Spectroscopic Properties of Dysprosium Oxide Containing Lithium Borate Glasses

In this paper, we discussed the optical and luminescence properties of dysprosium oxide containing lithium borate glasses along with the structural properties. Absorption spectra of these glasses show strong absorption bands in ultraviolet and visible regions. Increase in dysprosium oxide content decreases in optical energy band gap, which is explained on the basis of glass structure. These glasses show bright blue emission at 482 nm and yellow emission at 573.5 nm due to ⁴ F _9/2  →  ⁶ H _15/2 and ⁴ F _9/2  →  ⁶ H _13/2 transitions of dysprosium ions.     

Spectral studies on Cr ions doped in sodium-lead borophosphate glasses

Electron paramagnetic resonance (EPR), optical absorption and emission spectra of Cr³⁺ ions doped in (30−x) (NaPO₃)₆+30PbO+40B₂O₃+xCr₂O₃ (x=0.5, 2.0, 3.0, 4.0 and 5.0 mol%) glasses have been studied. The EPR spectra exhibit resonance signals with effective g values at g≈4.55 and g≈1.97. The EPR spectra of x=3.0 mol% of Cr₂O₃ in sodium-lead borophosphate glass sample were studied at various temperatures (295-123 K). The intensity of the resonance signals increases with decrease in temperature. The optical absorption spectrum exhibits four bands characteristic of Cr³⁺ ions in octahedral symmetry. From the analysis of the bands, the crystal-field parameter Dq and the Racah interelectronic repulsion parameters B and C have been evaluated. The emission spectrum exhibit one broad band characteristic of Cr³⁺ ions in octahedral symmetry. This band has been assigned to the transition ⁴T_2g (F)→⁴A_2g (F). Correlating EPR and optical data, the molecular bonding coefficient (α) has been evaluated.     

Optical and EPR Properties of Mn- and Eu-Activated LaMgAl11O19 Phosphor

LaMgAl₁₁O₁₉ phosphor doped with Eu and Mn ions has been prepared by the urea combustion route. The as-prepared phosphor was studied using X-ray diffraction, electron paramagnetic resonance (EPR), diffuse reflectance and photoluminescence studies. The EPR spectra of LaMgAl₁₁O₁₉:Eu, Mn phosphor exhibit signals with the effective g values at g = 1.98, 4.29 and 7.23. The resonance signals at g = 1.98 and 4.29 were attributed to Mn²⁺ ions in tetrahedral and rhombic environment, respectively. The resonance signal at g = 7.23 was attributed to Eu²⁺ ions. The optical spectrum of this phosphor exhibits an intense band in the visible region and this band has been attributed to spin-allowed ⁵E_g → ⁵T_2g transition of Mn³⁺ ions. Upon excitation at 324 nm, the material displays emission in the blue, green and red spectral region.     

The effect of Ce3+ ions on the spectral and decay characteristics of luminescence phosphate-borate glasses doped with rare-earth ions

The luminescent characteristics of Li₂O-B₂O₃-P₂O₅-CaF₂ (LBPC) glasses doped with Gd³⁺ and Tb³⁺ ions and codoped with Ce³⁺ are studied by pulsed optical spectrometry under electron beam excitation. It is found that in glass with Ce³⁺ and Gd³⁺ ions a decrease in the decay time of gadolinium luminescence in the 312-nm band (⁶ P _J → ⁸ S _7/2) was observed. It is shown that in the glass LBPC: Tb, Ce, an increase in the emission intensity in the main radiative transitions in terbium ion was observed. In the kinetics of luminescence band 545 nm of LBPC: Tb, Ce glasses, is present stage of buildup, the character of which changes with the doped of Ce³⁺ ions. The mechanism of energy transfer in LBP glasses doped with rare elements is discussed.     

Luminescence spectroscopy of Ce3+-doped ABaPO4 (A=Li, Na, K) phosphors

Ce³⁺ doped ABaPO₄ (A=Li, Na, K) phosphors were prepared by conventional high temperature solid-state reaction. The phosphors were investigated by XRD, photoluminescence excitation and emission spectra, and luminescence decay curves. The five 5d levels corresponding to the 4f¹→4f⁰5d¹ transition of Ce³⁺ ions were identified. The spectroscopic parameters, e.g., the 5d barycenter, the crystal-field splitting, and the Stokes shift, were discussed. LiBaPO₄:Ce³⁺ phosphor could be efficiently excited by the near-UV lights (330–420 nm) and showed a broad emission band in the range of 430–620 nm with the maximum wavelength at 468 nm. In contrast, Ce³⁺-doped NaBaPO₄ and KBaPO₄ showed only excitation bands in a limited UV region (230–370 nm) and have blue emission at 385 nm and 416 nm, respectively. The temperature quenching of luminescence and the chromaticity coordinates were reported. The luminescence properties were discussed by analyzing the crystal structure and the local surroundings of Ce³⁺ ions on the Ba²⁺ sites.     

Spectral Studies of Vanadyl-Doped Cadmium–Strontium Borosilicate Glass System

Glasses with composition CdO–(20-x) SrO–B₂O₃–SiO₂–x V₂O₅ (CdSBSi) (x = 0.5, 1, 1.5, 2, 2.5 mol%) were prepared by melt quenching technique. The amorphous nature of prepared glasses is confirmed by X-ray diffraction. Optical absorption spectra, electron paramagnetic resonance (EPR) and Fourier transform infrared (FTIR) measurements were also carried out for the prepared glass samples. The optical band gap energy (E _opt) and Urbach energy (?E) were calculated from their ultraviolet edges. The theoretical values of optical basicity (Λ _th) of glasses have been evaluated. The optical absorption spectrum exhibits two band characteristic of VO²⁺ ions in tetragonally distorted octahedral site symmetry. The two bands have been assigned to the transitions ²B₂ → ²B₁ and ²B₂ → ²E in the decreasing order of energy. The spin–Hamiltonian parameters (g and A), bonding parameters (β*² and $ \varepsilon_{\pi }^{*2} $ ), Fermi contact interaction parameter (K) have been evaluated from the EPR spectra. The VO²⁺ site symmetry is ascribed to a tetragonally (C_4v) distorted octahedron. FTIR spectra of these glasses were analyzed in order to identify the contribution of each component to the local structure. The physical properties of these glasses were also evaluated.     

Manifestation of up-conversion in Yb3+/Tm3+ doped Li2O–Y2O3–SiO2 glass system

In this study, we have investigated the principal role of Y₂O₃ on the emission features of Tm³⁺ ion and up-conversion phenomenon in Tm³⁺ and Yb³⁺ co-doped Li₂O–Y₂O₃–SiO₂ glass system. The concentration of Y₂O₃ is varied from 0 to 5 mol% while that of Yb³⁺ and Tm³⁺ is fixed. When the glasses are doped with Tm³⁺ ions, the intense blue and red emissions were observed, whereas Yb³⁺ doped glasses exhibited NIR emission at about 980 nm. When the glasses are co-doped with Tm³⁺ and Yb³⁺ ions and excited at 900 nm, the blue and red emission lines were observed to be reinforced and strengthened with increase in the concentration of Y₂O₃. The IR emission band detected at about 1.8 μm due to ³F₄ → ³H₆ transition of Tm³⁺ ions is also observed to be strengthened due to co-doping. The reasons for enhancement in the intensity of various emission bands due to co-doping have been identified and discussed with the help of rate equations for various emission transitions.     

Spectral studies on Mn ions doped in sodium-lead borophosphate glasses

Electron paramagnetic resonance (EPR), optical absorption, and luminescence spectral studies of Mn²⁺ ions doped in (30−x) (NaPO₃)₆+30PbO+40B₂O₃+xMnO₂ (x=1.0, 2.0, 3.0, 4.0, and 5.0 mol%) glasses have been studied. The EPR spectra exhibit resonance signals with effective g value at g_eff≈2.02 with six line hyperfine structure. A weak resonance signal with effective g value at g_eff≈4.3 is also observed for higher concentrations of Mn²⁺ ions. The EPR spectra of x =3.0 mol% of Mn²⁺ in sodium-lead borophosphate glass sample have been studied at various temperatures. It is observed that the resonance signal intensity decreases with increase in temperature. The optical absorption spectrum exhibits bands characteristic of Mn²⁺ ions in octahedral symmetry. From the analysis of the bands, the crystal-field parameter Dq and the Racah interelectronic repulsion parameters B and C have been evaluated. The emission spectrum exhibits single broad band in the green region.     

Spectral studies on Cu ions in sodium–lead borophosphate glasses

Electron Paramagnetic Resonance (EPR) and optical absorption spectra of Cu²⁺ ions in sodium–lead borophosphate glasses doped with different concentrations of Cu²⁺ ions have been studied. EPR spectra of all the glass samples exhibit resonance signals characteristic of Cu²⁺ ions. The values of spin-Hamiltonian parameters indicate that the Cu²⁺ ions in sodium–lead borophosphate glasses are present in octahedral sites with tetragonal distortion. The optical absorption spectra of all the glass samples show a single broad band, which has been assigned to the ²B_1g→²B_2g transition of Cu²⁺ ions. The optical band gap energy (E_opt) and Urbach energy (ΔE) are calculated from their ultraviolet absorption edges. The emission bands observed in the ultraviolet and blue region are attributed to 3d⁹4s→3d¹⁰ triplet transition in Cu⁺ ion. The FT-IR spectra show that the glass system contains BO₃, BO₄ and PO₄ structural units.     

Influence of ligand coordination of cobalt ions on structural properties of ZnO-ZnF2-B2O3 glass system by means of spectroscopic studies

The glasses of the composition 10ZnO-30ZnF₂-60B₂O₃ doped with different concentrations of CoO were prepared. Differential scanning calorimetric (DSC) studies, optical absorption, photoluminescence and infrared spectra of these glasses have been carried out. DSC studies have indicated that the resistance of the glass against devitrification increases with the increase in the concentration of CoO. Optical absorption spectra have exhibited one octahedral band due to ⁴T_1g(F)→²T_1g(H) and two tetrahedral bands due to ⁴A₂(⁴F)→⁴T₁(⁴P) ⁴A₂(⁴F)→⁴T₁(⁴F) transitions of Co²⁺ ions at about 525, 570 and 1400 nm, respectively. As the concentration of CoO is increased the tetrahedral bands are observed to grow at the expense of octahedral band. The luminescence spectra have exhibited two emission bands in the spectral regions of 600-700 nm and 800-900 nm due to ⁴T₁(⁴P)→⁴A₂(⁴F) and ⁴T₁(⁴P)→⁴T₂(⁴F) tetrahedral transitions of Co²⁺ ions, respectively. With the increasing content of cobalt ions in the glass matrix, the half width and intensity of these bands are observed to increase. The analysis of the results of these two spectra coupled with IR spectra has indicated that as the concentration of CoO is increased in the glass matrix, the tetrahedral occupancy of cobalt ions dominates over the octahedral occupancy and increase the rigidity of the glass network.     

Dy3+ doped SiO2–B2O3–Al2O3–NaF–ZnF2 glasses: An exploration of optical and gamma radiation shielding features

A series of Dy³⁺ doped zinc-aluminoborosilicate glasses with chemical composition 30SiO₂-(30-x) B₂O₃–10Al₂O₃–15NaF–15ZnF₂-xDy₂O₃ (x = 0, 0.5, 0.7, 1.0 and 1.5 mol %) were prepared by conventional melt-quenching method. Structural and optical properties of the glasses were analyzed through XRD, FTIR, UV–Visible–NIR and luminescence studies. Gamma radiation shielding parameters were obtained using PSD software. Nephelauxetic ratio (β) and bonding parameters (δ) calculated using absorption spectrum shows the decreasing ionic nature of the Dy ions. Judd-Oflet parameters (Ω₂, Ω₄ and Ω₆) obtained shows the covalency and asymmetric nature of dysprosium ions. The luminescence properties shows that Dy³⁺ doped glasses have two strong intense emission at blue (482 nm) and yellow (575 nm) region. Branching ratio and stimulated emission cross section calculated suggests the glasses suitability to act as lasing material. CIE colour coordinates and its colour correlated temperature (CCT) for the glasses were estimated and found that these prepared glasses lie in the warm white light region.     

Absorption phenomena in multicomponent phosphate glasses with Mn

The absorption and ESR spectra of multicomponent alumino-phosphate glasses doped with manganese (0·2–20 mol %) has been measured and compared with the absorption spectra of manganous and manganic ions in model solutions. The unirradiated glasses show in ultraviolet region increasing absorption below 200 nm with the shoulder at 235 nm and the absorption bands due to manganous oxygen complexes in octahedral symmetry. They are similar to the absorption bands of Mn²⁺ in concentrated H₃PO₄ acid. In irradiated glasses the bands at 200, 235, 275 (only if Mn is present) and a broad band at 540 nm appear. After the annealing at 450 C all radiation-induced bands disappear and the bands at 235 nm is more pronounced. The Mn³⁺ in H₃PO₄ solution exhibit the absorption spectrum with a weak band at 530 nm and a very intense band at 270 nm. It is therefore proposed that both the 540 and 275 nm bands in irradiated glasses can be assigned to octahedral oxygen complexes of Mn³⁺, i.e. to hole centres. The band at 200 nm which is practically independent of the modifiers (Be, Mg, Ca, Sr and Ba) is, therefore, associated with electron centres (electrons trapped in non-bridging oxygen vacancies). It is suggested that the band at 235 nm in irradiated and annealed glasses is associated with irreversible structural changes.The authors wish to express their appreciation to H.Dvoáková for preparing the solutions and E.Linhartová for careful measurements.     

Luminescence spectroscopy and energy transfer in Eu2+/Mn2+-doped KCaPO4 phosphors

Eu²⁺/Mn²⁺-doped KCaPO₄ phosphors were prepared by conventional solid-state reaction. X-ray powder diffraction (XRD), SEM, photoluminescence excitation, and emission spectra, and the luminescence decay curves were measured. Mn²⁺ singly doped KCaPO₄ shows the weak origin-red luminescence band peaked at about 590 nm. The Eu²⁺/Mn²⁺ co-doped phosphors emit two distinctive luminescence bands: a blue one centered at 480 nm originating from Eu²⁺ ions and a broad red-emitting one peaked at 590 nm from Mn²⁺ ions. The luminescence intensity from Mn²⁺ ions can be greatly enhanced with the co-doping of Eu²⁺ ions. The efficient energy transfer from Eu²⁺ to Mn²⁺ was verified by the photoluminescence spectra together with the luminescence decay curves. The resonance-type energy transfer via a dipole–quadrupole interaction mechanism was supported by the decay lifetimes. The emission colors could be tuned by changing the Mn²⁺-doping concentration.     

Enhancing up conversion luminescence effect of β-NaYF<Subscript>4</Subscript>: Yb<Superscript>3+</Superscript> and Tm<Superscript>3+</Superscript> by Li<Superscript>+</Superscript> ion doped approach

Up-conversion (UC) is a photoluminescence process which converts few low energy photons to a higher energy photon. This process has more potential usages in many different fields like bioimaging, solar spectrum tuning, and security encoding. Nowadays, researches about UC mostly focusing on biomedical signory and synthesis of nanoparticles. The synthesis of NaYF₄ nanoparticles executed under series of pH value condition results in different morphology and photoluminescence effect. Samples in low pH value created better consequent and quality than the specimen which had higher pH value. In addition, we observed NaYF₄ samples of doping Li⁺, realizing that the action of distorting in the local symmetry around rare-earth ions is caused by Li⁺ doping. The NaYF₄ microparticles which doped higher concentration of Li⁺ has strong fluorescence properties and intensities compared with their corresponding group of Li⁺-free, the blue emission 479 nm luminescence intensities and 454 nm luminescence intensities in NaYF₄:Yb³⁺, Tm³⁺ microparticles doped 20 mol% Li⁺ are enhanced 3 and 8 times, separately. And violet emission luminescence intensities around 345 and 360 nm are about 10 and 7 times, respectively. The result indicated that the improved UC luminescence of NaYF₄:Yb³⁺. Tm³⁺ microparticles with Li⁺ doping have potentially applications.     

Optical and luminescence properties of Dy3+ ions in K–Sr–Al phosphate glasses for yellow laser applications

Trivalent dysprosium (Dy³⁺)-doped K–Sr–Al phosphate glasses have been prepared and investigated for their optical and luminescence properties. Judd–Ofelt theory has been used to derive radiative properties for the ⁴F_9/2 level of Dy³⁺ ions. The luminescence spectrum of 1.0 mol% Dy₂O₃-doped glass shows intense yellow emission around 572 nm ascribed to ⁴F_9/2 → ⁶H_13/2 transition with 78 % branching ratio and emission cross section of the order of 2.48 × 10^?21 cm². Moreover, the quantum efficiency of the ⁴F_9/2 level has been found to be 76 %. The luminescence decay curves for the yellow emission (⁴F_9/2 → ⁶H_13/2) have been measured and analyzed as a function of Dy³⁺ ion concentration. The results revealed that Dy³⁺-doped phosphate glasses could be useful for yellow laser applications.     

Dy3+掺杂硼硅酸盐玻璃的发光特性

采用高温熔融法制备了Dy3+掺杂硼硅酸盐玻璃,通过测试激发光谱和发射光谱,研究了其光谱性质.研究了玻璃组分及Dy3+掺杂浓度对发射光谱及发光强度的影响,并计算了色坐标,均位于白光区域.通过改变玻璃组分及掺杂浓度,调节黄、蓝发射峰的强度比,在387 nm长紫外光激发下实现了单一基质上有效的白光发射.     

Luminescence of yttrium aluminum borate single crystals doped with manganese

The optical absorption and luminescence spectra of single crystals of yttrium aluminum borate YAl₃(BO₃)₄ doped with manganese ions are measured. It is established that the optical absorption spectra of yttrium aluminum borate single crystals doped with manganese ions are determined primarily by the contribution from the Mn⁴⁺ ions. The luminescence spectra of the YAl₃(BO₃)₄ single crystals doped with manganese exhibit narrow lines attributed to the Mn⁴⁺ ions and an extended multiband structure which is associated primarily with the contribution from the Mn²⁺ ions.     

EPR and optical studies on transition metal doped LiRbB4O7 glasses

Electron paramagnetic resonance and optical investigations of copper and chromium doped LiRbB₄O₇ glasses are carried out. From the results and discussions, it is predicted that both the transition metal ions exhibit octahedral environment. In the case of Cr³⁺, the site symmetry is near octahedral, whereas in the case of Cu²⁺, it is tetragonally distorted octahedral environment. Crystal field, spin-Hamiltonian and bonding parameters are evaluated. The bonding parameters are suggesting ionic.     

Dielectric and spectroscopic investigations of lithium aluminium zirconium silicate glasses mixed with TiO2

Li₂O–Al₂O₃–ZrO₂–SiO₂ glasses mixed with different concentrations of TiO₂ (ranging from 0 to 5.0?mol%) were synthesised and their dielectric properties (dielectric constant, loss tan?δ, a.c. conductivity σ) investigated over wide ranges of frequency and temperature. Studies of optical absorption, ESR, infrared (IR) and photoluminescence properties have also been undertaken. A decrease in dielectric parameters with increasing concentrations of TiO₂ has been observed and this is attributed to an increasing proportion of titanium ions occupying network-forming positions rather than going into interstitial positions. A.C. conductivity in the high-temperature region appears to be connected both to electronic transfer and ionic movements, but conduction attributed to such processes seems to be hampered by the entry of titanium ions into the network-forming positions. Analysis of the results of the IR spectral studies have indicated that there is a decreasing degree of disorder in the glass network with increasing TiO₂ content. The optical absorption and ESR spectral studies have revealed that titanium ions exist in both Ti³⁺ and Ti⁴⁺ states in the glasses. Luminescence spectra exhibited an emission band in the visible region and the luminescence efficiency increased with TiO₂ content. The excitation of substitutionally positioned octahedral Ti⁴⁺ ions is identified as being responsible for the observed luminescence emission.     

Synthesis and Optical Properties of Eu3+ Ion Doped Nanocrystalline Hydroxyapatites

The Ca₁₀(PO₄)₆(OH)₂ hydroxyapatite (HA) nanopowders doped with Eu³⁺ ions were prepared using a wet synthesis method. Their structure and morphology were investigated. The XRD analysis has proven a single-phase of HA nanocrystallites. The average sizes of HA nanocrystallites calcinated at 400°C and 700°C were determined to be about 20 nm and 30 nm, respectively. The emission and excitation spectra as well as the fluorescence decay rates of Eu³⁺ ion doped HA nanocrystallites were measured. Particular attention was given to the spectroscopic properties of Eu³⁺ ions as a luminescent probe of nanocrystalline HA structure as a result of varying annealing temperature and dopant concentration. The Judd-Ofelt analysis of f-f transitions of Eu³⁺:HA nanocrystallites was performed. The effect of calcination temperatures on grain sizes and luminescence properties is noted and discussed.