Kinetics and Deformation during the Reaction of Yttrium‐Aluminum Perovskite and Alumina to Yttrium‐Aluminum Garnet
Kinetics and Deformation during the Reaction of Yttrium‐Aluminum Perovskite and Alumina to Yttrium‐Aluminum Garnet
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DOI：
10.1111/j.1151-2916.1994.tb09745.x
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发表时间：
1994-06
影响因子：
3.9
通讯作者：
R. Hay
中科院分区：
文献类型：
--
作者：
R. Hay
在1150° C和1550°C之间测量了定向凝固的钇铝钙钛矿和氧化铝的共晶物到钇铝石榴石的反应动力学，时间长达20 000 min。观察到11体积%的增加引起的变形。通过光学显微镜、SEM和TEM对样品进行了表征。用原子力显微镜测量了自应力松弛的表面位移。YAG在硅酸钇杂质处成核为20 nm厚的板。为了使成核发生，20-GPa的自应力必须松弛。YAG晶体生长呈抛物线型，激活能为550 kJ/mol。自应力松弛导致YAG中的蠕变硬化，形成可能增加生长速率的短路扩散路径。YAG中的最大流动应力估计为1- 3GPa，并且随着反应的进行而减小。推断的流动应力不应显著降低反应驱动力。最终，氧化铝的离轴蠕变主导的自应力松弛，因为它的流动应力远低于YAG的。
The kinetics of the reaction of directionally solidified eutec-tics of yttrium-aluminum perovskite and alumina to yttrium-aluminum garnet were measured between 1150° and 1550°C for times as long as 20 000 min. Deformation from the 11 vol% increase was observed. Samples were characterized by optical microscopy, SEM, and extensively by TEM. Surface displacements from self-stress relaxation were measured by atomic force microscopy. YAG nucleated at yttrium silicate impurities as 20-nm-thick plates. For nucleation to occur, the 20-GPa self-stress must relax. YAG growth was parabolic with a 550-kJ/mol activation energy. Self-stress relaxation caused creep polygonization in YAG, forming short-circuit diffusion pathways that may have increased the growth rate. The maximum flow stress in YAG was estimated to be 1–3 GPa and decreased as the reaction progressed. The inferred flow stresses should not have significantly decreased the reaction driving force. Eventually, off-axis creep of alumina dominated self-stress relaxation because its flow stress was much lower than that of YAG.