Metal Ions In Glass Research Articles

Redox equilibria and stereochemistry of metal ions in glass: a chemical bonding approach

Redox equilibria and stereochemistry of metal ions in glass: a chemical bonding approach

Optical properties of selected 4d and 5d transition metal ion-doped glasses

Charge transfer emission from transition metal ions in glasses and identification of their oxidation states.

Quantitation of Metal Ions in Archaeological Glass by Abrasive Stripping Square‐Wave Voltammetry Using Graphite/Polyester Composite Electrodes

AbstractA method for identifying Co, Cu, Sb, Sn, Fe, Zn, and Zr pigments in glasses using square‐wave voltammetry as the detection mode is described. It is based on the abrasive attachment of glass microsamples to graphite/polyester composite electrodes. Sample amounts less than 1 μg are used allowing for the study of archaeological samples. In all cases well‐defined anodic stripping peaks corresponding to the oxidation of metal deposits generated at potentials ranging from −0.6 to −1.6 V (vs. SCE) are obtained. This response is in agreement with that displayed by the corresponding metal oxides. Quantitative estimates of the relative population of metal ions in glasses are obtained from peak area measurements with an accuracy comparable to that obtained with SEM/EDX.

Study of chromium states in silica glass implanted with Cr+ ions to high fluences

Abstract The implantation of transition metal ions in glasses can lead to the formation of nanometer-sized colloidal particles embedded in a thin surface layer. In the present work, silica glasses implanted with Cr+ at energy E=200 keV, for fluences larger than 1017 ions/cm2 were studied by electron paramagnetic resonance, X-ray photoelectron and X-ray-excited Auger electron spectroscopies, visible optical spectroscopy and scanning transmission electron microscopy (TEM). It is shown that Cr is present in silica glass as isolated Cr3+ ions as well as chromium oxides (antiferromagnetic Cr2O3 and ferromagnetic CrO2) and chromium silicides. TEM indicates the presence of almost spherical colloidal particles about 10 nm in diameter.

Development of a platinum rotating disc electrode for dynamic electrochemical measurements in glass melts

A configuration is described and tested that enables electrochemical measurements at a rotating disc electrode in glass melt environments. In a glass melt with 10 mass% Fe 2O 3 at 1200°C, it was possible to reach a time independent steady-state current, through rotating the electrode. In aqueous solutions, time independent electrode signals show distinct advantages to study the oxidation–reduction behaviour and the properties of polyvalent elements. The influence of rotation rate was studied and the results obtained were compared with those obtained at a static disc electrode. The rotation speed dependence of the steady-state current obtained in a molten glass environment at 1200°C was shown to obey the Levich-equation. An expected advantage of time independent signals is the concentration determination of metal ions in glass melts continuously and online. This opens new perspectives concerning the online monitoring and automatic control of the glass production processes. Furthermore, the validity of the Levich-equation opens new possibilities for diffusion coefficient measurement of metal ions in glass melts.

Effect of basicity on chemical bonding of metal ions in glass and its relevance to their stability

An investigation is made concerning the negatively charged environment, which the oxygen atoms of a glass provide for hosted metal ions, and the extent to which this changes on varying the glass composition. For Mn2+, d–d spectra show that the changes in the (average) oxygen electronic density of the glass are faithfully transmitted to the metal ion, and previous results for Pb2+ and Tl+ suggest that this probably operates generally for uni- and dipositive ions. This principle also appears to operate for Fe3+ in glasses where it is sixfold coordinated. However, in silicate glasses, where the coordination is fourfold, the sites occupied by Fe3+ are, surprisingly, of much lower electron density than the average for the oxygen atoms of the glass. The relevance of this study to the stabilisation of oxidation states for redox reactions, such as the Fe2+/Fe3+ equilibrium, is discussed in terms of the extent of electron donation in the Fe3+–O bonding and the charges residing on the Fe3+ species.

Charges on metal ions in glass

Since metal ions bear a charge equal to their spectroscopic oxidation state only in the gas phase, it is necessary to consider how the positive charge is reduced for the chemically combined ion and also to devise criteria for assigning this charge. Here it is shown how interelectronic repulsion energies, obtained from optical spectroscopy, can be exploited, and the method is exemplified for the Tl + ion to show how its effective charge decreases with increasing basicity of the glass. Trends are reported for the alkali metal ions, especially in borate glasses where two types of site have been shown to exist. Consideration is also given to the degree of negative charge, provided by the oxygen atoms of the glass, at sites for the metal ions.

Spectroscopy of transition metal ions in inorganic glasses

Transition metal (TM) ions have been used as colouring agents in the glass industry for a long time. Recently, great attention has been paid to the TM ion doped glasses for the development of new lasers or luminescence materials. The absorption spectra of TM ions in different kinds of glasses have been studied extensively, but little work has been done for fluorescence and relaxation spectra. In this paper emphasis is laid on analysing the influence of chemical bond characteristics of the base glass on the spectra and the site structure of transition metal ions in glasses. Recent experimental results about the luminescence characteristics of low valence ions (such as Ti 3+, Cr 3+, V 2+, Mn 2+, Cu +, Mo 3+) in glasses are also reported.

Electron spin resonance of transition metal ions in glasses

Electron spin resonance (ESR) studies of transition metal ions in glasses have been briefly reviewed. The known relations of spin Hamiltonian parameters to structural geometries around the transition metal ion probes in glasses are summarized. RecentESR studies in glasses based on the use of Ti3+, VO2+, Mo5+, Cr3+, Fe3+, Mn2+ and Cu2+ have been emphasized. Merits ofESR in the context of structural elucidation have also been discussed.

Effect of thermal stabilization on the optical absorption of some transition metal ions in glass

The optical absorption of a 30Na2O, 70SiO2 glass containing iron, chromium or cerium has been studied after thermal stabilization at various temperatures around the transformation range of the glass. The optical absorptions due to iron(II), iron(III), cerium(III) and cerium(IV) have been found to increase with increasing stabilization temperature; the optical absorptions due to chromium(III) and chromium(VI) do not change significantly with stabilization temperature. The changes in optical absorption due to stabilization at different temperatures have been found to be reversible and reproducible. It has been argued that as the equilibrium volume of a given mass of glass increases with increasing stabilization temperature, and as the ligand field strength surrounding the transition metal ion does not increase due to this enlargement of volume while the optical absorption increases, the high temperature stabilization of a glass probably increases some local randomness of structure (creating extra distortion of the transition metal complex) and does not cause an uniform volume expansion of the glass.

Absorption Spectra of First‐Row Transition Metal Ions in Glasses

Certain optical transitions were calculated for the first‐row transition metal ions Ti3+, V3+, Cr3+, Fe2+ Co2+, and Ni2+ in a silicate matrix. The calculations were performed at 7 inter‐ionic distances for each ion because the metal‐ion‐to‐oxygen interionic distances are unknown; the silicate oxygen charge was varied from 1.00 to 2.00 in each case because the true charge on silicate oxygens is also unknown. Integrals used in the calculations were calculated using Slater and self‐consistent field wave functions, and computer programs were used to evaluate all integrals. Equations were derived for calculating all optical transitions for these ions in octahedral fields; the extension to fields of other symmetry is trivial. Several optical transitions were computed to obtain the calculated orders of magnitude for the optical transition. The results for self‐consistent field wave functions are lower than expected; they indicate that the transition metal ion in glasses is situated in fields near the size of aquo complexes.

Acid-Base Concepts in Relation to the Structure of Borate and Silicate Glasses

The conventional acid-base concepts in glass are discussed and a new hypothesis to define basicity of a borate or a silicate glass has been proposed. The role of non-bridging oxygen in glass is compared with that of hydroxyl ion in aqueous solutions. Chromium (VI), Vanadium (V), Uranium (VI), Cobalt (II), and Nickel (II) are found to exist in glass in acidic and basic forms with very different optical absorption; these ions can successfully be used as “colour indicators” to study the acid-base character of a glass. The influence of acid-base property on oxidation-reduction equilibrium of transition metal ions in glass is discussed.