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Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1993. / Vita. Abstract. Includes bibliographical references (leaves 24-27). Also available via the Internet.

Thesis (M.S.)--West Virginia University, 2001. / Title from document title page. Document formatted into pages; contains ix, 110 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 54-59).

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Fatigue and electrical degradation including low voltage breakdown of ferroelectric lead zirconate titanate Pb(Zr_xTi_{1 - x})O₃ (i.e. PZT) thin films are the major limitations for commercial memory applications of these films. It is noted that the presence of oxygen vacancies and their entrapment at the electrode-ferroelectric interfaces are the sources of the degradation phenomena. Attempts were made in this study to solve these problems: 1) by minimizing oxygen vacancy entrapment at the interfaces by employing RuO₂ electrodes; 2) by lowering the oxygen vacancy concentration in PZT films using donor doping (e.g. La³⁺ at Pb²⁺ site and Nb⁵⁺ at Ti/Zr⁴⁺ site). For this study, PZT thin films were prepared by a sol-gel method and deposited on both Pt/Ti/SiO₂/Si and RuO₂/SiO₂/Si substrates. The microstructure and electrical properties, such as hysteresis properties, fatigue, leakage current, time dependent dielectric breakdown (TDDB) and retention, were studied with regard to the Zr/Ti ratio, the excess lead, the annealing temperature, the electrode material and the doping amount. Furthermore, the pyrochlore to perovskite phase transformation of PZT on RuO₂ electrodes was also investigated. It was shown that PZT films (Zr/Ti=50/50) with 10 at.% excess lead annealed at 650°C for 30 min possessed the best electrical properties for ferroelectric memory application. In confirmation with earlier theoretical and experimental results, no polarization loss was observed up to 10¹¹ switching cycles for the PZT films deposited on RuO₂ electrodes. However, the low Schottky barrier at the interfaces between RuO₂ and PZT films resulted in a higher leakage current at a high electric fields. Donor doping of PZT films decreased carrier concentrations in PZT films, and thus, decreased the leakage current to acceptable limits. In addition, it was also noted that the pyrochlore to perovskite phase transformation of PZT on RuO₂ was similar to that of PZT on Pt electrodes. It can be concluded that the combination of RuO₂ electrodes and donor doping produced PZT films with high fatigue endurance and low leakage currents which are suitable for memory applications. / Master of Science

The present study was initiated to evaluate the pulmonary inflammatory and fibrotic responses induced by single and repeated exposures to glass fibers. Single and repeated intratracheal injections of glass fibers induced an acute inflammatory response which progressed to a chronic inflammatory and fibrotic response. Mice exposed to glass fibers in single or repeated doses demonstrated elevated numbers of eosinophils, neutrophils and macrophages and increases in cell-free protein in lung lavage fluid at five days post-exposure. These parameters, in addition to relative lung/body weight ratios and lung tissue hydroxyproline levels, were elevated in comparison to saline control animals at five weeks post-exposure. Although repeated exposures to glass fibers did not potentiate the cellular inflammatory response, they did induce a marked infiltration of eosinophils, a response not observed with either asbestos or silica exposures. These observations suggest that glass fibers may be more toxic to the lungs than previously thought.