High Energy Density Dielectrics Based on Bi-Perovskites
Date/Time: 2009-04-29 16:00
Location: Weniger 304
Event speaker: Prof. David Cann, School of MIME, OSU
Title: High Energy Density Dielectrics Based on Bi-Perovskites
Recent work has shown that a new family of perovskite compositions exhibits a high dielectric permittivity that persists to high electric fields even in bulk ceramics. To achieve energy densities approaching 100 J/cm3 dielectric materials must operate near the fundamental limits of permittivity and breakdown. Conventional approaches to this technical challenge include utilizing ferroelectric or antiferroelectric materials with permittivities in excess of 1000. However, these non-linear materials derive their high permittivity from domain contributions that saturate at relatively low fields ultimately resulting in limited energy densities. A new family of materials based on Bi(Zn1/2Ti1/2)O3 –ABO3 perovskite solid solutions have shown that high permittivities (K > 1000) can be obtained at high fields (E ~ 100 kV/cm) without saturation. While the composition of these compounds is similar to ferroelectric compounds, the mechanism for the dielectric response is tied to nanoscale chemical and structural heterogeneities. These results represent an energy density close to 0.5 J/cm3 in a bulk ceramic. Although impressive, in thin film embodiments this material may be capable of attaining field levels approaching 2000 kV/cm, which would translate to a 400X increase in energy density.