Single Crystal Growth and Hierarchical Ferroelectric Domain Structure of (1-x)BiFeO3-xPbTiO3 Solid Solutions

Besides outstanding multiferroic performance, BiFeO3 has recently demonstrated a potential for novel promising applications in domain wall nanoelectronics employing domain walls with different functional properties. Rarely observed in ferroelectrics, charged domain walls are of special interest for such applications as they possess enhanced electric conductivity. In this work, single crystals of the multiferroic (1-x)BiFeO3-xPbTiO(3) solid solution were successfully grown using a flux method. Structural characterization by X-ray diffraction confirmed perovskite rhombohedral R3c and tetragonal P4mm phases in crystals with x approximate to 0.2 and x approximate to 0.6, respectively. The domain structure of crystals was established with the help of polarized light microscopy, scanning electron microscopy, and piezoresponse force microscopy. In tetragonal crystals, a complex hierarchical structure of 90 degrees lamella domains is observed with the thickness of lamellae varying from dozens of nanometers to dozens of micrometers. In the rhombohedral composition, twin 109 degrees domains are realized with the domain width of about several micrometers. Besides, the nano- and submicrometer sized rounded 180 degrees domains are embedded randomly among twin domains in both tetragonal and rhombohedral crystals. Mechanical and electrical compatibility conditions are satisfied for all observed 90 degrees and 109 degrees domain walls. However, the 180 degrees walls in tetragonal crystals are proved to be charged. Successful fabrication of high-quality single crystals with the desirable structures of charged and uncharged domain walls can enhance the multiferroic performance and also open a door to explore promising domain boundaries related phenomena.