In recent years, the stability field of a monoclinic phase at the morphotropic phase boundary in lead zirconate titanate, $\mathrm{Pb}\left[{\mathrm{Zr}}_{1-x}{\mathrm{Ti}}_x\right]{\mathrm{O}}_3$, has been under discussion. In the present study, we investigated samples in the compositional range between $0.40⩽x⩽0.475$ and $x=0.55$ using high-resolution synchrotron x-ray diffraction in combination with transmission electron microscopy and electron paramagnetic resonance to correlate average structure and microstructural information. It is shown that the microstructure plays a crucial role in the analysis of diffraction data. The appearance of intensity in diffraction patterns formerly linked to a monoclinic phase [B. Noheda et al., Phys. Rev. B 61, 8687 (2000)] can directly be correlated to a miniaturization of the average domain structure of the material visible in the presence of nanodomains. The internal symmetry of the nanodomains is not necessarily monoclinic due to coherence effects in diffraction and is discussed with respect to martensitic theory.

• Received 23 October 2006

DOI:https://doi.org/10.1103/PhysRevB.75.184117