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首页> 外文会议>Symposium Proceedings vol.839; Symposium on Electron Microscopy of Molecular and Atom-Scale Mechanical Behavior, Chemistry and Structure; 20041129-1201; Boston,MA(US) >Accurate determination of orientation relationships between ferroelastic domains: the tetragonal to monoclinic transition in LaNbO4 as an example
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Accurate determination of orientation relationships between ferroelastic domains: the tetragonal to monoclinic transition in LaNbO4 as an example

机译：精确确定铁弹性域之间的取向关系：以LaNbO4的四方向单斜相转变为例

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摘要

LaNbO_4 crystallizes in a tetragonal high-temperature phase with space group I4_1/a, which transforms to a monoclinic phase upon cooling below 500℃. The low-temperature phase has space group I2/a (C2/c) with a monoclinic angle β=94.1°. This system serves as a useful model of a ferroelastic transition of the 4/mF2/m type using the notation of Aizu. This transition produces ferroelastic domains, the boundaries between which are parallel to the monoclinic b-axis. The orientation of these boundaries relative to the monoclinic a- and c-axes has been predicted by Sapriel for all 94 ferroelastic species, and calculations specifically for the LaNbO_4 system have been presented by Jian and Wayman. We present an accurate determination of the boundary orientation in LaNbO_4 using selected area electron diffraction. The boundary planes are parallel to the (20-5.10)/(5.1002) planes of the two domains, as opposed to the predictions of Jian and Wayman which indicate that the domain boundaries should be oriented parallel to the (20-4.04)/(4.0402) planes. Our experimental results are in good agreement with the results of a previous study. Furthermore, we present a simple geometric model for calculating the boundary orientation based only on the unit cell parameters of the monoclinic phase. This model gives a boundary orientation in excellent agreement with our experimental determination.
机译：LaNbO_4在具有空间群I4_1 / a的四方高温相中结晶，冷却至低于500℃时转变为单斜晶相。低温相具有单斜角β＝ 94.1°的空间群I2 / a（C2 / c）。该系统可作为使用Aizu表示法的4 / mF2 / m型铁弹性转变的有用模型。这种转变产生铁弹性域，它们之间的边界平行于单斜b轴。 Sapriel已针对所有94种铁弹性物种预测了这些边界相对于单斜A轴和C轴的方向，Jian和Wayman提出了专门针对LaNbO_4系统的计算。我们提供了使用选定的区域电子衍射技术精确确定LaNbO_4中的边界取向的方法。边界平面平行于两个域的（20-5.10）/（5.1002）平面，与Jian和Wayman的预测相反，Jian和Wayman的预测表明域边界应平行于（20-4.04）/（ 4.0402）飞机。我们的实验结果与先前的研究结果非常吻合。此外，我们提出了一个简单的几何模型，仅基于单斜晶相的晶胞参数来计算边界取向。该模型给出的边界方向与我们的实验结果非常吻合。

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