Phase Relations in the System Boron Oxide–Silica

Abstract

The suggested phase diagrams for the system B 2 O 3 ‐SiO 2 as drawn from the findings of previous investigators are presented. These diagrams show the wide controversy regarding this system. The principal difficulties in obtaining reliable equilibrium data are the volatilization of B 2 O 3 , the hydration of B 2 O 3 ‐rich glasses, and the great viscosity of B 2 O r SiO z melts. In this investigation firings were made in sealed platinum capsules. Where necessary, they were opened and studied under xylene to eliminate hydration. Phases were identified by optical and X‐ray methods. The liquidus was obtained by determination of the temperatures at which the stable phases of SiO 2 completely dissolved in the borosilicate melts. The criteria used for equilibrium are discussed.