Transition Metal Ions In Glasses Research Articles

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.

ChemInform Abstract: Electron Paramagnetic Resonance of Transition Metal Ions in Glasses: Recent Progresses

AbstractReview: 96 refs.

Effect of mixed transition-metal ions in glasses. Part III: The P 2O 5–V 2O 5–MnO system

Electrical and optical properties of phosphate glasses containing vanadium and manganese ions in the xP 2O 5–[(100 − x)(V 2O 5 + MnO)] (PVM) system have been investigated. This is the last article of a III-part series devoted to the electronic properties of phosphate glasses containing a mixture of transition ions. The first article was devoted to the electrical conductivity of glasses having the general composition: xP 2O 5–[(100 − x)(V 2O 5 + Fe 2O 3)] (PVF). Competitive transport of small polarons on V and Fe ion sites was found to contribute to a mixed transition-ion effect (MTE) in PVF glasses. Several features of MTE were found to be similar to the well known mixed alkali effect, observed in glasses containing two alkali ions. In the second article, optical absorption and electronic conduction of xP 2O 5–[(100 − x)(Fe 2O 3 + MnO)] (PFM) glasses were reported. In the absence of competitive transport between the two transition ions (since Mn ions were determined not to contribute to dc conduction), MTE was not observed. The most important feature of PFM glasses was a sharp increase in resistivity at a critical concentration of iron ions, similar to ‘metal–insulator transition’ (MIT). In the present article, we report a resistivity transition in PVM glasses which is similar to that exhibited by the glasses of the PFM series. While Fe ions contributed the carriers in the PFM glasses, V ions serve the same purpose in the PVM compositions. As the concentration of vanadium ions, n V, is decreased in the composition range 0.82 > n V > 0.40, resistivity ( ρ) increases marginally. For glasses with 0.2 < n V < 0.40, resistivity and the activation energy for dc conduction ( W) increase sharply with decreasing n V, marking the incidence of an MIT-type transition. As in the PFM glasses, the observation of MIT coincides with the transformation of small polarons to small bipolarons, which is confirmed by the shifting of the small polaron optical absorption band to higher energies with decreasing V concentration.

Effect of mixed transition-metal ions in glasses. I. The P 2O 5–V 2O 5–Fe 2O 3 system

Non-linear variation of certain physical properties with composition, similar to the mixed alkali effect (MAE), has been observed in phosphate glasses containing iron and vanadium ions in the xV 2O 5 · (50 − x)Fe 2O 3 · 50P 2O 5 series. With the total concentration of transition ions (TIs) constant, gradual substitution of one TI (e.g. Fe in the binary composition Fe 2O 3–P 2O 5) by the other (viz., V) increases dc resistivity ( ρ), activation energy for dc conduction ( W) and glass transition temperature ( T g) until these properties reach their maxima. Beyond the maxima, ρ, W and T g are observed to decrease with increasing TI-ratio, V/(V + Fe), until the binary P 2O 5–V 2O 5 composition is reached. The non-linear variation of the physical properties with TI-ratio has been termed the ‘mixed transition-ion effect’ or MTE. The similarities between MTE and MAE are remarkable because the former is electronic in nature while the latter has its origin in ionic motion. In the absence of a comprehensive theory, tentative arguments suggestive of the origin of MTE have been presented.

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.

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.

Ortho-para-positronium quenching by transition-metal ions in glass

Positron lifetimes have been studied in CaO.P2O5 glasses doped with various transition-metal ions (Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Ce). Present measurements show that all the transition-metal ions, except cerium, decrease I2 while the change in tau 2 is within experimental error. This is suggested to be due to 'spin-conversion' by which part of the o-Ps, by reacting with the transition-metal ion impurities in glass, are converted into p-Ps; the extent of conversion depends on the nature and the concentration of the impurity ions. Of all the transition-metal ions studied, vanadium(IV) is most effective and cerium(III) and cerium(IV) are least effective in quenching o-Ps; these have been explained as due to the unique nature of the vanadyl (VO2+) group and the shielded 4d electron of cerium respectively.

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.