published_or_final_version / abstract / Chemistry / Doctoral / Doctor of Philosophy

This research concerns the effects on samples of nominal composition Bil.8Pb0.2Sr2Ca2cu30y which were exposed to hot, dense argon in a ballistic compressor. The investigations were concentrated on two specimens which were exposed to hot, dense argon at about 1800 K (peak pressure 330 atm) and 1500 K (peak pressure 230 atm), respectively. Sample Bi #1 showed a completely melted surface structure after triple exposure in the ballistic compressor at 1800 K while the surface of sample Bi #7 was just partly melted after double exposure at 1500 K. Changes in flux trapping capability and qualitative Meissner effect were investigated in addition to the properties described by Duan, et al. ( 17, 18, 3 2] , who reported changes in critical temperature, crystal structure, surface morphology and composition after exposure of samples to hot, dense argon. After triple exposure in the ballistic compressor at a temperature of approximately 1800 K, sample Bi #1 showed an enhanced Meissner effect on the exposed side compared to the unexposed side of the pellet, while no difference in Meissner effect was found between the exposed and the unexposed side of sample Bi #7. EDS analysis showed that both samples are inhomogeneous in chemical surface composition. Oxygen loss due to exposure to hot, dense argon could not be demonstrated. X-ray analysis indicated that the melted surface layer of sample Bi # 1 after triple exposure to hot, dense argon contains smaller crystals than before exposure in the ballistic compressor. Tc measurements gave varying results which are explainable by the chemical inhomogeneity of the specimens. An increase in the amount of trapped flux due to exposure of the samples to hot, dense argon could not be demonstrated

Thesis (Ph.D.)--McMaster University (Canada), 1992. / Source: Dissertation Abstracts International, Volume: 54-12, Section: B, page: 6278. Adviser: W. R. Datars.

Thesis (Ph. D.)--University of Hong Kong, 2008. / Also available in print.

Thesis (M.Ch.E.)--University of Delaware, 2008. / Principal faculty advisors: Mark A. Barteau and Douglas J. Buttrey, Dept. of Chemical Engineering. Includes bibliographical references.

Typescript. Includes vita and abstract. Includes bibliographical references (leaves 130-137). Abstract also available online in ProQuest, free to University of Oregon users.

Thesis (Ph. D.)--University of Texas at Austin, 1999. / Vita. Includes bibliographical references (leaves 199-214). Available also in a digital version from Dissertation Abstracts.

Thesis (Ph.D.)--Texas Christian University, 2010. / Title from dissertation title page (viewed July 29, 2010). Includes abstract. Includes bibliographical references.

We developed a model to investigate the dielectric properties of the BaTiO₃ − Bi(Zn₁/₂Ti₁/₂)O₃ (BT-BZT) solid solution, which is a relaxor ferroelectric and exhibits long range disorder. The model uses ab initio methods to determine all polarization states for every atomic configuration of 2 x 2 x 2 supercells of BT-BZT. Each supercell is placed on a lattice with an Ising-like interaction between neighboring cell polarizations. This method allows us to consider long range disorder, which is not possible with ab initio methods alone, and is required to properly understand relaxor ferroelectric materials. We analyze the Monte Carlo data for a single lattice configuration using the multiple histogram method, and develop a modified histogram technique to combine data from multiple lattice configurations. Our calculated values of dielectric constant, specific heat, and polarization agree reasonably well with experiment. / Graduation date: 2012

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