Structural distortions in rare-earth transition-metal oxide perovskites under high pressure
Structural distortions in rare-earth transition-metal oxide perovskites under high pressure
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DOI：
10.1103/physrevb.101.224104
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发表时间：
2020-06
影响因子：
3.7
通讯作者：
J. Zhou
中科院分区：
文献类型：
--
作者：
J. Zhou
由于其结构的复杂性和广泛的可能的化学组合，钙钛矿氧化物显示出许多重要的技术物理性质。压力是一个有助于调节物理性质的热力学参数；然而，复杂的晶体结构对高压的响应还没有得到彻底的研究和合理化。本文研究了正交型钙钛矿氧化物{A}^{3+}{B}^{3+}{\mathm{O}}_{3}的原位高压X射线衍射谱，这种氧化物是通式为Rm{\mathm{O}}{3}$的稀土过渡金属氧化物。本研究所研究的四个钙钛矿族Rm{\mathm{O}_{3}$($M=\mathm{Ti}$，Cr，Mn，Fe)都具有与Pbnm空间群相同的正交晶系钙钛矿结构。在这些材料中，稀土元素的收缩导致不同程度的正交扭曲，这些扭曲主要与八面体位置旋转有关。压力引起的晶格参数变化表明，在钙钛矿型钙钛矿中，替代稀土元素的正交形变从抑制到放大，从{R=\mathm{O}}_{3}$变成了Lu。晶格参数对压强的依赖关系的这种不寻常的交叉与第一性原理计算的结果相矛盾，但可以用钙钛矿结构的内在扭曲来解释。
Owing to their structural complexity and wide range of possible chemical combinations, perovskite oxides exhibit many technically important physical properties. Pressure is a thermodynamic parameter which is useful for tuning physical properties; however, the response of the complex crystal structure to high pressure has not been thoroughly studied and rationalized. This study focuses on in situ high-pressure x-ray diffraction of the orthorhombic perovskite oxides ${A}^{3+}{B}^{3+}{\mathrm{O}}_{3}$, commonly found for the rare-earth transition-metal oxides of the $RM{\mathrm{O}}_{3}$ formula. Each of the four families of $RM{\mathrm{O}}_{3}$ ($M=\mathrm{Ti}$, Cr, Mn, Fe) perovskites in this study all crystallize in the same orthorhombic perovskite structure with the Pbnm space group. The lanthanide contraction in these materials leads to varying degrees of orthorhombic distortions that are primarily associated with octahedral site rotations. The pressure-induced change of the lattice parameters demonstrates an evolution from a suppression to an enlargement of the orthorhombic distortion for substitution of the rare-earth element from $R=\mathrm{La}$ to Lu in $RM{\mathrm{O}}_{3}$ perovskites. This unusual crossover of the lattice parameters' dependence on pressure contradict the results from first-principles calculation but can be rationalized by the intrinsic distortion of the perovskite structure.