The effect of P2O5 on the structure, sintering and sealing properties of barium calcium aluminum boro-silicate (BCABS) glasses

The effect of P2O5 incorporation on the sintering, flow and crystallization characteristics of BCABS glasses of composition (mol%) 35BaO–15CaO–5Al2O3–(37 − x)SiO2–8B2O3–xP2O5 (0 ≤ x ≤5) is investigated. It is observed that addition of P2O5, removes cations (Ba2+ and Ca2+) from the silicate network, resulting in an increase in polymerization. This is reflected by a reduction in TEC and an increase in sealing temperature. In addition, the removal of cations for charge compensation causes a change in major crystalline phases formed, from BaSiO3 to Ba(Al2Si2O8). In addition, beyond 3 mol% P2O5, crystallization of phosphate phases is evident. Based upon the flow temperature, glasses with 0, 1 and 2 mol% P2O5 are selected for sealing. In these glasses, conversion of Cr to Cr2O3 is observed, yielding improved adhesion. However, the 2 mol% P2O5 glass showed an increased crystallization tendency, resulting in incomplete sintering. Therefore, 1 mol% P2O5 seems a good compromise for sealing with improved adhesion.