Characterization of Metastable Phases Solidified from Undercooled LuFeO3 Melt
- Paper number
IAC-07-A2.4.05
- Author
Mr. Malahalli Shankare Gowda Vijaya Kumar, Tokyo Metropolitan University, Japan
- Year
2007
- Abstract
The low oxygen partial pressure of an ambient atmosphere (Po 2)is considerably effective to explore the unidentified phases in RE-Fe-O system, since two kinds of valence states i.e. Fe 2+ and Fe 3+, results in the change in crystal structures. Previously, we found the metastable hexagonal LuFeO 3 phase with the space group of P6 3cm (P6 3cm LuFeO 3) at Po 2= 5×10 3 -10 5 Pa and another unidentified hexagonal metastable phase (h-LuFeO 3) at Po 2=1×10 3 Pa during the containerless solidification of the LuFeO 3 melt [1]. However, the thermal stability and magnetic properties of these metastable phases were not reported. In the present study, we characterize the metastable phases formed under various Po 2. The samples grown under various Po 2 were heated up to 1673 K in the O 2 gas flow by differential thermal analysis (DTA) and thermogravimetric analysis (TGA) in order to elucidate the thermal stability of the metastable phases. The metastable phases, P6 3cm LuFeO 3 and h-LuFeO 3, transformed directly into stable orthorhombic LuFeO 3 phase at around 1200 ∘C by the solid state reaction, since no detectable peak was found in DTA curves. On the other hand, TGA results indicated the change in the sample mass increased with decreasing processed Po 2, which suggests that the formation of h-LuFeO 3 is related with the presence of Fe 2+ ions. Moreover, the magnetic property measurement by vibrating sample magnetometer showed that no detectable thermomagnetic transition for the Curie temperature of the metastable phases is observed. As a summary, both metastable phases, P6 3cm LuFeO 3 and h-LuFeO 3, exhibited the high thermal stability below 1200 ∘C. The h-LuFeO 3 does not show any functional properties whereas P6 3cm LuFeO 3 posses ferroelectricity because of the noncentrosymmetric structure.
[1] K. Nagashio and K. Kuribayashi, J. Am. Ceram. Soc 2002;85:2550
- Abstract document
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