Regensburg 2000 – scientific programme

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DF: Dielektrische Festkörper

DF 6: Gläser I

DF 6.1: Invited Talk

Wednesday, March 29, 2000, 14:30–15:10, H11

Pulsed Neutron Diffraction from Network Glasses — •Alex C. Hannon — ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX11 0QX, UK

Neutron diffraction is an invaluable tool for investigating the structure of disordered materials. By using high energy neutrons, obtainable only from a pulsed source, it is possible to attain very high maximum momentum transfers, Q_max, of order 50Å⁻¹. This leads to a high real-space resolution for the correlation function obtained by Fourier transforming such data. It is shown that, even for cases where the high real-space resolution does not reveal new detail, the high real-space resolution is advantageous because it leads to a peak function which has virtually no termination ripples; the lack of termination ripples results in a less ambiguous identification of features in the correlation function. Recent data for lead gallate [1] and calcium aluminate [2] glasses, taken on the Liquids and Amorphous Diffractometer [3] at the ISIS pulsed neutron source, are used to illustrate the talk. It is shown that the methods of chemical crystallography may be applied to a consideration of glass structure. Particular emphasis is given to the structural role of oxygen, which is shown to be mostly coordinated by three cations in these glasses. By considering the oxygen environment, a complete description of the network connectivity can be built up.

[1] A.C.Hannon, J.M.Parker and B.Vessal, J. Non-Cryst. Solids 196(1996)187-192. A.C.Hannon, J.M.Parker and B.Vessal, J. Non-Cryst. Solids 232-234(1998) 51-58.

[2] A.C.Hannon and J.M.Parker, submitted to J. Non-Cryst. Solids (1999).

[3] A.C.Hannon, in: ’Encyclopedia of Spectroscopy and Spectrometry’ eds. J.Lindon, G.Tranter and J.Holmes (Academic Press, London, 1999) volume 2 pp. 1479-1492.