Enhanced reversible barocaloric effect at low pressure in neopentyl plastic crystal solid solutions
The discovery of colossal barocaloric effects in neopentyl glycol (NPG) makes plastic crystals promising candidates for solid-state refrigerants with lower environmental impact than vapour compression fluids. Optimising operational temperatures and low-pressure operability remains challenging without compromising thermodynamic parameters. Here, we implement a strategy to improve the viability of NPG derivatives as barocaloric refrigerants. We blend pentaglycerine (PG) with NPG to lower the phase transition temperature, then dope the blend with 2% pentaerythritol (PE) to improve transition reversibility. In comparison with NPG under the same conditions, this ternary system has a seven-fold increase in reversible isothermal entropy change (|$ΔS_{(it,rev)}$ | = 13.4 J kg$^{-1}$ K$^{-1}$) and twenty-fold increase in operational temperature span ($ΔT_{span}$ = 18 K) at pressures of 1 kbar. Synchrotron x-ray diffraction and quasielastic neutron scattering reveal structural and dynamical effects that broaden the temperature range of the first-order phase transition due to intermolecular hydrogen bond network disruption by the molecular dopants. We propose that exploiting the compositional phase space of multi-component molecular blends is effective for designing practicable molecular BCs.