Physical Sciences and Mathematics Commons^™

Magnetic Properties Of The Bifeo₃-Pbtio₃-Pbzro₃ Ternary System, James Ivan Latham

Doctoral Dissertations

"The magnetic susceptibility and spontaneous magnetic moment of the perovskitic, polycrystalline solid solutions of BiFeO₃ with PbTiO₃, PbZrO₃, and [50PbZrO₃·50PbTiO₃] were determined using the Faraday method. Pure BiFeO₃ has a G-type antiferromagnetic structure. Although the perovskite BiFeO₃ exhibits a sharp peak in the susceptibility at the Néel temperature, it does not possess a spontaneous magnetic moment. The solid solutions investigated possessed a spontaneous magnetic moment throughout the multiple cell rhombohedral region of the BiFeO₃-PbTiO₃-PbZrO₃ ternary phase diagram, which extends from pure BiFeO₃ to …

A Theoretical Investigation Of Elastic And Voigt Transient Spherical Waves, And Plane Three-Element Viscoelastic Waves, Edward Hornsey

Doctoral Dissertations

"A mathematical model of explosive generated waves in rock is needed in many areas of engineering endeavor. Investigations to date have been unsuccessful in obtaining a model that satisfactorily represents real wave phenomena at all radial distances and in all of the important characteristics.

In this investigation, spherical waves in elastic and Voigt media were investigated. Series solutions for plane waves in a three-element viscoelastic medium were obtained. A dual exponential pressure pulse, P(t) = P_o (e^-αt-e^-ßt) was assumed because it can exhibit significant features of real pressure pulses while avoiding instantaneous rise time, which …

A Calorimetric Study Of The Effects Of Surface Energy In A Type Ii Superconductor, Robert Rex Rice

Doctoral Dissertations

"A calorimetric study of the effects of the interphase surface free energy has been conducted on ellipsoidal samples of first and second kind superconductors. The measurements were performed using a specially designed magnetization calorimeter by two different techniques. The measurements were made on lead, tin, lead-4at%thallium, and tin-6at% indium. The results confirm the existence and experted sign of the surface energy in a well annealed lead-4at%thallium sample, and indicate that the interphase surface energy in lead and tin is too small to be directly detected by this method. The measured latent heats of transition of lead and tin agree well …

High Frequency Ferroelectric Properties Of The Bifeo₃-Pbtio₃-Pbzro₃ Ternary System, Robert Travis Smith

Doctoral Dissertations

"High temperature dielectric measurements have been performed on the ferroelectric and antiferroelectric perovskitic polycrystalline solid solutions in the BiFeO₃-PbTiO₃-PbZrO₃ ternary system. The data were taken in the UHF frequency range with the use of a slotted line and specially constructed sample holder capable of operation at temperatures in excess of 800°C.

The Curie points have been found to occur at progressively higher temperatures with the increase of BiFeO₃ content in the solutions except in phase transition regions where minima can occur. The dielectric constants at the Curie temperatures have been found to decrease with …

Kilocycle Range Dislocation Damping In Dilute Magnesium Alloy Single Crystals, Robert Ray Nothdurft

Doctoral Dissertations

"The kilocycle range dislocation damping and Young's modulus of single crystals of magnesium and single crystals of magnesium containing small additions of lithium, zinc, or aluminum have been studied as a function of strain amplitude, temperature, and time during annealing and following a high strain amplitude vibration. The data are compared to the Granato-Lücke theory of dislocation damping, the Granato-Hikata-Lücke theory for the recovery of damping following plastic deformation, and the Yamafuji-Bauer theory for the recovery of damping following a high strain amplitude vibration. Reasonable qualitative agreement is obtained between the Granato-Lücke theory and the observed dependence of the damping …