Tentative Phase Relationships in the System CaHfTi2O7‐Gd2Ti2O7 with up to 15 mol% Additions of Al2TiO5 and MgTi2O5
Tentative Phase Relationships in the System CaHfTi2O7‐Gd2Ti2O7 with up to 15 mol% Additions of Al2TiO5 and MgTi2O5
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DOI：
10.1111/j.1151-2916.2002.tb00556.x
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发表时间：
2004-12
影响因子：
3.9
通讯作者：
D. Perera;M. Stewart;Huijun Li;R. Day;E. Vance
中科院分区：
文献类型：
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作者：
D. Perera;M. Stewart;Huijun Li;R. Day;E. Vance
研究了CaHfTi 2 O 7 Gd 2 Ti 2 O 7（锆英石-烧绿石）赝二元系在1500°C加热后的相关系，因为它们在设计用于固定不纯过剩钚的富焦绿石钛酸盐陶瓷中具有重要意义。将高达15mol%的MgTi 2 O 5和Al 2 TiO 5添加到CaHf Ti 2 O 7 Gd 2 Ti 2 O 7组合物中，以阐明二价和三价杂质对这些系统中相稳定性的影响。从X-射线衍射分析，扫描电子显微镜，和能量色散X-射线光谱，相形成和组成的稳定性限制进行了评估。在这些系统中观察到的主要相是烧绿石，钙钛矿，和多型的锆英石。2 M-、4 M-和30-锆石多型体的形成取决于铝或镁的含量。在镁系统中，观察到大面积的烧绿石，这表明适当离子尺寸的二价杂质可以容易地掺入烧绿石的八重位。暂定相界的位置进行了讨论相对于化学成分。
The phase relationships in the CaHfTi 2 O 7 Gd 2 Ti 2 O 7 (zirconolite-pyrochlore) pseudobinary system were investigated, after heating at 1500°C, because of their importance in the design of pyrochlore-rich titanate ceramics for immobilization of impure surplus plutonium. Up to 15 mol% of MgTi 2 O 5 and Al 2 TiO 5 were added to CaHfTi 2 O 7 Gd 2 Ti 2 O 7 compositions to elucidate the effects of divalent and trivalent impurities on the phase stability within these systems. From X-ray diffractometry analysis, scanning electron microscopy, and energy dispersive X-ray spectrometry, phase formation and compositional stability limits were evaluated. The main phases observed in these systems were pyrochlore, perovskite, and polytypes of zirconolite. The formation of the 2M-, 4M-, and 30-zirconolite polytypes was dependent on the amount of aluminum or magnesium present. In the magnesium system, a large area of pyrochlore-only was observed, which indicated that divalent impurities of appropriate ionic size could be readily incorporated in the eightfold site of the pyrochlore. The locations of the tentative phase boundaries are discussed with respect to the chemical composition.