Low melting glasses in ZnO-Fe2O3-P2O5 system with high chemical durability and thermal stability for sealing or waste immobilization

Abstract

Structure, chemical durability and thermal properties of two glass series (A and B) in ZnO-Fe2O3-P2O5 system were investigated in this study. Nominal compositions of A and B glass series are (100−x)[0.45ZnO-0.1Fe2O3-0.45P2O5]-xAO (in mol%, x=5, 10, AO=Al2O3, B2O3, SiO2) and (42.75−y)ZnO-9.5Fe2O3-42.75P2O5-5Al2O3-yBO (in mol%, y=5, 10, BO=Bi2O3, MoO3), respectively. For glasses in A series, the variations in thermal expansion coefficient and characterization temperature are slight with theses oxides addition; thermal stability improved with the addition of SiO2; chemical durability improved with the addition of B2O3 or Al2O3; A2 glass obtained by 5mol% Al2O3 addition has good comprehensive performance in A series, and it was chosen as base glass in B series. High thermal stability (TS=201°C), high chemical durability (DR=3.2×10−8g/cm2/min), relative low thermal expansion coefficient (α25–300°C=7.71×10−6/°C) are achieved simultaneously in B2 glass prepared by the substitution of 5mol% Bi2O3 for ZnO in A2 glass. A2, A4, A5 and B2 glasses have potential to be used in 490–600°C sealing applications. B2 glass also has the potential to be used in high level radioactive waste immobilization.