Monoclinic phase in the relaxor-based piezoelectric/ferroelectric (formula presented) system

A ferroelectric monoclinic phase of space group Cm (formula presented) type) has been discovered in (formula presented) by means of high-resolution synchrotron x-ray diffraction. It appears at room temperature in a single crystal previously poled under an electric field of 43 kV/cm applied along the pseudocubic [001] direction, in the region of the phase diagram around the morphotropic phase boundary between the rhombohedral (formula presented) and the tetragonal (formula presented) phases. The monoclinic phase has lattice parameters (formula presented) (formula presented) (formula presented) and (formula presented) with the (formula presented) axis oriented along the pseudocubic [110] direction. It is similar to the monoclinic phase observed in (formula presented) but different from that recently found in (formula presented) which is of space group Pm (formula presented) type).