The structural transformation from the pyrochlore structure, A2B2O7, to the fluorite structure, AO2, studied by Raman spectroscopy and defect chemistry modeling
The structural transformation from the pyrochlore structure, A2B2O7, to the fluorite structure, AO2, studied by Raman spectroscopy and defect chemistry modeling
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DOI：
10.1006/jssc.2001.9142
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发表时间：
2001-08-01
影响因子：
3.3
通讯作者：
Poulsen, FW
中科院分区：
文献类型：
--
作者：
Glerup, M;Nielsen, OF;Poulsen, FW
采用拉曼光谱研究了Y2 Ti 2-yZryO 7（y = 0，0.3，0.6和0.9）烧绿石氧化物。掺杂Zr+4（一种同价离子），逐渐诱导材料经历从完美烧绿石结构到缺陷烧绿石结构的结构变化，并终止于具有式（Y，Ti，Zr）（1）O-1.75的缺氧萤石结构，将较大的Zr+4离子置于Ti+4位引起这种结构转变。我们还研究了高Ti掺杂的YSZ陶瓷样品，它们都具有缺氧立方萤石结构。这些样品的化学式单位在（Y，Ti，Zr）（1）O-1.675和（Y，Ti，Zr）（1）O-1.90之间。在掺钛烧绿石样品和Ti，Y，Zr萤石样品中，在750 cm（-1）处观察到的谱带是由于氧在Ti周围的七重配位引起的。通过拉曼光谱观察到了这些样品的局域结构。最后我们报道了正交晶系Y_2TiO_5的拉曼光谱。一个缺陷化学模型已制定，定性地描述了观察到的辉石-萤石结构转变。(C)北京：科学出版社.
Pyrochlore oxides of the composition Y2Ti2-yZryO7,with y = 0, 0.3, 0.6, and 0.9, were studied using Raman spectroscopy. Doping with Zr+4, a homovalent ion, gradually induces the material to undergo a structural change from the perfect pyrochlore structure to a defect pyrochlore structure and ends at an oxygen deficient fluorite structure with the formula (Y, Ti, Zr)(1)O-1.75, Invoking the bigger Zr+4 ion on the Ti+4 site causes this structural transformation. We have also investigated highly Ti-doped YSZ ceramic samples, which all have an oxygen deficient cubic fluorite structure. These samples have formula units between (Y,Ti, Zr)(1)O-1.675 and (Y, Ti, Zr)(1)O-1.90. It is argued that a band observed at 750 cm(-1) in both the Ti-doped pyrochlore samples and in the Ti, Y, Zr fluorite samples is due to oxygen in seven fold coordination around Ti. Local structures are accordingly observed by Raman in these samples. We finally report a Raman spectrum of orthorhombic Y2TiO5. A defect chemistry model has been formulated, which qualitatively describes the observed pyrochlore-fluorite structural transition. (C) 2001 Academic Press.