V. Simon

EPR AND MAGNETIC SUSCEPTIBILITY STUDIES OF B2O3–SrO–Fe2O3 GLASSES

Structural and magnetic properties of B2O3–SrO– Fe2O3 glasses were explored by a controlled doping of 2B2O3·SrO vitreous matrix with iron oxide. The information concerning the structural units involving iron ions, their valence states and the types of interactions between them, was obtained using electron paramagnetic resonance (EPR) spectroscopy and magnetic susceptibility measurements.

Electron paramagnetic resonance study of Fe2O3Bi2O3GeO2 glasses

Abstract Homogeneous glasses of the system x Fe 2 O 3· (100 − x )[Bi 2 O 3· GeO 2 ] were obtained within 0 x ⩽ 20 mol%. EPR absorption spectra due to Fe 3+ (3d 5 ) ions show the g ≈ 4.3 line as the main feature. The site symmetry of Fe 3+ paramagnetic ions is predominantly rhombic. Mixed valence states of iron ions in samples with x > 5 mol% Fe 2 O 3 were detected.

Structural and magnetic properties of CuOTeO2B2O3SrO glasses

Glasses of the system 70TeO 2 .25B 2 O 3 . 5SrO doped with CuO up to 20 mol% were investigated. Mixed valence states (Cu 2 + and Cu + ) of copper ions were revealed. Depending on CuO concentration, Cu 2 + are distributed as isolated ions in axially distorted octahedral symmetric sites, or associated in clusters. The magnetic behaviour of the studied glasses was interpreted in terms of dipole-dipole interactions.

Magnetic properties of xCr2O3 · (1 − x)[Bi2O3 · PbO] glasses

Abstract EPR and magnetic susceptibility measurements have been performed on x Cr 2 O 3 · (1 − x )[Bi 2 O 3 · PbO] glasses with 0 x ≤ 30 mol%. These data show that the chromium ions are in the Cr 3+ valence state. For x ≤ 5 mol% most of these ions are isolated or experience dipole-dipole interactions, but for higher Cr 2 O 3 concentrations the dominant part of them are magnetically coupled by negative superexchange interactions.

SPECTROSCOPIC PROPERTIES OF B2O3–PbO–Nd2O3 GLASSES

Samples belonging to xNd2O3(100-x) [2B2O3·PbO] glass system, with 0≤ x≤ 40 mol%, are investigated by IR and UV–VIS spectroscopies in order to obtain evidence for the influence of Nd2O3 on the local order from 2B2O3·PbO glass matrix. Besides the IR absorption bands characteristic to lead and boron arrangements, typical absorption lines of Nd3+ ions around 4000 cm-1 and 6000 cm-1 are recorded. The 6000 cm-1 band appears only for the samples with x≥25 mol% Nd2O3. The split of some UV–VIS absorption bands arising from transitions of neodymium ions in doublet lines as well as the shift of the absorption bands as the Nd2O3 content increases denote the influence of the lead–borate matrix on the radiative transitions of the lanthanide ion.

EPR study of phosphate glasses containing two types of transitional metal ions

Abstract The following glass systems x(CuO·V2O5)(100 − x)[2P2O5 · PbO] and x·(MnO·V2O5)(100 − x)[2P2O5 · Na2O] with 0 ⩽ x ⩽ 40 mol% were prepared and investigated by EPR spectroscopy. The obtained data suggest an octahedral-tetrahedral (Td) distorted local symmetry for Cu2+ and Mn2+ ions, and a square—pyramidal (C4v) coordination for V4+ ions. The mixed exchange pairs (Cu2+−V4+, Mn4+) appear at high transition metal oxides content (x > 10 mol%).

THE INFLUENCE OF MELTING TEMPERATURE ON IRON ION DISTRIBUTION IN Bi2O3·PbO·As2O3 GLASS MATRIX STUDIED BY EPR

Glasses of the system xFe2O3·(1-x)[Bi2O3·PbO·As2O3] in the composition range 0.5≤x≤30 mol% were investigated when prepared at 1000°C and 1250°C, respectively. The study was performed by means of EPR of Fe3+ ions. The effects of melting temperature on the valence state and structural distribution of iron ions were shown.

STRUCTURAL EFFECT OF THORIUM ON THE LOCAL ORDER IN A PHOSPHATE GLASS MATRIX

The influence of ThO2 addition on the local order of 2P2O5 · Na2O glass matrix was investigated by IR and EPR spectroscopic analyses of non-irradiated and gamma-irradiated xThO2(100-x)[2P2O5 · Na2O] glass samples (0 ≤ x < 20 mol%). After the applied gamma irradiation treatments, the IR spectra are not significantly modified. The as-prepared samples and also the unirradiated samples examined after two years do not give rise to any EPR signal at the room temperature. The applied gamma irradiation treatments induce paramagnetic defects. The EPR spectra consist of doublets attributed to an electron trapped at a nonbridging oxygen vacancy.