Physical properties of the 0.12 KLu(WO4)2–0.88 K2W2O7 solution and single-crystal growth of KLu(WO4)2

We have obtained the solubility curve of KLu(WO4)2 in K2W2O7 solvent. From this curve, we have chosen a solution composition, 0.12 KLu(WO4)2–0.88 K2W2O7, for subsequent studies of physical properties, prior to choosing the growth conditions for single-crystal growth from a high-temperature solution. Near the saturation temperature, the density of the solution is 3.98×103 kg/m3, the surface tension is 0.108 N/m and the dynamic viscosity is 37.5×10−3 Pa s, values that are, a priori, suitable for single-crystal growth by Top Seeded Solution Growth-Slow Cooling (TSSG-SC) technique. Taking these results into account, the rotation rate for TSSG-SC was fixed at 40 rpm, while the axial and radial thermal gradients in the solution were 1.5 K/cm. Single crystals of KLu(WO4)2, transparent and free from macroscopic defects, have been obtained for cooling rates up to 0.2 K/h.