Final Report Summary - COSYMETCOX (Confined synthesis of metastable complex oxides)
The COSYMETCOX project aimed at studying the stabilization of metastable functional oxides by confinement and finding strategies to integrate these phases in devices. In particular the project focused in three especially relevant systems: mangetoelectric ε-Fe2O3; λ-Ti3O5, showing a room-temperature photoreversible phase transition and monoclinic La0.7Sr0.3MnO3 presenting an increased Curie temperature.
The project has been successful in developing a robust method to prepare ε-Fe2O3 films on technologically relevant substrates as SrTiO3, making possible to discover that this metastable polymorph of Fe2O3 is ferroelectric at room temperature. Since ε-Fe2O3 was already known to be ferrimagnetic at ambient conditions, it is thus the first multiferroic single metal oxide to be reported.
The confined synthesis of the monoclinic La0.7Sr0.3MnO3 was attempted in silica matrices using the metal nitrates dissolved in ethanol in co-synthesis with the preparation of the silica using tetraethylortosilicate. It was very surprising not to obtain, after thermally treating the gels, the expected manganite but large amounts of α-quartz. It was discovered that Sr2+ played a key role in the devitrification of the xerogel in α-quartz and exploited in the unprecedented growth of the piezoelectric α-quartz on silicon. The study of the mechanisms of crystallization of epitaxial quartz on Si(100) was subsequently integrated in the project.
Regarding the study of λ-Ti3O5, the obtained results were not new and somehow disappointing and the task was abandoned.
Finally, the project allowed exploring the crystallization of new metastable phases under negative pressures in liquids. Although this task faced several experimental hurdles, it is now an ongoing line in the research activity portafolio of the fellow.
The project has been successful in developing a robust method to prepare ε-Fe2O3 films on technologically relevant substrates as SrTiO3, making possible to discover that this metastable polymorph of Fe2O3 is ferroelectric at room temperature. Since ε-Fe2O3 was already known to be ferrimagnetic at ambient conditions, it is thus the first multiferroic single metal oxide to be reported.
The confined synthesis of the monoclinic La0.7Sr0.3MnO3 was attempted in silica matrices using the metal nitrates dissolved in ethanol in co-synthesis with the preparation of the silica using tetraethylortosilicate. It was very surprising not to obtain, after thermally treating the gels, the expected manganite but large amounts of α-quartz. It was discovered that Sr2+ played a key role in the devitrification of the xerogel in α-quartz and exploited in the unprecedented growth of the piezoelectric α-quartz on silicon. The study of the mechanisms of crystallization of epitaxial quartz on Si(100) was subsequently integrated in the project.
Regarding the study of λ-Ti3O5, the obtained results were not new and somehow disappointing and the task was abandoned.
Finally, the project allowed exploring the crystallization of new metastable phases under negative pressures in liquids. Although this task faced several experimental hurdles, it is now an ongoing line in the research activity portafolio of the fellow.