Structural, dielectric, and electrical studies of Sm-doped Sr0.95Ba0.05Bi2Nb2O9 lead-free relaxor ceramics

Abstract

Raw materials were etched by nitric acid to release utterly carbon dioxide. An excess of citric acid was then employed as fuel to prime the combustion reaction for the synthesis of Sr_0.95Ba_0.05Bi_2−xSm_xNb₂O₉ (x = 0 (SrBi₂Nb₂O₉), 0.1, and 0.2) compounds. X-ray diffraction, Fourier-transformed infrared, and Raman techniques revealed quite certain that there is a link between dopant amounts and structural changes. One is that the cell volume was smoothly reduced. Second, the bond force constant decreased slightly when the dopant was introduced into the lattice. Even though the SrBi₂Nb₂O₉ compound is not only doped by samarium but also by barium, samarium is the only dopant that affects dielectric and electrical properties. Doping with samarium enhances the dielectric constant at room temperature by reducing the Curie temperature, and it turns ferroelectric normal into relaxor behavior. The results of AC conductivity and electrical modulus laid out that one extreme defect was that a significant amount of cation exchange occurs in Sr_0.95Ba_0.05Bi_2−xSm_xNb₂O₉ samples and a large amount of oxygen vacancies were released. Overlapping large polaron tunneling model (OLPT) mechanisms was the adequate model for these compounds.