Date of Award
Doctor of Philosophy (PhD)
Joseph W Kolis
The second row third row transition metal ions and their compounds are quite interesting due to their strong spin-orbit coupling interactions, which make them very different from their 3-d counterparts. This places these 4-d and 5-d transition metal ions between 3-d transition metals where the splitting is dominated by orbital effects and rare earth ions where the splitting is dominated by spin-orbit interactions. This can lead to some unusual and novel physical properties which may eventually lead to novel device possibilities. However, the chemistry of these heavy d block oxides are largely ignored compared to 3-d transition metal chemistry.
In this work we have focused on the synthesis of oxides containing these heavy transition metal ions and lanthanides. The highly refractory nature of these heavy d block oxides pose limitations on the use of conventional high temperature synthetic routes. These high temperature synthetic routes typically result in many site defects, disorder, non-stoichiometry in crystal lattices and also impurities from high temperature crucibles, which has a great impact on the physical properties of these materials. Therefore, a low temperature synthetic route such as the hydrothermal technique is useful for these extremely refractory compounds. The exploration of mixed metal oxide systems containing Re, Ru, Ta and W has led to the identification of high quality single crystals of many novel and existing compounds. For example, single crystals of highly dense LnTaO4 compounds were obtained which would be potential laser host materials for high energy radiation. Several new structure types of Re, Ru, Ta and W systems were identified and this also revealed new structural possibilities for these transition metal ions. Solubility of the ReO2, RuO2, Ta2O5 and WO2 building blocks were achieved well below their melting point (600-750 ⁰C) and this minimized the common problems observed in conventional high temperature synthetic methods such as non-stoichiometry, lattice defects, disorder, and good quality single crystals were obtained with a good purity in most cases.
Kolambage, Mudithangani, "Hydrothermal Crystal Growth and Characterization of Refractory Oxides Containing 4d, 5d Transition Metal Ions and Lanthanides" (2020). All Dissertations. 2613.