| In the first part of this work, one of the most attractive features of the sol-gel process, namely the ability to prepare ceramics and glasses well below conventional firing temperatures, is used to grow ferroelectric crystals in an amorphous glass matrix. In the second part of this research, the structure of the ferroelectric crystals-glass nanocomposites is modified by the inclusion of an organic molecule in the oxide. Because the ferroelectric phase is able to order itself in some crystalline fashion before the degradation temperature of the organic molecule, a new class of material results. The term "organically modified glass ceramics" may be used, although this an unconventional use of the term "glass ceramic". The material does contain the basic characteristics of a glass ceramic: a crystalline phase and an amorphous phase; its unique feature is the simultaneous presence of an organic molecule in the oxide structure.; The first part of the work describes the growth of ferroelectric crystals in glass. Crystals of lithium niobate, LiNbO{dollar}sb3{dollar} and barium titanate, BaTiO{dollar}sb3{dollar} have been grown a silica matrix. Formulations containing 50 mole percent of the ferroelectric have been prepared. The growth of the crystals is followed with time and temperature, and it is shown that at temperatures as low as 200{dollar}spcirc{dollar}C, some local ordering of the ferroelectric phase occurs. Such locally ordered nanostructures, called "ferrons", had been observed previously in sol-gel derived ferroelectrics but they are observed here for the first time in a silica glass matrix. The ferroelectricity of the materials is studied by characterization of P-E hysteresis loops.; The second part of this work takes advantage of the low temperature of formation of these ferrons, and relates to the very active area of research that organically modified silicates (Ormosils) have become. The molecular structure of the glass-ferrons nanocomposite is modified by an organic molecule which was added at the solution stage. An organic molecule which exhibits polar properties was chosen for the study, triethoxysilyl-propyl-dinitrophenyl amine (TDP). The organic is grafted onto the siloxane network.; The properties of the organically modified ferroelectric-glass nanocomposite, such as P-E hysteresis loops, are studied. |
