Phase Diagrams of Sodium Tungstate and Sodium Molybdate to 45 kbar

Abstract

The phase diagrams of Na2WO4 and Na2MoO4 have been determined to 40–45 kbar. Two new high-pressure phases have been found for Na2WO4. The 440°C transition in Na2MoO4 consists of two transitions very close together. A further new high-pressure phase has been found. Crystallographic data are given for Na2WO4 I and Na2MoO4 III, both of which are orthorhombic, Space Group Pnam. The phase diagrams of Na2WO4 and Na2MoO4 are strikingly similar, and there are reasons for believing that every known polymorph of Na2WO4 has an isostructural counterpart in the phase diagram of Na2MoO4.