Optical properties of silver-doped aluminophosphate glasses

Silver-doped aluminophosphate glasses were prepared by the melt-quenching technique in which silver nanoparticles (NP) of different sizes were embedded upon heat treatment. Optical absorption and photoluminescence spectroscopy were used to study the optical properties of the material before and after thermal processing. Photoluminescence (PL) experiments revealed a broadband emission observed around 420 nm for the non-heat treated samples with a luminescence decay showing a bi-exponential behavior. Temperature dependence PL studies showed a thermal quenching effect on the broadband emission. Our data suggests that the emission is due to single Ag⁺ ions. Optical absorption measurements performed on the heat treated samples allowed for particle size estimation and the evaluation of the thermal stability of the glass system and its attributes as a host for NP inclusion. The nanocomposite showed a dip in the broadband emission of silver ions ascribed to absorption of Ag⁺ ions luminescence by surface plasmons in the silver particles.     

Structure and radiative properties of aluminophosphate glasses

The structure and radiative properties of aluminophosphate glasses in the system K₂O-Al₂O₃-P₂O₅ and BaO-Al₂O₃-P₂O₅ were investigated. The structural changes in glasses with the addition of alumina were investigated by using FTIR spectroscopy and NMR spectroscopy. In the case of the K₂O-Al₂O₃-P₂O₅ glasses, the aluminium atoms were mainly octahedrally coordinated and acted as network modifiers. The decrease in the spontaneous emission rate of K₂O-Al₂O₃-P₂O₅ glasses was due to the tightening of chains in terms of the addition of alumina to the glasses. The increase in effective linewidth was probably due to the increase of end groups in the glasses. In the case of BaO-Al₂O₃-P₂O₅ glasses, the addition of alumina had little effect on the radiative properties, probably due to the small structural change which occurred on its addition.     

Luminescence of trivalent samarium ions in silver and tin co-doped aluminophosphate glass

This work presents the spectroscopic properties of trivalent samarium ions in a melt-quenched aluminophosphate glass containing silver and tin. Addition of 4 mol% of each Ag₂O and SnO into the glass system with 2 mol% Sm₂O₃ results in Sm³⁺ ions luminescence under non-resonant UV excitation owing to energy transfer from single silver ions and/or twofold-coordinated Sn centers. Assessment of luminescence spectra and decay dynamics suggest the energy transfer mechanism to be essentially of the resonant radiative type. Moreover, a connection between the luminescent and structural properties of the rare-earth doped glass system was demonstrated. Raman spectroscopy characterization revealed that no significant variation in the glass matrix is induced by Sm³⁺ doping at the concentration employed. A comparison was made with a structural study performed on the Eu³⁺ doped system (containing 2 mol% Eu₂O₃ along with 4 mol% of each Ag₂O and SnO) where the radiative energy transfer mechanism was previously established. The data appears consistent regarding the lack of variation in glass structure upon the Eu³⁺ and Sm³⁺ doping in connection with the dominance of the radiative transfer in the matrix. Thermal treatment of the material leads to precipitation of Ag nanoparticles of a broad size range inside the dielectric as observed by transmission electron microspcopy. Assessment of ⁴G_5/2 excited state decay in Sm³⁺ ions shows no influence from the silver particles.     

Optical properties of oxide glasses containing transition metals: Case of titanium- and chromium-containing glasses

One of the major driving forces for the development of new glasses is the demand for high optical non-linearity with reduced cost and a higher damage resistance. Oxide glasses with large non-linear refractive index and non-linear absorption coefficient are promising materials for fiber telecommunication and for non-linear optical devices such as ultrafast optical switches, power limiters, real time holography, self-focusing, white-light continuum generation and photonic applications. To get insight into the optical absorption in amorphous materials, studies are still needed for revealing the nature of photoelectronic excitations in these materials by comparison with that in crystals which have been understood firmly based on band theory. Although the IR absorption loss in oxide glasses is larger than of fluorides, low light scattering loss is expected in these oxide glasses because they have lower glass transition temperature. In addition, small concentration of dopant such as alkaline metal and alkaline earth metal elements gives rise to the structural relaxation of the frozen-in density fluctuations even below glass transition temperature T_g, adding to the reduction of T_g as well. A review of the fundamentals and recent research advances in optical properties of oxide glasses containing chromium or titanium is presented.     

Optical and spectroscopic properties of soda lime alumino-silicate glasses doped with erbium and silver

Spectroscopic properties of Ag/Er co-doped soda lime silicate glasses have been studied with the aim of assessing the effective role of silver as a sensitizer for erbium. Changes in spectroscopic properties of Er³⁺ as a function of silver addition to the base composition have been measured. Transmission electron microscopy (TEM), absorption as well as photoluminescence measurements in the visible and infrared spectral region, particularly ⁴I_13/2 → ⁴I_15/2 transition of the Er³⁺ ion were performed; excitation wavelengths in the range from 325 to 808 nm were used. Enhancement of the Er³⁺ luminescence at 1.54 μm was observed when Ag was added.     

Compositional effects on the optical and thermal properties of potassium aluminophosphate glasses

The K₂O–Al₂O₃–P₂O₅ glass system has been examined and various compositions have been melted. Their optical and thermal properties have been measured to assess their potential for athermalisation. The addition of alumina (Al₂O₃) increases the refractive index (n) and glass transition temperature (T_g) and decreases the thermal expansion coefficient (α), consequently leading to positive thermo-optic coefficient (dn/dT). In addition to thermal expansion, polarisability of the glass also affects dn/dT. Generally, glasses must exhibit negative dn/dT to counter thermal expansion, in order to have potential application in athermalisation.     

Dielectric properties of silver borophosphate glasses

Dynamic behaviour of electrical conduction and polarization in silver borophosphate glasses has been studied over wide range of frequencies and temperatures. The dielectric spectrum showed a strong dispersion in C() with rise in temperature which distinguishes the conduction process from a pure steady state. The observed behaviour was found to be temperature activated with an activation energy of 0.39 eV. The data have been analysed in terms of admittance plots and a model has been proposed on the basis of this analysis.     

Oxyfluorotellurite glasses doped by dysprosium ions. Thermal and optical properties

The paper shows results of investigation of thermal and optical properties of oxyfluorotellurite (65 − x)TeO₂–20ZnF₂–12Pb₂O₅–3Nb₂O₅–xDy₂O₃ (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 ΔT and H’ increased with increasing Dy₂O₃ content indicating that the incorporation of dysprosium ions improves substantially thermal stability of glass system under study.Optical absorption and emission spectra of Dy³⁺ 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 ⁴F_9/2 luminescence of incorporated Dy³⁺ ions were recorded and analysed. Lifetimes and the luminescence dynamics were studied as a function of the Dy₂O₃ 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.     

Optical properties of tin diselenide films

SnSe₂ films were deposited on substrates at 300 K by a conventional thermal evaporation technique. The as-deposited films were amorphous and transformed to the crystalline phase on post-deposition annealing above 573 K in an inert atmosphere. The optical properties of the films were investigated, using spectrophotometric measurements of the transmittance and reflectance at normal incidence in the wavelength range 400–2000 nm. The refractive index data fit a single oscillator model with a dispersion parameter 5.149×10^–14 and 5.773×10^–14 eVm² for the amorphous and crystalline films, respectively. The high-frequency dielectric constant of the amorphous films decreased from 9.871 to 7.475 for the crystalline films. The analysis of the spectral behaviour of the absorption coefficient in the intrinsic absorption region revealed an indirect forbidden and a direct allowed transition with energy gaps 0.99 and 2.05 eV for the amorphous films and 0.96 and 2.02 eV for the crystalline films, respectively.     

Structure and dissolution investigation of calcium-bismuth-borate glasses and vitroceramics containing silver

Quaternary Ag₂O-CaO-Bi₂O₃-B₂O₃ glasses and glassceramics are investigated with regard to release behaviour and local structure. The dissolution behaviour in water and physiological serum shows that the cations are released rapidly or gradually and points out a multi-step process, generally characterised by higher rates in water than in physiological serum. The structural effect of silver addition to bismuth-borate glasses is observed from infrared spectroscopic data. The antibacterial activity of the investigated samples was tested on six bacterial media.     

Optical properties of lead-bismuth cuprous glasses

The optical transmission and absorption spectra in UV- VIS were recorded in the wavelength range 350–800 nm for different glass compositions in the system (CuO) _x (PbO) ₅₀−x(Bi₂O₃)₅₀ (x = 2.5, 5.0, 7.5, 10.0, 12.5, 15.0, 20.0). Absorption coefficient (α), optical energy gap (E_opt), refractive index (n_D), optical dielectric constant (ε′_∞), measure of extent of band tailing (ΔE), constant (β) and ratio of carrier concentration to the effective mass (N/m*) have been reported. The effects of compositions of glasses on these parameters have been discussed. It has been indicated that a small compositional modification of the glasses lead to an important change in all the optical properties including non-linear behaviour. The optical parameters were found to be almost the same for different glasses in the same family.     

Optical,infrared and DSC studies of sodium tetraborate glasses containing copper oxide

The optical absorption, density, DSC and infrared absorption spectra of a series of sodium tetraborate glasses are measured as a function of copper content up to 5 mol%. It is found that the addition of CuO shifts the fundamental absorption edges towards lower energies in the range from 6.17–3.48 eV. The addition of CuO does not seem to introduce any new absorption band as compared with the spectrum of a pure sodium tetraborate glass. DSC measurements showed endothermal peaks varying from 486–476 °C depending on the CuO content.     

Optical and ultrasonic properties of europium phosphate glasses

To provide an overall picture of the vibrational properties of phosphate glasses containing high concentrations of europium, measurements have been made of their ultrasonic wave velocities and attenuation, optical absorption spectra and laser-induced fluorescence. To examine their valence state, the fluorescence of the glasses has been examined. The spectra do not show any obvious sign of divalent europium ions, only trivalent europium ion fluorescence being observed. Room-temperature absorption spectra of these glasses also provide evidence of only the absorption bands of trivalent europium. The elastic stiffnessesC ₁₁ andC ₄₄ continue to increase down to low temperatures and the ultrasonic attenuation is characterized by a broad peak, properties which are consistent with thermally activated relaxations of two-level systems. The longitudinal and shear ultrasonic wave velocities decrease under pressure; the hydrostatic pressure derivatives (C ₁₁/P) _{T, P=0} and (C ₄₄/P) _{T, P=0} of the elastic stiffness tensor componentsC _IJ and (B/P) _{T, P=0} of the bulk modulus,B ₀, are negative. When compressed, the europium phosphate glasses, like their samarium analogues, show the interesting property of becoming easier to squeeze. Measurements, using a pulse superposition technique, of the effect of uniaxial stress on ultrasonic wave velocities have been used to determine the temperature dependences of the third-order elastic stiffness tensor components of (Eu₂O₃)_0.186(P₂O₅)_0.814 and (Eu₂O₃)_0.20(P₂O₅)_0.80 glasses between 77 and 400 K. The uniaxial and hydrostatic pressure dependences of the elastic constants quantify the cubic term in the strain Hamiltonian and the vibrational anharmonicity of the long-wavelength phonons of these glasses. The acoustic mode Grüneisen parameters are negative: application of pressure induces a decrease in the long-wavelength acoustic phonon mode frequencies. As the temperature is reduced the pressure-induced mode softening becomes enhanced. The hydrostatic pressure derivative (C ₁₁/P) _{T, P=0} is larger than (C ₄₄/P) _{T, P=0} over the whole temperature range, and the longitudinal acoustic mode Grüneisen parameter _L is larger than that _S of the shear wave: the longitudinal mode softens more with pressure than the shear mode. Murnaghan's equation-of-state is used to determine the compressionV(P)/V ₀.     

Optical properties of samarium doped zinc-tellurite glasses

Glasses with the composition, (Sm₂ O ₃) _x (ZnO)_(40-x)(TeO ₂)₍₆₀₎, were prepared by conventional melt quenching method. The density, molar volume, and optical energy band gap of these glasses have been measured. The refractive index, molar refraction and polarizability of oxide ion have been calculated by using Lorentz-Lorentz relations. Optical absorption spectra of these glasses were recorded in the range 300–700 nm at room temperature. The oxide ion polarizabilities deduced from two different quantities, viz. refractive index and optical energy band gap, agree well compared with other glasses. The nonlinear variation of the above optical parameters with respect to samarium dopant has been explained.     

Optical properties of europium-activated hafnium fluoride-based glasses

We have studied the optical absorption, luminescence, and electron paramagnetic resonance of EuF₃- and EuF₂-activated fluorohafnate glasses. The glasses prepared with EuF₂ contain both di- and trivalent europium. The fraction of divalent europium clusters in the glass host decreases with decreasing EuF₂ concentration. Eu²⁺ luminescence in the fluorohafnate glasses is quenched, which is due the overlap of Eu²⁺ excited state levels with the conduction band of the glass, resulting in nonradiative relaxation through Hf³⁺ levels in the conduction band. The Eu³⁺ luminescence spectra contain lines corresponding to transitions from several levels of the ⁵D multiplet to levels of the ⁷F multiplet. The relationship between transitions from different ⁵D levels depends on europium concentration and temperature.     

Optical and dielectric properties of potassium-doped tin selenide polycrystals

Journal of Materials Science: Materials in Electronics - In our current study, we have investigated the effect of potassium doping on AC conductivity and the dielectric properties of tin selenide...     

Optical properties of tin oxide on anodized aluminium

The solar selective properties of tin oxide on anodized aluminium have been investigated. It has been shown that the pyrolytic spray method can be used to apply an IR-reflecting coating on black pigmented anodized aluminium. This surface exhibits high solar selectivity and the excellent mechanical, chemical and thermal stability of this sandwich makes it an interesting alternative in solar energy applications.