High permittivity short-range orthorhombic Q phase in CaTiO3 modified NaNbO3 ceramics

The structural evolution and electrical behaviour of (1−x) NaNbO3-xCaTiO3(NN-CT) ceramics were investigated in this study. X-ray diffraction and full-pattern Rietveld refinement confirm that CT incorporation disrupts the long-range antipolar orthorhombic Pbcm phase. The dielectric permittivity peak shifts to lower temperatures as the CT concentration increases. The highest permittivity of 2365 was obtained for x = 0.15 at room temperature. Synchrotron X-ray scattering coupled with pair distribution function (PDF) analysis reveals the existence of a short-range ordered polar orthorhombic P21ma (Q) phase with a correlation length of approximately 5 nm. A slim ferroelectric polarisation-electric field (P-E) loop, consistent with short-range ordered behaviour, was obtained in the NN-0.15CT, yielding an enhanced recoverable energy density by over 300 % at 150 kV cm⁻¹compared to pure NN. These findings establish the role of CT doping in modifying structural and dielectric properties, contributing to the understanding of crystal symmetry evolution and its impact on the dielectric response of this promising, environmentally friendly lead-free perovskite oxide for high-performance dielectric applications.