Temperature and time-dependent changes of structure in phosphorus containing aluminosilicate liquids and glasses: in situ Raman spectroscopy at high temperature
Mj. Toplis et B. Reynard, Temperature and time-dependent changes of structure in phosphorus containing aluminosilicate liquids and glasses: in situ Raman spectroscopy at high temperature, J NON-CRYST, 263(1-4), 2000, pp. 123-131
The structural role of phosphorus in glasses and liquids of composition Na2
Si2O5 and Na1.8Al0.2Si2O5.1 has been studied by in situ Raman spectroscopy
in the temperature range 300-1500 K. Spectra collected at room temperature
indicate that the majority of phosphorus atoms occur in Na3PO4 and Na4P2O7
complexes, as confirmed by bands at similar to 935 and similar to 1025 cm(-
1), respectively. The amplitude of the band at 935 cm(-1) decreased relativ
e to that at 1025 cm(-1) with the addition of phosphorus. However, for addi
tions of P2O5 > 4 mol%, the relative proportions of these two bands are obs
erved to be dependent on the thermal history of the sample in the molten st
ate. In situ measurements on samples at temperatures above the glass transi
tion demonstrate that temperature-dependent structural changes occur and, f
urthermore, that there are time-dependent charges at fixed temperature. The
principal time-dependent change observed is an increase in the amplitude o
f the 935 cm(-1) band relative to that at 1025 cm(-1) with increasing time.
At lower temperature the intensity of 935 cm(-1) band increases immediatel
y upon cooling, whereas at higher temperature no changes are detected initi
ally, but change occurs after periods of up to 1 h. The kinetics of these t
ime-dependent changes are interpreted to be a consequence of liquid-liquid
immiscibility. (C) 2000 Elsevier Science B.V. All rights reserved.