On the Structure and Dielectric Study of Iso- and Alio-Valent Modified BaTiO3 Ceramics

Abstract

The perovskite family includes many titanates used in various electroceramic applications,for Example,electronic, electro-optical, and electromechanical applications of ceramics. Barium titanate, having a perovskite structure, is a common ferroelectric material with a high dielectric constant, which is widely utilized to manufacture electronic components such as mutilayer capacitors (MLCs), PTC thermistors, piezoelectric transducers, and a variety of electro-optical devices. Because of people’s demands, dielectric (essentially nonconducting) characteristics of ceramic materials are increasing rapidly. At the same time, people are attempting to reduce the size of all communication devices as small and as light as possible. Due to this trend, high dielectric constant materials such as barium titanate have nowadays become more and more important in ceramic materials.This thesis describes perovskite structure based on barium titanate composition. Oxide perovskites (ABO3) are important electroceramics having a large area of functionalities by virtue of their unique magnetic, dielectric, semiconducting or superconducting properties. These properties are related to the crystal structure, microstructure, and nature and distribution of point defects prevailing in the ceramics, which, in turn, depend on synthesis routes and processing parameters adopted. Extensive studies are reported in literature on these aspects of ceramics. The properties are also sensitive to such factors as atomic composition (non-stoichiometry), interfacial characteristics and chemical states as well as distribution, spatial and depth-wise, of the constituents of the material. Non-stoichiometry, oxygen non-stoichiometry in particular, is prevalent in perovskites. Oxygen vacancies, apart from bringing about structural modifications, act as donors and are responsible for the electrical conductivity of ceramics. The atomic composition in interfacial regions of polycrystalline materials is often different from the nominal or bulk composition. Therefore, a detailed study on these aspects of materials is desirable for a comprehensive assessment of their properties.This thesis presents investigations on the atomic composition and microstructural features of barium titanate and other electronic ceramics, namely, barium calcium titanates, barium praseodymium titanates and barium dysprosium titanates, by surface analytical techniques. The structural investigations of the ceramics have been carried out by X-ray diffraction, Energy Dispersive X-ray Spectroscopy (EDS) in association with scanning electron microscopy to probe the ceramographic study along with the compositional analysis.