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The temperature behavior of Tl4HgI6 photoluminescence spectra is presented. The emission spectra are studied in the temperature range between 4.5 and 300 K and in the spectral range 350–650 nm. Two main emission bands at ∼551 nm and ∼448 nm are observed corresponding to the emissions of HgI2 and Tll impurity centers. It is assumed that the low-temperature emission band at ∼520 nm corresponds to the recombination of the exciton. The luminescence peaks observed in emission spectra in the range between 350 and 410 nm correspond to the phonon repetitions. The excitation spectra of emission bands are measured at 4.5 K and compared with the electron density of states.

Yttrium alumino bismuth borosilicate (YABiBS) glasses doped with RE3+ ions (Eu3+, Dy3+, Dy3+- Eu3+) have been synthesized via standard melt quenching technique and their emission properties were investigated. Optical analysis of these glasses is characterized by absorption and luminescence. XRD spectra reveal that these glasses have amorphous nature. The absorption spectra of these co-doped glasses consist five bands of Dy3+ which are assigned to 6H15/2 → 6F3/2 (750 nm), 6F5/2 (796 nm), 6F9/2 (1085 nm), 6F11/2 (1264 nm), 6H11/2 (1677 nm) and another four bands of Eu3+ assigned to 7F0 → 5L6 (393 nm) Meza-Rocha et al. (2017) [5],5D2 (464 nm), 7F6 (2097 nm), and 7F1 → 7F6 (2202 nm). It is also witnessed a broad band having electronic transition 1S0 → 1P1 is due to Bi3+ ions. Optical band gaps, nephelauxetic ratio, and bonding parameters are discussed by using optical absorption data. Eu3+ single doped glasses show five emission bands, with the n-UV excitation wavelength 393 nm, in which characteristic feature red emission (612 nm) is recognized with transition (Meza-Rocha et al., 2017 [5])D0 → 7F2. At the same time, Dy3+ single doped glasses illuminated with the excitation wavelength of 385 nm shows their known natural emissions blue (481 nm) and yellow (574 nm), having transitions 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2 respectively. Emission for co-doped glasses Dy3+-Eu3+ are excited with the different selected ultraviolet wavelengths such as 464 nm, 392 nm, 385 nm, 363 nm, and 348 nm. It can be observed that tunable emission from both the ions (Dy3+, Eu3+) from orange reddish emission to white emission. The energy transfer from Dy3+ to Eu3+ is manifested by the quadrupole-quadrupole mechanism, which is confirmed by Inokuti-Hirayama (I H) modal based on lifetime decay curves. Also, the efficiencies and probabilities of energy transfer are determined based on the results of decay curves. The CIE color coordinates of DE1.0 glass with the excitation 348 nm gives x, y coordinates as (0.332, 0.342) which confers the good white emission. CCT value for this glass is around 5520 K shows that useful for cool WLED applications.

The paper deals with the results of comparative study on time-resolved pulsed optically stimulated luminescence (TR-OSL) response of ceramic YAP:Mn materials prepared by different methods. In parti...

This work consists of studies on the influence of thermally resistant transition metal oxides (TMO) viz., Ta2O5, Nb2O5 and ZrO2 on orange emission and NIR emission (1.3 μm) of Pr3+ ions in zinc borate glasses. Glasses of the composition 40ZnO–2Ta2O5/2Nb2O5/2ZrO2–56B2O3: 2Pr2O3 were synthesized by melt quenching technique. Optical absorption (OA), photoluminescence (PL) emission (in the wavelength region 500–2500 nm at λexc = 443 nm) and decay profiles of the two of the prominent transitions viz., 3P0 → 3H6 and 1G4 → 3H5 of Pr3+ ions were recorded. The spectra were analysed using standard J–O calculations and various radiative parameters associated with prominent transitions were estimated. Intensity of PL bands exhibited substantial increase due to addition of Ta2O5, Nb2O5 and ZrO2 to the host glass. Among the three studied glasses, ZrO2 mixed glasses exhibited the highest luminescence output. All the radiative parameters including quantum efficiency are observed to be the largest for ZrO2 mixed glasses. The results of IR spectral studies were also used for the analysis of emission spectra. The analysis indicated the degree of structural variations in the vicinity of luminescent Pr3+ ions is different due to addition of different transition metal oxides and such variations are found to be responsible for the changes in the PL output. Since a substantial improvement of PL emission corresponding to 1G4 → 3H5 transition is observed due to the admixing of TMOs, these glasses may be considered as the favourable candidates for the applications in telecommunications. Additionally, the emission in the green spectral region (which is predicted to be feeble under normal conditions) in the PL spectrum of Pr3+ ions is also found to be considerably increased and it is attributed to the transfer of energy from ZnO to Pr3+ ions in this region.

Zinc borate glasses doped with 2.0 mol% of Er2O3 and mixed with thermally resistant transition metal oxides viz., Ta2O5, Nb2O5 and ZrO2 were synthesized. Optical absorption and photoluminescence spectra and decay profiles of these glasses were recorded at ambient temperature. The spectra were characterized using Judd–Ofelt theory and various radiative parameters viz., transition probability, A, branching ratio, β, and the radiative lifetime, τ, of principal emission transitions of Er3+ ions in these glasses were evaluated. The results indicated a significant enhancement in the intensity of green emission (related to 4S3/2 → 4I15/2 transition) of Er3+ ions due to co-doping of the glass system with Ta2O5, Nb2O5 and ZrO2. Quantitative analysis of the results pointed out that ZrO2 is the most favorable oxide among the three co-dopants for achieving the highest quantum efficiency of green emission. Results were further analyzed based on the structural modifications taking place in the vicinity of Er3+ ions due to co-doping with Ta2O5, Nb2O5 and ZrO2 and the reasons for such improvement were identified by means of IR and Raman spectroscopy studies. Additionally, the 4S3/2 energy level of Er3+ ions (from which the green emission is originated) seemed to be additionally populated by the energy transfer from the excited state of ZnO and contributed to the amplification of green emission.

An influence of the rare earth ions (La, Er) concentration on the luminescent properties of Ga2S3-La2S3-Er2S3 glasses in the visible and near-infrared spectral region has been studied. The analysis of absorption spectra and luminescence allow understanding of the redistribution processes of radiation energy. The results suggest that favorable visible and near-IR luminescence of Er3+ ions can be further modified in Ga2S3-La2S3-Er2S3 chalcogenide glasses through the effect of doping concentration and modification of environment (rare earth ions of Lanthanum act as a network modifier) of the optically active ions by the matrices composition changes.

The work devoted to the investigation of a new luminescent and scintillation material based on the single crystalline films (SCFs) of Tm 3−x Lu x AG:Ce garnet; x = 0–1.5, grown by LPE method from PbO based flux. The best scintillation properties are achieved for SCFs of Tm 1.5 Lu 1.5 Al 5 O 12 :Ce composition. We have found that direct Tm → Ce and backside Ce → Tm energy transfer processes are observed in Tm 1.5 Lu 1.5 Al 5 O 12 :Ce. Due to elimination of traps in the 300–450 °C range, the relatively fast scintillation decay is realized in highly doped Tm 1.5 Lu 1.5 Al 5 O 12 :Ce SCFs. For this reason, Tm doping can be considered as a suitable way for improvement of the scintillation efficiency in other Ce 3+ doped garnet compounds.

UV emitting scintillating screens based on single crystalline films (SCFs) of Lu3Al5−xGaxO12:Pr garnet have been developed by the liquid phase epitaxy (LPE) growth method onto Y3Al5O12 (YAG) substrates using a lead-free BaO based flux. The absorbance, luminescence and scintillation properties of these SCFs have been investigated depending on the Ga content in the x = 0–1.9 range. We have found that the absorption and luminescence spectra of Pr3+ ions as well as the scintillation light yield (LY) and decay kinetics of Lu3Al5−xGaxO12 SCFs are non-linearly affected by the gallium concentration x in the mentioned solid solution due to preference for the distribution of Ga3+ and Al3+ ions between the tetrahedral and octahedral positions of the garnet host, respectively. The best scintillation properties of Lu3Al5−xGaxO12:Pr SCFs are achieved at the Ga content in the x = 1.0–1.2 range. The LY of the Lu3Ga1.2Al3.8O12:Pr SCF is comparable with the LY of the best reference LuAG:Pr single crystal counterpart and significantly (up to 3 times) overcomes the LY of LuAG:Pr and Lu3Al4–3.5Ga1.0–1.5O12 SCFs, grown onto the YAG substrates from the conventional PbO–B2O3 flux.

Detailed investigations of the spectroscopic properties of Cr3+ ions in β-Ga2O3: 0.05% Cr3+ single crystals grown by the floating zone technique have been performed in the temperature range 4.5–550 K. The luminescence of Cr3+ ions at low temperatures is due to narrow R-lines (2E → 4A2 transitions) and their vibronic sidebands, whereas the broad intense band (4T2 → 4A2 transition) dominates at temperatures above 200 K. The vibronic sidebands of R-lines with amplitude of less than 5 % of the R1 line at a temperature of 4.5 K cover the region of 700-735 nm. The temperature dependencies of the luminescence intensity and the decay time of Cr3+ ions indicate the same mechanism of quenching of R-lines intensity and shortening of lifetime for 2E of Cr3+ ions. The temperature dependence of the R1-line decay time of β Ga2O3: Cr3+ with maximal temperature coefficient │Δτ/ΔT│ = 0.023 ms/K at 120 K and maximal specific sensivitity │(Δτ/ΔT)τ-1│ = 0.017 K-1 at 160 K indicates an application potential of this phosphor for low-temperature fluorescence thermometry.

The range of emission cross-section in RE3+ ions play a key role in developing optical systems with high performance. The present work focuses on mid infrared and visible emission properties of Er3+/Ho3+ions in sodium-sulfo lead phosphate (GExHy) glasses. The EDS, XRD and FTIR spectra were performed for basic structural analysis. Besides, DC (down-conversion) and UC (up-conversion), photoluminescence (PL) spectra of the prepared GExHy glasses pumped at 379 nm and 980 nm are investigated. The favourable concentration of Ho2O3 was estimated from the analysis of NIR PL spectra for Ho3+: 2.0 μm and Er3+: 1.5 μm. In GExHy glasses, the increase in intensity near 2.0 μm with decrease in intensity at 1.5 μm infers to energy transfer process between Er3+ and Ho3+ ions. The maximum energy transfer efficiency of GExHy samples is 75.5% and with the increase of Ho3+ ions, the lifetime decay has been reduced from 5.06 ms to 1.24 ms. The absorption and stimulated emission cross-section of Er3+:1.5 μm and Ho3+: 2.0 μm were calculated. Moreover, FWHM × σ emi was calculated for Ho3+:5I7→5I8 transition to estimate the probable MIR laser emission. The CIE color coordinates were estimated from both DC and UC PL spectra. All the results indicated that the prepared GExHy glasses have promising material applications in mid-infrared solid-state lasers and telecommunications.