Detailed phase evolution analysis, electrical and ferroelectric properties of SrBi2Nb2O9-Bi4Ti3O12 intergrowth Aurivillius phase ceramics

A polycrystalline sample with 2-3 layered intergrowth SrBi2Nb2O9-Bi4Ti3O12 (SrBi6Nb2Ti3O21) ceramics was synthesized by solid-state reaction route using a two-step calcination process. The X-ray diffraction (XRD) analysis and structural refinement revealed pure SrBi6Nb2Ti3O21 phase formation that crystallized in an orthorhombic crystal structure with a 'I2cm' space group. The d-spacing values evaluated from HR-TEM were consistent with the standard XRD. Microstructural analysis using Scanning Electron Microscopy (SEM) justifies grain formation of average size -4.81 mu m possessing plate-like morphology. The epsilon vs T curves showed two dielectric anomalies at -250 C-350 C and -600 C-700 C. The diffuse dielectric peaks depict the relaxor behavior of the ceramics. The conduction mechanism is found to follow the overlapping large polaron tunneling model (OLPT), which elucidates the temperature dependence of power-law exponent 's' and ac conductivity. The relaxation mechanism follows the Maxwell-Wagner relaxation behavior. The ferroelectric hysteresis loop and Positive Up Negative Down (PUND) polarization test confirm the ferroelectric nature of SrBi6Nb2Ti3O21 intergrowth ceramics and the existence of a small value of intrinsic switchable polarization.