Microstructure and ferroelectric properties of (Ca1−xSrx)3(Ti1−yMny)2O7 ceramics.

(Ca_1−xSr_x)₃(Ti_1−yMn_y)₂O₇ (CSTMO) ceramics with hybrid improper ferroelectricity were prepared by conventional solid-state reaction method. Effect of Sr²⁺ and Mn⁴⁺ contents on microstructure, dielectric and ferroelectric properties have been systematically investigated. The XRD results show that CSTMO ceramics is single phase with orthorhombic structure. The lattice constants and average grain size increase with the increasing of Sr²⁺ content and decrease with the increasing of Mn⁴⁺ content. The introduction of Mn⁴⁺ deteriorates the densification of CSTMO ceramics to some extent, and the substitution of Sr²⁺ with higher content can improve the densification by promoting a rapid interdiffusion movement via grain-boundary. (Ca_0.8Sr_0.2)₃(Ti_0.9Mn_0.1)₂O₇ ceramics present the highest dielectric constant and dielectric loss, while the dielectric loss of (Ca_0.8Sr_0.2)₃(Ti_0.95Mn_0.05)₂O₇ ceramics has a significant reduction. The leakage current of CSTMO ceramics decreases with the increasing of Sr²⁺ and Mn⁴⁺ content. The leakage behavior suggests that the Ohmic conduction and Schottky emission dominate the leakage current of CSTMO ceramics. Moreover, the remnant polarization decreases with the increasing of Sr²⁺ because of its suppression for the rotating and tilting angle (a⁻a⁻c⁺) of oxygen octahedron. And the electrical polarization decreases with the increasing of Mn⁴⁺ content due to the instability of MnO₆ rotation. [ABSTRACT FROM AUTHOR]