Single crystal growth of CoTi 2 O 5 by solid state reaction synthesis

• Published in: Journal of the American Ceramic Society 2019-09, Vol.102 (9), p.5050-5062
• Main Authors: Anderson, Kevin P., Giri, Anit K., Vinci, Richard P., Chan, Helen M.
• Format: Article
• Language: English
• ISSN: 0002-7820; 1551-2916
• DOI: 10.1111/jace.16379

Materials in single crystal form are often sought after because the absence of grain boundaries can result in unique properties relative to the polycrystal, but producing these materials is typically a slow and complex process. In this work, pseudo single crystals of the pseudobrookite compound CoTi 2 O 5 were synthesized by solid‐state reaction from a duplex grain mixture of CoTiO 3 and TiO 2 . The size of the crystallites was >250 µm. The transformation and subsequent microstructural evolution of the CoTi 2 O 5 was studied by scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), and X‐ray diffraction (XRD). A novel growth mechanism was identified whereby a single crystal CoTi 2 O 5 front advances simultaneously along multiple CoTiO 3 /TiO 2 diphasic boundaries. The single crystal domains were composed of subgrains approximately 5 µm in diameter; differences in the subgrain size and misorientation were related to the growth mechanism and the initial grain size of the duplex CoTiO 3 –TiO 2 mixture. CoTi 2 O 5 is a little characterized compound, and this study represents the most significant microstructural study of CoTi 2 O 5 to date. The findings may be applied to similar pseudobrookite compounds such as MgTi 2 O 5 and Al 2 TiO 5 .