Flux growth of hexagonal bipyramidal ruby crystals

Hexagonal bipyramidal ruby (Al2O3:Cr) crystals were easily grown by the evaporation of MoO3 flux isothermally. The crystal growth was conducted by heating a mixture of solute (Al2O3 + 0.5 mass% Cr2O3) and flux (MoO3) at 1100 °C, followed by holding the solution at this temperature for 5 h. The ruby crystals obtained lengths up to 1.8 mm and widths up to 1.7 mm and were transparent-red. Their form was a bipyramid bounded by well-developed {1123} faces. Molybdenum trioxide was found to be a very suitable flux for growing bipyramidal ruby crystals. Copyright © 2004 American Chemical Society.