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

Al-2(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 Al-2(WO4)(3) by the modified Czochralski method. Crystals were grown from a WO3-rich composition and the composition range suitable for crystallization is narrow (similar to 4% mel). 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. (C) 1999 Elsevier Science B.V. All rights reserved.