Changing the crystal phase structure and dielectric properties of Sr4-xBaxSmFe0.5Nb9.5O30 ceramics by adjusting the vacancy

In this paper, a new type of lead-free ceramic of Sr4-xBaxSmFe0.5Nb9.5O30 (x = 0, 0.25, 0.5, 0.75 and 1, abbreviated as SBSFN) was prepared by high-temperature solid-phase synthesis. With the increase of x, the packing fraction in the unit cell increases, the vacancy decreases, and the orthogonal phase transforms into the tetragonal phase. The XRD and refinement results show the distortion in the BO6 octahedron variety as the vacancy decreases. When x increases from 0.5 to 1, and the peak value of the dielectric constant (epsilon r) increases from 215 to 665 (10 kHz). With the fluctuation of the composition, the relaxation phenomenon is obvious. The impedance data show that there are crystal grains and grain boundaries at high temperature, and all samples undergo a relaxation thermal activation process. The breakdown field strength and remnant polarization of the ceramics increase with increasing x, which indicates that the ferroelectric properties of these ceramics improve.(c) 2022 Elsevier B.V. All rights reserved.