Stability of the monoclinic phase in the ferroelectric perovskite PbZr1-xTixO3 - art. no. 014103

Recent structural studies of ferroelectric PbZr1-xTixO3 (PZT) with x=0.48, have revealed a monoclinic phase in the vicinity of the morphotropic phase boundary (MPB), previously regarded as the boundary separating the rhombohe dral and tetragonal regions of the PZT phase diagram. In the present paper, the stability region of all three phases has been established from high-re solution synchrotron x-ray powder-diffraction measurements on a series of h ighly homogenous samples with 0.42 less than or equal tox less than or equa l to0.52. At 20 K, the monoclinic phase is stable in the range 0.46 less th an or equal tox less than or equal to0.51, and this range narrows as the te mperature is increased. A first-order phase transition from tetragonal to r hombohedral symmetry is observed only for x=0.45. The MPB, therefore, corre sponds not to the tegragonal-rhombohedral phase boundary, but instead to th e boundary between the tetragonal and monoclinic phases for 0.46 less than or equal tox less than or equal to0.51. This result provides important insi ght into the close relationship between the monoclinic phase and the striki ng piezoelectric properties of PZT; in particular, investigations of poled samples have shown that the monoclinic distortion is the origin of the unus ually high piezoelectric response of PZT.