Potassium lithium niobate: single-phase domain boundary in the 30 mol% K2O isopleth of the ternary system Li2O–K2O–Nb2O5 and characterization of single-crystal fibers

K3Li2−xNb5+xO15+2x (x < 0.5, KLN) crystals are very promising for blue-light second harmonic generation, and their growth conditions are important to know. For this purpose, the limit of the solid solution range in the 30 mol% K2O isopleth of the ternary system Li2O–K2O–Nb2O5, to which KLN crystals belong, was investigated by powder X-ray diffraction (XRD). Several crystals with different compositions x were also pulled by the LHPG (laser-heated pedestal growth) technique and characterized by energy-dispersive system (EDS) microprobe analysis, absorption spectra measurements, phase matching studies, and Raman microspectroscopy.