Phase Formation and Dielectric Studies of Some BaO-TiO2-ZrO2 Based Perovskite System

High permittivity barium titanate zirconate (BTZ) is often used for dielectrics in commercial multilayer ceramic capacitors, actuators applications, and is a highly promising material for dynamic random access memory (DRAM) and microelectromechanical system (MEMS) applications due to its very stable, high insulating characteristic against voltage. Especially, the material is promising for environmental friendly application in compared to Lead (Pb) based compositions. Different solid solutions in the system have been synthesized via solid state reaction route. Detailed phase formation behaviors of the solid solutions were investigated through; (i) phase identification, (ii) phase quantity determination, (iii) change in lattice parameters and crystallite sises, (iv) evolution of phase formation kinetics and reaction mechanism, and (v) structure and microstructure evolution by Rietveld refinement method. The study on reaction mechanism concludes that; titanates form more easily in the system than zirconates. Then titanate inter-diffuses into zirconate, where latter phase acts as diminishing core Coming to the Rietveld structural refinement on the four-component system, the solid solution system Ba1-xSrx(Ti0.5Zr0.5)O3 remains cubic up to x<0.6 and becomes tetragonal in the range x >0.6 to x=1.0. Composition with x=0.6 contains both the cubic and tetragonal phases. The solid solution system (Ba0.5Sr0.5)(Ti1-xZrx)O3 remains cubic up to x≤0.6, and the solid solution breaks around x=0.8 with the formation of second phase of tetragonal type. Compositions with x=0.8 contain both the cubic and tetragonal phases and suggest to have a super-lattice structure due to the presence of two dissimilar structures. The Ba0.5Sr0.5ZrO3 has orthorhombic structure. Solubility of Ca and Mg in BaTi0.6Zr0.4O3 was also studied by Rietveld method. The Study concludes that Mg forms single phase solid solution with BaTi0.6Zr0.4O3 in the studied composition range and the structure remains cubic at room temperature. But solubility of Ca with BaTi0.6Zr0.4O3 breaks at around 20 atom % of Ca. The composition Ba0.9C0.1Ti0.6Zr0.4O3 remains cubic. With increase in Ca content, a different phase, orthorhombic CaTiO3, grows along with tetragonal Ba0.8C0.2Ti0.6Zr0.4O3. Detailed composition dependency microstructure and dielectric behavior of the different solid solution in the system has been studied. Temperature dependency dielectric behaviors of some of the selected compositions have been studied.