Microstructure, dielectric and ferroelectric properties of (1-x)Bi0.5Na0.5TiO3-x(0.8Ba0.9Sr0.1TiO3-0.2BiFeO3) lead-free ceramics

(1-x)Na0.5Bi0.5TiO3-x(0.8Ba0.9Sr0.1TiO3-0.2BiFeO3)[(1-x) NBT-x(0.8BST-0.2BFO), x = 0, 0.04, 0.08, 0.12]) ceramics were prepared by conventional solid reaction method, and the effects of composition on the microstructure and electrical properties were comparatively studied. The X-ray diffraction results confirm a pure perovskite structure and a cubic structure of the ceramics possess, no obvious impurity phase can be observed. In addition, compared with x = 0, the diffraction peak intensities of other components shift to the left side, indicating that BST and BFO have been entered into the NBT lattice in varying degrees. There are two different morphologies of grains, indicating the uniform distribution of composition, and the grain size along the length direction ranges from 6.19 μm (x = 0.08) to 14.35 μm (x = 0.04). The addition of 0.8BST-0.2BFO retards the grain growth and induces two dielectric anomalies at high temperatures, and the relaxation process has been proved. The dielectric constant of the sample x = 0.08 is the lowest, which is smaller than 800, while it raises to larger than 1000 when x = 0.04. The Curie temperature decreases significantly after doping. After a large amount of BST and BFO doping, the ferroelectric long-range order of the ceramics is destroyed, and the hysteresis loop changes to elongated shape. When the doping amount is x = 0.04, a larger remanant polarization ~ 25 μC/cm2) is obtained. The ferroelectric hysteresis loops with high concentration of 0.8BST-0.2BFO show more slim shape, indicating stronger relaxation behavior.