Structural, dielectric and Raman spectroscopy investigations of Ba1-xBi2x/3(Fe0.5Nb0.5)0.025Ti0.975O3 ceramics

This research work reports the structural, dielectric, and Raman scattering studies of Ba1-xBi2x/3(Fe0.5Nb0.5)(0.025)Ti0.975O3 (x = 0-0.15) polycrystalline samples synthesized by the solid state reaction method. The crystalline structure, Raman, and die-lectric properties were investigated. The ceramic samples whose compositions x <= 0.075 exhibit a tetragonal P4mm symmetry, while the compositions with 0.10 <= x <= 0.15 crystallize in a cubic phase with a Pm3_m space group. Dielectric studies reveal a transition from classical to relaxor ferroelectrics with an increasing substitution rate x in Ba1-xBi2x/3(Fe0.5Nb0.5)(0.025)Ti0.975O3 ceramics. The relaxor behavior observed for 0.10 <= x <= 0.15 was highlighted by a significant dielectric anomaly, in which the maximum temperature Tm was substantially dependent on frequency and went towards low temperature with rising Bi. For the compound x = 0.15, the maximum of epsilon(r) is around 3000 at room temperature (293 K) and the value of delta T-m is 33 K. These values of E' r in the literature. The relaxor behavior was modeled using the Vogel-Fulcher relation. The Raman spectroscopy analysis demonstrates that the influence of the rate of Ba2+ substitution by Bi3+ may be shown via E (TO2) and A(1) (TO3) modes. In the same line, the substantial displacement at the off-centered A location can be attributed to the Bi impurity causing the formation of polar clusters, which drove the transition from classical to relaxor ferroelectrics. This is supported by the ste-reochemical effect of the 6s(2) lone pair electrons of Bi3+ as well as the significant ionic radius difference between Ba2+ and Bi3+. Furthermore, a thermal study of Raman spectral response to composition backs up our dielectric findings. and delta Tm are very important for relaxor materials by comparing them with those that are already published