Compounds in the series La1-xTiO3 have been prepared in the powder and single crystalline forms. The structures of these compounds were studied with x-ray, neutron, and electron diffraction techniques. In all cases, a distortion from the ideal perovskite structure was found.
Throughout the series, transitions occur in structural, magnetic, and electrical properties. The structure of La.67TiO3 was found to be of a distorted perovskite type arising from distortions in the titanium octahedra as a result of an ordering of the lanthanum positions and A-site cation vacancies. Although this phase has been reported many times, the crystal structure has not been determined. The La.67TiO3 and La.70TiO3 phases have the same structure and were assigned to the Pmmn space group. At La75.TiO3, a Ti3+ concentration of 2 8%, the symmetry of the structure changes from Pmmn to Imma, and distortion of the perovskite structure is caused by octahedral tilting within the lattice. A further structural transition occurs at a Ti3+ concentration of 64%, La8gTiO3, where the symmetry changes from Imma to Pnma. Again distortions from the ideal perovskite structure are caused by octahedral tilts within the system.
Transitions were also observed in electrical and magnetic properties. These transitions occur at the same Ti3+ concentrations as the transitions observed in the structural properties, which suggests a correlation between properties based on Ti3+ concentration.
The occurrence of A-site cation vacancies within the lattice is directly related to the Ti3+ concentrations within the individual materials. Changes in the Ti3+ concentration affect the size of the unit cell as well as the electrical and magnetic properties which range from insulators at low Ti3+ concentrations to metals at high Ti3+ concentrations. / Thesis / Master of Science (MSc)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/29263 |
| Date | January 1993 |
| Creators | MacEachern, Marlene J. |
| Contributors | Greedan, J. E., Chemistry |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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