INVESTIGATION OF KTIOPO4 CRYSTALS UNDER AN ELECTRIC-FIELD BY SYNCHROTRON X-RAY TOPOGRAPHY

The phenomena produced by the application of an electric field along t he polar axis c on single crystals of KTiOPO4 were investigated using optical microscopy and synchrotron X-ray topography. Fine lines parall el to the c axis are formed immediately after the application of a d f ield followed by grey bands growing slowly under an elevated field fro m the cathode. An improvement in the crystalline quality appears when an alternating field with a frequency of 1 Hz is applied for several h ours to the sample. The inversion twin boundary displays a better visi bility under an applied field. The present paper summarizes these effe cts with particular emphasis on the lines parallel to the c axis. The new results, especially measurements in an alternating electric field and experiments at low temperatures, suggest that the origin of these lines is not quasi-one-dimensional ionic conductivity, but a strongly anisotropic and inhomogeneous polarization in narrow channels connecti ng the electrodes.