Phenomenological analysis of positive and negative electrocaloric effects in Rochelle salt

Abstract

Ferroelectrics exhibiting both positive and negative electrocaloric effects stand out as promising materials for achieving high-efficiency solid-state refrigeration. The phase transition is acknowledged as a crucial factor in designing such materials. This study investigates the electrocaloric behavior and its correlation with phase transitions in Rochelle salt single crystal using Landau thermodynamic theory. Analysis of free energy density, ferroelectric, and dielectric data uncovers a complex temperature-dependent phase transition sequence of paraelectric–ferroelectric–paraelectric. This imparts Rochelle salt single crystal with intriguing field-induced phase transition behaviors and electrocaloric responses. Pronounced positive and negative electrocaloric effects are, respectively, observed near the high-temperature and low-temperature Curie point. The opposite sign of entropy differences between the ferroelectric and the two paraelectric phases is identified as the origin of the difference in electrocaloric response. These findings not only enhance our understanding of the electrocaloric effect but also provide a design solution for materials with the coexistence of positive and negative electrocaloric effects.