Investigation of KTiOPO4 crystals under an electric field by synchrotron X-ray topography

摘要

The phenomena produced by the application of an electric field along the polar axis c on single crystals of KTiOPO4 were investigated using optical microscopy and synchrotron X-ray topography. Fine lines parallel to the c axis are formed immediately after the application of a d field followed by grey bands growing slowly under an elevated field from the cathode. An improvement in the crystalline quality appears when an alternating field with a frequency of 1 Hz is applied for several hours to the sample. The inversion twin boundary displays a better visibility under an applied field. The present paper summarizes these effects 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 connecting the electrodes.