Chemical Durability and Structural Properties of Al 2 O 3 -CaO-Na 2 O-P 2 O 5 Glasses Studied by IR Spectroscopy, XRD and SEM

Abstract

Various characterization techniques were used to study the composition of the glass series xAl2O3-(40 - x)CaO-10Na2O-50P2O5 (with 0 ≤ x ≤ 10) in terms of chemical durability, X-ray diffraction, IR spectroscopy and scanning electron microscopy (SEM). The improved chemical durability was attributed to the replacement of easily hydrated P-O-P bonds by covalent and resistant Ca-O-P and Al-O-P bonds. However, the change in the dissolution rate (DR) versus time showed a marked decrease in chemical durability with increasing the Al2O3 content to the detriment of the CaO content. The X-ray diffraction analysis of glasses annealed at 550˚C and 660˚C for 48 hours indicated the presence of pyrophosphate phases and predominant metaphosphates or cyclic metaphosphate phases when the Al2O3 content was ≤7.5 mol%. Nevertheless, Both, X-ray diffraction and IR spectroscopy confirmed the structural tendency change from metaphosphate (Q2) and pyrophosphate structural units (Q1)...