Concentration and temperature regions of phase crystallization in the system Li 2O–Al 2O 3–WO 3

Abstract

The concentration and temperature regions of formation of crystals from different phases of the ternary system Li 2O–Al 2O 3–WO 3 have been determined using the results on spontaneous crystallization in various high-temperature solutions of this system. It has been established that crystallization proceeds with no measurable evaporation of WO 3 when the temperature is below 1150 °C. For that reason, solution compositions varying within the limits of 10–40 mol.% for Li 2O, 2–20 mol.% for Al 2O 3 and 57–80 mol.% for WO 3 have been used. In these limits the crystallization regions of Li 2W 2O 7, WO 3, Al 2(WO 4) 3 and of the low- and high-temperature modification of LiAlW 2O 8 have been determined. The crystals isolated from the above five regions have been characterized by X-ray diffraction, thermal, atomic absorption and X-ray fluorescence analyses. The results obtained indicate the possibility of developing convenient methods for growing single crystals of the aluminum-containing phases, to be used, upon suitable doping with transition metal ions, as active media for tunable solid state lasers. The growth of Al 2(WO 4) 3 single crystals from a high-temperature solution in a solvent with the eutectic composition of Li 2O:WO 3=41:59 (molar ratio) has been demonstrated.