Fig. 4: Dependence of low-pressure reversibility on thermal contact.
From: Colossal barocaloric effects with ultralow hysteresis in two-dimensional metal–halide perovskites
The phase boundary determined from HP-DSC experiments for (a–d) (DA)2MnCl4 and (e–h) (NA)2CuBr4, using (a, b, e, f) single-crystal samples with improved thermal contact and (c, d, g, h) powder samples. Scan rates of 2 K min–1 were used for all experiments, and He was used as the pressure-transmitting medium. DSC traces at ambient pressure are show in the left panel, with transition peak width highlighted in red and blue shades for heating and cooling, respectively. Onset temperatures are highlighted in dashed gray lines, with thermal hysteresis marked using black arrows. The pressure dependence of the onset and completion transition temperatures is shown in the right panels, and these phase boundaries illustrate the impact of the transition width on the minimum pressure required to drive a reversible isothermal entropy change (Prev) and a reversible adiabatic temperature change (Prev,ad). Note that the isobaric HP-DSC data for the powder samples is shown in Supplementary Fig. 16. Reversible barocaloric effects for powder and single-crystal samples are summarized in Supplementary Table 7.
