Structure of Pb(Zr, Ti)O[sub 3] near the morphotropic phase boundary

Abstract

The atomic structure of Pb(Zr, Ti)O3 solid solutions near the morphotropic phase boundary (MPB) was examined using time-of-flight neutron diffraction. In addition to the conventional crystallographic refinement the atomic pair distribution function (PDF) analysis was used. Crystallographic analysis suggests that the average structure changes significantly through the MPB. However, the PDF analysis, which is more accurate in describing the local structure, shows that changes are more gradual. In particular the PDF suggests that the local environment of each element remains relatively invariant of composition. Ti is always ferroelectrically active, while Zr is not. Pb is always displaced against oxygen atoms and forms short bonds at about 2.45 A. What changes most with the Ti/Zr ratio is the distribution in the direction of Pb displacement. It is suggested that the population of local Pb displacements changes between 〈100〉 and 〈110〉 in the pseudocubic notation with the Ti/Zr ratio, and the MPB is a crossove...