Study of Structural and Electrical Properties of Li and Nb Modified BNT Thin Film and Observation of Enhanced Electrocaloric Effect near Room Temperature

A detailed investigation was done on Li and Nb modified Bi0.5Na0.5TiO3 (BNT) thin films where structural, dielectric, ferroelectric and electrocaloric properties were studied. All thin films were synthesized using pulsed laser deposition. Structural investigation revealed that addition of Li and Nb do not alter the parent rhombohedral structure and all compositions were observed to have rhombohedral structure. However Ferroelectric and dielectric analysis clearly revealed that addition of Li and Nb affect the Ferroelectric (FE) -Antiferroelectric (AFE) phase transition temperature (T ( d ), depolarization temperature) and bring it down towards the room temperature and consequently a mixed phase of FE and AFE was observed near room temperature for composition x = 0.06. A sudden change in polarization in x = 0.06 composition with increasing temperature, subsequently leading to significantly high ( partial differential P/ partial differential T) ( E ) along with FE-AFE transition contributed to large electrocaloric (Delta T) = - 4.32 K in composition x = 0.06 similar to 35 degrees C.