STRUCTURAL CHARACTERIZATION OF K3Li2Nb5O15 SINGLE CRYSTALS BY COMBINING HIGH-RESOLUTION X-RAY DIFFRACTOMETRY AND TOPOGRAPHY

High-resolution multiple-crystal multiple-reflection XRD is used for the structural characterization of nonlinear optical single crystals of K3Li2Nb5O15 (KLN) grown by the micro-pulling-down (mu-PD) method. The combination of high-resolution XRD and topography shows that the lattice parameters along the c-axis (c-parameters) decrease towards the seed crystals, because of the decrease in the K content and increase in the Nb content. However, the KLN single crystals exhibit multi domain structures in which discontinuous changes in the c-parameters are periodically observed along the growth direction, despite the compositional change being continuous. Large mosaic structures due to discontinuous tilt in the lattice planes are also observed at the boundaries between the domains. 29 refs.