Domain-like structures in strontium barium niobate

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Abstract
Domain-like structures are seen in the a-c plane of SrxBa1−x Nb2O6 crystals (SBN 100x) with a polarizing microscope, provided a poling field E 3 is applied. The pattern disappears on heating without field with the remanent polarization. Quite similar structures are seen in SBN 75 crystals with macroscopic defects or after grinding with a coarse abrasive. These “stress-induced” structures disappear only above 500°C in the same way as the incommensurate modulation. The structures fade away in both cases on cooling near - 100°C and reappear near - 40°C. These results are discussed, considering other macroscopic properties, in terms of field- (stress-) induced ferroelectric (ferroelastic) regions within the fully stabilized tetragonal parent phase. A mechanism for explaining the ferroelectric and ferroelastic phase transitions in tungsten-bronze-type crystals is proposed.