Doped Glass Matrix Research Articles

Effect of concentration of Er3+ on up-conversion luminescence in NaYF4 embedded oxy-fluoride glass-ceramics under 1550 nm excitation

Oxy-fluoride glass-ceramics (GC) has advantages such as low phonon energy of fluorides and the excellent physical and chemical properties of oxides. Here we report the synthesis of a series of transparent oxy-fluoride GCs with various doping contents of Er3+ (0.2 mol%-10 mol%) synthesized under different temperatures, and their UCL properties under the excitation of 1550 nm laser. We found that Er3+-doped glass matrix with NaYF4 fluoride nanocrystals demonstrated greatly enhanced UCL compared with as-prepared glass. The samples showed red light emission with 3 mol% Er3+ as the optimal doping content. The wavelength of UCL could be fine-tuned by the temperature of heat treatment, and 893 K seems to be the optimal temperature. We also studied the photoelectric conversion characteristics of the optimal Er3+ doped oxy-fluoride GCs with a polycrystalline silicon solar cell under the excitation of a 1550 nm laser as a possible strategy to effectively improve the photo-electric conversion efficiency of solar cells.

Impact of Rare-Earth Ion Doping on Dielectric Properties of Li2O-CaO-B2O3 Glass System

The dielectric constant (ε′), loss factor (tanδ), and ac conductivity (σ ac) of 30 Li2O-10 CaO-(60-x) B2O3: xLn2O3, where (x = 0 and 1) and (Ln = Pr, Nd, Sm, and Eu) were investigated using a frequency range of 102–105 Hz and temperature ranging from 30 °C to 250 °C in this work. Differential Scanning Calorimetry (DSC) technique was employed to confirm the glassy nature of the materials under study. The dielectric parameters ε′, tanδ, and σ ac rise when rare-earth ions are added to the glass matrix at any frequency or temperature. Dielectric breakdown and activation energies are lower in doped than in undoped glasses while ac current flows through them at room temperature. Rare-earth ion doping’s dielectric parameter values decrease with temperature as atomic number (Z) rises. The dielectric parameter values for the Pr3+ doped glass matrix are the highest. Quantum Mechanical tunnelling (QMT) model was used to describe the ac conduction behaviour of these glasses.

Influence of rare-earth ion doping on dielectric properties of lithium zinc borate glasses

The dielectric constant (ε′), loss factor (tanδ), and ac conductivity (σac) of 30 Li2O-10 ZnO-(60-x) B2O3: xLn2O3, where (x = 0 and 1) and (Ln = Pr, Nd, Sm, and Eu) were investigated using a frequency range of 102–105 Hz and temperature ranging from 30 to 250 °C in this work. Differential Scanning Calorimetry (DSC) technique was employed to confirm the glassy nature of the materials under study. The dielectric parameters ε′, tanδ, and σac rise when rare-earth ions are added to the glass matrix at any frequency or temperature. Dielectric breakdown and activation energies are lower in doped than in undoped glasses while ac current flows through them at room temperature. Rare-earth ion doping's dielectric parameter values decrease with temperature as atomic number (Z) rises. The dielectric parameter values for the Pr3+ doped glass matrix are the highest. QM tunnelling model was used to describe the ac conduction behaviour of these glasses.

A novel Eu3+-doped phosphor-in-glass for WLEDs and the effect of borophosphate matrix

Phosphor-in-glass (PiG) is a potential color convertor for high power WLEDs. A novel glass matrix with advanced performance is still a challenge. Recently, Eu3+ doped glass matrix has attracted much consideration mainly due to its red compensation. A new borophosphate matrix to realize Eu3+ red light was designed in the Na2O-ZnO-P2O5-B2O3-Eu2O3 system. Meanwhile, a series of PiGs composed of different concentrations of Y3Al5O12:Ce phosphor and the matrix were also fabricated by re-sintering. The crystallization of Eu3+ based phosphate offers a novel red emission quenching apart from normal concentration quenching in the glass system. No direct energy transfer but only little reabsorption occurs between Eu3+ and Ce3+ ions. The Ce3+ concentration effect is obvious on the electroluminescent color. The optimized color rendering index of 79.7, the CIE coordinates near natural white and the range of CCT from 3943 to 6097 K were obtained for the packaged white light emitting diodes (WLEDs) together with the excellent CCT stability higher than about 97.5% and the quadruple thermal conductivity than that of silicon resin. The work implies borophosphate glass based PiGs with fine transparence and energy conversion efficiency are promising for excellent WLEDs, while the LED by using the PiG sample without any yellow phosphor doped is of high color purity and has a potential use as the 465 nm blue source.

Structural characterization, Gd3+ → Eu3+ energy transfer and radiative properties of Gd/Eu in codoped Li2O–ZnO–SrO–B2O3–P2O5 glass

A series of Gd doped Li2O–ZnO–SrO–B2O3–P2O5 glasses and co-doped samples with different Eu3+ concentrations was synthesized through the conventional melt quenching route. The structural, morphological, and elemental distributions were investigated by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and energy dispersive X-ray analysis. The effect of Gd doping on the thermal properties of prepared glasses was studied by differential thermal analysis. Characteristics photoluminescence (PL) emissions of Gd3+ (6P7/2→8SJ/2) and Eu3+ (5D0→7FJ) were observed in the doped glass matrix. Strong PL emissions at 312 nm (6P7/2 → 8S7/2) shown by the Gd-doped glasses upon excitation at 274 nm suggests its prospect in phototherapy applications. Phonon energy of the glass matrix calculated from the phonon sidebands of Eu3+ spectra was obtained as 970 cm−1. The values of branching ratios and stimulated emission cross-sections obtained from Judd-Ofelt analysis indicate the suitability of the prepared Gd–Eu co-doped glasses for optical display devices. The Observed Ω2 > Ω4 suggests Eu3+ occupancy preferably at less centrosymmetric sites in the studied glass hosts. The change in the local symmetry environment of the dopant ions with Gd incorporation was further analyzed by determining the asymmetry ratio of Eu3+ emission in the co-doped glass. The emission spectra and luminescence lifetimes suggested the efficient energy transfer from Gd3+ to Eu3+. Co-doping of Gd led to better chromaticity values and improved color purity of Eu3+ red emission.

Novel bifunctional YAG:Ce3+ based phosphor-in-glasses for WLEDs by Eu2+ enhancement

A series of phosphor-in-glasses (PiGs) composed of different concentration of Y3Al5O12:Ce3+ (YAG:Ce3+) yellow phosphor and Eu2+ doped SiO2–B2O3–CaO–SrO luminescent glass matrix were fabricated by the low temperature co-sintering technology. Detailed measurements such as X-ray powder diffraction, thermal analysis, stable photoluminescence and decay time for the glass matrix, the phosphor and the PiGs were performed. Variable color rendering index, correlated color temperature, chromaticity coordinates and lumen efficiency of the white light emitting diodes (WLEDs) combined the PiGs with ultraviolet (UV) or blue chips were also recorded. The Eu2+ doped glass matrix emit blue light under the UV excitation due to the 4f65d1-4f7 transition of Eu2+ ion, so different from the conventional PiGs also embedded YAG:Ce3+ phosphors but only used for blue chips, the fabricated PiGs can act as bifunctional color converters for WLEDs to obtain blue and yellow emission simultaneously with different blue light sources pumped by UV and blue chips, respectively. The former blue light is from Eu2+ excited by UV radiation, while the latter is from blue chips indeed. The yellow emission intensity increases with more YAG:Ce3+ phosphors embedded along with the declining of the blue emission for the WLEDs pumped by both UV and blue chips, so 8 wt% YAG:Ce3+ based WLED show higher yellow emission intensity and the maximal lumen efficiency (about 46 lm/W), but the better concentration for the standard white light are lower, which are 2 wt% and 6 wt% for the WLEDs excited by UV and blue light with the chromaticity coordinates of (0.3180, 0.3539) and (0.3256, 0.3403), respectively. With the extended dual excitation mechanisms, the materials can be used potentially to be combined with other phosphors, particularly with non-nitride red phosphors for resin-free high power WLEDs.

Molecular Dynamics Simulation of Amorphous SiO2, B2O3, Na2O-SiO2, Na2O-B2O3, and Na2O-B2O3-SiO2 Glasses with Variable Compositions and with Cs2O and SrO Dopants.

Selection of suitable glass composition for vitrification of high-level radioactive wastes (HLWs) is one of the major challenges in nuclear waste reprocessing. Atomic and molecular level understanding of various structural, thermodynamical, and dynamical properties of a glass matrix can help in preliminary screening and thus reduce the dependency to some extent on tedious experimental procedures. In that context, extensive molecular dynamics (MD) simulations have been performed to calculate various microscopic properties of the glass matrix. The present article demonstrates that the "Buckingham potential-included long-ranged Coulomb interaction" can be utilized to simulate the glasses of varied compositions. The proposed simulation model has been validated for a wide range of glass compositions: pure glass matrix-SiO2 and B2O3; binary glass mixtures-SiO2-B2O3, Na2O-SiO2, and Na2O-B2O3; ternary glass-Na2O-SiO2-B2O3; and also the Cs2O- and SrO-doped matrix of sodium borosilicate. Most importantly, the MD results have been validated with those of in-house synthesized glasses. The effect of alkali addition on the density and network connectivity of the glass matrix has been explored. The results capture well the boron anomalies for varied concentrations of network formers and network modifiers. The intermediate structural ordering in glasses has been explored by calculating the partial and total structure factors. Further, the characteristic vibration density of states of constituent atoms in the glass matrix is determined. In addition, the glass structures with the addition of dopant oxides Cs2O and SrO have been examined as they are known to be prime heat-generating agents in HLWs. The results establish the structure and dynamics of the doped glass matrix to be a complex nature of the dopant's mass, concentration, charge, and ionic radius. The present MD results might be of great academic and technological significance for further studies in the field of vitrification and prediction of effects associated with the dopant's nature and concentration.

Laser beam irradiation of silver doped silicate glasses

Planar light waveguides prepared by Ag–Na ion exchange in molten salt bath are irradiated with Nd:YAG laser beams at different wavelengths in the IR and VIS regions, and for different energy density and repetition rate values. The samples are characterized by optical spectroscopy to determine the role of irradiation parameters in the Ag clustering process, including aggregation phenomena and possible cluster photofragmentation. The appearance of the characteristic plasmon resonance feature in the optical absorption spectra marks the formation of Ag clusters, as observed by electronic microscopy as well, and permits to follow the evolution of the whole clustering process upon increasing of the deposited energy density. Photoluminescence spectroscopy has given specific information concerning the presence of Ag multimeric aggregates, considered as embryonic structures for the growing nanoclusters. The systematic investigation presented in this work is expected to clarify some aspects of the interaction between the laser beam and the doped glass matrix, and to help establishing suitable methodologies for the controlled preparation of nanocomposite glasses.

Effect of lithium-potassium mixed alkali on spectroscopic properties of Er3+-doped aluminophosphate glasses

Er3+-doped lithium-potassium mixed alkali aluminophosphate glasses belonging to the oxide system xK2O-(15-x)Li2O-4B2O3-11Al2O3-5BaO-65P2O5 are obtained in a semi-continuous melting quenching process. Spectroscopic properties of Er3+-doped glass matrix have been analysed by fitting the experimental data with the standard Judd–Ofelt theory. It is observed that Judd–Ofelt intensity parameters Ωt (t = 2, 4 and 6) of Er3+ change when the second alkali is introduced into glass matrix. The variation of line strength Sed[4I13/2,4I15/2] follows the same trend as that of the Ω6 parameter. The effect of mixed alkali on the spectroscopic properties of the aluminophosphate glasses, such as absorption cross-section, stimulated emission cross-section, spontaneous emission probability, branching ratio and the radiative lifetime, has also been investigated in this paper.

Luminescence of an Er 3+-doped glass matrix containing CdS quantum dots

Er3+-doped glass matrix containing semiconductor CdS quantum dots was prepared by melt-quenching and subsequent heating. Transmission electron microscopy analyses evidenced that the material consists of an amorphous silica network and abundant separated 2–5 nm CdS quantum dots. Photoluminescence and photoluminescence excitation spectra demonstrated the existence of energy transfer from the CdS quantum dots to Er3+ ions although the transfer efficiency was low.

Persistent Spectral Hole Burning in Eu3+-doped Calcium Oxide- and Calcium Fluoride-based Aluminoborate Glasses

Abstract Eu3+-doped oxyfluoride glasses with composition of 30CaF2–10Al2O3–60B2O3 (mol %) and oxide glasses of 30CaO–10Al2O3–60B2O3 (mol %) were prepared in a reducing atmosphere. The persistent spectral hole burning (PSHB) was characterized over a temperature range from 10 to 300 K, and the hole-burning efficiency between Eu3+-doped glass matrix of 30CaF2–10Al2O3–60B2O3 and 30CaO–10Al2O3–60B2O3 was compared.

Physical and optical properties of phthalocyanine doped inorganic glasses

Physical and optical properties of various free base and metallic phthalocyanine (Pc) doped glass matrix are reported for the first time. Absorption spectral measurements of H2Pc, MnPc, NiPc, CoPc, CuPc, MoOPc, ZnPc and FePc doped borate glass matrix have been made in the 200–1100 nm region and the spectra obtained are analyzed in the 2.1–6.2 eV region to obtain the optical band gap (Eg) and the width of the band tail (Et). Other important optical and physical parameters viz. refractive index (n), molar extinction coefficient (∈), density (ρ), glass transition temperature (Tg), molecular concentration (N), polaron radius (rp), intermolecular separation (R), molar refractivity (Rm) are also reported.

Three-dimensional phonon confinement in CdSe microcrystallites in glass

Results are presented which demonstrate the existence of unambiguous three-dimensional quantum confinement of phonons within crystallites of the II-VI semiconductor CdSe, which were prepared by the method of diffusive growth within a doped glass matrix. The confinement was investigated by means of Raman scattering from zone centre longitudinal optical (LO) phonons. These Raman spectra illustrate LO phonon peaks showing a low-energy shift and broadening with decreasing crystallite size. The experimental measurements are compared with a theoretical model of phonon confinement which includes a size distribution parameter. The experimental results are in good agreement with the predictions of this model. Surface vibrational modes and the effects of hydrostatic pressure from the glass matrix do not appear to be of significance in the samples investigated.