Synthesis of sodium beta alumina films by heat treatment of sodium aluminum oxides

Abstract

Sodium beta alumina (Na-β-alumina) films were synthesized by heat treatment of NaAl₆O_9.5 and γ-NaAlO₂ films at temperatures of 1 373-1 573 K. Single-phase γ-NaAlO₂ and NaAl₆O_9.5 films were prepared by laser chemical vapor deposition at the deposition temperatures of 976 and 1 100 K, respectively. Subsequent heat treatment of the films resulted in the formation of Na-β-alumina with α-Al₂O₃ at temperatures above 1 373 K for NaAl₆O_9.5 and 1 473 K for γ-NaAlO₂. On heat treatment at temperatures of 1 473-1 573 K, the faceted morphology with terraces of the as-deposited (110)-oriented γ-NaAlO₂ films transformed to a porous morphology with platelet grains comprising Na-β-alumina and α-Al₂O₃. On heat treatment at temperatures of 1 373-1 473 K, the pyramidal, faceted grains of as-deposited NaAl₆O_9.5 films transformed to planer, shapeanisotropic morphology in the film of mixed Na-β-alumina and α-Al₂O₃. A dense morphology was observed in both the as-deposited and heat-treated NaAl₆O_9.5 films.

Keywords

sodium beta alumina / heat treatment / chemical vapor deposition / morphology

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