Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. We report on extensive experimental studies on thin film, single crystal, and ceramics of multiferroic bismuth ferrite BiFeO 3 using differential thermal analysis, high-temperature polarized light microscopy, hightemperature and polarized Raman spectroscopy, high-temperature x-ray diffraction, dc conductivity, optical absorption and reflectivity, and domain imaging, and show that epitaxial ͑001͒ thin films of BiFeO 3 are clearly monoclinic at room temperature, in agreement with recent synchrotron studies but in disagreement with all other earlier reported results. We report an orthorhombic order-disorder ␤ phase between 820 and 925 ͑Ϯ5͒°C, and establish the existence range of the cubic ␥ phase between 925 ͑Ϯ5͒ and 933 ͑Ϯ5͒°C, contrary to all recent reports. We also report the refined Bi 2 O 3 -Fe 2 O 3 phase diagram. The phase transition sequence rhombohedral-orthorhombic-cubic in bulk ͓monoclinic-orthorhombic-cubic in ͑001͒BiFeO 3 thin film͔ differs distinctly from that of BaTiO 3 . The transition to the cubic ␥ phase causes an abrupt collapse of the band gap toward zero ͑insulator-metal transition͒ at the orthorhombic-cubic ␤-␥ transition around 930°C. Our band structure models, high-temperature dc resistivity, and light absorption and reflectivity measurements are consistent with this metal-insulator transition.

The original manuscript gives assignment of all A 1 ͑LO͒ and E͑TO͒ phonon modes and the lowest-frequency A 1 ͑TO͒ mode in bismuth ferrite ͑BiFeO 3 ͒ single crystal. The scattering geometry for observing A 1 ͑TO͒ modes is Y͑ZZ͒Ȳ . However, the room-temperature spectrum in this orientation was quite weak, and the peaks appeared as shoulders over the strong Rayleigh scattering. Therefore, A 1 ͑TO͒ modes could not be extracted accurately due to heavily dominating Rayleigh scattering. At least two of the three higher-frequency A 1 ͑TO͒ modes ͑127, 168, and 212 cm −1 marked with "?" in Fig. 2͒ listed as A 1 ͑TO͒ in Table I are incorrect, because such assignments violate the required alternation of A 1 ͑TO͒ and A 1 ͑LO͒ modes with increasing frequency. The alteration rule follows from the requirement that the poles and zeroes of the dielectric constant along a given axis of any medium must necessarily alternate.

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