Centrosymmetric to non-centrosymmetric transition in the Ca_2−xMn_xTi₂O₆ double perovskite system studied through structural analysis and dielectric properties

We have used high-pressure synthesis to synthesize samples of Ca_2−xMn_xTi₂O₆ double perovskite, where x varies between 0.2 and 1. The synthesized materials were structurally characterized with powder X-ray diffraction (XRD). Rietveld refinement of the XRD patterns was used to study the change from CaTiO₃ (x = 0) to the composition CaMnTi₂O₆ (x = 1) where half of the Ca(ii) ions are replaced by smaller Mn(ii) ions. We analyzed the peak shapes in the XRD patterns, as well as lattice parameters, and it appears that smooth symmetry change from the centrosymmetric space group Pbnm to the non-centrosymmetric space group P4₂mc occurs between x = 0.3 and x = 0.5. We also confirmed the centrosymmetric to non-centrosymmetric transition by characterizing the dielectric properties of the materials with ferroelectric measurements.