Influence of lanthanum doping on the morphotropic phase boundaryof lead zirconate titanate

A phase diagram for morphotropic ( Pb 0.985 La 0.01 ) ( Zr 1 − x Ti x ) O 3 is proposed based on a combination of X-ray and neutron powder diffraction experiments and complemented by transmission electron microscopy. Dependent on composition three regions are characterized. The stability range of tetragonal microdomains for high Ti contents, the stability range of rhombohedral microdomains for low Ti contents, and an intermediate stability range of nanodomains. All three regions exhibit a corresponding low temperature configuration. Temperature dependent diffraction revealed that lanthanum doping reduces the sensitivity of the structure to changes in temperature and composition. A continuous transition from pseudorhombohedral to tetragonal symmetry with an intermediate two-phase region at the morphotropic phase boundary is observed. A similar transition of low temperature superstructure phases from pseudorhombohedral to pseudotetragonal with an intermediate monoclinic phase governed by a continuous change in the oxygen octahedral tilt system from a − a − a − over a − a − c − to a 0 a 0 c − is identified.