Relaxor behavior of bismuth layer-structured ferroelectric ceramic with m=2m=2

In this paper, the crystal structure, dielectric and ferroelectric studies of PbBi2Nb2O9 and Pb0.8Ba0.2Bi2Nb2O9 ceramics are reported. X-ray structural studies along with Rietveld refinement confirmed it to be an m=2m=2 member of the Aurivillius family of oxides and the refined lattice parameters are calculated. The orthorhombic distortion decreases with increasing dopant radius. The decrease of the orthorhombic distortion further causes a decrease of the Curie temperature. It can be inferred that substitution of Pb by the larger cation Ba2+ would lead to a lower thermal energy for phase transition. Broad dielectric maxima, which shift to higher temperature with increasing frequency, and the value of the relaxation parameter γγ which is above 1 (estimated from the linear fit of the modified Curie–Weiss law with other empirical parameters ΔTm, ΔTrelax) indicate the relaxor nature for PBBN ceramics. Well-developed P–EP–E hysteresis loops are obtained from PBBN samples. The PrPr values are improved to 10.5 μC/cm2 at 423 K when Ba2+ is introduced into the PBN-based ceramic.