Predicted and Real Habits of Flux Grown Potassium Lutetium Tungstate Single Crystals

The laser host crystals of KLu(WO4)2(KLuW) with large dimensions up to 43 × 35 × 16 mm3 have
been grown along b, a*, c, and [1̄11] crystallographic directions, respectively, from the melt by the top-seeded solution
growth slow-cooling method. The crystal structure was refined by using a four circle X-ray diffractometer:  The unit
cell parameters are a = 10.591(5) Å, b = 10.244(6) Å, c = 7.500(3) Å, and β = 130.73(2)° with Z = 4, in space group
C2/c. The experimentally grown crystal shapes developed along different crystalline directions were compared to
the predicted habits, and the influences of seed orientations on the crystal growth habits, quality, and utilization
ratio are analyzed by Bravais−Friedel Donnay−Harker law and PBC‘ theory. We found that crystals grown along
c directions have higher utilization ratios and good optical qualities. Crystals with a high growth rate but worse
quality along the b and a* directions can be obtained. Too flat and inner macrodefects extended from the seeds
make low utilization ratios for crystals grown along the b and a* directions.