Surface tension of barium chlorapatite crystals grown from flux

Large, well-formed crystals of barium chlorapatite [Ba5Cl(PO4)(3)] were grown from a sodium chloride flux. The prismatic crystals of Ba5Cl(PO4)(3) were bordered by(10 (1) over bar0} and {10 (1) over bar1} faces. The crystals have a tendency to elongate in the (0001) directions. Contact angles of water, formamid, ethylene glycol, and diethylene glycol droplets on the Ba5Cl(PO4)(3) crystals were observed. The surface tension, that is, the surface free energy of the grown crystals, was calculated in order to study the relationship between the morphology and the surface tension of the crystal. The contact angles of water, formamid, ethylene glycol, and diethylene glycol droplets on the (10 (1) over bar0) face of a Ba5Cl(PO4)(3) crystal were 40degrees, 37degrees, 30degrees, and 26degrees, respectively, and the contact angles of those liquids on the (10 (1) over bar1) face were 20degrees, 18degrees, 16degrees, and 14degrees, respectively. The surface tension of the crystal faces were calculated from the observed contact angles using harmonic mean and geometric mean equations. The calculated surface tensions of the crystal faces were 58 1 and 69 I mN/m for the (10 (1) over bar0) and (10 (1) over bar1) faces of a Ba5Cl(PO4)(3) crystal, respectively. The fact that the surface tension of the (10 (1) over bar0) face is smaller than that of the (10 (1) over bar1) face indicates that the (10 (1) over bar0) face is more stable than the (10 (1) over bar1) face. The energetic stability of the (10 (1) over bar0) face corresponds to the morphology of the Ba5Cl(PO4)(3) crystal, which elongates in the [000] directions.