Synthesis and Characterization of La and Nb substituted Bi4Ti3O12 ferroelectric ceramics

Polycrystalline ceramic samples of Bi3.5La0.5Ti3-yNbyO12 (y=0.02, 0.04, 0.06 & 0.1) have been synthesized by standard solid state reaction method. The effect of lanthanum substitution on Bi-site and Nb substitution on Ti-site on the structural and electrical properties of Bi4Ti3O12 powders was investigated by X-ray diffraction, dc conductivity and dielectric measurements. A better agreement between the observed and calculated X-ray diffraction pattern was obtained by performing the Rietveld refinement with a structural model using the non centrosymmetric space group Fmmm. The substitution of Nb for Ti ions modified the dielectric properties leading to more resistive ceramic compounds. The activation energies of all the compounds were calculated by measuring its dc electrical conductivities. The temperature dependent dielectric behavior of all the compounds have also been studied and the results are discussed in detail. The substitution of La and Nb on the Bi and Ti site decreased the T-c and improved the ferroelectric and dielectric behaviour.