Liu Rongchuan

An investigation of the structural effects of Fe3+ in the alkali-silicate glasses

Abstract The coordination states of Fe3+, B3+ and Al3+ ions in the alkali-silicate glasses have been determined. The structural effects of these cations coexisting in the glass, and the effects of the iron and boric oxide anomaly on glass density, are also analysed.

Mössbauer studies on iron in polybasic silicate glass

Abstract Mossbauer absorption spectroscopy was used to study the behaviour of iron in varying concentrations and different reducing conditions in SiO 2 Na 2 OAl 2 O 3 ZnO glass systems. The results indicate that, for the glasses studied, the ferrous and ferric cations are in both tetrahedral and octahedral coordination in the matrix. The ratio of the number of Fe 2+ ions in tetrahedral to the total number of Fe 2+ ions is approximately constant to 0.6, and this ratio, similar to Fe 3+ ions, is not composition-dependent. In addition, the line width is not affected by varying iron content and reducing condition of the glass. Ferric iron is prodominantly octahedrally coordinated when the iron concentration is low. The results of Mossbauer analysis above are also well consistent with the ones of wet chemical analysis, which is greatly different from some results studied before.

Investigation of anomalous transitions in LiNbO3 by Mossbauer spectroscopy

According to Ismailzade et al.1 LiNbO3, shows eleven anomalies in lattice parameters below the ferroelectric phase transition Tc = 1153°C. A later detected anomaly near 75°C is the most intensively investigated. An easy cracking of LiNbO3, on cooling from 80 to 60°C is reported by Xu Ziran et a1.2 Additional anomalies in birefringence,2 ultrasonic attenuation3 and Mossbauer parameters4 have been observed. Although a phase transition is suggested to occur at 75°C by some author,2, 3 the behaviour of LiNbO3 at 75°C is still not completely understood.2, 5 Encouraged by interesting results obtained in initial Mossbauer investigations of Hsia et al.4 we undertook detailed studies of the anomalies near 75 and 125°C in LiNbO3.

A Mössbauer investigation of the formation process of glauconite

Glauconites are of particular interest for the understanding of the characteristics of marine deposits. The glauconite formation processes in the sediments of the Yellow Sea and the East China Sea were investigated by Mössbauer spectroscopy. Valence states and lattice sites of the iron ions could be distinguished. The glauconization processes are accompanied by changes of isomer shift and quadrupole splitting of the Mössbauer isotope.

Mössbauer study on Eu-Ba-Cu oxide superconductor

Onset of superconductivity of the new high Tc superconductor Eu-Ba-Cu-O was found to be 92K. The valence of Eu ion and the Debye temperature of this superconductor were determined using Mossbauer spectroscopy. The experimental results show abnormal changes of isomer shift and lattice-softening nearby the transition temperature Tc. It seems that high Debye temperature is not a necessary condition for this high Tc superconducting system.

Study of the similarity of structural surroundings of Fe3+ ions in some oxide glasses by Mössbauer spectroscopy

A study of Fe3+ environments in alkali silicate glasses has been performed. The Mössbauer parameters indicate Fe in octahedral as well as in tetrahedral surroundings. The broad linewidth of the Mössbauer subspectra indicates a distribution of the hyperfine parameters due to local distortions. Using a distribution fitting program we obtained information about the distortions of octahedral and tetrahedral Fe ion surroundings from the distribution of the electric field gradient (EFG).