Growth of Barium Chlorapatite Crystals from a Sodium Chloride Flux

Large and well-formed crystals of barium chlorapatite [Ba5Cl(PO4)3] were grown for the first time from a sodium chloride flux. The solubility of Ba5Cl(PO4)3 in NaCl increased with increasing temperature, reaching about 1.9 mol% solubility at 1100 °C. The crystal growth of Ba5Cl(PO4)3 was conducted by heating a mixture of solute and flux at 1100 °C for 10 h, and then cooling to 500 °C at a rate of 5 °C h−1. Colorless and transparent prismatic crystals with lengths of up to 12 mm and widths of 3 mm were grown from high-temperature solutions containing 0.4—2.2 mol% solute. The most suitable solute content for the growth of prismatic crystals was 1.2 mol%. The prismatic crystals were bounded by the {} and {} faces. The aspect ratios were in the region of 1.1 to 4.8. Needle crystals with lengths of up to 4 mm and widths of 60 μm were obtained during every growth run. The needle crystals were elongated in the <0001> directions, with aspect ratios ranging from 43 to 56. The major constituents were almost homogeneously distributed in the prismatic and needle crystals.