Crystal growth of aluminum tungstate Al2(WO4)3 by the Czochralski method from nonstoichiometric melt

Al2(WO4)3 is a solid electrolyte with interesting transport and luminescence properties. This is a promising material for chemical sensor applications and in single-crystal form it is a potential laser host. A few attempts to grow this crystal are discussed in the literature but the only crystals of significant size have been obtained from a Na2W4O13 flux. There is also some ambiguity about the phase diagram of Al2O3–WO3 system. In this work, using DTA experiments, we have established the starting composition and growth conditions for obtaining good quality single crystals of Al2(WO4)3 by the modified Czochralski method. Crystals were grown from a WO3-rich composition and the composition range suitable for crystallization is narrow (∼4%mol). It was possible to determine growth conditions in such a way, that evaporation of WO3 partially compensates a compositional shift in the melt during growth process and a significant amount of starting material can be crystallized.