E. Culea

The network modifier and former role of the bismuth ions in the bismuth-lead-germanate glasses.

The present work is focused on the enhancement of network former environment in lead-germanate glasses by bismuth ions doping. A series of bismuth-lead-germanate glasses with the xBi2O3·(100-x)[7GeO2·3PbO] composition glass where 0≤x≤30 mol% Bi2O3 were synthesized by melt-quenching method. The FTIR, UV-VIS spectroscopy and cyclic voltammetry were conducted on these samples to evaluate the doping effect of structure of the host matrix network. Our results indicate that direct incorporation of Bi2O3 into the lead-germanate network modifies the lead-germanate network and the internal structure of glass network is rearranged. The structural flexibility of the lead-germanate network is possible due to its incapacity to accommodate with the excess of oxygen atoms and the creation of bridging oxygen ions. Optical gap energy and refractive index were obtained as a function of Bi2O3 content. Gap energy values decrease as Bi2O3 content increased from 0 to 10 mol%. Further increase of Bi2O3 concentration beyond 10 mol% increased the gap energy values. These behaviors of the glass system can be explained by two mechanisms: (i) for x≤10 mol% Bi2O3--increase of degree of disorder of the host matrix because Bi2O3 is network modifier and (ii) for x>10 mol%--Bi2O3 acts as a network former. Cyclic voltammetry measurements using the glass system with 10Bi2O3·90[7GeO2·3PbO] composition as working electrode show the mobility of the lead ions, in agreement with UV-VIS data.

FTIR spectroscopic study of some lead germanate glasses

The structures of two lead germante glasses – yGeO2(100-y)PbO and xNd2O3(100-x)[GeO2PbO] – are investigated by the Fourier transform infrared (FTIR) spectroscopy. The structural role of germanium, lead and neodymium ions is discussed. The presence of GeO4, GeO6 and PbO4 structural units was evidenced in the studied glass networks. In the case of the xNd2O3(100-x)[GeO2PbO] glasses it was shown that the ratio of the mentioned structural units depends on the Nd2O3 content of the samples. Therefore Nd2O3 play the network modifier role in studied glasses.

Structural, Spectroscopic, and Magnetic Characterization of Cobalt(III) Oxide–Disodium Tetraborate Glasses

ABSTRACT Co2O3–Na2B4O7 glasses were prepared by melt-quenching and characterized by X-ray diffraction, density measurements, infrared spectroscopy, diffuse reflectance ultraviolet–visible spectroscopy, and magnetic measurements. Results show that addition and successive increase of cobalt oxide determines important properties of the glasses. An increase in cobalt oxide concentration converted BO4 structural units into BO3 units and led to intensification of magnetic interactions between cobalt ions. The presence of cobalt(III) in glasses was confirmed by optical spectroscopy and magnetic data.

The local structure of gadolinium-borate-tellurate vitroceramics investigated by FTIR and EPR spectroscopy

The present study provides interesting information concerning devitrification behavior of xGd2O3(100-x)[6TeO24B2O3] vitreous system with 0 ≤ x ≤ 30 mol%. The structural changes have been analyzed with increasing rare earth concentration. Two halos characteristic of the amorphous compounds can be observed in XRD diffraction pattern for sample with x ≥ 20 mol% Gd2O3. These changes can be explained only if we admit that the adding of gadolinium oxide now participate in the network as [GdOn] structural units yielding a change from the continuous borate-tellurate network to the continuous gadolinium-borate-tellurate network with interconnected through Gd-O-B and Gd-O-Te bridges. The EPR spectra of the studied glass ceramics reveal an increase of the content of Gd+3 ions in network former and modifier positions. Therefore, Gd+3 ions will coordinate more with non-bridging oxygens leading the decreased of the number of individual Gd+3 ions.

Raman Spectroscopic Characterization of Rare Earth Ions Doped Bismuth-Based Glasses

The xReO(1−x)[3Bi2O3⋅PbO] glass systems with diferent rare earth ions (ReO = CeO2, Tb4O7) have been prepared and examined with the aim of determining their structural characteristics. Raman sprectroscopy and density measurements were used to characterize the samples. Raman spectroscopy data permitted to identify some of the structural units that built up the lead bismuthate vitreous network. Density data were used to calculate the Poisson’s ratio in terms of the Makishima‐Mackenzie model.