There has been much recent research on the development of lead-free ceramics to replace lead zirconium titanate, which is widely used in a variety of electronic devices including actuators, sensors, transducers and capacitors. In the present proposal we investigate bismuth niobium titanate-barium strontium titanate based materials, which are of particular interest as their high dielectric constant and low dielectric loss can be utilized for energy storage in capacitors (which have higher power density compared to batteries). Their energy density is significantly better than many ferroelectric ceramics currently used for energy storage. The aim of the present work is to establish the structure property relationships in this system and confirm the structural details of the critical phase transitions in this system.