Ionic conductivity of sodium zinc silicates in the compositional region Na2ZnSiO4-Na2ZnSi2O6

The compositional region Na₂ZnSiO₄-Na₂ZnSi₂O₆ has been investigated by means of X-ray powder diffraction measurements on samples quenched from elevated temperatures. Four different phases have been observed. The powder pattern of the high and low temperature modification of Na₂ZnSiO₄ could thus be indexed on the basis of an orthogonal cell, while for Na_1.6Zn_0.8Si_1.2O₄ a cubic unit cell could be used. These phases are all structurally related to high-cristobalite. The powder pattern of the compound Na₂ZnSi₂O₆ has been indexed on the basis of a monoclinic unit cell. The variation of the ionic conductivity x in Na_xZn_0.5xSi_2-0.5xO₄ (1.25 ? x ? 2) has been determined. The best conductivity, 1 × 10^-2 (Ω cm)^-1 at 600 K is found for the composition Na_1.85Zn_0.925Si_1.075O₄.