M.Sc Thesis


M.Sc StudentHanady Yassen
SubjectHydrothermal Synthesis and Characterization of Doped and
Un-Doped Nano-Sized Barium Titanate Powder
DepartmentDepartment of Chemical Engineering
Supervisor Professor Tsur Yoed


Abstract

Manufacturing technology is known to have a strong effect on the structure and properties of barium titanate ceramics. Hydrothermal synthesis as a preparation technique was investigated in this work and a particle size of ~24nm was obtained.

          Doping of barium titanate ceramics by aliovalent dopants leads to many changes in the material properties, such as the conductivity especially at high temperatures, the morphology, the dielectric behavior, etc. The mutual influence of impurities and lattice defects follows from the necessity of excess charge compensation. It is known that the addition of a small amount of Nb has significant effects on the electrical properties of BaTiO3. However, how Nb is distributed locally, and what structural variations it causes have not been studied in depth. With this in mind, the effect of dopants (Nb) ions on the microstructure and electrical properties of BaTiO3 crystals was investigated. Pure BaTiO3 and  series of doped barium titanate powders were prepared by two different methods and were examined by: XRD, HR-SEM, TEM, Particle size analysis techniques, Zeta potential measurements, Specific surface area, DSC measurements, Impedance Spectroscopy and, to investigate the dopant distribution, SIMS analysis and electron microscopy were performed. The influence of the preparation method on the properties of the powder is discussed. Significant differences were detected by all the probes used in the properties of the prepared powders. Samples doped by coating have properties that meet the X7R standard.