Opposite extreme structural relaxation behaviour in glassformers; a Brillouin scattering study of B2O3 and Ca/sub 0. 4/K/sub 0. 6/ (NO3)/sub 1. 4/
Brillouin scattering in B2O3 and Ca/sub 0.4/K/sub 0.6/(NO3)/sub 1.4/ shows that the two liquids may be taken as opposite extremes in a representation of the general behavior of structural relaxation in glass forming liquids. In B2O3, which is a typical network glassformer, transverse Brillouin modes are observed above the glass transition over the large temperature range T approx. 800 K, which is the widest range reported so far for shear waves in liquids. From the ability of B2O3 to support shear stresses it is concluded that the intermediate range order persists in the liquid state over the wide temperature range T approx. 1.4 T/sub g/. In case of Ca/sub 0.4/K/sub 0.6/(NO3)/sub 1.4/, which represents a non-network ionic glassformer, transverse modes were only observed in the limited range T approx. 0.4 T/sub g/ in which their velocity drastically decreased. The observation reflects the rapid collapse of the structure with increase in temperature typical for liquids which are weakly bonded. It is also supported by the finding that in the non-network Ca/sub 0.4/K/sub 0.6/(NO3)/sub 1.4/ system, longitudinal structural relaxation processes become fast enough to be observed by Brillouin scattering already at temperatures /approximately/ 1.5 T/sub g/, while in the network glassformer B2O3 structural relaxation is still not observed at a temperature of 2.4 T/sub g/. The average shear relaxation times were obtained in the wide time range (10 Z s - 1 s) from the shifts of the transverse modes. In an Arrhenius plot of the relaxation times, the data of the two liquids fall close to the opposite curves for relaxation behavior. The structural differences of the two systems are discussed in terms of some characteristics of the relaxation time such as its non-Arrhenius temperature dependence and its non-exponential time dependence. 30 refs., 11 figs.
- Research Organization:
- Argonne National Lab., IL (USA)
- DOE Contract Number:
- W-31109-ENG-38
- OSTI ID:
- 6618441
- Report Number(s):
- CONF-8809219-1; ON: DE89003889
- Resource Relation:
- Conference: Workshop on dynamics of disordered materials, Grenoble, France, 26 Sep 1988; Other Information: Portions of this document are illegible in microfiche products
- Country of Publication:
- United States
- Language:
- English
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75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
BORON OXIDES
BRILLOUIN EFFECT
CALCIUM COMPOUNDS
GLASS
STRESS RELAXATION
ARRHENIUS EQUATION
SCATTERING
SHEAR
SOUND WAVES
SPECTRA
STRESSES
TEMPERATURE DEPENDENCE
VELOCITY
ALKALINE EARTH METAL COMPOUNDS
BORON COMPOUNDS
CHALCOGENIDES
COHERENT SCATTERING
EQUATIONS
OXIDES
OXYGEN COMPOUNDS
RELAXATION
360202* - Ceramics
Cermets
& Refractories- Structure & Phase Studies
656002 - Condensed Matter Physics- General Techniques in Condensed Matter- (1987-)