Theoretical and experimental evidence for the post-cotunnite phase transition in zirconia at high pressure
Theoretical and experimental evidence for the post-cotunnite phase transition in zirconia at high pressure
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DOI：
10.1007/s00269-014-0728-3
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发表时间：
2015-05
影响因子：
1.4
通讯作者：
D. Nishio–Hamane;H. Dekura;Y. Seto;T. Yagi
中科院分区：
文献类型：
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作者：
D. Nishio–Hamane;H. Dekura;Y. Seto;T. Yagi
利用同步x射线衍射测量和基于密度泛函理论的从头计算研究了高压下氧化锆（ZrO2）的后钴隧道相变。该研究成功地证明了钴矿到fe2p型相变。静态焓差（ΔH）计算预测了Fe2P相在124gpa （LDA）和143gpa （GGA）时的出现，实验结果表明，当加热到3000k时，Fe2P相和钴隧道石相在175gpa时共存。两相在环境条件下均可淬灭。在实验压力范围内，Fe2P相的体积略小于钴矿相（~Δ 0.6%），表明Fe2P相为高压相。本研究中两相的共存可能归因于两相密切的结构关系导致的相变动力学缓慢。通过对孔雀石型结构进行简单的运算，可以推导出fe2p型结构模型，该结构由平行于孔雀石型单元胞b轴的几个锆排列组成1/2移位。结论认为，高压孔雀石到fe2p的相变可能是许多氧化物的共同趋势。
A post-cotunnite phase transition in zirconia (ZrO2) at high pressure was investigated by synchrotron X-ray diffraction measurements and ab initio calculations based on density functional theory. This study successfully demonstrated a cotunnite- to Fe2P-type phase transition. Static enthalpy difference (ΔH) calculations predicted the appearance of the Fe2P phase at 124 GPa (LDA) and 143 GPa (GGA), and experimental trials demonstrated the coexistence of the Fe2P and cotunnite phases at 175 GPa after heating to 3,000 K. Both phases were quenchable to ambient conditions. The volume of the Fe2P phase was slightly less (~Δ 0.6 %) than that of the cotunnite phase over the experimental pressure range, indicating that the Fe2P phase is the higher pressure phase. The coexistence of both phases in this study may be attributed to the slow kinetics of the phase transition resulting from the close structural relationship of the two phases. An Fe2P-type structural model can be derived by applying a simple operation to the cotunnite-type structure, consisting of a 1/2 shift of several zirconium arrangements parallel to theb-axis of the cotunnite-type unit cell. It is concluded that the high-pressure cotunnite-to-Fe2P phase transition may be a common trend in many dioxides.