Pressure-induced structural phase transitions in the multiferroic four-layer Aurivillius ceramic Bi5FeTi3O15.

The structural stability of the multiferroic four-layer Aurivillius ceramic Bi 5 FeTi 3 O 15 (BFTO) under hydrostatic pressure was investigated in situ by synchrotron X-ray powder diffraction (SXRPD) and Raman spectroscopy. Measurements performed up to 15 GPa allowed the identification of two well-defined structural phase transitions. The orthorhombic phase (at ambient conditions) transforms into a tetragonal one around 3.2 GPa and a new orthorhombic phase rises around 7.5 GPa. Both phase transitions are evidenced by the pressure dependence of the lattice parameters and vibrational mode frequencies. The analysis of the induced strain indicates that the transitions are of second-order and first-order, respectively. Subtle changes in the Raman spectra and powder patterns suggest the onset of a new phase around 10.5 GPa. [ABSTRACT FROM AUTHOR]