Relaxor transition and properties of Mn-doped Sr_xBa_1−xNb₂O₆ ferroelectric ceramics

Pure and Mn-doped Sr_xBa_1−xNb₂O₆ (SBN) ceramics were prepared by the conventional solid state reaction method and their morphology, phase structure, relaxor behavior, ferroelectric and energy storage properties were investigated to reveal the effects of Mn doping on their properties. The results show that all the samples are single tetragonal tungsten bronze structure and the Mn element having few influences on their microstructures. The dielectric constant of pure SBN samples shows a classical relaxor behavior with obvious frequency dispersion and fits well with the Vogel–Fulcher law. However, the dielectric constant of Mn-doped samples does not show frequency dispersion. Then the relaxor behaviors of both pure and doped samples were further investigated by fitting the dielectric constant to the modified Curie-Weiss law. It was found that the diffusion parameters (γ) of Mn-doped samples are close to those pure samples, which indicates that the Mn-doped samples still have relaxor characteristics even without the classical dielectric frequency dispersion. Compared with the pure samples, the Mn-doped samples have a slimmer polarization-electric field (P-E) hysteresis loop, which can also prove their relaxor behaviors. The investigations of energy storage properties reveal that the Mn-doped samples have a higher energy storage density and efficiency.