IS IT POSSIBLE TO STABILIZE DELTA-BI2O3 BY AN OXIDE ADDITIVE

This paper discusses whether the high-temperature stable modification δ-Bi2O3 can really be stabilized with an oxide additive. As a result, there is little possibility of the stabilization. All the stabilized δ phases reported by many researchers were nothing but the quenched high-temperature stable phases which form a solid solution based on δ-Bi2O3. These quenched phases can easily be obtained in the bismuth-rich region of each system with Ln2O3 (Ln=lathanoid or Y), TeO2, Nb2O5 or Ta2O5. Since the se quenched phases are metastable at a lower temperature, than about 700°C of which a critical temperature varies with composition and an oxide additive, on annealing at that low temperature they transform gradually into the low-temperature stable modification in the systems with Ln2O3 or decompose into two other phases in the other systems. © 1990.