FTIR AND DTA STUDY OF LANTHANUM ALUMINOSILICATE GLASSES

Structure and glass transition temperature of lanthanum aluminosilicat e (LAS) glasses, containing: (15-25) mol% La2O3, (15-35) mol% Al2O3 an d (40-70) mol% SiO2, were studied by FTIR spectroscopy and differentia l thermal analysis. The effects of La2O3 and Al2O3 content on the prop erties and structures of LAS glasses were evaluated. The Al+3 ion can assume both four-fold co-ordination, forming (AlO4/2) tetrahedra, and six-fold co-ordination forming (AlO6/2)(-3) octahedra. The amount of t hese depends on La+3 content; acting as network modifier, it can compe nsate the charge of three neighbouring (AlO4/2) units or one (AlO6/2)( -3) unit. (C) 1997 Elsevier Science S.A.