Fe-57 Mossbauer, XRD and DTA study of the crystallization behavior of calcium aluminate glass containing iron(III)

Fe-57 Mossbauer spectroscopy was applied to the crystallization study of IR -transmitting calcium aluminate glass, 60CaO.32Al(2)O(3).5Fe(2)O(3).3Eu(2)O (3), in which Fe(III) atoms occupy tetrahedral Al(III) sites. Heat treatmen t of calcium aluminate glass below and above the crystallization temperatur e causes the formation of mayenite, 12CaO.7Al(2)O(3) and brownmillerite, 4C aO.Al2O3Fe2O3, respectively. Mossbauer spectra of the glass ceramics indica te that Fe(III) atoms substitute Al(III) sites, having less covalent Fe(III )-O bonds and more distorted Fe(III)O-4 tetrahedra than they do in the orig inal glass. DTA revealed that crystallization of calcium aluminate glass is triggered by simultaneous cleavage of Ca-O and Al-O bonds.