Synergic effect of V2O5 and P2O5 on the sealing properties of barium-strontium-alumino-silicate glass/glass-ceramics

The effect of combined addition of P2O5 and V2O5 on structural and sealing properties of glasses with nominal composition (mol.%) 27SiO2-23SrO-32BaO-4Al2O3-10B2O3-(4-x)P2O5-xV2O5 is reported in the present study. 29Si,31P,51V,27Al and 11B MAS-NMR have been used to characterize the local environment in the glasses and glass-ceramics. The main network-forming elements (Si, Al, B) are not significantly affected, however, P and V show different local environment when they are associated in the composition. Characteristic temperatures (Tg, Tsoft, Tshrink) decrease when V2O5 is added to the glass composition, which enable to decrease the sealing temperature. However, the combined addition of P2O5 and V2O5 is favorable to avoid extensive crystallization during sealing operation. TEC of the glass and glass-ceramics samples is found compatible with those of metallic alloys and do not change after heat treatment. EPMA images show that the seals have good thermal and chemical stabilities when treated up to 1500 h at 800 °C. Sandwich seals tested under pressure are resistant to thermal cycling.