The system barium oxide-boric oxide-silica

Abstract

The equil. diagram for the system BaO-B2O3-SiO2 was constructed from data, obtained by the quenching method, on 178 ternary compns. One new compd., 3BaO.3B2O3.2SiO2, m. congruently 1009° and possessing an extremely flat primary field, was found; its optical and x-ray properties are described. The compns. and liquidus temps. of the 13 ternary invariant points are listed together with the cryst. phases in equil. with liquid. The BaO.4B2O3 and SiO2 primary phase areas included approx. 70% of the diagram, and over these areas existed a large region of 2-liquid immiscibility. Limited data indicate that the immiscibility gap decreases with increasing temp. Although the exact nature and extent of the 2BaO×3SiO2 solid-soln. field could not be ascertained, the eutectic matrix method was used to show that 2BaO.3SiO2 is probably a compd. The solid-soln. region between 2BaO.3SiO2 and BaO.2SiO2 is complex and extends into the interior of the diagram. An isofract diagram of the quenched glasses showed that BaO exerts the greatest influence on n. A self-adjusting, bridge-type controller for precise temp. control of a quenching furnace is described.