Crystal growth of bismuth tungstate Bi2WO6 by slow cooling method using borate fluxes

Ferroelectric Bi2WO6 (BWO) single crystals have been grown by a flux method below the phase transition (ferro- to paraelectric) temperature. Sodium chloride, LiBO2, Li2B4O7 (LBO), Na2B4O7 (NBO) and Na2B4O7·10H2O were selected as the flux. We found that LBO and NBO are suitable flux materials for crystal growth. The phase diagram of the BWO–LBO(NBO) system was investigated by the combination of the differential thermal analysis and the quench method. In the BWO–LBO(NBO) binary system, the mixtures of the end members without intermediate compounds were observed. On the basis of the phase diagram, we have obtained plate-like crystals with sizes up to 0.7 mm thickness from the solidified melts with the mole ratio BWO:LBO of 7:3. The crystals are single domain, yellow in color, and have well developed smooth {0 0 1} faces. The dielectric constant, ɛ33/ɛ0, of the crystals is 90 at room temperature and the ferroelectric behavior is available.