Research Fellows Directory
Dr Sohini Kar-Narayan
University of Cambridge
My research aims at developing an efficient and clean solid-state cooling technology based on the electrocaloric (EC) effect associated with phase transitions in ferroelectric materials. My interest lies in the development and understanding of new EC materials and the subsequent design of prototype cooling devices. Additionally, the piezoelectric and pyroelectric properties of these EC materials are attractive for energy harvesting applications.
EC refrigeration is a candidate for solid-state cooling that exploits electric field-driven temperature/entropy changes near phase transitions in ferroelectric materials. There has been renewed interest in the field of electrocalorics since the discovery of giant EC effects (~12 K) in ferroelectric thin films, prior to which EC temperature changes were restricted to a few Kelvin in bulk ferroelectrics. However, reports of large EC temperature changes in films have mostly been predicted from indirect thermodynamic analysis of electrical data, and are difficult to confirm via conventional thermometry/calorimetry as films cannot pump significant heat due to low thermal mass. I focus on novel techniques to accurately measure the EC effect in thin films of promising materials, and on modeling EC heat flow, to provide a basis for developing optimized EC devices for cooling applications.
At the same time, energy harvesting for small power applications is a hot research topic due to its potential applications in powering portable electronics, wireless sensors and medical implants, to name a few. Powering devices from scavenged ambient energy from the environment is an attractive avenue for replacing or extending the lifetime of traditional power sources such as batteries. My research in this area entails scavenging energy from mechanical vibrations and temperature variations of ambient environments using the piezoelectric and pyroelectric properties respectively of ferroelectric thin films, nanowires and multilayer capacitors.