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Germanate tellurite glasses doped with Eu3+ and Tb3+ were synthesized by the conventional melt-quenching method. There is no indication of the energy transfer between dopant ions in this host, but the co-dopants exhibit excellent color purity of 100% for Eu3+ and 80% for Tb3+. The co-doped glass exhibits yellow luminescence. The quantum yield of the Eu3+ emission is equal to 23% under 395 nm excitation. The thermal quenching of Eu3+ and Tb3+ luminescence occurs at different temperature ranges, which enables the thermal sensing properties of the material. The relative fluorescence intensity ratio (FIR) sensitivity of 0.16% K−1 was recorded in the wide range of temperatures spanning from −193 °C up to 0 °C. The temperature dependence of the decay times was also studied. The lifetime-based temperature sensitivity was determined to be 0.95% K−1 at 250 °C for Tb3+5D3 level emission and 0.3% K−1 at 225 °C for Eu3+5D1 level emission. [ABSTRACT FROM AUTHOR]

The application of ultraviolet-C light in the field of surface treatment or photodynamic therapy is highly prospective. In this regard, the stable fluorescent silicate SrO-CaO-MgO-SiO2-Pr2O3 glasses able to effectively convert visible excitation on the ultraviolet praseodymium emission were fabricated and examined. An unusual wide-range visible-to-UVC up-conversion within 240–410 nm has been achieved in Pr3+-doped glasses, revealing their potential advantage in different sophisticated disinfection technologies. The integrated emission intensity was studied as a function of light excitation power to assess a mechanism attributed to UVC luminescence. Especially, it was revealed that the multicomponent silicate glass qualities and praseodymium 3PJ excited state peculiarities are favorable to obtaining useful broadband ultraviolet up-converted luminescence. The glass dispersion qualities were determined between 450–2300 nm. The impact of praseodymium concentration on Vis-NIR spectroscopic glass qualities was evaluated employing absorption spectra, emission spectra, and decay curves of luminescence associated with two involved praseodymium excited states. Especially, efficient interionic interactions can be inferred by investigating the decrease in 1D2 state experimental lifetime in the heavily doped samples. Examination of absorption spectra as a function of temperature implied that excitation at 445 nm should be quite effective up to T = 625 K. Contrary to this, temperature elevation gives rise to a moderate lowering of the visible praseodymium luminescence. [ABSTRACT FROM AUTHOR]

The shielding and spectroscopic properties of Pr + 3 and Pr3+/Ho3+-codoped tellurite glass were investigated. The intensity parameters (Ω2 = 3.24-, Ω4 = 1.64-, Ω6 = 1.10 × 10−20 cm2) as well as the radiative lifetimes of 3F4 + 5S2 and 5I6 excited states of Ho3+ ions were equal to 301 μs and 3.0 μs, respectively. The former value appears to be much higher than that obtained from the lifetime measurement, indicating the presence of various energy transfer processes. The NIR spectrum of Pr3+/Ho3+-co-doped tellurite glass is dominated by strong Ho3+: 5I6 emission at around 1200 nm, being the result of the energy transfer from Pr3+ to Ho3+ ions. The shielding effectiveness of the prepared glasses showed good performance against high-energy photons. These findings suggest that the prepared glasses could be used in laser technology such as photodynamic therapy (PDT) treatment procedures and as shielding for radiation protection. [ABSTRACT FROM AUTHOR]

We have investigated the spectroscopic properties of Er3+-doped fluorotellurite glasses with the basic molar composition 75%TeO2-10%P2O5-10%ZnO-5%PbF2, modified by replacing 5% TeO2 by a metal oxide, namely WO3 or Nb2O5. The absorption edge of the glasses studied has been described within the Urbach approach, while the absorption and photoluminescence spectra have been analyzed in terms of the standard Judd-Ofelt theory, along with the photoluminescence decay of the 4I13/2 and 4S3/2 levels of the Er3+ ion. The absorption and emission spectra of the 4I15/2 ↔ 4I13/2 infrared transition have been analyzed within the McCumber theory to yield the peak emission cross-section and figure of merit for the amplifier gain. It appears that the fluorotellurite glass containing WO3 as a modifier is characterized by the largest figure of merit, indicating this matrix as a promising new host for doping with Er3+ ions. [ABSTRACT FROM AUTHOR]

Abstract The thermal and optical properties of oxyfluorotellurite (65-x)TeO 2 -20ZnF 2 -12PbO-3Nb 2 O 5 -xSm 2 O 3 (x = 0.5, 2 and 5) glass systems were investigated. Glass thermal stability were monitored by differential thermal analysis (DTA) and adequate thermal stability criteria ΔT, H' and S were determined. It was shown that the thermal stability of the investigated materials increases with the increasing of samarium ions content. The absorption and emission spectra of Sm3+ ions in oxyfluorotellurite glass were recorded in the wide spectral range from UV to NIR. Based on the Judd-Ofelt (J–O) procedure oscillator strengths, phenomenological Judd-Ofelt intensity parameters Ω 2,4,6, radiative transition probabilities, branching ratios and radiative lifetimes of luminescent levels were determined. The luminescence decay curves of the 4G 5/2 (Sm3+) excited state were recorded for three different concentrations of Sm3+ and corresponding experimental lifetimes were determined. Photoluminescence emission spectra were measured in the temperature range from 300 K up to 725 K to evaluate the materials under study as luminescent temperature sensor. Highlights • (65-x)TeO2-20ZnF2-12PbO-3Nb2O5-xSm2O3 (x = 0.5, 2, 5 mol%) glasses were prepared. • Thermal properties of glasses were analyzed as a function the Sm3+ concentrations. • The optical properties of Sm3+ ions in oxyfluorotellurite glass were assessed. • The materials under study were evaluated as luminescent temperature sensors. [ABSTRACT FROM AUTHOR]

The optical temperature sensing properties of a low-phonon fluoroindate glass co-doped with different trivalent lanthanide ions (IFG:Ln3+/Yb3+, Ln = Er, Tm, and Tm-Ho) were assessed using the fluorescence intensity ratio (FIR) technique. The temperature-dependent upconverted luminescence was carried out in the temperature range between 300 and 583 K using the thermally-coupled energy levels, non-thermally coupled levels, and their additional combinations. The highest relative sensitivity was obtained in the IFG:Tm3+/Yb3+ sample at 355 K (1.4% K−1), from 3F 2 , 3H 4 → 3H 6 FIR evaluation, while the maximum absolute sensitivity was found in the IFG:Ho3+/Yb3+ system at 583 K (0.020 K−1), from Tm(1G 4 →3H 6 +3H 4 →3H 6)-Ho(3F 4 →5I 7) FIR assessment. Furthermore, the chromaticity diagram (CIE) evidenced an important change of color when the temperature increased in IFG:Er3+/Yb3+ sample, because this showed an evident transition from green to yellowish. Also, the heating effect caused by 980 nm excitation is negligible in most of the samples. Additionally, their amorphous nature was confirmed by X-ray diffraction and their thermal stability was evaluated using differential thermal analysis resulting in a great glass thermal stability up to 583 ± 2 K. Therefore, IFG:RE3+/Yb3+ glass systems are considered as excellent candidate for temperature sensing. [Display omitted] • The temperature induces changes in the emission color of Er3+, Tm3+, and Ho3+ ions. • The fluoroindate glass matrix promoted thermal excitation between energy levels. • Thermal excitation favors some negligible radiative transitions. • The assessment of non-TCLs overcomes energy gap limitations and enhances sensitivity. • The FIR repeatability indicates good viability in optical temperature applications. [ABSTRACT FROM AUTHOR]

• Oxyfluorotellurite glasses singly-doped and co-doped Ho3+ and Yb3+ were prepared. • Influence of dopant concentration on thermal and spectroscopic properties. • The materials under study were evaluated as luminescent temperature sensors. The paper presents a thermal and spectroscopic properties of oxyfluorotellurite glasses (65- x)TeO 2 –20ZnF 2 –12PbO–3Nb 2 O 5 – x Ho 2 O 3 (x = 0.5, 2 and 5) and (65- x - y)TeO 2 –20ZnF 2 –12PbO–3Nb 2 O 5 – x Ho 2 O 3 – y Yb 2 O 3 (x = 0.5, y = 2 and x = 0.5, y = 5). The obtained data show that the thermal stability of TZPN glass samples depends on the content of rare earth elements (holmium (Ho3+) and/or ytterbium (Yb3+) ions) in the glassy matrix. It was also found that the spectroscopic characteristics of TZPN:Ho and TZPN:Ho,Yb glasses are found to be suitable as optical medium for mid infrared emission at ∼2.0 μm. The effective emission cross section was determined to be around 0.89 × 10−20 cm2 for transition 5I 7 → 5I 8 in TZPN:Ho glasses. However, the maximum absolute and relative sensitivities S A = 4.53 × 10−3 K−1 and S R = 0.53% K−1 at T = 675 K were established for TZPN:0.5%Ho,2%Yb. [Display omitted] [ABSTRACT FROM AUTHOR]

Optical absorption, luminescence excitation, and emission spectra as well as luminescence kinetics of the Sm- and Yb-doped glasses with lithium tetraborate (Li2B4O7) composition were investigated and analysed. The Sm- and Yb-doped lithium tetraborate glasses of high optical quality were obtained in air from corresponding polycrystalline compounds according to standard glass synthesis technology. The Sm and Yb impurities were added to the Li2B4O7 compound in the form of Sm2O3 and Yb2O3 oxides in amount of 0.4 mol%. Using optical and electron paramagnetic resonance spectroscopy it was shown that the Sm and Yb impurities are incorporated into the lithium tetraborate glass network as Sm3+ (4f5, 6H5/2) and Yb3+ (4f13, 2F7/2) ions, exclusively. All of the observed transitions in the absorption and luminescence spectra of Sm3+ and Yb3+ centres were identified. The luminescence kinetics of the Sm3+ and Yb3+ centres in the Li2B4O7 glass are characterised by a single exponential decay. Decay constants for the main emission transitions of the Sm3+ and Yb3+ centres in the lithium tetraborate glass were obtained at T = 300 K. Incorporation peculiarities and optical spectra of Sm3+ and Yb3+ ions in the lithium tetraborate glass have been discussed in comparison with other borate glasses and crystals. [ABSTRACT FROM AUTHOR]

Optical absorption and luminescence spectra as well as luminescence kinetics of the Nd3+ centres in glasses with Ca3Ga2Ge3O12:Nd composition, containing 0.2 and 1.0 wt% of the Nd2O3 were presented and analysed. The oscillator strengths and phenomenological intensity parameters Ωt (Ω2, Ω4, and Ω6) were obtained using standard Judd-Ofelt theory. Calculated Ωt parameters, radiative transitions rates, branching ratios and radiative lifetime for Nd3+ centres in the glass with Ca3Ga2Ge3O12 composition were analysed and compared with corresponding Nd3+ parameters in their crystalline analogue with garnet structure. Experimental lifetimes are compared with those calculated, and quantum efficiency of Nd3+ centres from 4F3/2 emitting level in the glass with Ca3Ga2Ge3O12 composition is estimated. Incorporation peculiarities and local structure of Nd3+ luminescence centres in the glass with Ca3Ga2Ge3O12 composition and corresponding Ca3Ga2Ge3O12:Nd3+ garnet laser crystals are considered. On the basis of extended X-ray absorption fine structure (EXAFS) spectra (L3-edge) of rare-earth elements analysis it has been shown that Nd3+ luminescence centres in the CaO-Ga2O3-GeO2 glass network occupy structural sites with the coordination number to oxygen N = 6. [ABSTRACT FROM AUTHOR]

Responding to the latest trends in luminescence thermometry, a new material of TZPN glass doped with Tb3+ ions was investigated for its use in the single band ratiometric approach. In contrast to the most of the Tb3+ doped phosphors emission intensity of Tb3+ ions in TZPN glass upon excitation matched to transitions from the ground 7F 6 level show strong thermal quenching of luminescence intensity. On the other hand for an excitation line matched to the absorption from the thermally coupled excited 7F 5 level, the emission intensity increases for temperature elevation. The ratio of these two signals is known to be an excellent temperature dependent parameter enabling a highly sensitive temperature readout. Strong thermal quenching of Tb3+ emission was discussed in terms of the thermally induced electron transfer from f state to the conduction band of the glass. In this work, it has been shown that optimization of the thermal quenching process is as important as the previously proposed optimizations of the intensity variability upon stimulation matched to excited state absorption. High relative sensitivities reaching 1–2%/°C were achieved, mainly because of the strong thermal quenching of the luminescence exhibited by the TZPN: Tb3+ glasses with different concentrations of dopant ions. • TZPN glasses doped with Tb3+ ions were applied to luminescence thermometry. • Excitation lines matching GSA and ESA allowed for SBR approach to be applied. • The observed rapid thermal quenching of GSA-excited luminescence was discussed. • Optimizing the GSA-excited emission allowed to achieve high sensitivities. [ABSTRACT FROM AUTHOR]

• Five different temperature sensing models were established for TZPN: Er glass system. • Glass material for optical systems operating in elevated temperature regimes. • Optical gain medium in the C- and L- telecom wavelength bands. • Stable intensity of laser emission in NIR region up to 525 K. In a comprehensive and novel approach, a diverse set of five functional models of temperature sensing were established for erbium-doped oxyfluorotellurite glass systems using temperature dependences of emission spectra and luminescence dynamics in the range from RT to up to 675 K. Maximum relative sensitivity at 300 K was established at 1.52%K−1 for the model based on thermally coupled levels and at 1.92%K−1 at 675 K utilizing the green-to-red ratio. To confirm usefulness of the models established for the considered glasses, material and spectroscopic analyses were performed. Differential thermal analysis yielded favorable results in terms of glass thermal stability, further improving with increase of dopant concentration. Radiative transition analysis was performed, along with calculation of absorption, emission and effective emission cross sections, yielding information on the lasing performance of the material. It was found that TZPN:Er is a promising material for temperature sensing and optical amplification in the C and L telecom bands. [ABSTRACT FROM AUTHOR]

Oxyfluorotellurite (65- x)TeO 2 –20ZnF 2 –12PbO–3Nb 2 O 5 – x Tm 2 O 3 (x = 0.5, 2 and 5) and (65- x - y)TeO 2 –20ZnF 2 –12PbO–3Nb 2 O 5 – x Tm 2 O 3 – y Yb 2 O 3 (x = 0.5, y = 2 and x = 0.5, y = 5) glass systems were manufactured. Glass thermal stability was examined by means of differential thermal analysis (DTA) and some thermal stability criteria ΔT , H ' and S were determined. Absorption spectrum was utilized to prepare Judd-Ofelt (J-O) calculations and consequently oscillator strengths, intensity parameters Ω 2,4,6 , radiative transition probabilities, branching ratios and radiative lifetimes of luminescent levels were estimated. Emission spectra and luminescence decay curves were measured as a function of temperature in the 300–625 K range. Based on the upconversion luminescence of Tm3+ the optical temperature sensor qualities have been evaluated for Tm3+/Yb3+ co-doped sample. The fluorescence intensity ratio (FIR) between transitions 700 nm (Tm3+:3F 2,3 → 3H 6)/800 nm (Tm3+:3H 4 → 3H 6) for 975 nm excitation and 700 nm (Tm3+:3F 2,3 → 3H 6)/470 nm (Tm3+:1G 4 → 3H 6) for 803 nm excitation were determined and an adequate relative thermal sensitivity S was estimated. The significant value of relative thermal sensitivity 1.12 %K−1 was determined when NIR Yb3+ and Tm3+ emission bands were analyzed, however. Effective emission cross section was calculated for 3F 4 → 3H 6 potential laser transition of thulium around 1.9 μm in single-doped Tm3+ glass. Furthermore, effect of temperature on down-converted and up-converted thulium and ytterbium emission and on relaxation dynamic of involved excited states was studied in details. • Oyfluorotellurite glasses singly-doped and co-doped Tm3+ and Yb3+ were prepared. • Thermal and optical properties of tested materials were determined. • Thermal properties of glasses depend on the Tm3+/Yb3+ ions concentrations. • Investigated materials have advantageous properties for NIR optical gain. • TZPN glasses activated with RE3+ ions can be used in luminescence thermometry. [ABSTRACT FROM AUTHOR]

• Er,Yb co-doped oxyfluorotellurite glasses for optical applications. • Down and up-conversion phenomena in TZPN:Er,Yb glasses. • Fluorescence Intensity Ratio for erbium thermally coupled excited states. • Influence of temperature-activated excitation energy flow on optical thermometry sensitivity. Oxyfluorotellurite glasses co-doped with erbium (0.5%) and ytterbium (2%, 5%) were manufactured from high purity reagents at 840 °C in air. Differential thermal analysis was used to estimate the temperatures of glass transition and glass crystallization of 2% and 5%Yb co-doped glasses. The effect of Yb3+ co-doping on relaxation dynamics of erbium excited states was demonstrated by the means of excitation, emission and fluorescence lifetime spectroscopy. Up-conversion luminescence spectra were studied in a function of temperature in the 295–675 K range, yielding information on thermal quenching of the emission and a temperature sensing model based on 2H 11/2 –4I 15/2 to 4S 3/2 –4I 15/2 erbium fluorescence intensity ratio. Application potential of the investigated material in optical sensor thermometry was evaluated. Maximum absolute and relative sensitivities were established at 6.45 × 10−3 K−1 at T = 675 K and 0.46 %K−1 at T = 400 K, respectively. [ABSTRACT FROM AUTHOR]

Optical, structural and morphological properties of Tm3+/Yb3+ co-doped NaYF 4 -based nano-glass-ceramic and a precursor glass have been investigated. The controlled heat-treatment of multicomponent oxyfluoride glass at 640 °C for 2 h was used to obtain crystalline precipitations. The differences in optical characteristics have been discussed analysing spectra recorded within wide VUV–VIS–NIR spectral range and considering relaxation dynamic of involved excited states. Optical spectra and luminescence decay curves were measured as a function of temperature in the range of 295–725 K. Based on up-converted emission spectra excited at 975 nm, temperature sensing properties of glass-ceramic were verified. The fluorescence intensity ratio between the up-converted emission bands located at around 795 nm (Tm3+:3H 4 –3H 6) and 695 nm (Tm3+:3F 3,2 –3H 6) was studied. The maximum relative temperature sensitivity was determined to be 0.35% K−1 at 445 K. • Tm3+,Yb3+ co-doped NaYF 4 -based oxufluoride nano-glass-ceramic. • Conversion of VUV excitation into thulium visible emission. • Impact of 295–725 K temperature on emission efficiency of Tm3+ and Yb3+. • Verification of Tm,Yb –co-doped glass-ceramic temperature sensor quality. [ABSTRACT FROM AUTHOR]

We have investigated the spectroscopic properties of Er3+-doped fluorotellurite glasses with the basic molar composition 75%TeO2-10%P2O5-10%ZnO-5%PbF2, modified by replacing 5% TeO2 by a metal oxide, namely WO3 or Nb2O5. The absorption edge of the glasses studied has been described within the Urbach approach, while the absorption and photoluminescence spectra have been analyzed in terms of the standard Judd-Ofelt theory, along with the photoluminescence decay of the 4I13/2 and 4S3/2 levels of the Er3+ ion. The absorption and emission spectra of the 4I15/2 ↔ 4I13/2 infrared transition have been analyzed within the McCumber theory to yield the peak emission cross-section and figure of merit for the amplifier gain. It appears that the fluorotellurite glass containing WO3 as a modifier is characterized by the largest figure of merit, indicating this matrix as a promising new host for doping with Er3+ ions. [ABSTRACT FROM AUTHOR]

Green and red up-conversion luminescence spectra corresponding to 2 H 11/2 , 4 S 3/2 → 4 I 15/2 and 4 F 9/2 → 4 I 15/2 transitions of Er 3+ ions in Er 3+ /Yb 3+ co-doped lead-free fluorogermanate glasses have been examined as a function of Yb 3+ concentration and temperature. The green-to-red luminescence intensity ratio diminishes with increasing Yb 3+ concentration. The luminescence intensity ratio for bands related to the 2 H 11/2 → 4 I 15/2 and 4 S 3/2 → 4 I 15/2 transitions of Er 3+ was determined and temperature sensitivity parameters were calculated. The maximal temperature sensitivities for Er 3+ /Yb 3+ co-doped glass samples increase with increasing Yb 3+ concentration and the highest value of 42.5 × 10 −4 K −1 at room temperature was obtained for 0.5Er-3Yb system. Based on gathered data it was concluded that Er 3+ /Yb 3+ co-doped lead-free fluorogermanate glasses are promising for optical temperature sensing. [ABSTRACT FROM AUTHOR]