Transmission electron microscopy observation of an incommensurate-commensurate transformation in tin-modified lead zirconate titanate

Antiferroelectric tin-modified lead zirconate titanate ceramics (PZST), with 42 at% Sn and 4 at% Ti, were studied by hot- and cold-stage transmission electron microscopy and selected area electron diffraction techniques. The previously reported tetragonal antiferroelectric state is shown to be an incommensurate orthorhombic state. Observations revealed the existence of incommensurate 1/x<110> superlattice reflections below the temperature of the dielectric maximum. The modulation wavelength for this incommensurate structure was found to be metastably locked-in near and below room temperature. An incommensurate-commensurate orthorhombic antiferroelectric transformation was then observed at lower temperatures.