A. Musinu

Coordination of Ag+ ions in AgI–Ag2O–B2O3 glasses by x‐ray diffraction

X‐ray diffraction measurements have been performed on glasses of the Ag2O–B2O3 and AgI–Ag2O–B2O3 systems. When silver iodide is present, the radial distribution function is dominated by a large peak at 2.85 A, due to Ag–I interactions, with a shoulder at ∼2.40 A, due to Ag–O pairs. The average number of Ag–I contacts has been calculated through analysis of the high angle structure functions si(s)’s, either by using the total si(s)’s or by using the partial si(s)’s, the latter obtained by subtracting the experimental structure function of the Ag2O–B2O3 glasses from that of the corresponding AgI‐doped glasses. The compatibility of the results obtained with recently proposed models of AgI–Ag2O–B2O3 glasses is examined.

Short-range order of Zn and Cu in metaphosphate glasses by X-ray diffraction

The coordination of Zn2+ and Cu2+ ions in two metaphosphate glasses was investigated by X-ray diffraction. An average coordination number of five oxygen atoms was obtained for both cations through the analysis of the short-range features of the radial functions. Furthermore, the consistency of diffraction data with the metaphosphate chain model was demonstrated. Structural implications of these results are discussed.

Coordination of Cu(II) in Cu(NO3)2 aqueous solutions

Two concentrated copper (II) nitrate solutions have been examined by x‐ray diffraction. The inspection of the radial distribution curves and the direct fitting of the structure functions suggested that a distorted arrangement of six oxygen atoms exists around the Cu2+ ion, probably in a tetragonally distorted, elongated octahedron. The best agreement with experimental data was achieved through a model in which extensive inner‐sphere complex formation between Cu2+ and NO−3 ions takes place.

Coordination of zinc and copper in phosphate glasses by EXAFS

Abstract The coordination of Zn2+ and Cu2+ ions in semiconducting phosphate glasses was investigated by EXAFS spectroscopy. A change in Zn coordination occurs when the glass composition deviates from metaphosphate. The results are consistent with the hypothesis that Cu(II) and Cu(I) occupy sites with different coordination geometries, but with entire coordination polyhedra similar for all copper atoms. The consistency of the structural model with the semiconducting properties of the glasses is examined.

Short range order in AgI–AgPO3 glasses by x‐ray diffraction

A structural investigation by x‐ray diffraction is presented on ionic conducting glasses of composition (AgI)x (AgPO3)1−x, with x=0.0, x=0.45, and x=0.55. The radial distribution functions of the AgI‐doped glasses, calculated from the experimental diffracted intensities, are dominated by a peak centered at about 2.80–2.85 A, which can be ascribed to Ag–I pairs. According to this, model interpretations showed that the diffraction effects are essentially due to the shortest and heaviest pair interactions (Ag–I and Ag–O), while there is no evidence of important structural details at medium range. The compatibility of the results obtained with current models of AgI–AgPO3 glasses is examined.

X‐ray diffraction study of AgX–Ag2O–B2O3 (X=Br,Cl) vitreous electrolytes

X‐ray diffraction measurements have been performed on glasses of the AgX–Ag2O–B2O3 (X=Br,Cl) systems. The only meaningful structural detail of the radial distribution functions is due to Ag–X interactions. The mean numbers of Ag–X contacts has been obtained through analysis of the high‐angle partial structure functions si(s), calculated by subtracting experimental structure function of the Ag2O–B2O3 glasses from that of the corresponding AgX–doped glasses. Calculations have been also performed for AgI–Ag2O–B2O3 glasses, and comparison between the results from systems containing different halides is made. The average number of Ag–X contacts is very similar in samples at equimolar composition, thus suggesting a close structural feature in AgX–doped glasses.

X‐ray diffraction study of CoCl2–LiCl aqueous solutions

Three 1 M solutions of CoCl2 at Cl−/Co2+ ratios of 4, 6, and 7 were examined by x‐ray diffraction. The Fourier transformed scattering data indicated inner complex formation between Co2+ and Cl− ions for the two solutions more enriched in Cl− ions. Coordination parameters of Co2+ ions were obtained by direct fitting of the structure functions.

A 29Si MAS and 1H NMR investigation of Fe2O3–SiO2 nanocomposites

Fe 2 O 3 -SiO 2 nanocomposites and silica matrices, prepared by a sol-gel method and submitted to the same heat treatments in the range 150-700°C, were investigated using the 29 Si magic angle spinning (MAS), nuclear magnetic resonance (NMR) technique. For the Fe 2 O 3 -SiO 2 samples, an analysis of the integrated NMR peak areas revealed that only 29 Si nuclei far from the iron ions were detected. As far as the host matrix is concerned, no structural modifications have been induced by the nanoparticles. The H NMR spectrum for the prepared silica matrix showed a signal due to solvation water, while the spectrum of the as prepared nanocomposite showed a much broader signal shifted to low field. The overall findings are discussed in terms of possible interactions between the nanoparticles, the host matrix and water molecules in the cavities at the nanoparticle-silica interface.

An X-ray diffraction study of the short-range order around Ni(II), Zn(II) and Cu(II) in pyrophosphate glasses

Abstract Three glasses with composition 0.30MeO · 0.35Na2O · 0.35P2O5 (Me = Ni, Zn, Cu) have been investigated by X-ray diffraction. The coordination for the metal ions has been determined by a fitting procedure which simulates the first three peaks of the radial distribution function. The coordination numbers are 6.2 for Ni2+, 4.7 for Zn2+ and 4.0 + 1.3 for Cu2+. The results concerning the phosphate network are consistent with the model for the structure of phosphate glasses at the pyrophosphate composition.

An X-ray diffraction study of sodium borate glasses

Abstract X-ray diffraction measurements have been performed on two pairs of sodium borate glasses of differing compositions. Glasses of given composition were obtained with two different thermal histories. The radial distribution functions of samples of the same composition appear similar. The short range order is not affected by the range of quenching rates explored.