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A series of Na 1-z K z Ba 1-y Sr y B 9 O 15 :Eu2+ were synthesized by the high temperature solid state method. H 3 BO 3 excess makes it easier for Eu2+ to enter Na+ site, and the single-phase "blue + green" double emission band can be observed, which is proved by thermoluminescence and the change of crystal structure. Moreover, there exists an intense energy transfer from the blue-emitting center to the green-emitting center, which is proved by the decay curve. The occupation of Eu2+ can be tuned by the introduction of Sr2+ and K+ in NaBaB 9 O 15. Further, the highly thermal-sensitive property of NaBaB 9 O 15 : 1%Eu2+ makes it feasible for its potential application in luminescent ratiometric thermometers with wide temperature range. In addition, the disorder degree of matrix cations increases with the incorporation of K+, which improves the thermal stability. Image 1 • Eu2+ can enter into Na+ site with the excessive H 3 BO 3 and muti-band emission is achieved. • Sr2+/K+ can adjust the occupied radio of Eu2+ in Ba2+ and Na+ site. • K+ can improve the thermal stability of NBB:Eu2+ due to the disorder degree of matrix cations. • NBB:1%Eu2+ could be a versatile solid-state probe. [ABSTRACT FROM AUTHOR]

Abstract It is well-known that the thermal quenching (which is caused by non-radiative transition) damages the efficiencies of fluorescent lamps and LED lamps, especially for the high-power devices. Therefore, it is important to reduce the thermal quenching for improving the performance of illumination devices. In this work, Zn 3 (BO 3)(PO 4):Mn2+,Tb3+ is designed which appeared abnormal thermal quenching behavior. The phosphor does not exhibit thermal quenching even up to 200 °C (for emission of Mn2+) and 150 °C (for emission of Tb3+). The abnormal phenomenon is related to the shallow effects which are caused by the Mn2+ and Tb3+ doping in the host. Meanwhile, the thermal active phonon-assisted excitation also prevents the thermal quenching, which results in the broadening and blue-shift of the emission bands. Our result demonstrated that Zn 3 (BO 3)(PO 4):Mn2+, Tb3+ may be a potential candidate for the exploration of thermal stable materials. Graphical abstract Image 1 Highlights • Zn 3 (BO 3)(PO 4):Mn2+, Tb3+ was synthesized by solid state method. • An abnormal phenomenon is related to the defect of the host. • Thermal stability of phosphor was improved. [ABSTRACT FROM AUTHOR]

Abstract Series of Ce3+/Eu2+, Ce3+/Mn2+ and Ce3+/Eu2+/Mn2+ doped Ba 3 Y(PO 4) 3 samples were synthesized by a high temperature solid state reaction method. Phase formation, energy transfer, luminescence properties and thermal quenching properties were investigated carefully. The energy transfer from Ce3+ to Eu2+ and Ce3+ to Mn2+ in Ba 3 Y(PO 4) 3 were verified and discussed detailed. When Ce3+ and Eu2+ are co-doped, the energy transfer process from Ce3+ to Eu2+ is confirmed with electric dipole-dipole interaction. For Ce3+/Mn2+ co-doped phosphors, the energy transfer process from Ce3+ to Mn2+ is proved with electric dipole-dipole interaction. Besides, due to the existence of defects, the phosphors show excellent thermal stability. For Ce3+/Eu2+/Mn2+ tri-doped Ba 3 Y(PO 4) 3 , the energy transfer Ce3+→Eu2+ (Mn2+) and Eu2+→Mn2+ are confirmed. The energy transfer priority among Ce3+, Eu2+ and Mn2+ is analyzed in detail basing on the change of emission intensity. The obtained tri-doped phosphors contain red, green and blue component, thus they can emit warm white light basing on the energy transfer. The results show that they may be novel white-light-emitting phosphors for ultraviolet white light emitting diodes. Graphical abstract fx1 [ABSTRACT FROM AUTHOR]

Series of Sr 6 Ca 4 (PO 4) 6 F 2 :Ce3+, Tb3+, Sm3+ are prepared by a high temperature solid state method. Ce3+, Tb3+ or Sm3+ single-doped Sr 6 Ca 4 (PO 4) 6 F 2 can produce blue, green and red emission under ultraviolet excitation, respectively. However, the emission intensities of Tb3+ and Sm3+ are relatively weak due to their forbidden transition. In order to achieve white light, the spectral property and decay curves of Sr 6 Ca 4 (PO 4) 6 F 2 :Ce3+/Tb3+/Sm3+ are measured, not only the energy transfer of Ce3+-Tb3+, Ce3+-Sm3+ and Tb3+-Sm3+ was demonstrated, importantly, but also the single-phase white emitting phosphor Sr 6 Ca 4 (PO 4) 6 F 2 :0.14Ce3+, 0.07Tb3+,0.13Sm3+ was obtained by the energy transfer. [ABSTRACT FROM AUTHOR]