Structural, Electrical and Ferroelectric Properties of Substituted Barium Titanate

Abstract

The high dielectric constant of barium titanate (BT) and BZT-based electroceramics is responsible for selecting such materials for capacitor fabrication. Such materials have potential applications practical devices due to their good structural, electrical and ferroelectric properties. The properties can be tailored to suit specific requirements by molecular engineering using substitutions for both Ba site and Ti site. Due to this reason these materials have attracted the attention of many researchers. The present thesis is on the synthesis and characterization of such materials. The introduction and importance of the BT based ceramics is discussed in Chapter 1. Out of the different methods of preparation of ceramics solid state reaction route was adopted since it’s an easy, cheap and high yielding method. Chapter 2 mainly focused on the experimentation regarding the synthesis and characterization. Synthesis and characterization of BaZr0.10Ti0.90O3 is discussed in Chapter 3. The effect of Two-stage sintering is also discussed in this chapter. Substituents like lead for Ba results in the increase in tetragonal to cubic phase transition temperature (Curie temperature) and decrease in room temperature dielectric constant. The temperature dependence of dielectric constant of lead substituted materials found to be better in comparison to pure barium titanate and undoped barium zirconate titanate. Substituents like zirconium for Ti results in the decrease in Curie temperature of the material, while increases the room temperature dielectric constant. It was interested to investigate the effect of Pb2+, Ca2+ and Zr4+ on various physical properties of BaTi0.90Zr0.10O3 ceramics. The investigated structural, electrical and ferroelectric properties are discussed in Chapter 4. Owing to their special electronic configuration, aliovalent ions can act as donor as well as acceptors depending upon the amount of substitution. La3+ and Sm3+ ions act as softener for a very small amount of substitution. An investigation on the structural, electrical and ferroelectric properties of material composition Ba0.80Pb0.20Zr0.10Ti0.90O3 substituted with La3+ and Sm3+ up to 1 mol% is shown in Chapter 5. Chapter 6 includes the conclusion and summary of the results and significance of the ceramics prepared