Structure and crystallization kinetics of PbO-B2O3 glasses

Structure and crystallization kinetics of PbO-B2O3 glasses containing 10-80 mol% PbO were investigated. The analyses of IR spectra reveal that PbO causes a change in the short-range order structure of the borate matrix. Between 10 <= PbO <= 20 mol%, PbO only acts as a network modifier. With the increase of PbO content, a progressive conversion of [BO3] to [BO4] units occurs and this promotes the formation of boron-oxygen rings, composed of the connection of bridge oxygen between [BO3] and [BO4] units. When the content is over 60 mol%, PbO plays the role of glass former. Four possible structure models have been suggested to explain the effects of PbO on glass network: (a) three coordinated boroxol rings modified by Pb2+; (b) formation of Pb-O-B covalent bands; (c) bridge networks between [BO3] and [BO4] units; (d) complex structures of Pb2+ modified boron-oxygen rings and chains. Moreover, The crystallization kinetics of PbO-B2O3 glasses was characterized by DSC analyses. When PbO >= 50 mol%, the increase of PbO leads to a decrease of thermal stabilities of the glasses. The increase of B2O3 contributes to the increase trends to crystallization of glasses. (c) 2006 Published by Elsevier Ltd and Techna Group S.r.l.