Vitrification in the BaO–B 2O 3–Al 2O 3–TiO 2 system containing small admixtures of PbO

Abstract

The fields of vitrification in different diagrams were identified for the system BaO–Al 2O 3–B 2O 3–TiO 2 containing 2.4–3.4 mol% admixtures of PbO and varied contents of other components. The glasses obtained were stable from spontaneous crystallization and had relatively low (1450 °C) melting temperature. Liquid phase immiscibility took place in all compositions investigated: TiO 2-rich and B 2O 3-rich glassy phases were formed. The contents of B 2O 3 and Al 2O 3 determined the structure of glasses synthesized, glasses with [B 2O 3] in the range of 7–20 mol% and [Al 2O 3] < 22 mol% showed metastable liquid phase separation. Higher contents of Al 2O 3 and/or B 2O 3 (i.e. [R 2O 3] > 37 mol%) promoted spinodal decomposition. The structure of the main vitreous phase in the glasses with metastable liquid formation is formed by polyanions containing TiO 6/2 and AlO 6/2 octahedra altogether with (B 3O 6) 3− rings, whereas the second vitreous phase includes BO 3/2, BO 4/2, TiO 4/2 and AlO 4/2 structural units.