Premium
Light Scattering Experiments during Freezing and Melting
Author(s) -
Bilgram J.
Publication year - 1997
Publication title -
crystal research and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.377
H-Index - 64
eISSN - 1521-4079
pISSN - 0232-1300
DOI - 10.1002/crat.2170320804
Subject(s) - melting point , cyclohexane , scattering , light scattering , crystal (programming language) , atmospheric temperature range , materials science , xenon , liquid crystal , layer (electronics) , freezing point , ice crystals , crystallography , chemistry , optics , thermodynamics , composite material , organic chemistry , physics , optoelectronics , computer science , programming language
Anomalous light scattering has been observed at the solid‐liquid interfaces of high purity systems during freezing as well as during melting. The model substances used are water, salol, cyclohexane and xenon. From light scattering experiments the existence of a layer of pre‐ordered material at the solid‐liquid interface is deduced. Light is scattered by long range fluctuations in this layer. The thickness of this layer is a few μM. The correlation length of the fluctuations in this layer has been determined to be ξ ≈ 260 nm. Dynamic and static light scattering experiments lead to the same correlation length. Xenon, salol and cyclohexane cover a range of a factor of 15 in viscosity at the melting temperature. Growth velocities have been varied by a factor of about 200. Thermal gradients at the solid‐liquid interface have been varied in a wide range. No dependence of the correlation length on these parameters or on substance has been found in the experiments. The observations do not depend on the crystallographic orientation of the crystal surface nor on the orientation of the crystal surface relative to gravity. The interface‐layer may be compared to the quasiliquid layer which has been found at crystal vapour interfaces at conditions close to the melting point. The existence of a pre‐ordered layer in‐between a crystal and its melt means that the crystal does not grow into the melt but into the pre‐ordered layer.