High-pressure transformations of ilmenite to perovskite, and lithium niobate to perovskite in zinc germanate
High-pressure transformations of ilmenite to perovskite, and lithium niobate to perovskite in zinc germanate
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DOI：
10.1007/s00269-006-0070-5
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发表时间：
2006-03
影响因子：
1.4
通讯作者：
H. Yusa;M. Akaogi;N. Sata;H. Kojitani;R. Yamamoto;Y. Ohishi
中科院分区：
文献类型：
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作者：
H. Yusa;M. Akaogi;N. Sata;H. Kojitani;R. Yamamoto;Y. Ohishi
在高压下进行的原位x射线粉末衍射测量证实了ZnGeO3中存在不淬灭的正交钙钛矿。zngeo3钛铁矿在30.0 GPa和1300±150 K的激光加热下转化为钙钛矿。释放压力后，铌酸锂相作为淬火产物被回收。在低于钛铁矿-钙钛矿过渡平衡相边界的压力下，在室温下对铌酸锂相进行再压缩，得到钙钛矿。在x射线衍射数据的基础上计算了钛铁矿、铌酸锂和钙钛矿相的体积模量。根据geo6八面体的旋转来考虑这些相之间的结构关系。八面体的轻微旋转对铌酸锂在室温下向钙钛矿的转变起着重要的作用。另一方面，钛钛矿-钙钛矿转变过程中，geo6八面体需要高温重排。对其他锗酸钙钛矿的可淬性与八面体旋转角度的关系也进行了讨论。
In-situ X-ray powder diffraction measurements conducted under high pressure confirmed the existence of an unquenchable orthorhombic perovskite in ZnGeO3. ZnGeO3ilmenite transformed into perovskite at 30.0 GPa and 1300±150 K in a laser-heated diamond anvil cell. After releasing the pressure, the lithium niobate phase was recovered as a quenched product. The perovskite was also obtained by recompression of the lithium niobate phase at room temperature under a lower pressure than the equilibrium phase boundary of the ilmenite–perovskite transition. Bulk moduli of ilmenite, lithium niobate, and perovskite phases were calculated on the basis of the refined X-ray diffraction data. The structural relations among these phases are considered in terms of the rotation of GeO6octahedra. A slight rotation of the octahedra plays an important role for the transition from lithium niobate to perovskite at ambient temperature. On the other hand, high temperature is needed to rearrange GeO6octahedra in the ilmenite–perovskite transition. The correlation of quenchability with rotation angle of GeO6octahedra for other germanate perovskites is also discussed.