A reversible wetting transition in strontium titanate and its influence on grain growth and the grain boundary mobility

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• 作者：Wolfgang Rheinheimer^a ; ^{wolfgang.rheinheimer@kit.edu" class="auth_mail" title="E-mail the corresponding author} ; Michael Bä ; urer^b ; Michael J. Hoffmann^a
• 关键词：Wetting transition ; Grain boundary mobility ; Anisotropy ; Abnormal grain growth ; Kinetic grain boundary shape
• 刊名：Acta Materialia
• 出版年：2015
• 出版时间：December 2015
• 年：2015
• 卷：101
• 期：Complete
• 页码：80-89
• 全文大小：3718 K

文摘

The impact of the oxygen partial pressure on grain growth in high purity strontium titanate is evaluated by observing microstructures, the grain growth constant k and the relative mobility of strontium titanate. The microstructures indicate a reversible wetting transition between 1460 °C and 1500 °C. The wetting second phase is titania-rich and free from any detectable solutes. Exaggerated grain growth was found close to the wetting transition and is explained by a temperature dependent anisotropy of the grain boundary mobility in conjunction with a high mobility of wetted grain boundaries.

The grain growth constant in reducing atmosphere shows two transitions at 1350 °C and at 1460 °C. At the first transition the grain growth constant decreases with temperature. A strong increase of k with temperature at the second transition is attributed to the wetting transition.

The relative grain boundary mobility of different orientations ({1 0 0}, {1 1 0}, {1 1 1}, and {3 1 0}) was measured in oxidizing and reducing atmosphere by observing the growth of oriented single crystals into polycrystals. At 1550 °C in reducing atmosphere the wetting liquid phase enhances the mobility by a factor of ∼10 compared to oxidizing atmosphere. Additionally, the atmosphere changes grain growth kinetics: in oxidizing, but not in reducing atmosphere growth stagnation occurs for long dwell times.