Metastability of corundum-type In2O3
Metastability of corundum-type In2O3
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DOI：
10.1002/chem.200701830
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发表时间：
2008-01-01
影响因子：
4.3
通讯作者：
Riedel, Ralf
中科院分区：
文献类型：
--
作者：
Gurlo, Aleksander;Kroll, Peter;Riedel, Ralf
方铁锰矿和刚玉型结构之间的结构关系的描述是特别感兴趣的，因为这两种结构的共同发生。方铁锰矿向氧化铟转变的代表性实例之一是刚玉型氧化铟的高压高温合成。湿化学合成和稳定的刚玉型In 2 O3在环境压力条件下要求重新解释的In-O相图以及澄清的In 2 O3的相变。需要澄清的问题之一是刚玉型In 2 O3的稳定性。在目前的工作中，我们研究了刚玉型氧化铟的稳定性，理论（密度泛函计算）和实验。采用改进的非醇盐溶胶-凝胶法，以硝酸铟在甲醇中的氨诱导水解反应为基础，合成了刚玉型In 2 O3。对刚玉型In 2 O3进行热分析（STA）以及结构研究，即，使用包括热处理后的原位XRPD表征的X射线粉末衍射（XRPD）对其进行检查。毫无疑问，我们第一次从理论上和实验上证明了刚玉型In 2 O3多晶型物的亚稳性。In 2 O3多晶型物似乎是亚稳态的整个压-压相图。加热时，刚玉型In 2 O3不可逆地转变为立方方铁锰矿型In 2 O3所示的STA以及原位加热XRPD实验。计算表明存在另一个高压修改的In 2 O3与正交结构，同型Rh 2 O3-II。我们预测这个新的阶段形成的压力超过15 GPa的立方方铁锰矿型和刚玉型修改的In 2 O3。
The description of structural relations between bixbyite- and corundum-type structures is of particular interest because of the common occurrence of both structures. One of the representative examples of the bixbyite to corundum transition is the high-pressure high-temperature synthesis of the corundum-type indium oxide. The wet chemistry synthesis and stabilisation of the corundum-type In2O3 under ambient pressure conditions calls for a re-interpretation of the In-O phase diagram as well as for the clarification of the phase transitions in In2O3. One of the questions to be clarified is the stability of the corundum-type In2O3. In the present work we studied the stability of the corundum-type In2O3 both theoretically (by density-functional calculations) and experimentally. The synthesis of the corundum-type In2O3 was performed by the modified non-alkoxide sol-gel method based on the ammonia-induced hydrolysis of indium nitrate in methanol. The corundum-type In2O3 was subjected to thermal analysis (STA) as well as to structural studies, that is, it was examined using X-ray powder diffraction (XRPD) including in situ XRPD characterisation upon thermal treatment. For the first time we have undoubtedly demonstrated, both theoretically and experimentally, the metastability of the corundum-type In2O3 polymorph. The In2O3 Polymorph appears to be metastable throughout the entire enthalpy-pressure phase diagram. Upon heating, corundum-type In2O3 transforms irreversibly into cubic bixbyite-type In2O3 as shown by STA as well as in situ heating XRPD experiments. Computations indicate the existence of another high-pressure modification of In2O3 with orthorhombic structure, iso-typic to Rh2O3-II. We predict this new phase to form at pressures exceeding 15 GPa from both the cubic bixbyite-type and the corundum-type modification of In2O3.