A reversible wetting transition in strontium titanate and its influence on grain growth and the grain boundary mobility. (December 2015)

• Record Type: Journal Article
• Authors: Rheinheimer, Wolfgang; Bäurer, Michael; Hoffmann, Michael J.
• Is Part Of: Acta materialia. Volume 101(2015)
• Page Start: 80
• Page End: 89
• Publication Date: 2015-12
• Subjects: Wetting transition -- Grain boundary mobility -- Anisotropy -- Abnormal grain growth -- Kinetic grain boundary shape; Materials -- Periodicals; Materials science -- Periodicals; Materials -- Mechanical properties -- Periodicals; Metallurgy -- Periodicals; Chemistry, Inorganic -- Periodicals; 620.112
• DOI: 10.1016/j.actamat.2015.08.069
• Languages: English
• ISSNs: 1359-6454

Abstract

Graphical abstract: Abstract: 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.