Electrical Relaxation Studies on Lanthanum and Vanadium Modified Bi 4 Ti 3 O 12.

Lanthanum and vanadium modified polycrystalline material of La0.75Bi3.25Ti2.9625V0.03O12(BLVT) of Aurivillius family, was prepared by conventional solid-state reaction method. X-ray diffraction showed single phase with orthorhombic structure. Electron microcopy was done on as-sintered and oxygen-annealed samples. Impedance studies of BLVT showed multiple impedance relaxations. Based on the impedance factor (related to full width at half maximum) and master plots, the relaxations are found to be collectively competitive. A broad dielectric peak and Curie-Weiss diffused parameter indicates diffused phase transition. Complex impedance analysis along with the log-log spectroscopic plots was studied on BLVT at 500°C. But complex impedance plot of BLVT showed single broad semicircle, unlike La0.75Bi3.25Ti3O12(BLT), which showed three semicircles on separately coated silver- and platinum- ceramic disks. However, complex modulus plot (complimentary to impedance) of BLVT showed three semicircles, which clearly indicates the tendency of formation of space charges, which might result in the accumulation of defects at electrode-ferroelectric interfaces, and considered to be a characteristic feature of the sample. In view of this, some of the BLVT samples were annealed in oxygen- and vacuum. Detailed ac-conductivity analysis suggests that double oxygen vacancies play vital role in conduction phenomenon. [ABSTRACT FROM AUTHOR]