Structural, spectroscopic, and dielectric characterizations of Mn-doped 0.67BiFeO3-0.33BaTiO3 multiferroic ceramics

0.67BiFeO(3)-0.33BaTiO(3) multiferroic ceramics doped with x mol% MnO2 (x = 2-10) were synthesized by solid-state reaction. The formation of a perovskite phase with rhombohedral symmetry was confirmed by X-ray diffraction (XRD). The average grain sizes were reduced from 0.80 mu m to 0.50 mu m as increasing the Mn-doped levels. Single crystalline nature of the grains was revealed by high-resolution transmission electron microscopy (HRTEM) images and electron diffraction patterns. Polar nano-sized ferroelectric domains with an average size of 9 nm randomly distributed in the ceramic samples were revealed by TEM images. Ferroelectric domain lamellae (71 degrees ferroelectric domains) with an average width of 5 nm were also observed. Vibrational modes were examined by Raman spectra, where only four Raman peaks at 272 cm. 1 (E-4 mode), 496 cm(-1) (A(1)-4 mode), 639 cm(-1), and 1338 cm(-1) were observed. The blue shifts in the E-4 and A(1)-4 Raman mode frequencies were interpreted by a spring oscillator model. The dieletric constants of the present ceramics as a function of the Mn-doped levels exhibited a V-typed curve. They were in the range of 350-700 measured at 10(3) Hz, and the corresponding dielectric losses were in range of 0.43-0.96, approaching to 0.09 at 10(6) Hz.