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Tb3+-doped Al2O3–B2O3–SrO glass was prepared by the melt annealing method, and the crystallization kinetics of the glass was studied by the thermal analysis method. The crystallization activation energy of the glass was calculated by the Kissinger method and the Ozawa method, the values of which were 271.83 ± 8.56 kJ mol−1 and 260.72 ± 8.20 kJ mol−1, respectively. Optical band gap and Urbach energy of Tb3+-doped glass and glass ceramic were calculated by absorption spectra. The results indicate that after heat treatment, the optical band gap of the glass ceramic is reduced compared to that of the glass. The emission intensity of Tb3+ in the glass ceramic is enhanced compared with that in the glass. Variable-temperature emission spectra show abnormal thermal quenching of Tb3+-doped glass and glass ceramic. The results show that Al2O3–B2O3–SrO glass ceramics doped with Tb3+ have high luminescence intensity and can be applied to green light emitting devices and display devices. [ABSTRACT FROM AUTHOR]

Tm 2 O 3 – Tb 4 O 7 –Sm 2 O 3 tri-doped glass ceramics containing eulytite-type structure were prepared by melt-annealing and crystallization. Controlling crystallization can be achieved by adjusting the heat treatment temperature or time. XRD Rietveld shows that rare earth ions are doped into the Ba 3 Gd(PO 4) 3 lattice. A significant reduction in optical band gap values was observed in glass ceramics after heat treatment. Emission spectra and decay curves verified the energy transfer from Tm3+ and Tb3+ to Sm3+, and white light emission was achieved by adjusting the doping concentration of Sm 2 O 3. Based on the temperature-dependent properties of the fluorescence intensity ratios of Sm3+/Tm3+ and Sm3+/Tb3+, the maximum value of the relative sensitivity (S r) was calculated to be 2.36% K−1. The results show that Tm 2 O 3 – Tb 4 O 7 –Sm 2 O 3 tri-doped glass ceramic can be a candidate material for w-LEDs and optical temperature measurement. [ABSTRACT FROM AUTHOR]

The La2O3–B2O3–SrO glass ceramics containing LaBO3 were prepared by melt crystallization method and doped with Tb3+/Eu3+ for luminescence performance investigation. The heat treatment conditions of the glass ceramics were determined by differential thermal analysis (DTA), X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM). The crystallization kinetics parameters such as crystallization activation energy Ec, Avrami index n were calculated by thermal analysis. Emission peaks at 489, 544 nm of Tb3+ and 590, 614 nm of Eu3+ were obtained under excitation at 377 nm. The tunable warm white light emission was obtained by varying the concentration of Eu3+ in Tb3+/Eu3+ co-doped glass ceramics. The temperature-dependent luminescence spectra show that at 150 °C the intensity of the emission peak can still reach more than 85% of the room temperature. Tb3+/Eu3+ co-doped La2O3–B2O3–SrO glass ceramics have high thermal stability and high luminescence properties, which can be applied to white LEDs and display devices. [ABSTRACT FROM AUTHOR]

Tb3+-doped transparent glass ceramics (GCs) containing Ba3Gd(PO4)3 crystal phase were prepared by the melting crystallization method. The heat treatment condition for GCs was determined as 740 °C/2 h by differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmittance curves. The optical energy bandgap values of glass ceramics (Eg=2.58 eV) are lesser than glass (Eg=3.47 eV). The fluorescence emission intensity results determined that the optimum doping concentration of Tb3+ was 0.4%. The reason for the concentration quenching is electrical multipolar interaction. It is notable that the emission intensity of Tb3+ with the same doping concentration in glass ceramics is stronger than that in precursor glass. The mechanism of enhanced luminescence is also discussed. The chromaticity coordinates move from the blue light region to the green light region with the change of concentration of Tb3+. Therefore, Tb3+-doped glass ceramics containing Ba3Gd(PO4)3 phase have color tunability and potential application value in solid-state lighting field. [ABSTRACT FROM AUTHOR]

In this paper, Tb3+-Sm3+ co-doped glass ceramics with K 3 Gd(PO 4) 2 crystal phase were successfully prepared by methods of melting curing crystallization. The optimal heat treatment conditions for the samples were determined to be held for 1.5 h at 750 °C by combining differential scanning calorimeter (DSC), x-ray diffraction (XRD) and scanning electron microscope (SEM). Under this condition, glass ceramics still have a high transmittance in the range of 400∼700 nm, up to 80 %. It was calculated that the optical band gap value of glass ceramic is smaller than that of glass, indicating that the sample structure was changed by heat treatment. Fluorescence lifetime and Dexter's theory demonstrate that Tb3+ transfers energy to Sm3+. By fixing the concentration of Tb3+ and changing the doping concentration of Sm3+, the luminous color of glass ceramics can be adjusted. At 458 K, the fluorescence intensity of Tb3+ and Sm3+ decreased to 89 % and 85 % of that at 298 K. Study shows that the prepared glass ceramics have potential applications in white light emitting diodes (WLEDs). • The Sm3+-Tb3+ doped glass ceramic containing K 3 Gd(PO 4) 2 was synthesized. • The transmittance of glass ceramic can reach 80 % in the visible region. • At 458 K, the luminous intensity of glass ceramics can reach more than 80 % of room temperature. • The thermal quenching activation energy of samples can reach 0.3057 eV. • The prepared glass ceramics can achieve tunable emission 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]

Tb3+-Yb3+ co-doped transparent glass ceramics (GCs) containing Y 2 Ti 2 O 7 crystal phases were synthesized by the melt crystallization. The light transmittance of GCs in the visible region reached 78%, and the average grain size was 278 nm under the optimal heat treatment conditions (720 °C/2 h). The GCs exhibited greater up-conversion luminescence intensity than precursor glass, and the reason for this result was explained in accordance with the Judd-Ofelt theory. Moreover, the introduction of Li+ did not change the crystalline phase of GCs. The emission intensity of the green light of the 8% Li + doped GCs was significantly enhanced by nearly 4.48 times under 980 nm excitation. The XRD refinement results suggest that the enhanced luminescence intensity is correlated with the change of the Y 2 Ti 2 O 7 crystal lattice caused by Li+ doping. The relevant luminescence mechanism was elucidated. The results suggest that Li+ doped transparent GCs open novel avenues for green UC applications. [ABSTRACT FROM AUTHOR]

Er3+-Yb3+ co-doped transparent glass-ceramics (GCs) containing Y 2 Ti 2 O 7 crystalline phase were prepared by the melting crystallization method. The qualitative relationship between light transmittance and three-dimensional structure parameters of glass-ceramic was studied according to the principle of stereology under different heat treatment conditions. As indicated by the research results, the light transmittance decreased with the increase in the equivalent spherical diameter (D 3S) and specific surface area per unit volume of the grains (S V). However, the light transmittance increased linearly with the increase in the discrete grains (S VP) and the mean free distance (λ). The up-conversion luminescence intensity was found to be most vigorous under Er3+ and Yb3+ doping concentrations of 0.5% and 0.9%, respectively, at 980 nm excitation. Considering the correlation between pump power and up-conversion emission intensity, the up-conversion luminescence mechanism was explored. As revealed by the results of color purity and chromaticity coordinates, Er3+-Yb3+ co-doped GCs containing Y 2 Ti 2 O 7 have promising applications in green up-conversion luminescence. [ABSTRACT FROM AUTHOR]

Pr3+-Er3+ co-activated glass-ceramics containing Ba 3.75 Gd 0.833 Nb 10 O 30 crystalline phase were prepared as a multifunctional material. The optimum heat treatment condition was determined to be 750 °C/90 min, as this condition is most favorable for luminescence. As the Pr3+ concentration increases, the emissions of 3P 0 and 1D 2 energy levels show different trends, leading to a shift in luminescence from orange to yellow. With the introduction of Er3+, the co-doped sample achieves orange-yellow-green tunable luminescence. The 0.3%Pr3+-0.3%Er3+ co-doped sample exhibits alternating yellow-orange-green luminescence during continuous excitation in the range of 250–500 nm, which has potential applications in optical anti-counterfeiting. In the temperature interval of 298–458 K, the maximum temperature sensitivities based on the NTCLs of Pr3+ and Er3+ were 0.82 × 10−2 K−1 (S a) and 1.40 % K−1 (S r). Meanwhile, the thermal repeatability ratio is higher than 92.3 %, which proved that it is a potential temperature sensing material. In addition, the concentration quenching, energy transfer and luminescence phenomena involved were analyzed in depth and their mechanisms were explained. [ABSTRACT FROM AUTHOR]

Transparent glass ceramic with Ba 2 NaNb 5 O 15 as the main crystal phase was prepared, and the appropriate heat treatment condition was selected as 710 °C/150 min through various characterizations. The luminous intensity and thermal stability were enhanced significantly when the glass ceramic was used as the luminous matrix. After introducing Ti4+ ions as charge compensators, the luminescence performance and thermal stability were further improved, and the reasons for this were analyzed. At 458 K, the luminous intensity of 0.5%Eu3+ doped glass ceramic containing 0.5%Ti4+ can maintain about 65% of room temperature with a chromaticity shift of 5.16 × 10−2. The relative and absolute sensitivities of 0.7%Er3+ doped glass ceramic were 4.04 × 10−3 K−1 and 1.31% K−1. Introducing Ti4+ ions would weaken the population redistribution ability of 2H 11/2 and 4S 3/2 levels and reduce the temperature sensitivity. However, the sample containing Ti4+ shows good thermal stability, its green emission at 458 K has a small chromaticity shift of 6.45 × 10−3. The research shows that the glass ceramic can be used as a good luminescent host material, and Eu3+/Er3+ doped glass ceramic can be used in the fields of LEDs or temperature sensing. [ABSTRACT FROM AUTHOR]

A series of NaGd(MoO 4) 2 glass ceramics containing Eu3+-Tb3+ were fabricated using the melt-curing crystallization method. These glass ceramics were subjected to various analyses, such as differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM), and light transmittance curve analysis, to determine the optimal heat treatment conditions, which were determined to be 680 ℃/1.5 h. The XRD Rietveld analysis results confirmed the successful incorporation of Eu3+ and Tb3+ ions into the NaGd(MoO 4) 2 lattice structure. Moreover, the glass ceramics exhibited a smaller optical bandgap than the precursor glass, as observed by absorption spectroscopy. The energy transfer from Tb3+ to Eu3+ was demonstrated through the excitation spectra, emission spectra, and fluorescence decay curves. The primary mechanism responsible for this energy transfer was identified as a dipole dipole interaction. The ability to produce multicolor tunable emission was achieved by varying the Eu3+ doping concentration at a fixed Tb3+ concentration. The fluorescence intensity ratio and temperature dependence of Tb3+ and Eu3+ were used to calculate the relative sensitivity (S r), which reached a maximum of 3.34 % K−1 at 458 K. In conclusion, Eu3+-Tb3+ co-doped glass ceramics have promising potential for application in the fields of light-emitting diodes and temperature sensing. • Eu3+-Tb3+ co-doped NaGd(MoO 4) 2 glass ceramics were prepared. • The transmittance of glass ceramic can reach 80 % in the visible region. • The maximum relative sensitivity of the glass ceramics were obtained to be 3.34 % K−1 at 458 K. [ABSTRACT FROM AUTHOR]

• Sm3+, Eu3+ doped NaNbO 3 glass ceramics were prepared and red light emission was realized. • The energy transfer efficiency was 49.44 % for 0.8 % Sm3+, 1.0 % Eu3+ doped NaNbO 3 glass ceramics. • The color purity was 95.7 % for 0.8 % Sm3+, 1.0 % Eu3+ doped NaNbO 3 glass ceramics. • The thermal quenching activation energy of glass ceramics was 0.236 eV and color offset value was 1.83 × 10−3, indicating good thermal and color stability. The lack of red light in commercial white LEDs limits the application in solid-state lighting. So preparing high-performance red luminescent materials is currently the main challenge. In this study, a series of Sm3+, Eu3+ co-doped glass ceramics containing NaNbO 3 crystalline phase were successfully prepared using the melt-curing-crystallization method. By differential scanning calorimetry analysis, X-ray diffraction analysis, scanning electron microscopy analysis and light transmittance analysis, the optimal heat treatment conditions for glass ceramics were determined to be 570 °C for 90 min. With the increase of Eu3+ concentration, the emission peaks of Sm3+ at 565 nm, 602 nm and 649 nm gradually decreased, indicating that there was energy transferred between Sm3+ and Eu3+. The emission intensity of the 0.8 mol% Sm3+, 1.0 mol% Eu3+ co-doped NaNbO 3 glass ceramics at 438 K still reaches 87 % of room temperature. Sm3+, Eu3+ co-doped NaNbO 3 glass ceramics have potential application value in the field of white LEDs. [ABSTRACT FROM AUTHOR]

• 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]

Dy3+ doped ZnMoO 4 glass-ceramics was prepared by traditional melt crystallization method. The crystalline phase, microscopic morphology, transmittance, the optimal heat treatment condition and luminescence properties of the samples were discussed. The emission peaks are located at 482 nm, 574 nm and 663 nm due to 4F 9/2 →6H 15/2 , 4F 9/2 →6H 13/2 and 4F 9/2 →6H 11/2 transitions of Dy3+ under 387 nm. When the doped concentration of Dy3+ exceeded 0.4%, it was proved that the multi-stage interaction between adjacent ions causes concentration quenching by calculating the critical distance between Dy3+. The chromaticity coordinate (CIE) showed the luminescence color of the samples in the white light region, indicating that Dy3+ doped glass-ceramics containing ZnMoO 4 were expected to be applied in white-light emitting diode (w-LED). [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]