High-Temperature Flux Growth as a Tool for the Preparation of Mixed-Framework Metal-Y Silicates: A Systematic Evaluation of the Influence of Experimental Parameters

Abstract

We report new aspects of the application of the flux-growth method for the preparation of single crystals of silicates, in particular, mixed-framework (octahedral–tetrahedral) metal-Y silicates, in air. The detailed investigations involve flux-growth syntheses in the system BaO–K2O–Y2O3–SiO2–MoO3, in which various important run parameters have been varied in a systematic way (heating and cooling rates, Tmax and duration of holding step, continuous or stepwise cooling, total duration of run, amount of MoO3 solvent, Y2O3/SiO2 molar ratio, size and filling volume of platinum crucible). The results demonstrate that the crystallization of various silicate structure types are strongly controlled by the Y2O3/SiO2 molar ratios and the amount of MoO3 solvent in the precursor mixtures. A decrease of the Y2O3/SiO2 ratio, i.e., an increasing amount of SiO2, promotes an increasing structural complexity of the silicates; nesosilicates crystallize at comparatively low SiO2 concentrations, sorosilicates at intermediate o...