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Synchrotron-radiation topographic observations have shown that the Cu-doped (Ba0.25Sr0.75)0.9(K0.5Na0.5)0.2Nb2O6 crystal has a strong ferroelectric x-ray anomalous-scattering effect at the wavelength near the absorption edge of Ba atoms. The reversal of anomalous contrast of antiparallel domains in the crystal was directly revealed in the topographs of hkl and hkl̄ reflections. It was found that the domain walls are all polar and are formed to compensate the charges resulting from the inhomogeneous distributions of the metal atoms in the bulk crystal.

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Single crystals of potassium sodium strontium barium niobate (KNSBN) and cobalt-modified KNSBN were prepared using the Czochralski technique. The ferroelectric hysteresis loops and the infrared reflectivity spectra were collected. Compared with the undoped KNSBN crystals, the cobalt-modified crystals have stable hysteresis loops, whose spontaneous polarization is about 0.17 C/m2 and coercive field strength is about 670 V/mm, but those of the undoped KNSBN crystals are about 0.04 C/m2 and 530 V/mm, respectively. The measured infrared reflectivities vary with the orientations of the dipole moments owing to the Co doping. The c axis becomes the most stable orientation of the dipole moments, and the polarization can be locked and does not recede when the cobalt-modified crystals are polarized into a single domain.

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