XRD, Dielectric, Raman and M & ouml;ssbauer Spectroscopy Studies of a Bi1-xBaxFe1-x(Zn1/3Nb2/3)(x)O-3 System Prepared by the Solid-State Reaction

The solid-state reaction technique was used to produce polycrystalline Bi1-xBaxFe1-x(Zn1/3Nb2/3)(x)O-3 at different substitutions for x = 0, 0.025 and 0.05 (referred to as BFO, BBFZN25, and BBFZN50, respectively). Both x-ray diffraction and Raman spectroscopy revealed that the substitution did not affect the rhombohedral structure of BFO. However, the substitution did not prevent the formation of a second phase, which was identified as Bi25FeO39. The amount of this impurity phase was extracted through Rietveld refinement and was further corroborated by Mossbauer spectroscopy. Lattice parameters were found to be increased owing to substitution of larger ions on average. The substitution not only had an impact on average crystallite size, microstrain and dislocation density of BFO, but also had a significant effect on its dielectric properties. As a result, the dielectric permittivity was enhanced, with a notable reduction in dielectric loss. In particular, the magnitude of dielectric permittivity for the optimal composition BBFZN25 reached a value of 360 at room temperature (RT), which is much greater than that for pure BFO. This higher dielectric constant may be attributable to the larger average crystallite size. The reduction in dielectric loss, at RT, suggests an improvement in the electrical resistivity of BFO, caused by the reduction of the creation of oxygen vacancies and the generation of Fe2+. The non-formation of Fe2+ was verified through Mossbauer spectroscopy. The remarkable increase in the dielectric constant for BBFZN25 at higher temperatures (T > RT) is attributed to the interfacial polarization occurring at grain-grain boundary and internal barrier layers related to the Bi25FeO39 phase.

Automated summary

The solid-state reaction technique was used to produce polycrystalline Bi1-xBaxFe1-x(Zn1/3Nb2/3)(x)O-3 at different substitutions. The substitution did not affect the rhombohedral structure of BFO but did lead to the formation of a second phase, Bi25FeO39. The substitution also had an impact on the dielectric properties, with an increase in dielectric permittivity and a reduction in dielectric loss.