Münster 1997 – wissenschaftliches Programm

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SY: Von der Flüssigkeit zum Glas

SY 3: Von der Flüssigkeit zum Glas III

SY 3.3: Poster

Donnerstag, 20. März 1997, 15:00–19:00, Aula

Phase Formation Kinetics in Glasses Studied in Situ with Small- Angle X-ray Scattering — •U. Lembke, R. Br"uckner, and R. Kranold — Universit"at Rostock, Fachbereich Physik,18051 Rostock

Growth and ripening of silver chloride clusters in a supersaturated sodium borate glass are investigated in situ during isothermal treatment. The small-angle X-ray scattering experiments performed using a high-temperature sample chamber and Synchrotron radiation provide a variety of structural data of the precipitating phase. The evolution of the mean particle radius ⟨ R ⟩ of the silver chloride clusters with increasing time t of heat treatment shows an intermediate stage between diffusion-limited independent growth (⟨ R⟩ ² ∝t) and diffusion-limited asymptotic ripening (⟨ R⟩ ³ ∝t). This intermediate stage is characterized either by a continuously decreasing growth rate or by a discontinuous transition with a growth rate temporarily even smaller than that for ripening. The type of the transition stage is shown to depend on the supersaturation of the glass with silver halide, the interface tension between the phases and the effective diffusion coefficient. In this context, the influence of 1 mol% MoO₃, added to the glass melt, on the kinetics of silver chloride precipitation is discussed. The experimental findings are compared with the results of model computations. The work was partially supported by the German BMBF under grant No. 03-KR4ROK-1.