Investigations of Low Temperature Phase Transitions in BiFeO3 Ceramic by Infrared Spectroscopy

In this paper, results of new infrared FIR-MIR measurements (wavenumber range of 4000-100 cm(-1)) in the range of the temperature 300 divided by 8 K of the BiFeO3 ceramic are presented. Below 200 K only one symmetric band at ca. 800 cm(-1) is visible. The full width at half maximum of this band decreases exponentially on cooling. The shape of the band at ca. 545 cm(-1) connected with A1 (TO) mode also changes between 60-40 K, this is in the vicinity of the phase transition at 50 K. Initially a broad band reveals its components as shoulder bands. Theirs FWHM decrease with cooling.