Synthesis and Properties of Zektzerite, LiNaZrSi6O15, and its Isotypes

J. M. Marr and F. P. Glasser
Department of Chemistry, University of Aberdeen, Meston Walk, Old Aberdeen AB9 2UE, Scotland

Synopsis: Zektzerite and its isotypes with Zr4+ replaced by Ti4+ or Sn4+ are readily synthesized by fusion of the constituent oxides at 1550 °C followed by recrystallization of the melt or quenched glass at 750–850 °C and I bar pressure. Indexed powder X-ray data for synthetic zektzerites are presented in miniprint Table I. The powder patterns are consistent with an A-centred orthorhombic symmetry. Refined cell dimensions are given in Table III.

The Ti, Zr, and Sn zektzerites melt incongruently. Table IV records melting-point data. The coefficients of thermal expansion of Zr and Ti zektzerite have been determined by X-ray dilatometry. Both have moderately low coefficients of expansion: numerical values are given in miniprint Table II.

Zektzerites contain a six-repeat unit doublechain silicate anion. Although they are chemically similar to milarites, the latter contain double-ring Si12O30 anions. Despite the difference in anion constitution both have structures in which many chemically similar atoms occupy similar positions. The effect of this similarity on the physical properties (e.g. X-ray powder pattern) is enhanced by the similar size and shape of their orthorhombic unit cells. The presence of vacant sites in zektzerite that are potentially available for cation occupancy suggests that chemically complex substitutions may occur; for example LiNa2ScSi6O15 has been synthesized and is believed to be isostructural with zektzerite and emeleusite, LiNa2FeSi6O15.

Mineralogical Magazine; March 1979 v. 43; no. 325; p. 171-173; DOI: 10.1180/minmag.1979.043.325.19
© 1979, The Mineralogical Society
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