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Highly sensitive optical thermometers based on unconventional thermometric coupled levels of Tm <sup>3+</sup> following a Boltzmann-type distribution in oxyfluoride glass ceramics
摘要： Oxyfluoride glass ceramics (GCs) containing b-PbF2 nanocrystals (NCs) doped with Tm3+ and Yb3+ were synthesized by a conventional melt-quenching method and a subsequent glass crystallization route. In b-PbF2:Tm3+/Yb3+ GCs, Tm3+/Yb3+ is surrounded by fluoride with a low phonon energy, ensuring its intense emissions at 362 (1D2 - 3H6), 450 (1D2 - 3F4), 478 (1G4 - 3H6), 648 (1G4 - 3F4), 700 (3F2,3 - 3H6) and 800 (3H4 - 3H6) nm excited by 976 nm laser. Furthermore, temperature-dependent upconversion luminescence (UCL) behaviors of b-PbF2:Tm3+/Yb3+ GCs were systematically investigated to explore the thermometric performance with the assistance of the fluorescence intensity ratio (FIR) method by employing conventional TCELs of 3F2,3/3H4 following a Boltzmann distribution and two unconventional coupled levels of 3F2,3/1D2 and 3F2,3/1G4 governed by a Boltzmann-type distribution. Impressively, the relative sensitivity (Sr) of 3F2,3/1D2 states (I700nm/I362nm), 3F2,3/1G4 states (I700nm/I478nm), and 3F2,3/3H4 states (I700nm/I800nm) was obtained in this work as values of 1.30% K-1, 1.38% K-1, and 0.87% K-1, respectively. Compared with the conventional TCELs of 3F2,3/3H4, the two unconventional coupled levels of 3F2,3/1D2 and 3F2,3/1G4 present preferable properties as temperature probes enabling optical ratiometric thermometers. The research in this work provides an important advance in exploring other innovative FIR methods for optical thermometers to enable an intense and precise probing signal and detect temperature accurately.
关键词： fluorescence intensity ratio,Yb3+,oxyfluoride glass ceramics,Tm3+,Boltzmann-type distribution,optical thermometers
更新于2025-09-16 10:30:52
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - A Novel Saturable Absorber: Transparent Glass-Ceramics Based on Co <sup>2+</sup> :Li(Al,Ga) <sub/>5</sub> O <sub/>8</sub> Spinel Nanocrystals
摘要： Cobalt ions (Co2+) embedded in tetrahedral (Td) sites are known for their intense absorption around 1.5 μm. Crystals such as spinel, MgAl2O4, doped with Co2+ ions in Td sites are recognized as excellent saturable absorbers (SAs) for eye-safe erbium lasers. Due to the relative difficulty to grow high-quality Co:MgAl2O4 crystals and fixed position of the Co2+ absorption band in spinel single-crystals, other Co2+-doped materials were proposed such as transparent glass-ceramics (GCs) and ceramics based on various spinels [1]. Transparent GCs offer a size-scalable synthesis method based on glass melting technology and variable spectroscopic properties as compared to crystals, and much higher laser induced damage threshold (LIDT) as compared to ceramics. GCs based on MgAl2O4 spinel nanocrystals modified by the addition of Ga3+ cations allow one to extend the SA properties until 1.7 μm [2]. In the present work, we describe the synthesis, structure, optical spectroscopy, nonlinear properties and passive Q-switching (PQS) performance of novel transparent GCs based on Co2+:Li(Al,Ga)5O8 nanocrystals. A lithium gallium aluminosilicate glass nucleated by TiO2 was doped with 0.1 mol% CoO. The GCs were produced by secondary heat-treatments at 680-850 oC for 6 h resulting in highly transparent, blue-colored samples, Fig. 1(a). The precipitation of nanosized spinel crystals was confirmed by XRD and TEM, Fig. 1(b,c), and Raman spectroscopy. The transparent GCs exhibited a broadband absorption band at 1.3-1.65 μm due to the 4A2(4F) → 4T1(4F) transition of Co2+ ions in Td sites in Li(Al,Ga)5O8 nanocrystals, Fig. 2(a). The saturable absoption of GC heat-treated at 750 oC for 6 h was studied by Z-scan method at 1540 nm using ns pulses. The saturation fluence FS is 0.50±0.05 J/cm2 and the LIDT exceeded 20 J/cm2, Fig. 2(b). This transparent GC was used to fabricate a SA for PQS of a compact diode-pumped Er,Yb:glass laser. This laser generated stable 7.4 ns / 1.34 mJ pulses at 1535 nm (peak power: 181 kW). The developed GC are promising as SAs for erbium lasers based on glass and crystalline materials (e.g., Er:YAG lasers emitting at 1617 nm and 1645 nm). This is because the broadband absorption of Co2+ ions in GCs is notably red-shifted as compared to Co:MgAl2O4 crystals which, in turn, is caused by the different spinel nanophase composition.
关键词： transparent glass-ceramics,Ga)5O8,Co2+:Li(Al,spinel nanocrystals,passive Q-switching,saturable absorber
更新于2025-09-11 14:15:04
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Laser-stimulated piezo-optical and third harmonic generation studies for Na2O–Sb2O3 glass ceramics-influence of gold ions
摘要： Sodium antimonate glass ceramics with different concentrations of Au2O3 were synthesized. The prepared samples were characterized by XRD, XPS, SEM and TEM techniques. These studies have revealed that the samples consist of multiple crystalline phases composed of Sb3+, Sb5+, Au3+ ions, and Au0 particles; moreover these studies have indicated growing proportion of Au0 particles and Sb5+crystal phases (Na2Sb2O6) with increase of Au2O3 concentration. IR and Raman spectral studies have pointed out an increasing degree of polymerization of the glass network with increase of Au2O3 content while optical absorption studies indicated surface plasmon resonance effects. Nd: YAG laser (λ = 1320?nm and pulse width 8?ns) was used for inducing third harmonic generation (THG) signal. Later, THG signal intensity of Nd: YAG laser (λ = 1064?nm and pulse width of 20?ns) vs fundamental beam power density was recorded. The results indicated the maximum intensity for the samples containing a low concentration of Au2O3. For inducing piezo-optical effects, Nd: YAG laser (λ = 1064?nm) and its doubled frequency beam λ = 532?nm (with simultaneous mechanical pressure) were used. The cw He-Ne laser of 20?mW (with beam diameter about 0.5?mm) was used as probing beam for measuring the piezo-optical effects in the photo-polarized samples. The variation of the intensity of the THG beam and piezo-optical coefficients were found to be the maximal for the samples mixed with small quantities of Au2O3. The detailed analysis of XRD, SEM, EPR, IR, optical absorption spectral results suggested that concentrations of Na3SbO3 and also Au2O3 crystal phases are maximal in these?samples and are responsible for the maximal photoinduced effects, while the increasing presence of Na2Sb2O6 crystal phases and Au0 metallic particles are found to be hindrance for generation of third harmonic beams and also piezo-optical effects. Overall, the obtained results of nonlinear optical (NLO) and piezo-optical studies indicated that Na2O-Sb2O3 glass ceramics containing small traces of Au2O3 are useful for considering them for nonlinear optical triggering devices and piezo-electric devices.
关键词： Sodium antimonate glass ceramics,piezo-optical effects,Nd: YAG laser,Au2O3,third harmonic generation
更新于2025-09-11 14:15:04
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Crystallization kinetics and the dielectric properties of SrO-BaO-Nb2O5-B2O3 glass-ceramics
摘要： Glass-ceramics materials of SrO-BaO-Nb2O5-B2O3 system have been prepared by conventional melt-casting followed by controlled crystallization. The crystallization kinetics, phase evolution, microstructure, breakdown strength and dielectric properties have been explored by differential scanning calorimetry (DSC), X-ray diffractometer (XRD), scanning electron microscope (SEM), and multifunction LCR meter. The results reveal that crystallization mechanism of this glass is believed to be three-dimensional interfacial growth. It was observed that predominant crystalline phase is Ba0.39Sr0.61Nb2O6 in these glass-ceramics crystallized at 750 °C, and the grain size increases with increase in crystallization time. The uniform microstructure can be seen clearly in glass-ceramics crystallized at 750 °C for 3 h, and the obtained glass-ceramics was found to possess optimal properties. Moreover, glass-ceramic with a dielectric constant of 58, the dielectric loss of 0.007 and breakdown strength of 1010 kV/cm could be achieved. In addition, energy storage density of glass-ceramics reached a maximal value of 2.62 J/cm3. To our knowledge, studies on SrO-BaO-Nb2O5-B2O3 glass-ceramics without SiO2 as a glass network former are few, and the melting temperature of the B2O3-based glass is lower than that of SiO2-based glass, which is conducive to the purpose of energy saving. These findings indicate that this glass may be a candidate for high energy-storage capacitors.
关键词： Energy storage density,Glass-ceramics,Crystallization,Dielectric properties
更新于2025-09-10 09:29:36
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Yb3+/Tb3+/Ho3+: phosphate nanophase embedded glass ceramics: enhanced upconversion emission and temperature sensing behavior
摘要： Yb3+/Tb3+/Ho3+ tri-doped transparent phosphate glass–ceramics (GCs) were successfully synthetized by a conventional melt-quenching technique with subsequent glass crystallization. The formation of phosphate nanocrystals (NCs) with leucite structure was confirmed by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), selected-area electron diffraction (SAED). The variation of the decay curves confirms the accumulation of active centers into the NCs lattice. Hence, the UC emission intensity of Yb3+/Tb3+/Ho3+ doped GC610 sample is greatly enhanced relative to that in precursor glass (PG). And the UC energy transfers processes were systematically analysis. The result shows that the energy transfer of Ho3+→Tb3+ exists while Yb3+ as a sensitizer ion. Furthermore, the temperature-dependent UC luminescence and temperature sensing behaviors of the prepared materials based on the thermally coupled levels of Tb3+: 5D4 and Ho3+: 5F5 in the temperature range of 298–648 K were systematically investigated, to explore its possible application as optical thermometric medium, by utilizing the fluorescence intensity ratio (FIR) technique. The relative sensitivity (Sr) of 7.5 × 10?3 K?1 and absolute sensitivity (Sa) of 22 × 10?3 K?1 are achieved in the Yb3+/Tb3+/Ho3+ tri-doped GC. This GC materials is a very promising candidate for optical temperature sensors.
关键词： Yb3+/Tb3+/Ho3+ tri-doped,phosphate glass–ceramics,upconversion emission,temperature sensing,optical thermometry
更新于2025-09-10 09:29:36
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Nd3+ doped new oxyfluoro tellurite glasses and glass ceramics containing NaYF4 nano crystals ??1.06?μm emission analysis
摘要： Oxyfluoro tellurite glasses with chemical composition TeO2-ZnO-YF3-NaF (TZYN), doped with Nd3+ in different concentrations were prepared by the melt-quenching technique. Judd–Ofelt analyses of Nd3+ ions in the precursor glasses were performed to evaluate the phenomenological intensity parameters Ω2,4,6. From the NIR emission spectra, characteristic parameters such as effective band with (?λeff) and stimulated emission cross section (σP) were calculated for the three observed transitions, 4F3/2 → 4I9/2, 4I11/2 and 4I13/2 and compared to other reported glasses. Based on the luminescence decay times of 4F3/2 excited state, the quantum efficiency was evaluated and it is highest for a 0.2 mol% Nd3+ doped glass (G-Nd2). Glass ceramics were obtained by controlled heat treatment of the glasses at 390oC for 5h (as determined by DSC), which is greater than the glass transition temperature Tg. Moreover, DSC results revealed that precipitation of the NdYF4 nanocrystalline phase (TC1) decreased with increasing Nd3+ concentration. X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) investigations reveal that spherical NaYF4 nano-crystals are distributed homogeneously across the glassy matrix. The emission intensity of the 4F3/2→4I11/2 transition at 1.60 μm was enhanced in glass ceramics as compared to glasses because of the occupancy of the Nd3+ in NaYF4 nanocrystlline phase. The experimental lifetime value of 4F3/2 also enhanced from 124 to 187 μs from G-Nd2 glass to GC-Nd2 glass ceramic and decreased with increasing Nd3+ concentration.
关键词： Nd3+ doped,glass ceramics,1.06 μm emission analysis,NaYF4 nano crystals,oxyfluoro tellurite glasses
更新于2025-09-10 09:29:36
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Ultrapure NIR-to-NIR Single Band Emission of β-PbF2: Yb3+/Tm3+ in Glass Ceramics
摘要： An ultrapure near infrared (NIR) emission entered at 800 nm upon 976 nm laser excitation (NIR-to-NIR) was observed in β-PbF2: Yb3+/Tm3+ glass ceramics (GCs). The ultrapure NIR-to-NIR single band emission originated from the 3H4 → 3H6 transition of Tm3+ with the ratio of NIR emission, and a blue band up to 9,633 was obtained. Through detailed analysis of the crystal structure and the energy transfer between Tm3+ and Yb3+, it is elucidated that the host lattice with low phonon energy cooperative with the energy mismatch results in a dramatic population of the 3H4 state as well as ultrapure NIR-to-NIR single band emission. Moreover, up-conversion (UC) emission properties and the decay lifetimes of β-PbF2: Yb3+/Tm3+ in GCs were explored thoroughly. The results illustrate that efficient cross relaxation (CR) processes between Tm3+ generate the energy redistribution in UC emission spectra, further concentrating energy to NIR emission. These two issues can be treated as crucial factors on ultrapure NIR-to-NIR single band emission in β-PbF2: Yb3+/Tm3+ in GCs. The ultrapure NIR-to-NIR single band emission through 976 nm laser excitation is advantageous for enhancing resolution and has potential application in bio-imaging fields.
关键词： Energy mismatch,Fluoride nanocrystal doped with Tm3+,Glass ceramics,Single band,Cross relaxation
更新于2025-09-09 09:28:46
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High Pressure effect on fluorescence lifetime <i>τ</i> for magnetic dipole <sup>5</sup> D <sub/>0</sub> → <sup>5</sup> F <sub/>1</sub> transitions in YAG:Eu <sup>3+</sup>
摘要： The fluorescence lifetime for magnetic dipole 5D0→7F1 transition in yttrium aluminum garnet doped with Eu3+ (YAG:Eu3+) crystal was studied under the pressure of up to 10.4 GPa at room temperature. The fluorescence lifetime τ (5D0→7F1 transition) slowly decreased with pressure. The pressure effect on τ (5D0→7F1 transition) was explained with a model which considered pressure effect on line position: inter-ionic distance, ion volume, molecular volume, ion polarizability, molecular polarizability, sample refractive index, and surrounding hydrostatic medium refractive index. The fluorescence lifetime τ calculated by the presented model was in close correspondence with the experimental values.
关键词： rare earth,fluorescence lifetime,YAG:Eu3+,optical properties,glass ceramics,High pressure
更新于2025-09-04 15:30:14
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Electrical characteristics of PbO–CaO–TiO2–SiO2–B2O3 glass ceramics doped with germanium
摘要： Various glass samples in the compound 55[(PbxCa1?x)O?TiO2]-44[2SiO2?B2O3]-1Ge (0 ≤ x ≤ 0.7) were fabricated by using the melt-quenching technique and their glass ceramics (GC) were obtained by controlled crystallization of the glass samples. The identification of phase and crystal structure with measurement of cell parameters was carried out using X-ray diffractometer (XRD). XRD results revealed the presence of the single phase formation of rutile (TiO2). The surface morphology of the synthesized GC samples was evaluated using a scanning electron microscope (SEM). The electrical behaviour of three selected GC samples with x = 0.0, 0.3 and 0.7 was being widely studied using impedance and immittance spectroscopy. The lead free GC sample, x = 0.0 possesses a high dielectric constant, 91,252 at low frequency (50 Hz) and high temperature (500 °C) due to space charge polarization that was ascertained by impedance spectroscopy of the tested samples. The fitting of impedance spectra with a modelled equivalent circuit was performed and different values of resistance and capacitance were calculated.
关键词： Dielectric constant,Rutile TiO2,Glass ceramics,Impedance spectroscopy,Space charge polarization
更新于2025-09-04 15:30:14
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Structure, dielectric properties of low-temperature-sintering BaTiO <sub/>3</sub> -based glass–ceramics for energy storage
摘要： The 0.85BaTiO3–0.15Bi(Mg2/3Nb1/3)O3 (BTBMN) ceramics with low-melting-temperature B2O3–Na2B4O7–Na2SiO3 (BNN) glass addition were prepared by the solid state method. The composition of the glass–ceramics was BTBMN–x wt.% BNN (x = 0, 1, 3, 5, 7, 9, 12, 15; abbreviated as BG). The sintering characteristics, phase structure, microstructure, dielectric properties and energy storage properties were systematically investigated. The sintering temperature of BTBMN ceramics was greatly reduced by the addition of BNN glass. The second-phase BaTi(BO3)2 was observed in the BG system until the glass content reached 15 wt.%. The addition of BNN glass significantly reduces the grain size of BTBMN ceramics. With the increase of BNN glass content, dielectric constant of BG glass–ceramics at 1 kHz gradually decreased, the maximum dielectric constant (εm) of BG glass–ceramics gradually decreased, while the temperature corresponding to the maximum dielectric constant (Tm) increased, the ferroelectric relaxation behavior decreased and the temperature stability of the dielectric constant gradually improved. As the BNN glass content increased, the breakdown electric field strength (BDS) of BG glass–ceramics increased first and then decreased, and the polarization values reduced gradually, while the trend of energy storage performance is similar to BDS. When the BNN glass content was 3 wt.%, the energy storage properties of the BG glass–ceramics were optimal, and a recoverable energy storage density (Wrec) of 1.26 J/cm3 and an energy storage efficiency (η) of 80.9% were obtained at the electric field strength of 220 kV/cm. The results showed that BG glass–ceramics were promising for energy storage capacitors.
关键词： Lead-free,glass–ceramics,relaxation,energy storage properties,BaTiO3
更新于2025-09-04 15:30:14