A neutron diffraction study of 2M(2)O center dot 5B(2)O(3) (M=Li, Na, K, Rb, Cs %26 Ag) and 2MO center dot 5B(2)O(3) (M=Ca %26 Ba) glasses

作者：Wright Adrian C^*; Sinclair Roger N; Stone Cora E; Shaw Joanna L; Feller Steven A; Kiczenski T J; Williams Richard B; Berger Heidi A; Fischer Henry E; Vedishcheva Natalia M

来源：Physics and Chemistry of Glasses-European Journal of Glass Science and Technology Part B, 2012, 53(5): 191-204.

A neutron diffraction investigation has been performed to investigate the effect of the network modifying cation size and charge on the structure of a series of binary borate glasses of composition 2M(2)O center dot 5B(2)O(3)(M=Li, Na, K, Rb, Cs %26 Ag) and 2MO center dot 5B(2)O(3) (M=Ca %26 Ba). The diffraction patterns were recorded using a twin-axis diffractometer, and Fourier transformed to yield the real-space correlation function, T(r). The first peak in the corrected, normalised diffraction pattern, I(Q), is employed to estimate the spacing between the network-modifying cations occupying adjacent network cages, and the fraction of four-fold co-ordinated boron atoms, x(4), is obtained from the area under the first (B-O) peak in T(r). With the exception of 2CaO center dot 5B(2)O(3), and within the experimental uncertainty, no evidence is found to indicate the presence of significant numbers of nonbridging oxygen atoms. The way in which the distribution of superstructural unit species present varies with the network modifying cation is investigated by comparison with theoretical calculations based on the model of associated solutions. Finally, conclusions are drawn in respect of the first M(O) co-ordination shell and the important role of both the network modifying cation and superstructural units in determining the structure of binary alkali and alkaline earth borate glasses.

• 出版日期2012-10