Relaxor dielectric properties of lead-free Bi4Ti3O12/Bi4.5Na0.5Ti4O15 intergrowth ceramics

Abstract Intergrowth ceramic series Bi4Ti3O12/Bi4.5Na0.5Ti4O15 have been prepared through solid state reaction. X-ray diffraction analysis shows the coexistence of Bi4Ti3O12 and Bi4.5Na0.5Ti4O15 phases with slight lattice distortion. Scanning electron micrographs present the growth of grains and grain boundaries with different contents of Bi4.5Na0.5Ti4O15. The relaxation dielectric properties of the ceramics have been observed. The room-temperature dielectric constant at 100 Hz is initially increased and then decreased with the increase of Bi4.5Na0.5Ti4O15. The impedance spectroscopy and the electrical modulus are also measured for explaining the dielectric behavior. The Nyquist plots display different semicircle arcs at 300 and 600 K. The imaginary part of electrical modulus has two peaks in the range of the measuring temperature. They prove the common influence of grains and grain boundaries on the dielectric properties. For further fitting the experimental data by Arrhenius theory, activation energy is obtained for grains and grain boundaries. Finally, the relaxor dielectric properties are attributed to the competition mechanism from the different growth situation of grains and grain boundaries with increasing Bi4.5Na0.5Ti4O15. Therefore, this kind of ceramics ought to be promising candidates for multifunctional device applications.