Publication
Journal of Physical Chemistry
Paper

Compound repetition in oxide systems. Solid phases in the system Li2O-Ta2O5 and Na2O-Ta2O5

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Abstract

The system Li2O-Ta2O5 has been studied in the range 45-100 mole % Ta2O5 by X-ray analysis of samples reacted in the solid state at 1350°. Three compounds have been identified and have been assigned the compositions, Li2O·3Ta2O5, Li2O· Ta2O5 and 3Li2O·Ta2O5. The system Na2O-Ta2O5 has been similarly studied in the temperature interval 700-1300°. Three compounds have been identified in the highest temperature samples. These have been assigned the compositions Na2O·3Ta2O5, Na2O·2Ta2O5 and Na2O·Ta2O5. Earlier work also has indicated the existence of an Na2O·3Ta2O5 compound. Analogous lithium and sodium compounds are not isomorphic while the 1:2 sodium compound is isomorphic with the 1:2 potassium analog and the 1:3 sodium salt is isomorphic with a metastable potassium analog. The 1:1 sodium compound has been indexed on the basis of a perovskite-derived orthorhombic unit cell with a two-fold "b" multiplicity. The 1:2 compound exhibits a perovskite-derived bronze structure and has been indexed on the basis of an orthorhombic unit cell with a two-fold "b" multiplicity. The 1:3 sodium salt also has a bronze structure and has been indexed on the basis of an orthorhombic unit cell with two-fold "a" and "b" multiplicities. No solid solution was detected in either system. The results of the sodium system are correlated with those reported in an earlier work, and predictions are made about the melting behavior of the different salts and their repetition in higher weight systems.

Date

01 May 2002

Publication

Journal of Physical Chemistry

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