Magnetic-field-induced orientation in Co-doped SrBi2Ta2O9 ferroelectric oxide

Co-doped SrBi2Ta2O9 (SBT) compounds have been synthesized using solid-state reaction between the starting oxides Bi2O3, Ta2O5 and CoO and the carbonate SrCO3. High-resolution x-ray diffraction data were collected on a four-circle diffractometer using synchrotron radiation. The structure of the orthorhombic phase (space group A(1)2am, one formula unit, a = 5.5194((1)) Angstrom, b = 5.5191((1)) Angstrom and c = 25.0309((2)) Angstrom) has been refined using the Rietveld method. Chemical occupancies, atomic positions and spontaneous polarization were deduced from the structural refinement. In order to determine the effects on ferroelectric properties of the Sr-by-Co substitution, the dielectric response was measured over the temperature range 450-750 K on heating and cooling and at several frequencies. Finally, the magnetic field effect on Co-doped SBT powder was investigated by means of x-ray diffraction. It appears that the magnetic field induces a strong fibre texture, with the (c) over right arrow -axes of grains being aligned with the direction of the applied field. This original and unusual phenomenon suggests a new method for the deposition of SBT thin films with enhanced ferroelectric properties.