In Situ Measurement of Phase Transition of Layered Perovskite BaLn2Mn2O7

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The BaLn2Mn2O7 (Ln = rare earth) has a Sr3Ti2O7-type structure with double block oxygen octahedra belonging to the Ruddlesden-Popper-Type homologous series AO(ABO3)2. In-situ measurement of the phase transition for BaLn2Mn2O7 was performed using single-crystal X-ray diffraction and a high-temperature transmission electron microscope (TEM). Two types of transitions were observed in BaPr2Mn2O7: the transition from primitive tetragonal (P42/mnm) to body-centered tetragonal (I4/mmm) at around 400 K and the first-order phase transition at around 1040 K. Multiple phase transitions were also observed in BaEu2Mn2O7, with one from P42/mnm to I4/mmm at around 400 K and another, above 550 K, as a first-order phase transition. The high-temperature phase had a 1.5% lattice mismatch along the c-axis compared with the low-temperature phase. We succeeded in recording for the first time in-situ structural change in BaGd2Mn2O7 as a movie by high-temperature TEM. The high-temperature phase nucleated parallel to the (00l) plane as a layer above 550 K and grew until covering the entire inspected region at around 1023 K. The first-order phase transition was caused by the structural and/or electrical distortion of the layered perovskite structure composed of Jahn-Teller ion Mn3+.

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Edited by:

Pietro VINCENZINI, Vojislav V. MITIC, Alois LOIDL and Dino FIORANI

Pages:

113-117

DOI:

10.4028/www.scientific.net/AST.67.113

Citation:

H. Nakano et al., "In Situ Measurement of Phase Transition of Layered Perovskite BaLn2Mn2O7", Advances in Science and Technology, Vol. 67, pp. 113-117, 2010

Online since:

October 2010

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$35.00

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