SAXS/WAXS STUDIES OF THE DEVITRIFICATION OF CR-DOPED CORDIERITE GLASS USING SYNCHROTRON-RADIATION.
NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS.
(pp. 184 - 189).
ELSEVIER SCIENCE BV
In situ simultaneous Small Angle X-ray Scattering (SAXS) and Wide Angle X-ray Scattering (WAXS) experiments have been carried out on Cr-doped cordierite (Mg2Al4Si5O18) glass. Samples were initially pre-treated at 875 degrees C close to the glass transition to promote nucleation and this was followed by further treatments at 920 degrees C and 1040 degrees C to generate dispersed crystal growth. The initial treatment revealed no changes in the SAXS or the WAXS data, but the subsequent treatments at higher temperatures revealed large changes in microcrystallinity developing with time. In particular taking the SAXS data for q < 0.05 Angstrom(-1) the average Guinier radius, R(g), was found to increase with heat treatment from initial values of similar to 10 Angstrom to final values of similar to 30 Angstrom. I(q) versus q(-n) plots (for q greater than or equal to 1/R(g)) revealed increasing values of n indicative of changes in mesostructure from rough to smooth fractal architecture. From the WAXS data that was obtained concurrently two separate crystalline phases were identified during devitrification-spinel (MgAl2O4) and a stuffed quartz (MgxAl2xSi1-xO2(1+x))-each growing at different rates. The growth of spinel correlates well with the SAXS invariant, reflecting the major contrast in electron density between this phase and that of the residual glass. For the heat treatment conditions employed, WAXS reveals that the stuffed quartz phase appears later than the spinel phase and also grows less rapidly. For prolonged annealing, a SAXS feature develops at similar to 0.022 Angstrom(-1), corresponding to an average interparticle distance of similar to 280 Angstrom. This is considerably longer than the statistical separation of Cr atoms in the glass (14 Angstrom) and suggests some clustering of Cr takes place as devitrfication progresses.
|Title:||SAXS/WAXS STUDIES OF THE DEVITRIFICATION OF CR-DOPED CORDIERITE GLASS USING SYNCHROTRON-RADIATION|
|Event:||1st European Conference on Synchrotron Radiation in Materials Science|
|Dates:||1994-07-03 - 1994-07-08|
|Keywords:||STRUCTURAL STATES, MG-CORDIERITE, SPECTROSCOPY|
|UCL classification:||UCL > School of BEAMS > Faculty of Maths and Physical Sciences
UCL > School of BEAMS > Faculty of Maths and Physical Sciences > Chemistry
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