The objective of this thesis is to evaluate the readiness of SADC economies to complete the process of monetary integration in the region and to form a monetary union and adopt a common currency. This is done against the backdrop of optimal currency area (OCA) theory. Given this objective, the study hypothesizes that the majority of SADC economies in the region are potential candidates to bring the proposed monetary union into existence sometime in the future, if not in 2018 as proposed by SADC secretariat. The study uses a mix of different methodologies ranging from developing a conceptual framework to empirical investigation in order to answer the research questions and to test the hypotheses. In addition to theoretical reviews and discussions, four findings emerge as fundamental from the four essays. First, from the Triples test the study has not found significant evidence to reject the null hypothesis of „structural symmetry‟ among ten SADC member countries. 10 out of 15 members (i.e.66.67 percent) have exhibited structural symmetry in their real business cycles over the study period. However, close to 50 percent of the member states have weak cyclical co-movements with a low relative intensity. Taking the experience of the EMU where just five countries are able to create havoc in the entire union, we can safely say that the findings from the combined three tests from the first essay confirm that there is still work that needs to be done to coordinate economic policies in the region to improve real economic integration before entry into the proposed monetary union in 2018. In Essay 2, the study finds that the generalised purchasing power parity (GPPP) hypothesis holds for SADC economies given the stationary panel of RER series with one cointegrating relationship as exhibited by trace statistics and the existence of a long run co-integrating relationship amongst the system of real exchange rates. This implies that there is potential for relative prices to converge in the region in the long run, hence SADC is a potential OCA, based on the criteria of price convergence. However, the slow speed of adjustment towards GPPP long run equilibrium should be a warning for the possible ineffectiveness of policy to defend these countries against external shocks. In Essay 3, the Brock, Dechert, and Scheinkman (BDS) test and Fourier approximation confirm the non linear nature of real exchange series in SADC economies. This finding further supports an OCA in the region comprising those countries included in the study. The findings in this essay further strengthen the findings from the previous two essays that claim that member states could constitute a monetary union in the region at some future date. Lastly, the fourth essay, using a long run dynamic panel model finds that there are common policy variables determining the real exchange rate (RER)/ the real effective exchange rate (REER) series of SADC economies. The RER/REER equilibrium analysis reveals that SADC economies are characterised by persistent misalignment. This calls for further policy coordination and policy harmonisation in the region. By considering findings from all the four essays the study finds that nine SADC countries can potentially constitute SADC-OCA namely; Botswana, Madagascar, Malawi, Mozambique, Seychelles, South Africa, Swaziland, Tanzania and Zambia. Angola and Mauritius disqualified from a SADC-OCA at least for the sample period considered in this study. Lesotho, DRC, and Zimbabwe are not included due to data limitations, otherwise Lesotho could join the qualifying group of countries given long experience with the Common Monetary Area (CMA). To reap benefits SADC economic integration initiatives, it requires realistic time span, political will, common understandings and awareness, commitment and self-disciplined policy actions from member states and their fellow citizens. / Thesis (PhD)--University of Pretoria, 2014. / tm2015 / Economics / PhD / Unrestricted

Owing to their versatile orbital character with both local and highly dispersive degrees of freedom, transition metal oxides span the range of ionic, covalent and metallic bonding. They exhibit a vast diversity of electronic phenomena such as high dielectric, piezoelectric, pyroelectric, ferroelectric, magnetic, multiferroic, catalytic, redox, and superconductive properties. The nature of these properties arises from sensitive details in the electronic structure, e.g. orbital mixing and orbital hybridization, due to non-stoichiometry, atomic displacements, broken symmetries etc., and their coupling with external perturbations. In the work presented here, these variations of the electronic structure of crystals due to structural and electronic defects have been investigated, exemplarily for the quasi-binary system SrO - SrTiO3 - TiO2. A number of binary and ternary structures have been studied, both experimentally as well as by means of electronic modeling. The applied methods comprise Resonant X-ray Scattering techniques like Diffraction Anomalous Fine Structure, Anisotropy of Anomalous Scattering and X-ray Absorption Fine Structure, and simultaneously extensive electronic calculations by means of Density Functional Theory and Finite Difference Method Near-Edge Structure to gain a thorough physical understanding of the underlying processes, interactions and dynamics. It is analyzed in detail how compositional variations, e.g. manifesting as oxygen vacancies or ordered stacking faults, alter the short-range order and affect the electronic structure, and how the severe changes in mechanical, optical, electrical as well as electrochemical properties evolve. Various symmetry-property relations have been concluded and interpreted on the basis of these modifications in electronic structure for the orbital structure in rutile TiO2, for distorted TiO6 octahedra and related switching mechanisms of the Ti valence, for elasticity and resistivity in strontium titanate, and for surface relaxations in Ruddlesden-Popper phases. Highlights of the thesis include in particular the methodical development regarding Resonant X-Ray Diffraction, such as the first use of partially forbidden reflections to get the complete phase information not only of the tensorial structure factor but of each individual atomic scattering tensor for a whole spectrum of energies, as well as the determination of orbital degrees of freedom and details of the partial local density of states from these tensors. On the material side, the most prominent results are the identification of the migration-induced field-stabilized polar phase and the exergonic redox behavior in SrTiO3 caused by defect migration and defect separation.

Owing to their versatile orbital character with both local and highly dispersive degrees of freedom, transition metal oxides span the range of ionic, covalent and metallic bonding. They exhibit a vast diversity of electronic phenomena such as high dielectric, piezoelectric, pyroelectric, ferroelectric, magnetic, multiferroic, catalytic, redox, and superconductive properties. The nature of these properties arises from sensitive details in the electronic structure, e.g. orbital mixing and orbital hybridization, due to non-stoichiometry, atomic displacements, broken symmetries etc., and their coupling with external perturbations. In the work presented here, these variations of the electronic structure of crystals due to structural and electronic defects have been investigated, exemplarily for the quasi-binary system SrO - SrTiO3 - TiO2. A number of binary and ternary structures have been studied, both experimentally as well as by means of electronic modeling. The applied methods comprise Resonant X-ray Scattering techniques like Diffraction Anomalous Fine Structure, Anisotropy of Anomalous Scattering and X-ray Absorption Fine Structure, and simultaneously extensive electronic calculations by means of Density Functional Theory and Finite Difference Method Near-Edge Structure to gain a thorough physical understanding of the underlying processes, interactions and dynamics. It is analyzed in detail how compositional variations, e.g. manifesting as oxygen vacancies or ordered stacking faults, alter the short-range order and affect the electronic structure, and how the severe changes in mechanical, optical, electrical as well as electrochemical properties evolve. Various symmetry-property relations have been concluded and interpreted on the basis of these modifications in electronic structure for the orbital structure in rutile TiO2, for distorted TiO6 octahedra and related switching mechanisms of the Ti valence, for elasticity and resistivity in strontium titanate, and for surface relaxations in Ruddlesden-Popper phases. Highlights of the thesis include in particular the methodical development regarding Resonant X-Ray Diffraction, such as the first use of partially forbidden reflections to get the complete phase information not only of the tensorial structure factor but of each individual atomic scattering tensor for a whole spectrum of energies, as well as the determination of orbital degrees of freedom and details of the partial local density of states from these tensors. On the material side, the most prominent results are the identification of the migration-induced field-stabilized polar phase and the exergonic redox behavior in SrTiO3 caused by defect migration and defect separation.

To support the growing global demand for energy, new sustainable solutions are needed both economically and environmentally. Thermoelectric waste heat recovery and energy harvesting could contribute by increasing industrial process efficiency, as well as powering stand-alone devices, microgenerators, and small body appliances.The structural complexity of quaternary chalcogenide materials provides an opportunity for engineering defects and disorder, to modify and possibly improve specific properties. Cu2ZnSnS4 (CZTS, often kesterite), valued for the abundance and non-toxicity of the raw materials, seems particularly suited to explore these possibilities, as it presents several structural defects and polymorphic phase transformations. The aim of this doctoral work is to systematically investigate the effects of structural polymorphism, disorder, and defects on the thermoelectric properties of CZTS, with particular emphasis to their physical origin. A remarkable case is the order-disorder transition of tetragonal CZTS, which is found responsible for a sharp enhancement in the Seebeck coefficient due to a flattening and degeneracy of the electronic energy bands. This effect, involving a randomization of Cu and Zn cations in certain crystallographic planes, is verified in bulk and thin film samples, and applications are proposed to exploit the reversible dependence of electronic properties on disorder. Low-temperature mechanical alloying is instead discovered stabilizing a novel polymorph of CZTS, which disordered cubic structure is studied in detail, and proposed deriving from sphalerite-ZnS. The total cation disorder in this compound provides an uncommon occurrence in thermoelectricity: a concurrent optimization of Seebeck coefficient, electrical and thermal conductivity. These findings, besides providing new and general understanding of CZTS, can cast light on profitable mechanisms to enhance the thermoelectric performance of semiconducting chalcogenides, as well as delineate alternative and fruitful applications.