Master of Science, University of Akron, 2007, Physics

The perovskites ABO3 are the most important class of dielectric materials. The perovskite SrTiO3 and the perovskite-related material CaCu3Ti4O12 are studied in this work. In the first part of this work, we find the structural temperature of SrTiO3 by performing molecular dynamics simulations and investigate electronic and structural properties of SrTiO3 by performing ab initio calculations. A strong chemical bonding nature between Ti and O is found. This is responsible for the TiO6 octahedron behavior throughout the phase transition. In the second part, ab initio calculations on CaCu3Ti4O12 are performed. We investigate the electronic properties of this material. An antiferromagnetic character of CaCu3Ti4O12 is observed. Furthermore, we investigate the electronic properties of new materials of different Ca, Cu ratios. This is the first time to perform ab initio calculations to study Ca1+xCu3-xTi4O12. We find that with the increase of with increase of Ca in the material, the optimized lattice constant and band gap increase, and insulator character becomes much more pronounced in the material. This is in good agreement with the experimental results.

Committee: Alper Buldum (Advisor); Ang Chen (Advisor); Jutta Luettmer-Strathmann (Committee Member) Subjects:

Master of Science, University of Akron, 2006, Physics

Dielectric materials have been widely used in electronic industry. Recently an oxide ceramic CaCu3Ti4O12 (denoted as CCTO) is reported to be very promising because it possesses a very high dielectric constant. However, further research on its dielectric properties indicates that this material has a high dielectric loss, which seriously blocks its practical application. In this work, pure CCTO ceramic, and two series of CCTO derivatives, i.e., “CCTO + CaTiO3” and “CCTO + MnO2” ceramics were prepared, and their phase assemblies, structure, dielectric properties, and conducting properties are studied. The relaxation mechanism was investigated for CCTO and its derivatives. It is for the first time revealed that the relaxation time follows the Vogel-Fulcher relation instead of the Arrhenius relation.

Committee: Ang Chen (Advisor) Subjects: