Crystallization of Anorthite-Seeded Albite Glass by Solid-State Epitaxy

Authors

  • Chunling Liu,

    1. Materials Research Laboratory, The Pennsylvania State University, University Park, Pennsylvania 16802
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    • Member, American Ceramic Society.

  • Sridhar Komarneni,

    1. Materials Research Laboratory, The Pennsylvania State University, University Park, Pennsylvania 16802
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    • Member, American Ceramic Society.

    • *

      Also with the Department of Agronomy.

  • Rustum Roy

    1. Materials Research Laboratory, The Pennsylvania State University, University Park, Pennsylvania 16802
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    • Member, American Ceramic Society.


  • G. H. Beall—contributing editor

  • Supported by the U.S. Air Force Office of Scientific Research under Grant No. AFOSR-89-0446.

Abstract

Stoichiometric albite glass (NaAlSi3O8) was seeded with 5 wt% crystalline anorthite (CaAl2Si2O8) to make albite glass-ceramics. The epitaxial crystallization of the albite glass to the glass-ceramics was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectrometry (EDS). High albite was observed as the major crystallization product over the temperature range of 800–1200°C. No crystalline albite could be crystallized from pure albite glass without seeds. Small amounts of nepheline (NaAlSiO4), however, crystallized along with albite after heat treatments at temperatures lower than 1000°C. The platelike microstructure of albite crystals was revealed in the seeded glasses. The albite blades grew epitaxially from the anorthite seeds, and the Ca content decreased in the direction away from the seeds. The degree of crystallization and the grain size were dependent upon the heat treatment conditions. By increasing the particle size of the seed, the crystallization process was retarded and the resultant microstructure was degraded. The seeding efficiency was also lowered by adding nonisostructural hexagonal anorthite seeds which produced less albite but more nepheline crystals. Crystallization of albite glass by seeding with 5 wt% anorthite is much greater than with the surface nucleation which takes place in a homogeneous 95 wt% albite + 5 wt% anorthite glass.

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