Ferroelectric–ferroelastic rare earth (RE) molybdates RE2(MoO4)3 have been prepared by the conventional solid-state synthesis and X-ray powder diffraction has been collected using two diffractometers PANalytical
X'Pert Pro at room temperature. The crystal structures have been calculated by Rietveld refinement, using a new symmetry modes procedure in order to evaluate the correlation between the distortions, with respect to
the paraelectric–paraelastic structure, with the ionic radii. Although the coordinates of the oxygen atoms are not very precise and accurate, we have observed different behavior of the ferroelastic–ferroelectric order
parameter.
