The theory of ferroelectricity, and in particular the ferroelectric behavior of barium titanate, are discussed and qualitative agreement is obtained with experimental results. Limitations of the theory are pointed out. Experimental procedure used to manufacture samples of polycrystaline barium titanate ceramic, and to investigate their ferroelectric properties is outlined. The phenomena of permanent polarization and hysteresis are investigated in the ferroelectric temperature range, and are discussed. An electric equivalent of the Barkhausen effect is observed. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The dielectric polarization processes, conduction mechanisms and space charge effects occurring in tantalum / tantalum pentoxide / metal devices are investigated. The dielectric properties are analyzed on the basis of an ionic relaxation process with a nearly flat distribution of activation energies. This distribution leads to step response polarization currents following an inverse time law. The effect of an injected electronic space charge on the response of the device due to the removal of a step voltage is analyzed and results are given demonstrating this effect. The devices used exhibit a rectification behaviour. For tantalum positive the currents follow a Schottky law and for tantalum negative, the bulk Poole-Frenkel law. Hysteresis effects are observed as well as the effects of a space charge on the Schottky law currents. On one sample, sufficiently high fields causes an increase in the conductance by a factor of 10³ to 10⁵. For this deformed sample, no hysteresis or rectification is observed and the currents follow a Schottky law for both polarities. The validity of the ionic relaxation model is discussed in light of the observed dielectric losses at low temperatures. The experimental results indicate that an electronic rather than an ionic process could be responsible for the dielectric losses. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

Aniline Black, a polymer containing p-benzoquinodiimine groups, was synthesized chemically or electrochemically by the oxidation of aniline. The polymer salts showed the conductivity of 10⁻¹-10⁻³ ohm⁻¹cm⁻¹. Polymers containing anthroquinodiimine units were also prepared by polycondensations. The syntheses of model compounds containing p-benzoquinodiimine were attempted. Multiazobisphenol monomers were synthesized. 4,4'-(3,3'-Dimethyl-4,4'-biphenylenebisazo) bisphenol 7, 4,4'-[azobis(p-phenyleneazo)] bisphenol 8, and 4,4'-(2-methoxy-1,4-phenylenebisazo) bisphenol 10 displayed liquid crystal (l.c.) properties, while model derivatives of 7, 8, and 4,4'-(4,4'-stilbenebisazo) bisphenol 9 did likewise. Monomers and derivatives of 4-[(4-hydroxyphenyl)azo]-1-naphthol 5, and 4,4'- [oxybis(p-phenyleneazo)] bisphenol 6 showed no l.c. behavior. New thermotropic polyesters based on these multiazobisphenols were synthesized. Sebacates of 5, 6, 7, 8, and 10 showed l.c. behavior, while polymers based on isophthalic or 5-t-butylisophthalic acid did not do so. Polyformals were also synthesized from these momoners, only that of 4 showed weak l.c. behavior. The correlation between the structure of these polymers and their tractabilities, electrical properties, liquid crystal behaviors was studied. Polymers and copolymers containing p-azoarylene and p-azoxyarylene groups were synthesized by oxidative coupling of various aromatic diamines. Films were cast directly from the reaction mixtures or from the polymer solution. The films were n-doped by sodium naphthalide or p-doped by iodine. They showed electrical conductivities of 10⁻⁴ to 10⁻⁵ ohm⁻¹cm⁻¹. AB monomers containing dipolar p-phenyleneazo groups were synthesized: 4-(4-hydroxy-2-methoxyphenylazo) benzoic acid 21, 4-[4-(4-hydroxy-2-methoxyphenylazo)-2-methoxyphenylazo] benzoic acid 22, and 4-(4-hydroxy-2-methoxyphenylazo)-3-nitrobenzoic acid 23. The monomers were polymerized by direct polycondensations. The polyester synthesized from 21 formed a red, transparent film. A polymethacrylate containing dipolar p-phenyleneazo groups in the side chains was also prepared by the free radical polymerization of 1- [3-methoxy-4-(p-nitrophenylazo)-phenoxy] hexyl methacrylate 28.

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Call number: LD2668 .T4 1936 S31

LD2668 .T4 1966 C34 / Master of Science

Call number: LD2668 .T4 1966 H326 / Master of Science

published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / abstract / Physics / Master / Master of Philosophy

published_or_final_version / Civil Engineering / Master / Master of Philosophy