Colossal barocaloric effect with a wide working-temperature span in octylamine hydrochloride

Abstract

Barocaloric solid-state refrigeration has aroused more attention since the breakthrough of plastic crystals. However, most reported materials with a single-phase transition generally exhibit a narrow working-temperature span. Herein, the layered C₈H₁₇NH₃Cl compound is reported and shows a sequence of phase transitions from the initial triclinic phase to the final tetragonal phase near room temperature. These multiple-phase transitions result in a broad working-temperature span (ΔT) of ∼65 K and a maximum isothermal entropy change of 119 J kg⁻¹ K⁻¹ under a pressure of 100 MPa. Simultaneously, ΔT is 25 K with a constant isothermal entropy change of 50 J kg⁻¹ K⁻¹ under the pressure of 100 MPa. The resultant refrigerant capacity is 3101 J kg⁻¹. Raman analysis indicates that the molecular conformation disorder induced by the sequence of phase transitions is responsible for the excellent colossal barocaloric effect. This work not only indicates that the layered C₈H₁₇NH₃Cl compound could be a promising competitor for barocaloric refrigeration near room temperature but also recommends that the multiple phase transitions are an effective route to broaden the working-temperature span.