Electrical conduction mechanisms in BaTiO₃-based ferroelectric capacitor ceramics with an emphasis on the X7R type were studied. Dominant charge carriers in this material were identified as conduction band electrons below a temperature of 850°C. This was substantiated by the following results: negative Seebeck coefficients, zero galvanic cell voltage, and evidence of space charge-limited currents in MLC capacitors and related ceramic. Effects of chip thickness on the electrical parameters, as well as the I-V characteristics, were studied. Chip electrical parameters such as resistivity, dielectric constant, and activation energy were found to be independent of chip thickness. Effects of ambient were also studied and differences in current-voltage behavior were attributed to surface effects. Complex impedance spectroscopy proved to be a useful technique in separating grain, grain boundary, and contact contributions to the total impedance. Impedance plots for X7R ceramic revealed negligible contact impedance. The most probable electrical transport mechanism in X7R ceramic is small polaron hopping, although the possibility of combining small polaron hopping and grain boundary transmission cannot be excluded. / Ph. D.

A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy. August 2014. / The process of the computational discovery of materials for future technologies is a combination of numerical techniques and general scientific intuition to select elements and combine in order to form novel types of materials. Modern ab initio methods based on density functional theory are capable of predicting with a high level of accuracy the most stable ground state atomic configurations of any given material. Once the ground state configurations are established, the electronic, optical and mechanical properties of the novel bulk nitrides may be determined. Electronic properties of C3N4, CN2, SiN2, GeN2, C2N2(NH), Si2N2(NH), Ge2N2(NH) and Sn2N2(NH) are analysed by computing the Kohn-Sham band structures. The optical properties are investigated by calculating the real and the imaginary parts of the frequency-dependent dielectric constant. The mechanical properties are determined by calculating elastic constants, Young’s modulus, Poisson’s ratio, Vickers hardness, shear and bulk moduli.

Modeling of patch antennas and resonators on arbitrary dielectric substrates using surface RWG and volume edge based basis functions and the Method of Moments is implemented. The performance of the solver is studied for different mesh configurations. The results obtained are tested by comparison with experiments and Ansoft HFSS v9 simulator. The latter uses a large number of finite elements (up to 200K) and adaptive mesh refinement, thus providing the reliable data for comparison. The error in the resonant frequency is estimated for canonical resonator structures at different values of the relative dielectric constant ƒÕr, which ranges from 1 to 200. The reported results show a near perfect agreement in the estimation of resonant frequency for all the metal-dielectric resonators. Behavior of the antenna input impedance is tested, close to the first resonant frequency for the patch antenna. The error in the resonant frequency is estimated for different structures at different values of the relative dielectric constant ƒÕr, which ranges from 1 to 10. A larger error is observed in the calculation of the resonant frequency of the patch antenna. Moreover, this error increases with increase in the dielectric constant of the substrate. Further scope for improvement lies in the investigation of this effect.

Thesis (Elec.E)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1982. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING / Includes bibliographical references. / by Huan Lim Lee. / Elec.E

Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 158-172). Available also in a digital version from Dissertation Abstracts.

Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 147-155). Available also in a digital version from Dissertation Abstracts.

Thesis (Ph. D.)--University of Texas at Austin, 2003. / Supervisor: Jack C. Lee. Vita. Includes bibliographical references. Available also from UMI Company.

Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 101-108). Available also in a digital version from Dissertation Abstracts.

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Driven by ever growing demands of miniaturization, increased functionality, high performance and low cost for microelectronic products and packaging, embedded passives will be one of the key emerging techniques for realizing the system integration which offer various advantages over traditional discrete components. Novel materials for embedded capacitor applications are in great demand, for which a high dielectric constant (k), low dielectric loss and process compatibility with printed circuit boards are the most important prerequisites. To date, no available material satisfies all these prerequisites and research is needed to develop materials for embedded capacitor applications. Conductive filler/polymer composites are likely candidate material because they show a dramatic increase in their dielectric constant close to the percolation threshold. One of the major hurdles for this type of high-k composites is the high dielectric loss inherent in these systems. In this research, material and process innovations were explored to design and develop conductive filler/polymer nanocomposites based on nanoparticles with controlled parameters to fulfill the balance between sufficiently high-k and low dielectric loss, which satisfied the requirements for embedded decoupling capacitor applications. This work involved the synthesis of the metal nanoparticles with different parameters including size, size distribution, aggregation and surface properties, and an investigation on how these varied parameters impact the dielectric properties of the high-k nanocomposites incorporated with these metal nanoparticles. The dielectric behaviors of the nanocomposites were studied systematically over a range of frequencies to determine the dependence of dielectric constant, dielectric loss tangent and dielectric strength on these parameters.