Co-doped Glass Ceramics Research Articles

Energy transfer and color tunability in high-thermal-stability Dy3+/Tb3+ co-doped K3YF6 transparent oxyfluoride glass ceramics

The production process and comprehensive analysis of the co-doping of Dy3+ and Tb3+ in K3YF6 oxyfluoride glass-ceramics (GCs) are delved. The primary focus is on investigating the luminescent properties and energy transfer (ET) mechanisms within these systems. The embedding of well-formed K3YF6 nanocrystals within the matrix was verified through detailed analyses using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Fine-tuning the Tb3+ concentration facilitated the achievement of tunable emission, ranging from a subtle yellow to a yellowish green hue, demonstrating the remarkable flexibility in color manipulation. Fluorescence analysis unmistakably demonstrates the occurrence of energy transfer occurring between Dy3+ and Tb3+ ions, attaining a peak energy transfer efficiency of 51.33 %. Additional analysis applying Dexter's energy transfer formula affirms that the fundamental mechanism of energy transfer between Dy3+ and Tb3+ ions is dipole-dipole interaction. The K3YF6 glass ceramics (GCs) incorporating Dy3+/Tb3+ nanocrystals exhibit a remarkable thermal stability, retaining 89.07 % of their original relative emission intensity at 423 K when stimulated by 350 nm light. These findings indicate that Dy3+/Tb3+ co-doped K3YF6 GCs hold significant potential in solid state lighting, positioning them as a candidate for future lighting.

The effect of SiO2 crystallization in enhancing the luminescence of Dy3+-Sm3+ co-doped glass ceramics for cool white light application.

The present work investigates the structural and luminescence behaviour of Dy3+-Sm3+ co-doped glass ceramics obtained through heat treatment of precursor glasses. The growth of SiO2 polycrystalline particles and evolution of these crystallites in the glass domain are witnessed via XRD and FESEM study. The presence of network vibrational bands, hydroxyl groups and the increased quantity of bridging oxygens (BOs) in glass ceramics are analysed through FTIR spectroscopy study. The absorption study (UV-Visible-NIR) showed the possible electronic transitions of Dy3+ and Sm3+ ions. The red shift in the absorption band edges and the lower bandgap values are obtained as a result of improved heat treatment in glass ceramics. Emission studies show the enhanced luminescence intensity of glass ceramics under 350 and 402 nm excitations. Decay measurement of glass ceramics showed the improved lifetimes of Dy3+ and Sm3+ ions to have appeared in microseconds (×10-6s). The colour characteristics of glass ceramics analysed using CIE colour chromaticity diagram and correlated colour temperature (CCT) values suggest the neutral to cool white light emissions. Therefore, prepared glass ceramics with SiO2 polycrystalline phase are considered to be suitable materials in cool white LEDs applications.

Effect of Li+ on luminescence properties and thermal stability of glass ceramics containing SrMoO4

Dy3+, Eu3+ co-doped glass ceramics (GCs) containing SrMoO4 crystalline phase were prepared by melt-curing-crystallization method. The most favorable heat treatment conditions for the glass ceramics were found to be 610 °C/2 h by differential scanning calorimetry (DSC), ultraviolet spectrophotometer (UV–Vis), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The best doping concentrations of Dy3+ and Eu3+ in this glass ceramic were 0.8 % and 0.6 %, concentration quenching caused by dipole-dipole interactions occurs when the content of rare earth ions in GCs continues to increase. The chromaticity coordinates of the Dy3+- Eu3+ co-doped glass ceramics changed from cool white light to warm white light with the addition of Eu3+ concentration. At the optimal doping concentration (0.8 % Dy3+-0.6 % Eu3+), the chromaticity coordinate of glass ceramics is (0.3972, 0.3331), and the related color temperature is 3047 K. The luminescence intensity can still reach about 80 % of room temperature at 180 °C, and its thermal quenching activation energy is 0.233 eV. This suggests that glass ceramics have excellent thermal stability. After adding an appropriate amount of Li+, the crystalline phase of the glass ceramics remained unchanged and the luminous intensity of the glass ceramics increased by a factor of about 1.4 in the same environment. The thermal quenching activation energy of the glass ceramic doped with 0.2 % Li+-0.8 % Dy3+-0.6 % Eu3+ was 0.344 eV. The experimental results indicate that GCs has potential application prospects in the field of solid-state lighting.

Synthesis and upconversion luminescence properties of Ho3+-Yb3+ co-doped glass ceramics containing LiGd(WO4)2

Ho3+-Yb3+ co-doped glass ceramics containing LiGd(WO4)2 were prepared by melt crystallization method. By using the methods of differential scanning calorimetry (DSC), X-ray diffraction (XRD), transmittance, and scanning electron microscopy (SEM), the optimal heat treatment condition for the samples was identified to be 580 °C/140 min. In these conditions, the transmittance of glass ceramic is about 75 % in the 380–780 nm range. In the upconversion emission spectra, strong green emission (543 nm) and red emission (650 nm) due to 5F4/5S2, 5F5→5I8 transitions are observed at 980 nm excitation. Additionally, the optimum doping concentrations of Ho3+ and Yb3+ were 0.12 % and 0.4 %. The crystal field changes around dopant ions were analyzed using J-O theory and Eu3+ probe to explain the up-conversion luminescence enhancement of glass ceramics containing LiGd(WO4)2. The chrominance coordinates of 0.12 % Ho3+-0.4 % Yb3+ co-doped glass ceramics are located in the green light region, and the color purity is 95.6 %. In summary, Ho3+-Yb3+ co-doped transparent glass ceramics containing LiGd(WO4)2 have potential applications in infrared detection and green solid-state lasers.

Color tunability and temperature sensing capabilities in Dy3+/Sm3+ co-doped transparent oxyfluoride glass ceramics containing K3YF6 nanocrystals

This paper presents the preparation and characterization of transparent oxyfluoride glass ceramics (GCs) that contain nanocrystals of K3YF6 co-doped with Dy3+ and Sm3+. The study investigates the luminescence characteristics, the process of energy transfer (ET) and the behavior of the ratio-metric temperature sensing. The formation of well-defined nanocrystals of K3YF6 in the glass substrate was confirmed by X-ray diffraction (XRD) and transmission electron microscopy (TEM). By varying Sm3+ concentration, a tunable emission ranging from pale yellow to orange-red was observed. Energy transfer from Dy3+ to Sm3+ ions was confirmed through fluorescence spectra and decay curves. Sample K3YF6, containing 0.5 mol%Dy3+/1.2 mol%Sm3+, showed an absolute sensitivity (Sa) of 0.635 % K−1 and relative sensitivity (Sr) of 0.401 % K−1. These findings underscore the promising applications of K3YF6: Dy3+, Sm3+ GCs in multicolor displays and high-performance temperature sensing devices.

Preparation, luminescence and thermal stability of Tb3+/Eu3+ doped glass ceramics containing KAlSiO4 crystalline phase

The melt-crystallisation process was used to successfully synthesised Tb3+/Eu3+ doped glass ceramics with KAlSiO4 crystalline phase. The optimum heat treatment condition was determined to be 560 °C/90 min by DSC, XRD, SEM and optical transmittance curves, under which the optical transmittance of the glass ceramic in the visible region can reach 80%. Fluorescence spectroscopy was used to determine the energy transfer between Tb3+ and Eu3+, and it was discovered that the energy transfer mechanism was brought on by dipole-dipole interactions. The chromaticity coordinates of the 0.9%Eu3+-0.9%Tb3+ doped sample are (0.3627, 0.3389), it is close to the color of white light. According to variable temperature spectroscopy analysis, emission intensity of Eu3+/Tb3+ co-doped glass ceramics at 458 K can be maintained at 97% and 70% of room temperature at 543 and 614 nm, respectively, demonstrating that the sample has good thermal stability. The results of this study demonstrate the potential of Eu3+/Tb3+ co-doped glass ceramics with KAlSiO4 crystalline phase for use in white light emitting diodes, solid state colour development and other fields.

Preparation and luminescence properties of Tb3+-Sm3+ co-doped K3Gd(PO4)2 crystalline glass ceramics

In this paper, Tb3+-Sm3+ co-doped glass ceramics with K3Gd(PO4)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).

Tb3+–Yb3+ doped glass ceramics containing NaBi(MoO4)2: preparation and upconversion luminescence

A series of Tb3+–Yb3+co-doped transparent glass ceramics (GCs) containing NaBi(MoO4)2 were synthesized.

Preparation and improved luminescent properties of Tb3+/Yb3+ co-doped Na2O–CaO–SiO2–Al2O3–ZnO–CaF2 transparent glass-ceramics

Transparent glass-ceramics containing CaF2 single-phase or CaF2/Ca5(PO4)3F two-phase were obtained by heat-treating the precursor glass. Compared with the precursor glass, the glass-ceramics containing CaF2 crystal with low phonon energy greatly enhance the emission intensity. Further research was conducted on the influence of various crystallization procedures on the luminescent properties of the glass-ceramic, and the procedure crystallized at 660 °C for 4 h was determined to be the optimal heat treatment. The SEM results indicate that the crystal size of the glass-ceramics is in the nanometer scale, which guarantees the possibility of its optical application. The three-photon absorption process of the Tb3+/Yb3+ co-doped glass-ceramics containing CaF2 single-phase was confirmed based on the up-conversion emission spectra excited at different power of 980 nm laser. The chromaticity coordinates of the Tb3+/Yb3+ co-doped glass-ceramic are located in the green region, indicating its potential applications in green lighting and other optical display devices.

Synthesis and up-conversion luminescence properties of Ho3+-Yb3+ co-doped glass ceramics with perovskite structure

By using melt solidification crystallization method, Ho3+-Yb3+ co-doped transparent glass ceramics (GCs) containing LaTiO3 microcrystal were successfully prepared. The structure of the GCs was characterized by X-ray diffraction (XRD), which proved that LaTiO3 microcrystal was precipitated in the precursor glass (PG). The structures of PG and GCs were studied by infrared spectrum, which showed that a new absorption peak appeared in the GCs, which was attributed to the stretching vibration of the Ti-O bond in the [TiO6] octahedral group, and it further demonstrated the precipitation of the LaTiO3 microcrystal. By studying the up-conversion luminescence (UCL) properties, it is found that there were three emission peaks at 546, 652 and 484 nm, which are attributed to the 5F4/5S2 → 5I8, 5F5 → 5I8 and 5F3 → 5I8 transitions of Ho3+, respectively, and the optimal doping concentrations of Ho3+ and Yb3+ were determined. The chrominance coordinate of Ho3+-Yb3+ co-doped glass ceramic (GC) is situated in the green light area and the color purity is as high as 98.03 %. The researches above show that Ho3+-Yb3+ co-doped GCs with LaTiO3 microcrystal have a wide application prospect in green luminescence.

Thermally stable Dy2O3/Sm2O3 co-doped glass ceramics containing La2Sn2O7 crystal with tunable luminescence

By using the melt crystallization process, Dy2O3/Sm2O3 co-doped glass ceramics (GCs) containing La2Sn2O7(LSO) crystal were successfully prepared. By using X-ray diffraction (XRD), the sample's phase was determined, and scanning electron microscopy (SEM), the sample's morphology was examined. The optimal heat treatment condition of glass ceramics was determined to be 650 °C/1.5 h. Under 362 nm excitation, the energy transfer of Dy3+→Sm3+ was observed in Dy2O3/Sm2O3 co-doped glass ceramic samples from the emission spectrum. Electric dipole-electric dipole interaction is identified as the mechanism of energy transfer from Dy3+ to Sm3+ according to the Dexter formula for energy transfer. The emission spectra of 0.5%Dy2O3-0.4%Sm2O3 co-doped glass ceramic samples in a range from 298 K to 458 K show that the samples have high thermal stability, and the thermal quenching activation energy at 575 nm has been estimated to be 0.265 eV. According to chromaticity coordinates and correlated color temperature, warm white light emission may be achieved by co-doping Dy2O3/Sm2O3 glass ceramics. The findings demonstrate Dy2O3/Sm2O3 co-doped glass ceramics containing La2Sn2O7 crystal have a potential application prospect in warm white light-emitting diodes (w-LEDs).

Up-conversion color tunable and red luminescence of Ho3+/Yb3+ co-doped glass ceramics containing NaLaSiO4 crystals

By using the melt-annealing method, silicate precursor glasses were prepared. Optimal heat treatment conditions for glass ceramics at 610 °C for 90 min were established through a series of tests. Glass ceramics containing NaLaSiO4 crystals with β-K2SO4 structure were successfully synthesized after heat treatment. XRD patterns of glass ceramics were successfully fitted using Rietveld refinement, with rare earth ions entering the lattice by replacing sites of La resulting in a reduction in cell volume. A tunable emission from green light to red light was achieved by varying the Yb3+ doping concentration. By varying the concentration of Ho3+, the intensity of the up-conversion emission was significantly increased while maintaining high color purity in red light. The optimal concentration of Ho3+ was 0.4%, when the red light color purity was 98.9%. These results indicate that glass ceramics containing NaLaSiO4 crystals co-doped with Ho3+-Yb3+ could be used for up-conversion color-tunable emission and red luminescence.

Warm to neutral white light emissions from Dy3+–Eu3+ co-doped glass ceramics containing NaBSiO4 crystalline phase for W-LEDs applications

This paper reports on the structural, optical and luminescence studies of Dy3+–Eu3+ co-doped glass ceramics that are obtained via thermal treatment method. The initial confirmation on glass ceramics with the formation of NaBSiO4 crystalline phase was made through XRD study. The FTIR study showed the vibrations of network formers (B2O3, SiO2) and other functional groups. The quantity of non-bridging oxygens (NBOs) are increased in the glass ceramics with increase in annealing temperature. The absorption spectra (UV–visible-NIR) showed the possible transitions of Dy3+ and Eu3+ ions in the glass ceramics. A red-shift in the absorption band-edge and reduction in the optical band gap values were obtained for glass ceramics owing to their heating temperatures. Photoluminescence studies showed the excitations of Dy3+ and Eu3+ ions under 575 nm and 613 nm emission wavelengths. The obtained NaBSiO4 crystalline phase in the glass ceramics has enhanced the luminescence intensity, and lifetimes of Dy3+ and Eu3+ ions compared to unheated precursor glass when excited under 350 nm and 393 nm. Color chromaticity diagram and correlated color temperature (CCT) values showed a shift in the color of light from warm white of precursor glass to neutral white of glass ceramics. The overall results justify the possibility of considering the Dy3+-Eu3+ co-doped glass ceramics as efficient materials for solid-state lighting applications like W-LEDs.

Structural environment influence on Faraday effect in Tb3+ and Pr3+ co-doped fluorophosphate glass and glass-ceramics containing TbOF nanocrystals

The influence of structural environment of lanthanide ions on the co-doping Faraday effect is explored within fluorophosphate glasses and glass ceramics. In a first part, the crystallization process of a glass with a nominal composition 35 NaPO3 – 15 BaF2 – 50 TbF3 is explored in function of duration and temperature of the ceramization process. X-ray diffraction analysis and STEM-HAADF allowed the identification of crystalline TbOF cubic fluorite phase in these glass-ceramics, with a maximum crystalline fraction of 42 ± 2 wt% for a crystallite size of 46 nm for the sample heat-treated 10 h at 394 °C. In a second part, TbOF glass-ceramics following the composition law 35 NaPO3 – 15 BaF2 – 0.5 ((100-x) TbF3 – x PrF3) with x = 0, 1, 2, 3, 4 and 5 are prepared at the optimal heat treatment of 10 h at 394 °C corresponding to maximal crystalline fraction and optical transmission. The Verdet constants of these co-doped glass-ceramics are characterized and compared to the ones of the parent glasses. The maximum co-doping efficiency reaches 1.075 for the glass-ceramic, compared to a value of 1.037 for the corresponding co-doped glass samples. The structural organization around the lanthanide cation site increases the co-doping influence on the Faraday Effect by optimization of the superexchange interaction.

Nd3+/Sm3+ codoped NaLa(WO4)2 glass ceramic: A novel optical heater

Transparent Nd3+/Sm3+ codoped tungstate silicate glass ceramics were prepared and used for the photothermal conversion process. XRD patterns, TEM image and the enhanced Raman signals confirm the appearance of the tetragonal scheelite NaLa(WO4)2 nanocrystals in the vitreous phase. In comparison to the precursor glass, the enhancement of photoluminescence of Nd3+ ions in the glass ceramics attributes to the enrichment of Nd3+ ion in the precipitated low phonon-energy tetragonal scheelite NaLa(WO4)2 nanocrystals. The rapid reduction of photoluminescence of Nd3+ ions in the Nd3+/Sm3+ codoped glass ceramics demonstrates that a strong energy transfer from Nd3+ to Sm3+ takes place, which provides more non-radiative relaxation channels and is beneficial for the improving the photothermal conversion efficiency. Under the irradiation of 808 nm laser diode, a significant temperature rise is observed in the Nd3+/Sm3+ codoped glass ceramics and may be used as a good optical heater.

Synthesis and luminescence properties of Er3+-Yb3+ doped glass ceramics with tridymite structure

By melt annealing technique, Er3+-Yb3+ co-doped precursor glass (PG) was prepared. Glass ceramics (GCs) containing KZnPO4 crystal phase with tridymite structure were obtained by heat treatment of PG. The optimum heat treatment conditions of GCs are 670 °C for 60 min. Under these conditions, the average grain size of GC is about 205 nm, and the light transmittance in the visible region is about 80%. Through the analysis of the Rietveld refinement results of XRD, the lattice constants a and b of KZnPO4 crystal decreased from 18.155 Å to 18.109 Å, and c decreased from 8.504 Å to 8.451 Å. Therefore, it is inferred that Er3+ and Yb3+ replace the Zn2+ in the lattice. The green up-conversion luminescence of GC is about 10 times that of PG excited by 980 nm laser. The optimal doping concentrations of Er3+ and Yb3+ in GCs are 0.5% and 1.0%, respectively. The calculation results of chromaticity coordinates show that Er3+-Yb3+ co-doped GCs with KZnPO4 crystal phase is a promising green up-conversion luminescent material.

Upconversion luminescence and effect of pump power on optical thermometry of Yb3+/Er3+ co-doped YOF self-crystallization glass ceramics

The optical thermometry based on the fluorescence intensity ratio (FIR) method overcomes many disadvantages of traditional contact temperature measurement, and appropriate host materials can improve the temperature sensing sensitivity. Herein, Yb3+/Er3+ co-doped YOF glass ceramics (GC) were prepared, and the luminescence and temperature sensing properties were researched under 980 nm excitation with different pump power. The FIR of thermal couple energy level (TCEL) and non-thermal couple energy level (NTCEL) was used to evaluate the temperature sensing sensitivity. The higher pump power results in a decrease in relative sensitivity (SR) due to the thermal effect and increased rate of energy transfer and non-radiative relaxation process between dopants and host. The maximum relative sensitivity of this sample reaches 1.59 × 10−2 K−1 at 310 K with a pump power of 0.2 W, which shows that this GC is a prospective application in optical thermometry.

Enhanced up-conversion luminescence of Tb3+-Yb3+ doped glass ceramics by doping Li+

Tb3+-Yb3+ co-doped transparent glass ceramics (GCs) containing Y2Ti2O7 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 Y2Ti2O7 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.

Tb4O7-Sm2O3 co-doped glass ceramics containing Ba3Gd(PO4)3: Preparation, tunable emission and temperature sensing properties

Tb4O7-Sm2O3 co-doped transparent glass ceramics (GCs) containing Ba3Gd(PO4)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 Sm2O3 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.

Luminescence and energy transfer of Sm3+/Eu3+ co-doped transparent glass ceramics

Luminescence and energy transfer of Sm3+/Eu3+ co-doped transparent glass ceramics