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The thermal and optical properties of oxyfluorotellurite (65-x)TeO2-20ZnF2-12PbO-3Nb2O5-xSm2O3 (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 Ω2,4,6, radiative transition probabilities, branching ratios and radiative lifetimes of luminescent levels were determined. The luminescence decay curves of the 4G5/2 (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.

Oxyfluorotellurite (65-x)TeO2–20ZnF2–12PbO–3Nb2O5–xLn2O3 (Ln = Nd3+ and Yb3+, x = 0.5, 2 and 5) and (65-x-y)TeO2–20ZnF2–12PbO–3Nb2O5–xNd2O3–yYb2O3 (x = 0.5, y = 2 and x = 0.5, y = 5) glass systems were fabricated and their optical and thermal properties were investigated. Absorption and emission spectra of RE admixture ions in oxyfluorotellurite glasses were measured and examined at room temperature in the wide spectral region. Oscillator strengths, phenomenological Judd-Ofelt (J–O) intensity parameters, radiative transition probabilities, branching ratios and radiative lifetimes of luminescent levels were determined. Luminescence decay curves of the 4F3/2 (Nd3+) and 2F5/2 (Yb3+) excited states were recorded and comprehensively analyzed for the single-doped Nd3+ and Nd3+–Yb3+ co-doped samples. Relaxation dynamics of luminescent levels were studied as a function of the Nd3+ and Yb3+ concentrations. An effective non-resonant phonon assisted energy transfer from neodymium to ytterbium was observed and studied. It was found that good thermal stability combined with proper spectroscopic parameters of examined Nd, Yb-doped oxyfluorotellurite glasses imply the suitability of these materials for the design of NIR-emitting efficient optical devices. Furthermore, the ability of the Nd3+ ions in oxyfluorotellurite glass host as luminescent temperature sensor was verified. Relative intensity ratios of neodymium transitions originated in 4F7/2/4F3/2 and 4F5/2/4F3/2 thermally coupled closely-located excited states have been adequately determined and studied.

The paper shows some results related to thermal and optical properties of Eu3+ -doped (65-x)TeO2-20ZnF2-12PbO-3Nb2O5-xEu2O3 glass systems. Concentration of the Eu2O3 was different (x = 0.5, 2 and 5 mol%) so it could determine the influence of active admixture on relevant properties of oxyfluorotellurite glass. Thermal stability and crystalline phases formed by the glass matrix were examined by differential thermal analysis (DTA). The characteristic temperatures (glass transition temperature and oxide glass crystallization temperature) have been determined. Optical absorption and emission spectra of Eu3+ ions in oxyfluorotellurite glasses have been investigated at room temperature in the ultraviolet (UV), visible (VIS) and near-infrared (NIR) region. Oscillator strengths, phenomenological Judd-Ofelt intensity parameters Ω2,4,6, radiative transition probabilities, branching ratios and radiative lifetimes of luminescent levels have been also estimated. Lifetimes and the luminescence dynamics were studied as a function of the Eu2O3 concentration.

GTSN: Nd (GeO2-TeO2-SrF2-Nb2O5–Nd2O3) glasses of varying (0.2–3%) Nd concentration were obtained using the melt-quenching method. Their thermal properties were evaluated using differential scanning calorimetry, showing highly favorable glass thermal stability. Glass structure was analyzed using XRD, IR and Raman spectroscopy. Combining the advantages of germanate, tellurite and fluoride optical systems, a promising glass laser material was achieved, as proven with optical spectroscopy methods, such as absorption, emission and fluorescence lifetime spectroscopies. Utilizing the fluorescence intensity ratios between emission bands from Nd excited levels, several models for luminescent thermometry were established for GTSN: Nd. One of the models was tested in a laser power-dependence experiment, allowing to estimate temperature increase during high power optical excitation. Great thermal stability and spectroscopic performance of the material, along with a built-in method for contactless temperature measurement, make GTSN: Nd a promising material for glass-based optically active elements.

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.

Oxyfluorotellurite (65-x)TeO2–20ZnF2–12PbO–3Nb2O5–xTm2O3 (x = 0.5, 2 and 5) and (65-x-y)TeO2–20ZnF2–12PbO–3Nb2O5–xTm2O3–yYb2O3 (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 Ω2,4,6, 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+:3F2,3 → 3H6)/800 nm (Tm3+:3H4 → 3H6) for 975 nm excitation and 700 nm (Tm3+:3F2,3 → 3H6)/470 nm (Tm3+:1G4 → 3H6) 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 3F4 → 3H6 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.

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 2H11/2–4I15/2 to 4S3/2–4I15/2 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.

The paper shows results of investigation of thermal and optical properties of oxyfluorotellurite (65 − x )TeO 2 –20ZnF 2 –12Pb 2 O 5 –3Nb 2 O 5 – x Dy 2 O 3 ( x = 0.5, 2 and 5) glass systems. Thermal stability and the onset of crystallization of the materials were monitored by differential thermal analysis (DTA). It was found that characteristic parameters, namely glass transition temperatures ( T g ), onset of crystallization temperatures ( T c ) and thermal stability criteria Δ T and H ’ increased with increasing Dy 2 O 3 content indicating that the incorporation of dysprosium ions improves substantially thermal stability of glass system under study. Optical absorption and emission spectra of Dy 3+ ions in oxyfluorotellurite glass were investigated at room temperature in the visible (VIS) and near-infrared (NIR) region. Oscillator strengths, phenomenological Judd–Ofelt (JO) intensity parameters Ω 2,4,6 , radiative transition probabilities, branching ratios and radiative lifetimes of luminescent levels were determined. Decay curves of the 4 F 9/2 luminescence of incorporated Dy 3+ ions were recorded and analysed. Lifetimes and the luminescence dynamics were studied as a function of the Dy 2 O 3 concentration. It was concluded that good thermal stability combined with desirable spectroscopic parameters of investigated dysprosium-doped oxyfluorotellurite glass point at the suitability of this material for the design of UV-excited visible phosphors.

Rare earths-doped oxyfluoride glasses based on germanium oxide and lead fluoride were prepared from commercial raw materials. The glasses with general composition of 50GeO2-(50-x-y)PbO-yPbF2-xLnF3 (Ln=Pr3+-Yb3+), contained different concentrations of optically active dopants (x=0.2 mol.% and 2 mol.%) and PbF2 (y=15 mol.%). The differential thermal analysis (DTA) was used to determine both thermal characteristic and thermal stability properties of the glasses in the function of the kind of dopant, its concentration, and a glass composition. Characteristic glass temperatures such as glass transition temperature (Tg), glass crystallization temperature (Tc) and temperature corresponding to the maximum of the crystallization rate (Tpc) were evaluated. On the basis of obtained results, the thermal stabilities of glasses under study were evaluated using various thermal stability criteria (Dietzel factor ?T, Saad-Poulain factors H' and S). It was found that the increase in rare earth fluoride contents influenced thermal characteristics when the characteristic temperatures of the individual glass was shifted towards higher values. The effect of the PbF2 content and the kind of rare earth impurity on the glass stability was observed. Absorption spectra of lanthanide-doped glasses were measured at room temperature and used to determine the phenomenological intensity parameters Ot and next, to estimate radiative properties of lanthanide ions in this matrix. Radiative transition probabilities of luminescent states of Ln3+, branching ratios and radiative lifetimes were determined. The variation of the Ot along the lanthanide series was presented and discussed.

Glasses with composition 50GeO2–(50–x–y)PbO–yPbF2–xLnF3 (Ln = Tb3+, Dy3+, Ho3+, Er3+, Tm3+, Yb3+) were synthesised in the bulk form. The content of PbF2 was constant and amounted to 5 mol%, whereas the concentration of luminescent ions was 0.2 and 2 mol%. Absorption and emission spectra were investigated. The results were analysed in the framework of the Judd–Ofelt theory giving the values of the Ω2,4,6 intensity parameters, radiative probabilities Wr and radiative lifetimes τrad. The dynamics of luminescent levels was studied and experimental lifetimes were determined. Some generalisations with regards to radiative and non-radiative relaxations in GeO2–PbO–PbF2 doped with Ln3+ from Pr3+ to Yb3+ are carried out.

Glasses with composition 50GeO 2 -(50-x)PbO-5PbF2-xLnF3 (Ln = Pr 3+ -Yb 3+ ) were prepared from commercial raw materials. The content of PbF 2 was constant and amounted to 5 mol% whereas the concentration of luminescent ions was diverse (0.2 and 2 mol%). Thermal stability of the glasses were monitored by differential thermal analysis (DTA). It has been found that increase of rare-earth fluoride content from 0.2 mol% to 2 mol% brings about a shift of the glass crystallization onset from 450 °C to 487 °C for Nd-doped samples and from 466 °C to 482 °C for Tm-doped samples. Optical absorption and emission spectra of Ln active ions in oxyfluoride glass have been investigated at room temperature in the ultraviolet (UV), visible (VIS) and near-infrared (NIR) region. Oscillator strengths, phenomenological Judd-Ofelt intensity parameters Ω 2,4,6 , radiative transition probabilities, branching ratios and radiative lifetimes of luminescent levels have been estimated. Analysis of decay curves of luminescence revealed that the increase of rare-earth fluoride content from 0.2 mol% to 2 mol% shortens the lifetime of the 4 F 3/2 level of Nd 3+ from 224 μs to 90 μs.

Oxyfluoride glasses with composition 50GeO 2 –(50 − x )PbO– x PbF 2 ( x ≤ 15 mol%) containing praseodymium or thulium were melted from commercial raw materials in normal atmosphere. Based on the results of differential thermal analysis (DTA), glass transition temperatures and oxide glass crystallisation temperatures have been derived. Then the glass samples were thermally treated in order to achieve controlled precipitation of PbF 2 . Process of formation of glass ceramics has been monitored with the aid of the DTA and X-ray measurements. The control acoustic emission (AE) measurements confirm the DTA results. It has been found that after heat treatment the crystallisation temperatures of investigated materials have been changed due to the PbF 2 content and kind of doped ions. The influence of the kind of doped ions on the glass stability was observed. The effect of thermal treatment on the absorption spectra and kinetics of the fluorescent levels of Pr 3+ and Tm 3+ was studied. In the case of Tm 3+ doped systems it was found that this effect on the relaxation of the 1 G 4 level was weak, whereas the decay of the 3 H 4 level was slower by a factor of 3 roughly with respect to that recorded with as-melted glass. Relaxation rates of the 3 P 0 and 1 D 2 levels of Pr 3+ showed marked dependence on both the PbF 2 and Pr 3+ content in as-melted glass and in glass ceramics.

Oxyfluoride glasses with composition 50GeO 2 –(50 − x )PbO– x PbF 2 ( x ⩽ 15 mol%) containing praseodymium or thulium were melted from commercial raw materials in normal atmosphere. Glass samples were then thermally treated in order to achieve controlled precipitation of PbF 2 . The effect of thermal treatment on the relaxation of excited levels within 4f n configurations of praseodymium and thulium is found to be qualitatively similar. Non-exponential decay curves of luminescence in as-melted glasses become nearly exponential with corresponding longer lifetimes in thermally treated samples. Substantially different behavior of samples containing praseodymium with respect to those containing thulium has been found upon excitation in the 50–300 nm spectral region. Efficient VUV-excited visible emission has been recorded with both as-melted and thermally treated glass containing Pr 3+ . No visible emission has been recorded upon VUV excitation of glass and glass-ceramics samples containing thulium.

Observations of the acoustic emission accompanying the solid–solid (polymorphic) phase changes in silver iodide and silver chalcogenides were performed. It has been found that the temperature dependencies of both the number of acoustic events and their counting rate, registered when heating the investigated materials, display distinct anomalies at the temperature corresponding to the polymorphic phase transition occurring in a given substance. The phase transition temperatures determined from the position of these anomalies agree well with the results of control DSC measurements, as well as with the literature data on the temperatures of the transition of investigated materials to the state of superionic conductivity.