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Abstract 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 CoTi2O5were synthesized by solid‐state reaction from a duplex grain mixture of CoTiO3and TiO2. The size of the crystallites was >250 µm. The transformation and subsequent microstructural evolution of the CoTi2O5was 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 CoTi2O5front advances simultaneously along multiple CoTiO3/TiO2diphasic 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 CoTiO3–TiO2mixture. CoTi2O5is a little characterized compound, and this study represents the most significant microstructural study of CoTi2O5to date. The findings may be applied to similar pseudobrookite compounds such as MgTi2O5and Al2TiO5.
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Crystalline Mesoporous Complex Oxides: Porosity‐Controlled Electromagnetic Response
Abstract A colloidal‐amphiphile‐templated growth is developed to synthesize mesoporous complex oxides with highly crystalline frameworks. Organosilane‐containing colloidal templates can convert into thermally stable silica that prevents the overgrowth of crystalline grains and the collapse of the mesoporosity. Using ilmenite CoTiO3as an example, the high crystallinity and the extraordinary thermal stability of its mesoporosity are demonstrated at 800 °C for 48 h under air. This synthetic approach is general and applicable to a series of complex oxides that are not reported with mesoporosity and high crystallinity, such as NiTiO3, FeTiO3, ZnTiO3, Co2TiO4, Zn2TiO4, MgTi2O5, and FeTi2O5. Those novel materials make it possible to build up correlations between mesoscale porosity and surface‐sensitive physicochemical properties, e.g., electromagnetic response. For mesoporous CoTiO3, there is a 3 K increase of its antiferromagnetic ordering temperature, compared with that of nonporous one. This finding provides a general guideline to design mesoporous complex oxides that allow exploring their unique properties different from bulk materials.
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- PAR ID:
- 10457582
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Functional Materials
- Volume:
- 30
- Issue:
- 15
- ISSN:
- 1616-301X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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