GROWTH OF BETA-ALUMINA (NA2O.11AL2O3) SINGLE-CRYSTALS BY THE FLUX METHOD

The crystal‐growth process and growth conditions of β‐alumina (Na2O · Al2O3) were investigated using the Na2B4O7‐Na3AlF6 flux method. β‐Alumina (electric fusion brick) was used as both nutrient and seed. Weight loss of the flux varied widely for various runs: ≅ 10 wt% of flux evaporated at 100 h, ≅ 17 wt% at 150 h, and 43 wt% at 600 h. When β‐alumina crystal was grown, only 20 wt% Na2B4O7 was added to the Na3AlF6 flux. The linear growth rates of the β‐alumina single crystal grown by an Na3AlF6‐20 wt% Na2B4O7 flux method at 1040°C and Δt= 18°C were ≅ 1.0 × 10−3 mm/h (a face) and ≅0.3 × 10−3 mm/h (c face). The β‐alumina single crystals grown were bounded by only c[001] and a[100] and were colorless and transparent. Copyright © 1990, Wiley Blackwell. All rights reserved