Dielectric properties, Mossbauer study, ESR spectra of Bi2FeTa2O9.5 with pyrochlore structure

The pyrochlore with the composition Bi2FeTa2O9.5 was obtained by solid-phase synthesis. The electronic state and the nature of the local environment of iron atoms were studied by electron spin resonance (ESR) and Mossbauer spectroscopy. In the Bi2FeTa2O9.5 ESR spectra a dipolar-broadened line with g similar to 2.05 from Fe3+ ion clusters are observed. This line is the superposition of components with widths of about 150 and 400 mT. On the low-field wing of the band, there is a feature with g similar to 4.3 relating to trace amounts of isolated Fe3+ ions in an octahedral position with a strong rhombic distortion. The Mossbauer spectrum of the Bi2FeTa2O9.5 compound demonstrates a slightly asymmetric doublet. The form of the doublet is re-produced by a superposition of a doublet and a singlet. About 93% of the spectral area of the paramagnetic part of the spectrum falls on the Fe(III)-doublet with IS = 0.365 +/- 0.0020 mm/s, QS = 0.604 +/- 0.034 mm/s, correlated with Fe3+ ions in regular axial octahedral positions. The remaining part is represented by a Fe(III)singlet with IS = 0.176 +/- 0.0288 mm/s from Fe3+ ions in a symmetric environment. The electrical properties of the compound were studied at temperatures of 20 - 450 degrees C in the frequency range of 25 Hz - 1 MHz. It was found that synthesized ceramics exhibit dielectric properties. The permittivity and the dielectric loss tangent at 20 degrees C were determined and are 57 and 0.003 (1 MHz), respectively. (C) 2022 Published by Elsevier B.V.

Automated summary

The pyrochlore compound Bi2FeTa2O9.5 was synthesized by solid-phase synthesis. Electron spin resonance (ESR) and Mossbauer spectroscopy were used to investigate the electronic state and local environment of iron atoms. The compound exhibited dielectric properties, and its electrical properties were studied in a wide temperature and frequency range.