Influence of short-range and long-range order on the evolution of the morphotropic phase boundary in Pb Zr[sub 1−x]Ti[sub x] O₃

Abstract

The local structures of rhombohedral, monoclinic, and tetragonal phases across the morphotropic phase boundary (MPB) of Pb(Zr[sub 1−x]Ti[sub x])O₃ are discussed in terms of the progression from short-range to long-range and back to short-range structural order. It is shown that, provided one considers the structures on a suitably small length scale, all three phases can be considered to be monoclinic at the local level and that there need not be any discrete phase boundaries across the MPB. Electron diffraction experiments showing significant variations in diffuse streaking, illustrating the progression from short-range to long-range order, are presented in support of this model. It is suggested that it is the change in the range of structural order that plays the most important role in the increase in electrical and electromechanical properties around the MPB.