Phase equilibria in the subsystem barium disilicate - dibarium trisilicate

Abstract

The subsystem BaO.2SiO2 (I)-2BaO.3SiO2 (II) was studied by the quenching method. I has a reversible phase transition at 1350°. The mineral sanbornite corresponds to the low-temp. form. 5BaO.8SiO2 (III) and II have congruent m.ps. at 1446° and 1447°, resp., with a eutectic at 1437° and 39 mole % BaO. 3BaO.5SiO2 (IV) has an incongruent m.p. at 1423° to form III and liquid. A eutectic of I and IV occurs at 1410° and 34 mole % BaO. No solid soln. was found. II is monoclinic with a = 12.51 A., b = 4.69, c = 6.97, and b = 93°23'.