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The coexistence mechanism of Eu2+ and Eu3+ ions in YAl3(BO3)4 host under different reducing conditions is investigated and confirmed in great detail, which can be described by three aspects as following. First, Eu3+ is protected by the layered structure of YAl3(BO3)4. Second, the number of the interstitial defects ((Al)i...,(Y)i...) increases with increasing Eu2+ to maintain the charge balance of the system. And these defects can capture free electrons which are used for the reduction of Eu3+. Finally, free holes become more and more with the number of nonequivalent substitution defects (EuY') increasing, which make the 5d electrons of Eu2+easily escape to the conduction band and Eu2+ convert to Eu3+. This work will be of great significance to research coexistence of multiple valence ions in the structure of borate and defect motion with nonequivalent substitution. [ABSTRACT FROM AUTHOR]

Series of NaBa 0.97 Ce 0.03 B 9 O 15 : x Tb3+, y Sm3+, z Dy3+ are synthesized by the traditional high temperature solid-state method. Ce3+ is used as a sensitizer to improve the spectral properties of Tb3+, Sm3+ and Dy3+ by the way of energy transfer which is proved by the fluorescence decay curves. And the mechanisms of energy transfer from Ce3+ to Tb3+, Sm3+ and Dy3+ are all determined as dipole-dipole interaction. The color of NBB:3%Ce3+, x Tb3+, 0.5%Sm3+ can shift from light violet thought white to yellow. And NBB:3%Ce3+, z Dy3+ can give out white light and move to green field. Moreover, the thermal stability makes NBB:3%Ce3+, 0.2%Dy3+ be a potential candidate for the self-referencing luminescent thermometry. Image 1 [ABSTRACT FROM AUTHOR]

A series of color-tunable NaBa1−zSrzB9O15:Ce3+,Mn2+ phosphors were synthesized by a high temperature solid state method. Luminescence property, energy transfer, thermal stability and cation substitution were investigated in detail. Due to energy transfer, NaBaB9O15:Ce3+,Mn2+ presents violet to green luminescence and manifest a broad excitation range from 200 to 350 nm. The energy transfer mechanism of Ce3+–Mn2+ is identified as a dipole–dipole interaction. NaBa1−zSrzB9O15:Ce3+,Mn2+ displays both Ce3+ violet and Mn2+ green and orange emissions under ultraviolet excitation. It is observed that Sr2+ partial substitution for Ba2+ could adjust the ratio of Mn2+ emission intensity in different cation sites, which results from preferred sites’ occupation with modification of the crystal structure. Furthermore, increase in temperature can enhance the energy transfer from Ce3+ to Mn2+, which enhances the Mn2+ emission intensity sharply. The highly thermal-sensitive property of NaBa1−zSrzB9O15:Ce3+,Mn2+ makes it feasible for its potential application in luminescent ratiometric thermometers with wide temperature range. [ABSTRACT FROM AUTHOR]

A series of color-tunable NaBa1−zSrzB9O15:Ce3+,Mn2+ phosphors were synthesized by a high temperature solid state method. Luminescence property, energy transfer, thermal stability and cation substitution were investigated in detail. Due to energy transfer, NaBaB9O15:Ce3+,Mn2+ presents violet to green luminescence and manifest a broad excitation range from 200 to 350 nm. The energy transfer mechanism of Ce3+–Mn2+ is identified as a dipole–dipole interaction. NaBa1−zSrzB9O15:Ce3+,Mn2+ displays both Ce3+ violet and Mn2+ green and orange emissions under ultraviolet excitation. It is observed that Sr2+ partial substitution for Ba2+ could adjust the ratio of Mn2+ emission intensity in different cation sites, which results from preferred sites’ occupation with modification of the crystal structure. Furthermore, increase in temperature can enhance the energy transfer from Ce3+ to Mn2+, which enhances the Mn2+ emission intensity sharply. The highly thermal-sensitive property of NaBa1−zSrzB9O15:Ce3+,Mn2+ makes it feasible for its potential application in luminescent ratiometric thermometers with wide temperature range. [ABSTRACT FROM AUTHOR]

A new Dy(III) complex, [KDy(sbtc)(H2O)2]·2H2O (1) (KH3sbtc: 5-sulfo-1,2,4benzenetetricarboxylic acid potassium salt), has been synthesized by solvothermal reaction of Dy2O3and KH3sbtc, and characterized by single crystal X-ray diffraction studies, elemental analysis, and FTIR. Single crystal X-ray diffraction reveals that1has a 3-D architecture, and there is only one crystallographically independent Dy(III) and K(I) in1. The coordination geometry of Dy(III) is a distorted monocapped tetragonal antiprism and K(I) is also a distorted monocapped tetragonal antiprism. The whole sbtc4−is aμ8-bridge linking four different Dy(III) cations and four different K(I) cations, giving a 3-D network structure. Thermal stability and solid luminescence of1were also investigated. [ABSTRACT FROM AUTHOR]

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 (Zn, M) 3 (BO 3)(PO 4) (M = Ca, Mg):Ce3+ were synthesized by a high temperature solid state method, and the luminescence properties were investigated. Zn 3 (BO 3)(PO 4):Ce3+ presents two emission bands, which shows the different changing trends with increasing Ce3+ concentration. When introduced Mg2+ and Ca2+ into Zn 3 (BO 3)(PO 4), (Zn, M) 3 (BO 3)(PO 4) (M = Ca, Mg):Ce3+ also shows two emission bands because Ce3+ occupies three kinds of Zn sites and transits from 5d energy level to double ground state. Therefore, the two emission bands of Zn 3 (BO 3)(PO 4):Ce3+ should be assigned to the different occupancy sites of Ce3+. Moreover, the selective emission was realized and the emission intensity of Ce3+ was enhanced by the cationic substitution. Graphical Abstract Unlabelled Image Highlights • Series of (Zn, M) 3 (BO 3)(PO 4) (M = Ca, Mg):Ce3+ were synthesized. • (Zn, M) 3 (BO 3)(PO 4) (M = Ca, Mg):Ce3+ shows two emission bands. • Two emission bands of Zn 3 (BO 3)(PO 4):Ce3+ are assigned to the different occupancy sites. [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]

Abstract Luminescence mechanism of self-activated phosphor Ca 0.75 Sr 0.2 Mg 1.05 Si 2 O 6 (CSMS) originating from oxygen vacancy defects has been deeply investigated by regulating synthesis temperature. The results demonstrate that the luminescence comes from three different oxygen defects in the crystal structure. For Ce3+ doped CSMS (ICSD#68180), two concentration quenching phenomena can be observed at x = 0.03 and 0.12 as the result of the formation of new substance CaMgSi 2 O 6 (ICSD#17043), which leads to the actual concentration of Ce3+in CSMS (ICSD#68180) is far less than the doping concentration since part of Ce3+ ions enter CaMgSi 2 O 6 (ICSD#17043). The emission spectra of CSMS: x Ce3+ shifts from 388 nm to 405 nm with increasing Ce3+ content, which mainly should be due to the 5d energy center of Ce3+ shifting down and the crystal field split. Graphical abstracts 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]