Abstract
The flux growth experiments of stoichiometric LiNbO
3 crystals were carried out at a low vertical temperature gradient from the fluxed melts with molar ratios of K
2O/LiNbO
3=0.16 and 0.19. The crystals were pulled along different directions perpendicular to
X-cut,
Y-cut,
Z-cut and facet-cut planes. Crystal structure and inclusions-related defects were analyzed by X-ray diffraction (XRD) method. The stoichiometry of the as-grown crystal, which depended on its ultraviolet absorption edge, was studied by measuring its transmittance spectrum. The shape and facet morphology of crystal-melt interfaces for different growth directions were studied by X-ray orientation and projection analysis. It was found that the crystals grown under our thermal conditions exhibited a very strong tendency towards faceting. Highly convex and facet-bounded interfaces were observed for the growth directions perpendicular to the
Z-cut,
X-cut and
Y-cut planes. The central part of the interface was always broken and contained a lot of inclusions due to the formation of many small pyramids consisting of (0
1
2),
(1
1
̄
2)
and
(
1
̄
02)
facets. It was shown that the growth direction perpendicular to the facet was favorable for growing high quality stoichiometric LiNbO
3 crystals at the low vertical temperature gradient.