Bi-based perovskite solid solutions for high energy density thin films

Graduation date: 2010Electrical energy storage devices are currently the main limiting factor in many electrical devices and with the increasing demands placed on electrical power over fossil fuels, high energy density materials are essential. Previous research by Huang et al. on bulk (1-x)Bi(Zn₁/₂Ti₁/₂)O₃-xABO₃ solid solution systems led to the discovery of an excellent dielectric material. The optimal compositions, which corresponded to morphotropic phase boundaries, were found to be 0.1Bi(Zn₁/₂Ti₁/₂)O₃-0.9BaTiO₃ and 0.3Bi(Zn₁/₂Ti₁/₂)O₃-0.7NaNbO₃. Measurements, made on bulk ceramics, showed that these materials possess dielectric constants as high as 3000 at 10 KHz for BT-BZT and 1200 for NN-BZT with low loss tangents (tan δ<0.01) up to high temperatures\ud (T>400 °C). Most notably, these high dielectric constants persist to high fields (E≤100 kV/cm) and the material exhibits a linear dielectric response at room temperature. Since most current and future applications of a high-K dielectric will require thin film geometry, we seek to duplicate these bulk properties in thin films. The purpose of this research was to investigate the dielectric properties of these two very promising compositions in thin film form in order to find a high-K material with low loss, minimal temperature dependence and a linear dielectric response