In-situ observation of phase transformations in layered perovskite BaEu2Mn2O7
In-situ observation of phase transformations in layered perovskite BaEu2Mn2O7
复制标题
DOI：
10.1016/j.jeurceramsoc.2009.05.011
复制
发表时间：
2010
影响因子：
5.7
通讯作者：
H. Nakano;N. Ishizawa;N. Kamegashira
中科院分区：
文献类型：
--
作者：
H. Nakano;N. Ishizawa;N. Kamegashira
层状钙钛矿BaLn 2 Mn 2 O 7（Ln=稀土）具有Sr 3 Ti 2 O 7型结构，其具有属于Ruddlesden-Popper型同系AO（ABO 3）2的双块氧八面体。BaEu 2 Mn 2 O 7在高温TEM下表现出多次相变，从四方相I（P42/mnm）到单斜相III（I4/mmm）。在277°C以上，来自相III的弱反射开始出现在沿着c方向的选定区域衍射图案上，并且随着温度的升高逐渐变得更强。最后，所有的反射都来自750°C以上的相III。这表明了一级相变，并且在淬火试样中也清楚地观察到低温相和高温相的共存。在这些结构的差异是沿着c轴的周期性和高温相的1.5%的长的c长度比低温相。
The layered perovskite 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. The BaEu2Mn2O7shows multiple phase transformations upon heating by high-temperature TEM, from tetragonal phase I (P42/mnm) to monoclinic phase III via phase II (I4/mmm). Weak reflections from phase III started to appear on the selected area diffraction pattern along the c-direction above 277°C and became stronger gradually with increasing temperature. Finally, all of the reflections were from only phase III above 750°C. This shows a first-order phase transformation, and the coexistence of low- and high-temperature phases was also observed clearly in a quenched specimen. The differences in those structures are the periodicity along the c-axis and the high-temperature phase's 1.5% longer c length than that of the low-temperature phase.