Surface and near-surface structure of silicate glasses

This paper presents analytic results, derived by diffractional low and large angle X-ray scattering methods, currently applied in our laboratory, as well as novel methods of electron emission microscopy and interference-phase optical microscopy for studying the internal structure, and that of surface and near-surface layers of raw and stepwise-etched, composite oxide silicate glasses of the type SiO₂-Na₂O-CaO-MgO. The structural and topographic studies are supplemented with quantitative analysis of chemical composition on a micro-scale and in micro-regions by electron microprobe and microscopic measurements of the temperature characteristics in a series of the above glasses. Moreover, a discussion is given of chemical corrosion, surface strcuture and topography, and the distribution of micro and macro-inhomogeneity regions in surface layers. Structural parameters are obtained which described the surface and internal structure of silicate glasses well adapted to the construction of an approximate aperiodic nodal model. The applications of the latter and the accuracy of its parameters are discussed.     

Sb3+对Tb3+激活硅酸盐玻璃发光性能的影响

利用高温熔融法分别制备了Sb3 ,Tb3 单掺和共掺的硅酸盐发光玻璃,并分析了它们的光谱性质。根据对Sb3 和Tb3 掺杂硅酸盐玻璃的激发光谱、发射光谱和发光衰减时间等特性的分析,研究了澄清剂Sb2O3的加入对Tb3 激活硅酸盐玻璃发光性能的影响。结果表明,在紫外光激发下,Tb3 激活硅酸盐玻璃中存在Sb3 离子至Tb3 离子的能量传递,但能量传递效率较低,能量传递表现为Sb3 离子的3P1能级与Tb3 离子的5D3能级之间的能量无辐射共振转移。同时Sb3 离子的加入将在Sb3 离子和Tb3 离子的激发重叠区域(200～350nm)对Tb3 离子的激发产生不小的负面影响,尚不足以通过Sb3 离子至Tb3 离子的能量传递得以弥补。因此在使用Sb2O3作为Tb3 激活硅酸盐发光玻璃的澄清剂时,应当注意权衡Sb3 离子对Tb3 离子发光性能的影响。     

Approximate chemical analysis of volcanic glasses using Raman spectroscopy

The effect of chemical composition on the Raman spectra of a series of natural calcalkaline silicate glasses has been quantified by performing electron microprobe analyses and obtaining Raman spectra on glassy filaments (~450 µm) derived from a magma mingling experiment. The results provide a robust compositionally‐dependent database for the Raman spectra of natural silicate glasses along the calcalkaline series. An empirical model based on both the acquired Raman spectra and an ideal mixing equation between calcalkaline basaltic and rhyolitic end‐members is constructed enabling the estimation of the chemical composition and degree of polymerization of silicate glasses using Raman spectra. The model is relatively insensitive to acquisition conditions and has been validated using the MPI‐DING geochemical standard glasses 1 as well as further samples. The methods and model developed here offer several advantages compared with other analytical and spectroscopic methods such as infrared spectroscopy, X‐ray fluorescence spectroscopy, electron and ion microprobe analyses, inasmuch as Raman spectroscopy can be performed with a high spatial resolution (1 µm²) without the need for any sample preparation as a nondestructive technique. This study represents an advance in efforts to provide the first database of Raman spectra for natural silicate glasses and yields a new approach for the treatment of Raman spectra, which allows us to extract approximate information about the chemical composition of natural silicate glasses using Raman spectroscopy. We anticipate its application in handheld in situ terrestrial field studies of silicate glasses under extreme conditions (e.g. extraterrestrial and submarine environments). © 2015 The Authors Journal of Raman Spectroscopy Published by John Wiley & Sons Ltd     

Density and structural changes of silicate glasses under high pressure

ABSTRACT

Density and structural changes of matter in their liquid or amorphous form, such as silicates melts, molecular fluids, or glasses, are of extreme importance to model the interior of planetary bodies. However, measuring the evolution of amorphous materials under extreme conditions of pressure and temperature remains challenging mainly because of the sample dimensions and the weak interaction with X-ray probes. This contribution highlights recent developments to measure the density of amorphous material, mainly silicate glasses made of light elements, to high pressure conditions. In particular, the X-ray absorption method at synchrotron sources is discussed as a new opportunity for high pressure experiments on glasses, fluids, and melts. Recent achievements using X-ray Raman scattering spectroscopy to obtain data on the local electronic environment of the main constituents of silicate glasses at high pressure are also presented. Finally, perspectives of these recent developments are discussed as well as their potential for high pressure research in the next years.     

Nuclear and electronic contributions to the third-order nonlinearity in different glasses

Using, a time resolved optical heterodyne Kerr effect experiment along with a Raman light diffusion experiment, we have measured the nuclear (non-instantaneous) and electronic (instantaneous) contributions to the nonlinear index of refraction in tellurite niobium-doped and silicate lead-doped glasses. The experimental set-up and the procedure used to measure the nuclear and electronic contribution are detailed. Our experimental results clearly indicate that the ratio between the instantaneous and the non-instantaneous contribution remain constant while the doping concentration or the temperature of the sample vary. These ratios are ∼5 and ∼10 in tellurite niobium-doped and silicate lead glasses, respectively.     

Li~+对Tb~(3+)掺杂硅酸盐玻璃闪烁性能的影响

利用高温熔融法制备了Li+掺杂Tb3+激活硅酸盐闪烁玻璃。通过Li+掺杂Tb3+激活硅酸盐玻璃的紫外可见透射光谱、发射光谱和发光衰减时间谱,研究了Li+的加入对Tb3+掺杂硅酸盐玻璃发光性能的影响。结果表明:适量Li+的加入可有效增强Tb3+激活硅酸盐玻璃的发光强度,且相比于不掺杂Li+的Tb3+掺杂硅酸盐玻璃而言,当掺入质量分数为2.0%的Li+时,Tb3+在玻璃中的最佳掺杂质量分数由12.8%提高至15.3%。其原因是Li+掺杂增加了玻璃体系中非桥氧的数量,从而有利于改善Tb3+在玻璃体中的均匀性,降低Tb3+间因非辐射跃迁而引起的能量损失,以及提高Tb3+的最佳掺杂质量分数。但当掺入Li+的质量分数超过2.0%时,会对Tb3+激活硅酸盐玻璃的闪烁光强产生负面影响,这是因为过多的非桥氧阻碍了X射线激发能达到Tb3+离子的能量传递。     

Environmental effects on initiation and propagation of surface defects on silicate glasses: scratch and fracture toughness study

The glass composition and surrounding environment can play an important role in the initiation and propagation of surface defects, which affect the practical strength of glass. We have studied how the environment and glass composition affect the tribological and indentation properties of multicomponent silicate glasses. Soda lime silica and aluminosilicate glasses were studied to compare the effects of the alkali ion and glass network type on surface defect formation. Although both glasses contained leachable sodium ions, the surface wear of soda lime glass decreased with increasing humidity while sodium aluminosilicate glass had an observable increase in surface wear. This indicated that sodium ion and water activity on/in glass surfaces vary depending on the glass network structure. The exchange of Na⁺ with K⁺ in aluminosilicate glass increased the elastic modulus, hardness, and resistance to fracture substantially; however, it did not improve the surface scratch resistance in humid environments. This suggested that the improved fracture toughness for the K-exchanged aluminosilicate glass is mainly due to the improved bulk properties; surface wear can readily take place regardless of Na/K-exchange.     

紫外激光照射引起的硅酸铅玻璃结构的变化

采用紫外-可见吸收光谱和电子自旋共振谱(ESR)对硅酸铅玻璃薄膜和体材料受紫外激光照射前后的结构变化进行了研究。研究发现：266 nm的紫外激光照射硅酸铅玻璃体材料时,能使其Urbach能量增大,即玻璃结构的无序性增大。电子自旋共振谱研究表明,266 nm激光照射不会在硅酸铅玻璃中产生顺磁缺陷中心, 也不会对硅酸铅玻璃薄膜在235 nm附近的吸收峰产生影响,但用248 nm紫外激光照射则观察到了235 nm吸收峰的光漂白现象。     

Bismuth silicate glass containing heavy metal oxide as a promising radiation shielding material

Optical and FTIR spectroscopic measurements and electron paramagnetic resonance (EPR) properties have been utilized to investigate and characterize the given compositions of binary bismuth silicate glasses. In this work, it is aimed to study the possibility of using the prepared bismuth silicate glasses as a good shielding material for γ-rays in which adding bismuth oxide to silicate glasses causes distinguish increase in its density by an order of magnitude ranging from one to two more than mono divalent oxides. The good thermal stability and high density of the bismuth-based silicate glass encourage many studies to be undertaken to understand its radiation shielding efficiency. For this purpose a glass containing 20% bismuth oxide and 80% SiO₂ was prepared using the melting–annealing technique. In addition the effects of adding some alkali heavy metal oxides to this glass, such as PbO, BaO or SrO, were also studied. EPR measurements show that the prepared glasses have good stability when exposed to γ-irradiation. The changes in the FTIR spectra due to the presence of metal oxides were referred to the different housing positions and physical properties of the respective divalent Sr²⁺, Ba²⁺ and Pb²⁺ ions. Calculations of optical band gap energies were presented for some selected glasses from the UV data to support the probability of using these glasses as a gamma radiation shielding material. The results showed stability of both optical and magnetic spectra of the studied glasses toward gamma irradiation, which validates their irradiation shielding behavior and suitability as the radiation shielding candidate materials.     

Rare earth ions doped full-color luminescence glasses for white LED

Silicate and phosphate glasses co-doped with rare-earth ions (REIs)(Ce³⁺, Tb³⁺, Eu³⁺) are presented in the present work. Their photoluminescence properties were studied by excitation and emission spectra. A combination of blue, green and red bands is shown for both silicate and phosphate glasses that allows the observation of white light when the glass is excited by UV light. The relative emission intensity ratios of the green to the red can be tuned by varying the concentrations of activator and/or sensitizer as well as the composition of glass matrices.     

Atomic structure and strength of inorganic glasses

The role of the atomic structure in the fracture processes is considered using borate, silicate, and phosphate glasses as an example. Primary attention is focused on the degree of connectivity of the atomic structure. It is shown that the degree of connectivity is a major factor responsible for the structural strength of glasses under conditions excluding the influence of both accidental surface defects and the environment. The change in the Young’s modulus as a measure of elastic deformation and the change in the hardness as a characteristic of irreversible deformation are analyzed. The ultimate elastic strain experienced by a glass at the instant of fracture is examined. It is found that the ultimate elastic strain is approximately equal to 10% for glasses with a three-dimensional atomic structure and 5% for glasses with a two-dimensional (layered) or chain structure. It is assumed that this behavior of the strength as a function of the degree of connectivity of the atomic structure is associated with the degree of uniformity of the external load distribution over atomic bonds.     

Er3+/Yb3+共掺碲钨酸盐玻璃的热稳定性和1.5μm波段的光谱性质

制备了Er³⁺/Yb³⁺共掺的碲钨酸盐玻璃样品,TeO₂-WO₃-R_mO_n(R_mO_n=PbO,BaO,La₂O₃,Bi₂O₃),研究了样品的热稳定性和1.5μm波段的光谱性质。碲酸盐中引入WO₃的目的是为提高基质的声子能量,使Er³⁺离子⁴I_13/2→⁴I_15/2的多声子弛豫速率增加,从而提高⁴I_13/2能级上的Er³⁺离子数,这对提高1.5μm处的荧光强度有利,另外加入WO₃也能提高碲酸盐玻璃的抗析晶能力。测试了样品的FT-IR光谱,发现碲钨酸盐玻璃样品中存在着TeO₄、TeO₃、WO₄和WO₆结构体。周围环境的不对称性导致Er³⁺在1.5μm处的光谱有非均匀的展宽和大的受激发射截面。Er³⁺在70TeO₂-20WO₃-10Bi₂O₃玻璃中⁴I_13/2→⁴I_15/2能级发射的荧光半峰全宽(FWHM)为77nm,应用McCumber理论计算的受激发射截面(σ^peak)为1.03×10^-20cm²。其FWHM×σ_peak乘积远大于掺Er³⁺的铋酸盐、磷酸盐、碲酸盐和硅酸盐玻璃,说明碲钨酸盐玻璃是一种制备宽带光纤放大器优良基质材料。     

Z-scan study of nonlinear absorption of gold nano-particles prepared by ion implantation in various types of silicate glasses

Metal nano-clusters composite glasses synthesized by ion implantation have been shown as promising nonlinear photonic material. In this paper, we report on the nonlinear absorption measurements of gold nano-particles implanted in four structurally different types of silicate glasses. All targets containing gold nano-particles in a layer 500 nm under the surface of the glass have been prepared by ion implantation with subsequent annealing. The targets were characterized by UV–VIS absorption spectroscopy, transmission electron microscopy (TEM) and by the Z-scan technique. The resulting nano-particles differed in size, range of particle size and shape as well as depth distribution characteristic for glasses with different chemical compositions. With the Z-scan technique, it can be shown that the nano-particles produced in silicate glasses exhibit substantial two-photon absorption (TPA). The TPA coefficient differed depending on size, shape, and depth distribution of the metal nano-clusters and the structure and composition of the glass substrates. The highest TPA coefficient (16.25 cm/GW) was found for the glass BK7 in which the largest non-spherical nano-particles have been observed in the thinnest layer.     

Acoustic studies of gradient glasses

The results of investigation of the propagation of longitudinal ultrasonic waves in glasses with a regular volume distribution of elastic properties resulting in the narrowing of a beam of ultrasonic waves at the output of the sample are presented. Such glasses have not been used in acoustics previously. They were used by us for the creation of the first samples of inhomogeneous acoustic lenses. The results obtained in the investigation of inhomogeneous acoustic lenses based on specially developed inhomogeneous glasses and methods for their production are discussed. It is shown that the noticeable effect of focusing ultrasonic waves in the range 2–14 MHz is observed already for glass samples with dimensions 10–20 mm. Other possible applications of inhomogeneous acoustic lenses, for example, as a medium for ultrasonic delay lines and acousto-optical cells, are discussed.     

The spectroscopic and energy transfer characteristics of the rare earth ions used for silicate glass fibre lasers operating in the shortwave infrared

The continuing growth in the research and development of high power diode‐pumped fibre lasers relates to the exceptional thermal management provided by the extended geometry of the fibre and the small quantum defect associated with the 1 μm emitting Yb³⁺ ion. Lengthening the emission wavelength of diode‐pumped fibre lasers further into the infrared is important for many applications ranging from medicine to defence; however, extending the emission wavelength remains a challenge. This review will examine in detail the spectroscopy and the energy transfer processes that impact Tm³⁺‐doped and Ho³⁺‐doped silicate glasses that are used for fibre lasers in the 1.9 μm to 2.1 μm region of the shortwave infrared spectrum. We will explore a number of important applications that function in the shortwave infrared region that will benefit from using these light sources and I will suggest the reasons for choosing silicate glass over other glasses as the host material for this wavelength range.     

Glasses for erbium-doped fiber amplifiers: A comparison based on the ultimate spectral efficiency of information transmission

A new figure of merit—the ultimate spectral efficiency of information transmission in the regime of unsaturated gain in the case of a quasi-two-level scheme of pumping—is proposed to compare host glasses for erbium-doped fiber amplifiers (EDFAs) that are considered as a constituent of an optical communication system. It is shown that the amplifiers based on silicate glasses possess the best characteristics, whereas the amplifiers based on phosphate and tellurite glasses have somewhat worse and substantially worse characteristics, respectively.     

Leaching of lead silicate glasses in acid environment: compositional and structural changes

Lead silicate glasses (45.3 weight % of lead oxide) were leached in aqueous static solutions of HNO₃ at pH=2 and T=90 °C for different leaching times, to study the weathering mechanism of lead glasses in an acidic environment.The leached surface was analysed by different analytical techniques like RBS (Rutherford backscattering spectrometry), XPS (X-ray photoelectron spectroscopy) and SEM-EDS (scanning electron microscopy-energy dispersive spectrometry). Even the leaching solutions were analysed by ICP-AES (inductively coupled plasma-atomic emission spectroscopy) to measure the amount of lead and other ions that migrate from the glass to the solution.The results obtained show that the leached layer, depleted of lead and alkaline ions, is some hundreds of nanometres thick. It is about ten times thinner than the one obtained on richer glasses (66 weight % of lead oxide), but the kinetics of the leaching process is exactly the same: a stabilisation takes place after two days of leaching and a Pb-enriched surface thin layer (a few nanometres thick) is formed. PACS 61.85; 33.60.F; 79.60.-i; 61.43.F; 61.16.B; 68.35.B     

Diffusion behavior of transition metals in field-assisted ion-exchanged glasses

The use of ion-exchange techniques for doping silicate glasses with transition metals has attracted much attention in the last decades for its potential in several applications, namely, light waveguides technology, luminescent materials, and for the possibility to realize systems in which metal nanocluster formation is controlled by suitable post-exchange techniques. In this framework, the control of metal distribution inside the glass is a central issue for both the understanding of the incorporation process and for the definition of effective preparation protocols. In this experiment, metallic films (Ag, Cu, Au, Co) were deposited onto the substrates by the rf-sputtering technique. Metal ions then penetrate to substitute glass alkali by means of field-assisted ion-exchange, realized at different temperature and electric field values. In particular, we present in this paper the Au doping of silicate glasses, successfully realized for the first time with this method. The gold diffusion profiles, as measured by Secondary Ion Mass Spectrometry (SIMS), indicate that the migration depends on the experimental parameters (temperature and electric field), but also on the local structure, as well as on chemical phenomena occurring at the metal/glass interface.     

Li~+对硅酸盐玻璃中Yb~(3+)、Tm~(3+)上转换效率的影响

利用高温熔融法制备了不同Li~+含量的掺杂Yb~(3+)、Tm~(3+)的硅酸盐玻璃样品,玻璃样品在980 nm半导体激光器的泵浦下能够产生477 nm的蓝光和654 nm的红光。由上转换的荧光强度和泵浦功率的双对数拟合直线得到,添加Li~+能够增加上转换过程中Tm~(3+)向上跃迁的几率,Tm~(3+)的3F2和1G4能级的粒子数布居增加,从而提高辐射跃迁的几率。红外光谱和拉曼光谱表明Li~+的添加对玻璃基质的声子能量影响不大,却使得声子态密度减小,使上转换效率提高,从而提高Yb~(3+)、Tm~(3+)在硅酸盐玻璃中的发光强度。     

Fracture of silicate glasses: ductile or brittle?

Atomic force microscopy is used to investigate the possibility of cavity formation during crack growth in silicate glasses. Matching areas on both fracture surfaces were mapped and then compared. For silica glass, and soda-lime-silicate glass, the fracture surfaces matched to a resolution of better than 0.3 nm normal to the surface and 5 nm parallel to the surface. We could find no evidence for cavity formation in our study and suggest that completely brittle fracture occurs in glass.