Dielectric properties and method of characterizing ceramic powders and multiphase composites

Barium Titanate was the first developed ferroelectric ceramic material and it is mostly used in capacitors. The reason behind a wide range of applications is that the barium titanate boasts of high dielectric properties. A phase transition from cubic to tetragonal at normal working temperatures provides enhanced dielectric properties in this electronic material. For any application and design, the most inquired property is the dielectric constant. Knowing or predicting the dielectric constant is very much required as it forms the pre-requisite for the design of any component. This is the major objective of the present work. Driven by the nanotechnology and miniaturization of electronic devices along with volumetric efficiency, synthesis forces us to consider ever decreasing particle size of ferroelectric materials. Therefore, when we prepare or custom design nanoparticles, it is imperative to determine the electrical properties of the as-synthesized particles.; To estimate the quality of a synthesized powder relative to an already existing commercial powder, a method has been introduced to characterize the powder for dielectric constant. Chapter 1 is mainly discussed about the crystal structure, different phases, and the dielectric principles involved with barium titanate powder.; Chapter 2 is focused on the same method that has been introduced to measure the dielectric constant of polymer/ceramic composites. In this work, the dielectric constant of polyvinyl cyanoethylate/barium titanate composite was determined. The obtained results are compared with the many available theoretical models to predict the dielectric constant of the composites. Then these results are extrapolated to comprehend the dielectric constant values of ceramic particles as these values form the base for the design of the composite.; Chapter 3 is focused on the determination of dielectric constant of a polymer/ceramic composite embedded with metallic nano-particles. The same polymer/ceramic composite that was discussed about in chapter 2 was considered with a 0.8 weight fraction of the ceramic. The precision and simplicity of the method can be exploited for predictions of the properties of nanostructure ferroelectric polymer/ceramic composites.; The characterization method developed and demonstrated in Chapters 2 & 3 is further applied for the barium titanate particle characterization. Chapter 4 is dealt with the presence of the lattice hydroxyls that is believed to be the major cause of the reduced tetragonality in the barium titanate ceramic powder. The sub-micron commercial barium titanate powder is treated with N-Methyl-2-Pyrrolidinon (NMP) to obtain a tetragonal powder. The dielectric constant of a single particle of this NMP treated cubic powder is reported to be around 64% higher than the as-received cubic powder. The dielectric properties of the barium titante ceramic powder that is determined does depend inversely on the lattice OH content as confirmed by FTIR spectroscopic analysis and TGA results.