02Mn2+ (BAM:Eu2+, Mn2+) was prepared by flux assisted solid-state reaction method. The effects of (NH4)2CO3 and LiF on the morphology and luminescent properties were studied. The usually obtained BAM:Eu2+, Mn2+ particles had hexagonal shape. We found that the thickness of the particle was affected by the amount of LiF and spherical-like particles can be obtained. The significant change on morphology from plate-like to spherical-like shape led to a highly enhanced luminescence of BAM:Eu2+, Mn2+. The maximum luminance intensity of prepared samples was 108% in comparison with the commercial BAM:Eu2+, Mn2+ under UV excitation.Highlights► The thickness of the plate-like BAM was affected by the amount of LiF flux. ► Spherical-like BAM particles with hexagonal surface could be obtained. ► The maximum luminance of the samples was 108% in comparison with commercial BAM.

A new silicate phosphor MgGd4Si3O13:Ce3+,Tb3+ was successfully synthesized with the objective of application in ultraviolet-excited light emitting diodes (LEDs) and field emission displays (FEDs). The structural and photoluminescence (PL) properties of un-doped MgGd4Si3O13 were studied. The PL properties and the energy transfer from Gd3+ to Tb3+ and Ce3+ to Tb3+ in Ce3+ and Tb3+ singly- and co-doped MgGd4Si3O13 were discussed. Ce3+ occupying two different crystalline sites show diverse PL properties and distinct energy transfer efficiencies to Tb3+. The cathodoluminescence (CL) spectra, depending on the accelerating voltage and probe current, were also studied. Excellent degradation resistance properties with good colour stability were obtained with continuous low-voltage electron-beam excitation.