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• Transparent glass-ceramic containing Ba 2 YNbO 6 crystal phase was prepared. • The luminous intensity and hardness of glass-ceramic were increased by about 50% and 30%. • At 473 K, the color coordinate shift of glass-ceramic in the warm white area was 5.4 × 10−3. In this work, Dy3+-Eu3+ doped precursor glass and transparent glass-ceramics containing Ba 2 YNbO 6 crystal phase have been designed by the melting crystallization method. It was proved by XRD and XPS that the target crystal phase was successfully obtained. 750 ℃/180 min was selected as the heat treatment condition, after analyzing the micro-morphology, fluorescence spectra, transmittance curves and Vickers hardness of glass-ceramics. Under this condition, the luminescence intensity and Vickers hardness of glass-ceramic were about 50% and 30% higher than that of precursor glass, respectively. The chromaticity coordinate of the 2.0%Dy3+-1.0%Eu3+ co-doped glass-ceramic was (0.4158, 0.3862), and the correlated color temperature was 3179 K. Its excellent stability to thermal quenching at LED working temperature (423–473 K) was observed and the luminescence intensity can be maintained above 89.6% of room temperature. The activation energy of 2.0%Dy3+-1.0%Eu3+ co-doped glass-ceramic was estimated to be 0.3548 eV by temperature-dependent emission spectra, and the color coordinate shift was small, about 5.4 × 10−3. The research results show that the glass-ceramic has good warm white luminescence properties and fluorescent thermal stability. [ABSTRACT FROM AUTHOR]

Abstract The Tb3+ mono-doped and Eu3+-Tb3+ co-doped transparent glass-ceramics (GCs) were fabricated via melt-quenching technique and subsequent heating. The crystal structural and luminescence properties of the samples were systematically investigated via X-ray diffraction (XRD), scanning electron microscope (SEM), transmittance, excitation and emission spectra, and fluorescence lifetime, respectively. The emission spectra of Tb3+ mono-doped GCs are composed of several sharp emission lines about at 410 nm, 436 nm, 488 nm, 545 nm, 587 nm and 622 nm, respectively. Among them, when the Tb3+ mono-doped concentration is 0.7mol%, the brightest green light is generating at 545 nm due to 5D 4 →7F 5 transition of Tb3+ ions. The effective energy transfer from Tb3+ to Eu3+ was observed by fluorescence spectra and fluorescence lifetimes of Eu3+-Tb3+ co-doped GCs. In addition, the emission of Eu3+-Tb3+ co-doped GCs from light green-white-yellow can be achieved by adjusting the doping concentration of Eu3+ and Tb3+. These results indicate that Eu3+-Tb3+ co-doped GCs have potential applications in the field of white light emitting diodes (w-LEDs). Graphical abstract Image 1 Highlights • The Tb3+ mono-doped and Eu3+-Tb3+ co-doped glass-ceramics are prepared. • The optimum doping concentration of Tb3+ ions is 0.7mol%. • The mechanism of energy transfer from Tb3+ ions to Eu3+ ions is studied. • The energy transfer efficiency is up to 71%. [ABSTRACT FROM AUTHOR]

Er 3+ /Yb 3+ co-doped transparent glass ceramics containing Na 3.6 Y 1.8 (PO 4 ) 3 crystals were prepared by high-temperature melting and subsequent heat treatment the precursor glass, and their up-conversion luminescent properties were investigated. The optimum heat treatment condition of glass at 630 °C for 2 h were determined by a series of experimental results, and confirmed the existence of Na 3.6 Y 1.8 (PO 4 ) 3 crystals in glass ceramics. The up-conversion luminescence spectra of the glass ceramic samples under pulsed excitation at 980 nm revealed luminescence bands corresponding to Er 3+ ion transitions in the green ( 4 F 7/2 - 4 I 15/2 , 2 H 12/2 - 4 I 15/2 , 4 S 3/2 - 4 I 15/2 ) and red ( 4 F 9/2 - 4 I 15/2 ) spectral regions. The fluorescence spectra reaches a maximum when the molar ratio of Er 2 O 3 to Yb 2 O 3 is 1:7. Luminescence quantum yield of the samples was measured by using an integrating sphere. The transmission spectra proved that the glass ceramics sample still maintained a high transparency up to 83% in the visible region. [ABSTRACT FROM AUTHOR]

Tb 4 O 7 -Sm 2 O 3 co-doped transparent glass ceramics (GCs) containing Ba 3 Gd(PO 4) 3 crystalline phase were prepared by melt crystallization. The heat treatment condition for GCs was determined to be 740 ℃/2 h by differential scanning calorimetry, X-ray diffraction, scanning electron microscopy and transmittance curves. The optical energy bandgap value of glass ceramics is smaller than that of glass. The fluorescence lifetime and Dexter theory demonstrated the energy transfer from Tb3+ to Sm3+. The luminescence color can be adjusted in the white range when the Sm 2 O 3 doping concentration is changed. At 473 K, the luminous intensity of Tb3+ and Sm3+ can be maintained 86.63 % and 89.36 % of that at room temperature, respectively. The maximum values of the absolute and relative sensitivity of the glass ceramics are 0.00525 K−1 and 2.33 % K−1, respectively. This study shows that the obtained luminescent glass ceramics have potential applications in ultraviolet excited white light emitting diodes and optical thermometry. • Tb 4 O 7 -Sm 2 O 3 doped glass-ceramics containing Ba 3 Gd(PO 4) 3 is synthesized. • The existence of the energy transfer from Tb3+ to Sm3+ was certified. • The tunable emission in the white light range was realized by adjusting the doped concentration. • Tb 4 O 7 -Sm 2 O 3 doped glass-ceramics had good optical temperature sensing performance. [ABSTRACT FROM AUTHOR]

GdPO 4 :Yb 3+ /Tb 3+ powders were synthesized by a solid state reaction. The XRD patterns indicated that the obtained GdPO 4 :Yb 3+ /Tb 3+ powders have the monoclinic phase. Under the excitation of lights in the ultraviolet region, GdPO 4 :Yb 3+ /Tb 3+ powders show dominate green emission in the visible light region and emission band peaking at 980 nm in the infrared region along with shoulders at 1001 nm and 1024 nm, which originate from the 5 D 4 → 7 F j (j = 6, 5, 4 and 3) transitions of Tb 3+ and 2 D 5/2 → 2 F 7/2 transitions of Yb 3+ ions, respectively. Under the excitation of 980 nm, GdPO 4 :Yb 3+ /Tb 3+ powders show dominate green emission in the visible light region, which is based on the cooperative energy transfer between two Yb 3+ ions and one Tb 3+ ion. The results present successful doping of rare earth ions in particles with both up and down conversion fluorescence properties that can be used as potential spectrum converter in solar cells. [ABSTRACT FROM AUTHOR]

Er 3+ doped and Er 3+ –Yb 3+ co-doped ZnO–WO 3 –B 2 O 3 –SiO 2 glass-ceramics have been prepared by melt-crystallization method and their properties are examined by differential scanning calorimetry (DSC), scanning electron microscopy (SEM), X-ray diffractometry (XRD) and fluorescence spectroscopy. The results reveal that Er 3+ ions or Er 3+ –Yb 3+ ions have already entered into the crystalline field. The up-conversion mechanism of Er 3+ –Yb 3+ co-doped ZnO–WO 3 –B 2 O 3 –SiO 2 glass ceramics is analyzed, and the effect of Yb 3+ concentration on the intensity of up-conversion is investigated. With the increase of pump power, the intensity of green emission at 530 nm increases faster than that at 552 nm. The fluorescence spectrum reaches a maximum when the molar ratio of Er 2 O 3 to Yb 2 O 3 is 1:7. [ABSTRACT FROM AUTHOR]

• Dy3+-Eu3+ co-doped glass-ceramics containing ZnMoO 4 was prepared. • The existence of the energy transfer from Dy3+ to Eu3+ was certified. • Warm white light were achieved by adjusting the doped concentration. Dy3+-Eu3+ co-doped glass-ceramics (GCs) containing ZnMoO 4 were successfully prepared. The temperature range of heat treatment was preliminarily determined by differential scanning calorimeter (DSC) and thermogravimetry (TG). The crystalline phase was determined by X-ray diffraction (XRD), the structural feature was analyzed on the basis of Rietveld refinement, the morphology was observed by scanning electron microscopy (SEM), the absorption coefficients were calculated by light transmission curves. Combined with the above analysis, the optimal heat treatment condition was discussed. Through the fluorescence spectra and decay curve, there existed an energy transfer between Dy3+ and Eu3+, and the energy transfer efficiency from Dy3+ to Eu3+ increased with the increase of Eu3+ concentration. By calculating the critical distance and linearly fitting the data, it could be concluded that the mechanism of energy transfer was dipole-dipole interaction. With the changed of Dy3+-Eu3+ doped concentration, the color coordinates of these samples can be tuned in the white light region, and the 0.4% Dy3+-0.7% Eu3+ co-doped glass-ceramics obtained warm white light emission with low correlated color temperature (CCT). These results clearly showed that Dy3+-Eu3+ co-doped GCs containing ZnMoO 4 could be used as a potential candidate material in the field of white light-emitting diodes (w-LEDs). [ABSTRACT FROM AUTHOR]

• Er3+-Yb3+ doped glass ceramic containing NaBi(MoO4) 2 is synthesized. • The effect of Er3+ incorporation on the deviation angle of diffraction peak is discussed. • The up-conversion luminescence properties of Er3+-Yb3+ glass ceramics is studied. The molybdate precursor glass was prepared by the melting-annealing method. After heat treatment of the precursor glass, the glass ceramics containing NaBi(MoO 4) 2 crystal phase were successfully synthesized. The transmittance of the precursor glass and glass ceramics and up-conversion emission spectra at 980 nm were measured and analyzed. The effect of Er3+-Yb3+ doped concentration on the up-conversion luminescence intensity of glass ceramic samples was studied, and finally the best doped concentrations of Er3+ and Yb3+ were 0.6% and 1.0%, and the doped concentration ratio is 3:5. The Er3+-Yb3+ co-doped transparent glass ceramics containing NaBi(MoO 4) 2 have potential applications in green up-conversion luminescence. [ABSTRACT FROM AUTHOR]

Sm3+ doped precursor glass (PG) was obtained successfully via melt-quenching method and glass ceramic (GC) was precipitated via subsequent heat treatment. Combining the X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses, the optimum heat treatment condition is determined is 635 °C/3 h. The FTIR spectra of the precursor glass and glass ceramic indicate that the enhancement of the luminescent intensity of glass ceramics is related to the MoO 4 2− group appearance. From the transmittance curve of the glass ceramic presents its transmittance can reach 78% in the visible region. The emission spectra indicate the optimum doped concentration of Sm 2 O 3 is 0.3 mol%. Concentration quenching caused by dipole-dipole interaction will occur when Sm 2 O 3 is greater than 0.3 mol%. The calculation results of chromaticity coordinates (CIE) indicates that Sm3+ doped glass ceramic containing SrMoO 4 crystallite may be promising as reddish orange emitting materials. • Sm3+ doped glass ceramic containing SrMoO 4 is synthesized. • The critical distance between Sm3+ is 3.031 nm. • The luminescence properties of Sm3+ doped GC is stronger than PG. [ABSTRACT FROM AUTHOR]