Münster 1999 – scientific programme
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DF: Dielektrische Festkörper
DF 6: Poster
DF 6.22: Poster
Thursday, March 25, 1999, 09:30–12:30, Aula
Zero-angle X-ray scattering of metaphosphate glasses — •R. Kranold1, G. Walter1, A. Barz2, and D. Stachel2 — 1Department of Physics, Rostock University, D-18051 Rostock — 2Otto Schott Institute, Friedrich Schiller University Jena, D-07743 Jena
Frozen-in fluctuations in chemical composition and/or topological density are inherent in any glass. According to thermodynamic theory, the zero-angle X-ray scattering, S(0), of a single-phase, single-component liquid at temperature T can be expressed by
| S(0)=<z>2 / <z2>ϱN k T κT (T) , (1) |
where ϱN is the average topological density, k is the Boltzmann constant, κT(T) is the isothermal compressibility at temperature T, and z is the number of electrons in the formula unit of the liquid. The application of (1) to glasses requires T to be replaced by the glass transition temperature, Tg.
Among phosphate glasses, most interest has been directed to those with metaphosphate composition, Me(PO3)v; v is the valency of the metal ion, Me. At metaphosphate composition, all PO4 tetrahedra form Q2 units as well established by 31P NMR. Consequently, binary metaphosphate glasses represent single-component systems. The S(0) values of Me(PO3)v glasses containing different monovalent, divalent and trivalent Me ions were extracted from X-ray scattering data using the methods described in Ref. [1]. The κT(Tg) values of these glasses calculated from (1) are compared with the values of the room-temperature glassy compressibility, κg, obtained from ultrasonic experiments.
This work was supported by the BMBF (Grant 03-KR5ROK-9).
[1] G. Walter, R. Kranold, W. G"ocke, N. Enenkel: J. Appl. Cryst. 24 (1991) 616.