Structure of borosilicate glasses and melts: A revision of the Yun, Bray and Dell model

Within the framework of structural studies of borosilicate glasses, a revision of the Yun, Bray and Dell (YBD) model is proposed here. The YBD model is slightly modified in order to take into account more recent experimental results, and in particular the formation of Na2O center dot B2O3 center dot 2SiO(2) danburite-like units in borosilicate glasses. The following more general formula is proposed for R*, the threshold value of R (R = [Na2O]/[B2O3]), beyond which glass depolymerisation begins upon addition of modifier to the glass: R* = 0.5 + K/2N where N is the average number of SiO2 units included in the borosilicate groups (reedmergnerite and danburite-like), and K = [SiO2]/[B2O3]. (C) 2009 Elsevier B.V. All rights reserved.