Strong anisotropy of KTiOPO4 crystals under an electric field observed by synchrotron radiation topography

In-situ white-beam synchrotron radiation topographic observations under an electric field have been made on KTiOPO4 family crystals. The investigation shows a strong enhancement of diffracted intensity of hkl reflections (l not equal 0) and the topographic extinction contrast, when the field is applied along the polar axis. Doped and undoped samples with grown-in defects are studied in detail. It is believed that the movement of K+ ions driven by the field leads to a local accumulation of charges and the lattice distortion. All the field-related phenomena appear to be related to the one-dimensional ionic conductance.