room-pressure in the temperature range of 500-650 °C. Comparative studies by high-temperature X-ray diffraction, electron diffraction, thermal analysis, and magnetic investigation revealed the existence of a complex pathway to decomposition, depending on the heating rate, pressure, and atmosphere that involves different metastable phases. In particular the as-prepared monoclinic phase (I) transforms to a second monoclinic form (II) at 210 °C and then to an orthorhombic phase (III) at 490 °C. These phase transitions, fast and reversible, occur on heating with a drop in volume and are moved at higher temperatures when pressure is decreased. The transition from II to III, typically observed in inert atmosphere, can be detected also in air when the heating rate is kept sufficiently high. When III is heated in an oxygen-containing atmosphere a slow irreversible transition to variants IV and then V takes place with kinetics depending on temperature, heating rate, and oxygen partial pressure. Both IV and V are oxidized ferromagnetic phases containing Mn4+ characterized by a modulated structure based on fundamental triclinic perovskite cells. Their magnetic behavior shows a strong analogy with thin films of BiMnO3, suggesting for the latter an oxidized nature and for the former a possible multiferroic behavior.

High-Temperature Polymorphism in Metastable BiMnO3 / Montanari, E; Calestani, Gianluca; Migliori, A; Dapiaggi, M; Bolzoni, F; Cabassi, R; Gilioli, E.. - In: CHEMISTRY OF MATERIALS. - ISSN 0897-4756. - 17(25):(2005), pp. 6457-6467. [10.1021/cm051576w]

High-Temperature Polymorphism in Metastable BiMnO3

CALESTANI, Gianluca;
2005-01-01

Abstract

room-pressure in the temperature range of 500-650 °C. Comparative studies by high-temperature X-ray diffraction, electron diffraction, thermal analysis, and magnetic investigation revealed the existence of a complex pathway to decomposition, depending on the heating rate, pressure, and atmosphere that involves different metastable phases. In particular the as-prepared monoclinic phase (I) transforms to a second monoclinic form (II) at 210 °C and then to an orthorhombic phase (III) at 490 °C. These phase transitions, fast and reversible, occur on heating with a drop in volume and are moved at higher temperatures when pressure is decreased. The transition from II to III, typically observed in inert atmosphere, can be detected also in air when the heating rate is kept sufficiently high. When III is heated in an oxygen-containing atmosphere a slow irreversible transition to variants IV and then V takes place with kinetics depending on temperature, heating rate, and oxygen partial pressure. Both IV and V are oxidized ferromagnetic phases containing Mn4+ characterized by a modulated structure based on fundamental triclinic perovskite cells. Their magnetic behavior shows a strong analogy with thin films of BiMnO3, suggesting for the latter an oxidized nature and for the former a possible multiferroic behavior.
2005
High-Temperature Polymorphism in Metastable BiMnO3 / Montanari, E; Calestani, Gianluca; Migliori, A; Dapiaggi, M; Bolzoni, F; Cabassi, R; Gilioli, E.. - In: CHEMISTRY OF MATERIALS. - ISSN 0897-4756. - 17(25):(2005), pp. 6457-6467. [10.1021/cm051576w]
File in questo prodotto:
File Dimensione Formato  
1444355.pdf

non disponibili

Tipologia: Documento in Post-print
Licenza: Creative commons
Dimensione 862.02 kB
Formato Adobe PDF
862.02 kB Adobe PDF   Visualizza/Apri   Richiedi una copia

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11381/1444355
Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 82
  • ???jsp.display-item.citation.isi??? 76
social impact