Lattice parameter fluctuations of relaxor ferroelectrics determined by X-ray diffraction method

Relaxor ferroelectrics possess prominent dielectric and piezoelectric properties thus have been utilized in many advanced electromechanical devices. However, the atomic-scale mechanism of their excellent electromechanical properties remains vague, which hinders the development of high-performance ferroelectrics. In this work, we investigated the lattice parameter fluctuations for Pb(Mg_1/3Nb_2/3)O₃–PbTiO₃ relaxor ferroelectric ceramics, with a comparison of non-relaxor ferroelectric ceramics, including BaTiO₃, SrTiO₃, and Pb(Zr,Ti)O₃, at their respective paraelectric phase by X-ray diffraction. We found that the fluctuations of lattice parameter were much larger in relaxor ferroelectrics than that in conventional ferroelectrics in the paraelectric phase, revealing a significant distinction between relaxor ferroelectrics and conventional ferroelectrics from the respect of atomic arrangement. Transmission electron microscopy experiments and X-ray scattering-intensity simulations indicated that the large fluctuations of lattice parameter in relaxor ferroelectrics can be attributed to the ordered–disordered arrangement of B-site cations at the nanoscale. This work offers a new method to study the chemical arrangement difference between relaxor ferroelectrics and conventional ferroelectrics and may help us to explore the atomic-scale origin of ultrahigh piezoelectric properties in relaxor ferroelectrics.