Low Silica Calcium Aluminosilicate Research Articles

Thermo-optical properties of iron-doped low silica calcium aluminosilicate glasses determined by photothermal methods

The aim of this work is to investigate Fe 3+ and Fe 2+ influence on the thermo-optical properties of low silica calcium aluminosilicate glass. Conventional optical absorption spectroscopy, thermal relaxation calorimetry and thermal lens spectrometry were applied to analyze the samples. The results provided the specific heat, the thermal diffusivity and the optical absorption coefficient as a function of the ions concentration. A significant variation in these parameters was observed, revealing the influence of the iron ions on the glass structure.

Fluorescence quantum efficiency in Nd2O3-doped aluminosilicate glasses by multiwavelength thermal lens method

In this work the multiwavelength thermal lens method is applied to determine the absolute value of fluorescence quantum efficiency of low silica calcium aluminosilicate glasses doped with different concentrations of neodymium dioxide melted under vacuum condition. The experiments were performed using five different excitation wavelengths: 514, 532, 750, 810 and 890 nm. The results were in agreement with those provided by the Judd-Ofelt model.

The temperature coefficient of the optical path length as a function of the temperature in different optical glasses

An interferometric technique was used to determine the temperature coefficient of the optical path length (dS/dT) as a function of the temperature in several optical glasses. The temperature range was between 25°C and 180°C. The studied samples included undoped and doped oxide glasses, such as low silica calcium aluminosilicate, phosphates, borates and also chalcogenides. The oxide glasses had dS/dT between 10×10−6K−1 and 20×10−6K−1, while for the chalcogenides, these were around 70×10−6K−1. The results showed that dS/dT’s increased with the temperature in all samples. For samples doped with Nd the dS/dT values were found to be independent of concentration. On the other hand, for the phosphate glass doped with Cr, dS/dT increased about 5% when compared with the Nd doped one. In conclusion, the used interferometric method, which is a considerably simpler and a lower cost technique, and is a useful tool to measure dS/dT in semi-transparent glasses as a function of the composition and temperature.

Bonding preferences of non-bridging O atoms: Evidence from17O MAS and 3QMAS NMR on calcium aluminate and low-silica Ca-aluminosilicate glasses

The fraction of O atoms as non-bridging O atoms (NBO) can be well approximated based on composition alone in many silicate glasses, but the NBO preference for specific network forming cations is much less well known. Using oxygen-17 ( 1 7 O) NMR on low-silica calcium aluminosilicate (CAS) glasses this study shows that Al-NBO (155 ppm) can be readily distinguished from Si-NBO (110-120 ppm), and that there is a strong preference for the latter. This study also presents a consistent equilibrium constant formulation that indicates that for thermodynamic modeling of most CAS melts with Si > Al, Al-NBO are of minor importance, although they could be significant in some models of diffusion and viscosity. Al-27 one pulse NMR and analyses of spinning side bands show that AlO 5 and AlO 6 species are below detection limits (<0.5% in the low-silica (SiO 2 < 20 mol%) glasses of this sludy (NBO/T = 0.6 to 0.8). In addition, 1 7 O MAS NMR does not detect any obvious (<2%?) Al 2 O triclusters; hence calculations of NBO assignments can be assigned unambigunously.

Thermal lens determination of the temperature coefficient of optical path length in optical materials

In this work thermal lens spectrometry is applied to determine the temperature coefficient of optical path length in several optical materials. Polymer, fluoride and low silica calcium aluminosilicate glasses and YAG, YVO4, YLF, LiSAF, and LiSGaF crystals were analyzed. The results showed the ability of the thermal lens method to obtain the absolute values of this so important optical parameter, which is crucial for those who work in the designing of solid state laser cavity.

Elastic moduli of low-silica calcium alumino-silicate glasses

The elastic properties of a series of low-silica calcium alumino-silicate (LSCAS) glasses are investigated by room temperature ultrasonic pulse-echo technique. Both longitudinal and transverse velocities of these glasses are composition dependent. The experimental results are used to obtain elastic moduli. The correlation of elastic stiffness, the cross-link density, and the fractal bond connectivity of the glass are discussed. The values of elastic moduli (including Young’s modulus, bulk modulus, shear modulus and Poisson’s ratio), derived from experimental data for our glasses are compared with those theoretically calculated in terms of Makishima–Mackenzie model and a model by Rocherulle et al.

Thermal relaxation method to determine the specific heat of optical glasses

In this work the thermal relaxation method is applied to determine the specific heat of the following optical glasses: undoped chalcohalides (As 2S 3 and 40PbI 2+30Sb 2S 3+30As 2S 3); undoped and Nd 2O 3 doped phosphate (38.66P 2O 5+40.22ZnO+21.12Na 2O) and low silica calcium aluminosilicate (47.4CaO+41.5Al 2O 3+7.0SiO 2+4.1MgO) glasses. For the latter the samples were melted both under vacuum and air conditions. Our results show that the specific heats of silica calcium aluminosilicate samples prepared under vacuum conditions were larger than that of the samples melted under air atmosphere. For chalcohalide glass sample (40PbI 2+30Sb 2S 3+30As 2S 3) the occurrence of a glass transition at 171 °C was observed. These results indicate that this simple and low cost method is an useful tool to measure the specific heat of glasses as a function of the temperature.

Temperature dependence of fluorescence quantum efficiency of optical glasses determined by thermal lens spectrometry

In this work thermal lens spectrometry is applied to determine the fluorescence quantum efficiency, η, of Nd 2O 3-doped low silica calcium aluminosilicate glasses as a function of the temperature. The experiments were performed in the temperature range between 22 and 180 ° C. The results showed that the decrease in η observed with increase in the temperature of the samples was larger for the larger Nd 2O 3-doping concentrations. This observation indicates that the non-radiative relaxation processes induced by Nd–Nd ion interactions may be the dominant mechanism responsible for the η reduction. The results indicate that the thermal lensing technique is a useful tool to evaluate the effect of the active medium temperature in the performance of laser systems.

Thermo-optical properties of OH-free erbium-doped low silica calcium aluminosilicate glasses measured by thermal lens technique

Thermal lens spectrometry (TLS) of thermo-optical properties of low silica content calcium aluminosilicate glasses (27.1Al 2O 3, 58.1CaO, 7.9SiO 2 and 6.9MgO in mol%) was performed. The thermal diffusivity was 5.7×10 −3 cm 2/ s for undoped sample and 4.7×10 −3 cm 2/ s for 1.48 mol% Er 2 O 3 -doped one. The d s/d T for undoped samples was 8.6±0.1×10 −6 K −1 . The thermal conductivity was around 14 mW/cm K with some dependence on Er 2O 3 concentration. The fraction of the absorbed energy converted into heat by Er 2O 3-doped samples was about 60%.

Spectroscopic properties of water free Nd 2O 3-doped low silica calcium aluminosilicate glasses

In this work, low silica calcium aluminosilicate glasses (LSCA) doped with different concentrations of Nd 2O 3 were prepared under vacuum conditions and investigated through spectroscopic measurements. UV, visible and near IR optical absorption spectra, IR luminescence spectra, and fluorescent time decay were measured. Judd–Ofelt model was used in conjunction with these data to calculate intensity parameters (Ω 2,Ω 4 and Ω 6 ), emission cross-section, radiative lifetime, branching ratio and fluorescence quantum efficiency. The up-conversion properties of Nd 3+ were investigated following ( 4 G 5/2+ 2 G 7/2) excitation, and both visible and UV up-conversion have been observed. These results combined with its high fluorescence quantum efficiency and excellent mechanical properties, suggest that this glass may be a candidate to be used as laser host material for near IR with a further possibility of application in the UV and visible spectral regions.

Rare-earth doped low silica calcium aluminosilicate glasses for near and mid infrared applications

The combination of properties such as chemical durability, transformation temperature, thermo-mechanical properties, refractory properties, phonon energy of about 800 cm −1 and infrared transparency up to 6 μm, recommend low silica (<7 wt%) calcium aluminosilicate glasses as hosts for laser applications. We have been investigating the physical properties of these glasses prepared by melting under vacuum conditions. This preparation procedure ensured minimum in OH content in the low silica calcium aluminosilicate glass hosts with fluorescence quantum efficiency of about 0.92 and 2.8 μm photoluminiscence, in samples co-doped with Er and Yb. In this paper, we review the thermal, mechanical and optical properties of these minimum OH content rare-earth-doped oxide glasses and discuss their potentials for near- and mid-infrared applications. Particular emphasis is given to the discussion of the new and promising optical properties of Er–Yb doped samples for biomedical applications.

Structure and properties of low-silica calcium aluminosilicate glasses

The structure of three calcium aluminosilicate glasses with low-silica content (61CaO · 39Al 2O 3 (Ca0.39), 55CaO · 35Al 2O 3 · 10SiO 2 (Ca10.35) and 49CaO · 31Al 2O 3 · 20SiO 2 (Ca20.31)), synthesized by a standard quenching technique, were studied by X-ray and neutron diffraction. The data are consistent with the hypothesis that Si and Al are present in tetrahedral sites and Ca in octahedral sites for all compositions. Si–T (T=Si or Al) and Si–O2 contributions (where O2 means the second nearest oxygen) appear at 10 mol% silica content, which indicate that silicon enters the aluminate network.

Mode-mismatched thermal lens spectrometry for thermo-optical properties measurement in optical glasses: a review

In this work, the application of thermal lens spectrometry (TLS) to study thermo-optical and spectroscopic properties of optical glasses is described. The theoretical basis for quantitative measurements is discussed together with the advantages and limitations of the method as compared with conventional measurements. The technique is applied to determine the thermal diffusivities, temperature coefficient of optical path length changes, ds/ dT , and the fluorescence quantum efficiencies of several glasses such as fluorides, chalcogenides, chalcohalides, soda lime and low silica calcium aluminosilicate. For some of these glasses, the effect of glass composition on thermo-optical properties was studied. For aluminosilicate glasses was observed an 8% decrease of the thermal diffusivity with the increase of Nd 2O 3 doping. Five kinds of fluoride glasses were studied and it was observed that fluorindate and fluoaluminate present better thermo-optical properties compared to fluorozirconate glasses: thermal diffusivity ∼20% higher and ds/ dT ∼50% lower (in modulus). All fluoride glasses had negative ds/ dT and all the other glasses a positive ds/ dT . For fluoride glasses, the TLS measurements were performed up to the glass transition temperature ( T g ). Near T g thermal diffusivity decreases and ds/ dT increases, both by one order of magnitude. The TLS was used to determine fluorescence quantum efficiency and concentration quenching in Nd 3+-doped glasses (aluminosilicate and fluorozirconate). These results were compared with the Judd–Ofelt calculations.

Thermo-mechanical and optical properties of calcium aluminosilicate glasses doped with Er 3+ and Yb 3+

In this work a series of Er 2O 3 and Yb 2O 3 doped and Er 2O 3–Yb 2O 3 co-doped low silica calcium aluminosilicate glasses have been melted at 1470°C under vacuum conditions. Measurements of optical absorption coefficient, mass density, refractive index, Vickers micro-hardness, glass transformation temperature ( T g) and crystallization temperature ( T x) have been carried out. The results showed that these glasses dissolved ∼1.5 mol% Er 2O 3 and ∼1.1 mol% Yb 2O 3 in their structure without devitrification and also that only small changes (∼10%) have been measured in their thermal, mechanical and optical properties.