Interferometric studies of domain structures in potassium niobate single crystals

Abstract

Interferometric studies of domain structures in KNbO3 single crystals, grown by using excess of K2CO3 as a flux are reported. The surface deformations produced on the pseudocubic (001) planes by the stable patterns of 90°, 60° and 180° domains have been studied and discussed. If the observed plane is not the plane of the shear, the 90° domains are inclined at 30prime. The angle between the 60° domains is 57prime for the domain line, parallel to a pseudocubic edge. The head to tail coupling of dipoles across the 60° domain walls gives a step ladder structure on the surface. The nature of dipole coupling in a step ladder due to 90° domains cannot, however, be distinguished. The wedges are all 60° wedges, with the wedge angle 57prime. The theoretical formulae have been derived, and the values found to agree closely with the experimental values.