Ion transport and structure in silver borate glasses

A study of ionic conductivity in silver borate glasses is presented, which includes (i) a full characterization of the ion transport properties in the AgI:Ag₂O:B₂O₃ glasses, (ii) results for glasses where iodine is totally or partially substituted by another halide, (iii) mixed-cation effects. A substantial portion of the paper discusses the relationship between local order and ion transport properties of borate glasses and vitreous electrolyte systems.     

Nonlinear ion transport in liquid and solid electrolytes

This paper describes nonlinear ion transport properties of liquid and solid electrolytes. Typically, the relation between ionic current density and electric field becomes nonlinear at electric fields above 50–100?kV/cm. We review the 1st and 2nd Wien effect found in classical strong and weak electrolyte solutions as well as the strong nonlinear ion transport effects observed for inorganic glasses and for polymer electrolytes. Furthermore, we give an overview over models describing nonlinear ion transport in electrolyte solutions, in glasses and in polymers. Recent results are presented for the nonlinear ionic conductivity of supercooled ionic liquids. We show that supercooled ionic liquids exhibit anomalous Wien effects, which are clearly distinct from the classical Wien effects. We also discuss the frequency dependence of higher-order conductivity and permittivity spectra of these liquids.     

硫系玻璃的N^＋离子注入及表面改性研究

首次对Ａｓ－Ｇｅ－Ｓｅ三元系统和Ａｓ－Ｇｅ－Ｓｅ－Ｔｅ四元系统的硫系玻璃试样进行了Ｎ＋离子注入试验。结果表明，玻璃试样的显微硬度随Ｎ＋离子注入剂量的增加而提高，并且在注入剂量达到２．５×１０１６附近的数值时为最大。ＸＰＳ谱结果显示，在Ａｒ＋离子轰击６分钟后的试样表面出现Ｎ１ｓ的结合能峰，此外各元素的结合能峰也在Ｎ＋离子注入后发生了位移，并随Ａｒ＋离子轰击时间向高能方向移动。     

Ultrasonic attenuation studies of solid electrolytes

Experimental and theoretical aspects of the measurement of ultrasonic attenuation in ionic conductors are reviewed. The conditions under which relaxation peaks associated with ion transport may be observed in ionically conducting solids are assessed and procedures given for extracting characteristic hopping frequencies. A review of literature data on various beta aluminas and Ag ion conducting glasses is given.     

The ionic conductivity variation in rapidly quenched lithium-containing glasses

The lithium ion conductivity of a wide variety of rapidly quenched glasses is studied both as a function of lithium ion content and with various additives which are likely to affect the microstructure of the glass. In each of the glass systems studied a maximum ionic conductivity of ≈10^?3 (ohms cm)^?1 is observed at 500 K, but this value is reached for different Li ion concentrations in different systems. Experiments with additions to the glass composition suggest that the availability of vacant interstitial sites in glasses of this type is not a limitation to fast ion conduction.     

Self-organization and the physics of glassy networks

Network glasses are the physical prototype for many self-organized systems, ranging from proteins to computer science. Conventional theories of gases, liquids and crystals do not account for the strongly material-selective character of the glass-forming tendency, the phase diagrams of glasses or their optimizable properties. A new topological theory, only 25 years old, has succeeded where conventional theories have failed. It shows that (probably all slowly quenched) glasses, including network glasses, are the result of the combined effects of a few simple mechanisms. These glass-forming mechanisms are topological in nature and have already been identified for several important glasses, including chalcogenide alloys, silicates (window glass and computer chips) and proteins.     

Vitrification and transport properties in AgBr-doped chalcogenide systems

Vitrification and transport properties measurements for (AgBr)_x(As₂Se₃)_1−x glasses have been carried out in order to investigate the ion conduction phenomena of these systems. Glass samples were successfully obtained in a composition range of 0 ≤ x ≤ 0.65. The addition of AgBr leads these systems to an exponential increase of electrical conductivity. The ionic component of the electrical conductivity is dominant in highly AgBr-doped glasses. The vitrification brings the fast ion conduction to the present glass systems.     

Multi-ion and pH sensitivity of AgGeSe ion selective electrodes

Many chalcogenide glasses have been found to combine benefits such as good chemical durability, selectivity, and reproducibility for applications as solid-state sensitive membranes of ion selective electrodes (ISEs). In previous works, we have shown that ISEs with ionic conductive AgGeSe membranes have good sensitivity to Ag⁺ ions. In the present work, we explore the Ag_x(Ge_0.25Se_0.75)_100−x, 10≤x≤30 (at%) system as candidate for ISEs applications detecting several other ions (K⁺, Mg²⁺, Cr³⁺, Fe³⁺, Ni²⁺, Cd²⁺, Hg²⁺, and Pb²⁺). We evaluated ISEs fabricated with bulk as well as with thin film membranes. We found no dependence of the sensing properties on the Ag content of the ionic conductive membranes. Thin films exhibited the same properties than bulk membranes, indicating that these chalcogenide glasses have great potential for miniaturization. The ISEs showed a high response (Nernstian or super-Nernstian) to the presence of Hg²⁺, Pb²⁺, and Fe³⁺, a low response (sub-Nernstian) to the presence of Cr³⁺, and a total lack of response to the presence of Cd²⁺, Ni²⁺, Mg²⁺, and K⁺. We also tested how the pH of the solution affected the response of the ISEs. The potentials of the ISEs were practically constant in neutral or acidic solutions, while decreased drastically in basic solutions when the primary ion was not present. The latter phenomenon was caused by the slow dissolution of the membrane into the solution, meaning that long-term basic environments should be avoided for these ISEs. We concluded that ISEs with ionic conductive AgGeSe membranes are good candidates to integrate multi-electrode systems.     

The role of disorder in superionic conductors

This paper illustrates from a phenomenological point of view why the study of superionic conductors is essentially a study of disorders. Crystals that are good ionic conductors lack a long-range order in their mobile-ion sublattice. Moreover, low-temperature anomalies typical of amorphous materials appear to be rather common in superionic crystals. In several solid electrolytes the coupling between “disorder modes” typical of glasses and translational degrees of freedom of the ions can be shown to enhance ionic diffusion. The observed, or expected, properties of these superionic conductors are briefly discussed. The hypothesis that disorder may often play a dynamic role in ion transport in solids suggests ways to synthesize materials of technological interest.     

Recent advancement in metal containing multicomponent chalcogenide glasses

Amorphous semiconductors or chalcogenide glasses are the key materials in modern optoelectronics to make comfortable life of our society. Understanding of physical properties (like microstructure, thermal, optical, electrical) of these materials is important for their different uses. Predominant study of physical properties of the metal containing multicomponent chalcogenide glasses have attracted much attention, due to their interesting variable features and wide range of structural network modifications. Structural modifications in these materials are usually described with respect to the values of structural units (or average coordination number). In significance to this, the present work demonstrates the chronological development in the field of chalcogenide glasses along with scanning electron microscopy (SEM) morphologies. Optical, electrical and thermal correlative properties of recent developed Se_93?xZn₂Te₅In_x (0 ?? x ?? 10) metallic multicomponent chalcogenide glasses are discussed. Variation in SEM morphology, refractive index (n), extinction coefficient (K), optical energy band gap (E_g), electrical conductivity (??_av), crystallization activation energy (E_c) and glass forming ability (GFA) with structural units of Se-Zn-Te-In glasses have been demonstrated in this study. Subjected materials thermal, optical and electrical parameters have been achieved higher and lower in a respective manner at the threshold structural unit value ??r??.     

Applications of Spectroscopy in the Study of Glassy Solids Part I. Introduction, γ-Ray Spectroscopy (Mössbauer Effect), X-Ray Absorption Fine Structure,UV Absorption,and Visible Spectra

Abstract

Interest in glasses and the amorphous solid state in general, having for a long time been limited t o the separate camps of silicate glass technology and polymer science, has in the last few years become very general. This growth and diversification in scientific interest originates jointly in the discovery and utilization of glasses of quite new types e.g., the chalcogenide glasses, and the recognition by chemists and physicists alike that the glassy state is of very general occurrence in nature, with examples now being known from every class of chemical substance, whether metallic, vander Waals, covalent, or ionic in the interparticle bond character.     

Experimental study of the structure of chalcogenide glassy semiconductors in three-component systems of Ge-As-Se and As-Sb-Se by means of NQR and EPR spectroscopy

The structure of chalcogenide glassy semiconductors in three-component systems of Ge-As-Se and As-Sb-Se has been studied by means of both NQR (nuclear quadrupole resonance) and EPR (electron paramagnetic resonance) spectroscopy. It is investigated that in the glasses of both systems the value of the electric field gradient at the resonating nuclei grows with increasing concentration of the clusters As₂Se₃ and Sb₂Se₃, thereby increasing the NQR resonance frequencies. It appears that for the Ge-As-Se system the structural transition from a two-dimensional to three-dimensional structure occurs at average coordination number $\bar r$ = 2.45. The EPR spectral parameters of glasses depend on the composition, the average coordination number and the temperature, and these are discussed. The effect of ”ageing” for CGS (chalcogenide glassy semiconductors) of As-Sb-Se system due to partial crystallization of the sample is observed from the EPR spectra.     

On the super-linear frequency dependent conductivity of amorphous semiconductors

A super-linear frequency dependent conductivity has been observed experimentally in several amorphous semiconductors. An explanation for this behaviour is proposed, in particular for the case of chalcogenide glasses, where it is shown to be a consequence of a particular spatial probability distribution for charged centres. The fundamental mechanism for a.c. conduction in chalcogenide glasses is the same as that proposed previously; namely, the simultaneous hopping of two electrons over the barrier separating two oppositely charged centres, the barrier height being correlated with the intersite separation via the Coulomb interaction. It is demonstrated that this phenomenon should be most marked in those glasses having a large band-gap.     

Variable angle spectroscopic ellipsometry and its applications in determining optical constants of chalcogenide glasses in infrared

The principle of variable angle spectroscopic ellipsometry(VASE) and the data analysis models, as well as the applications of VASE in the characterization of chalcogenide bulk glasses and thin films are reviewed. By going through the literature and summarizing the application scopes of various analysis models, it is found that a combination of various models, rather than any single data analysis model, is ideal to characterize the optical constants of the chalcogenide bulk glasses and thin films over a wider wavelength range. While the reliable optical data in the mid-and far-infrared region are limited, the VASE is flexible and reliable to solve the issues, making it promising to characterize the optical properties of chalcogenide glasses.     

Compositional Trends of Radiation-Induced Effects in Ternary Systems of Chalcogenide Glasses

The effect of γ-irradiation on the optical transmittance spectra of pseudobinary stoichiometric and non-stoichiometric cuts of ternary systems of chalcogenide glasses was studied. The application of chemical-bond approach is proposed to explain the features of compositional dependencies of radiation-induced effects in these materials. It is shown that free volume concept must be taken into consideration at the presence of different radiation-sensitive structural units. The creation processes of coordination defects connected with the formation of free volume and coupled with the capability of the constituent atoms to passivation are the main factors determining the magnitude of the radiation-induced effects in chalcogenide glasses.     

Photoinduced stable second-harmonic generation in chalcogenide glasses

We report on photoinduced second-harmonic generation (SHG) in chalcogenide glasses. Fundamental and second-harmonic waves from a nanosecond pulsed Nd:YAG laser were used to induce second-order nonlinearity in chalcogenide glasses. The magnitude of SHG in 20G?20A?60S glass was 10(4) larger than that of tellurite glass with a composition of 15Nb(2)O (5) 85TeO(2) (mol.%). Moreover, no apparent decay of photoinduced SHG in 20G?20A?60S glass was observed after optical poling at room temperature. We suggest that the large and stable value of chi((2)) is due to the induced defect structures and large chi((3)) of the chalcogenide glasses.     

Using pressure,temperature and frequency as variables to study the dynamics of mobile ions in materials with disordered structures

Complementary ways for studying the motion of mobile ions in materials with disordered structures are obtained by varying pressure, tempe- rature and frequency. New results are presented based on a combination of experimental work and modelling. Pressure-dependent measurements on alkali borate glasses show there is a remarkable difference between the activation volumes for conduction and diffusion, with ΔV_σ< ΔV_D, implying that the Haven ratio decreases with increasing pressure. We propose a mechanism that is characterised by a directionally positive correlation between successive hops of different ions into a moving vacant site. The effect of increasing pressure is to increase the degree of directional correlation and thus to make the conduction pathways increasingly linear in aspect. In sodium borate glasses with much lower sodium content, a maximum has been observed when ionic conductivity is plotted versus temperature at fixed frequency. This feature is identified as being of the nearly constant loss (NCL) type, caused by localised flip-flop movements of interacting charges in the B₂O₃ network. In crystalline γ-RbAg₄I₅, a related localised effect has also been found, in this case caused by activated hops of silver ions confined within structural “pockets”. Finally, the frequency dependence of the ionic conductivity is reviewed in fragile ionic melts. Fragility is interpreted here as a consequence of the shape of the local ionic potentials, which unlike in glass do not reflect the pre-existence of empty cation sites for successive ions to hop into. This difference in short-range, short-time behaviour leads directly to the emergence of non-Arrhenius dc conductivity and fluidity behaviours in molten salts. We are thus able to establish a common phenomenological and theoretical approach to ion transport in a wide range of systems, largely based on broadband conductivity spectroscopy.     

Chalcogenide glasses as a medium for controlling ultrashort IR pulses: Part I

Chalcogenide glasses are ideal materials for developing fiber lasers and amplifiers, remote sensors, high-speed switches, and other devices that operate in the IR range of 1–10 μm. The nonlinear refractive index of chalcogenide glasses may exceed that of quartz glass by a factor of 100–1200 or even more. The data on the dispersion properties of some chalcogenide glass compositions in the IR range are presented. The possibility of forming waveguide structures with specified dispersion properties (in particular with a fixed wavelength at which the group velocity dispersion is zero) from these glasses is numerically investigated. It is shown by the example of completely glassy periodic waveguide structures with planar geometry that the use of photonic band gap modes makes it possible the change the position of zero dispersion in a wide wavelength range. In the calculations the contrast of waveguide structures was varied using parameters of glasses of different composition.     

Practical uses of femtosecond laser micro-materials processing

We describe several approaches to basic femtosecond machining and materials processing that should lead to practical applications. Included are results on high-throughput deep hole drilling in glasses in ambient air, and precision high-speed micron-scale surface modification of composite materials and chalcogenide glasses. Ablation of soda-lime silicate glass and PbO lead-silicate is studied under three different sets of exposure conditions, for which both the wavelength and pulse duration are varied. Ablation rates are measured below and above the air ionization threshold. The differences observed are explained in terms of self-channeling in the ablated hole. Fabrication of practical devices such as waveguides and gratings is demonstrated in chalcogenide glass. Received: 11 December 2002 / Accepted: 20 January 2003 / Published online: 28 May 2003 RID="*" ID="*"Corresponding author. Fax: +1-407/8233-570, E-mail: mrichard@mail.ucf.edu