Anisotropy of piezocaloric effect at ferroelectric phase transitions in ammonium hydrogen sulphate

Mikhaleva, Ekaterina A.; Gorev, Mikhail V.; Molokeev, Maxim S.; Kartashev, Andrey V.; Flerov, Igor N. Journal Of Alloys And Compounds. https://doi.org/10.1016/j.jallcom.2020.155085

The role of anisotropy of the thermal expansion in formation of piezocaloric effect (PCE) near ferroelectric phase transitions in NH₄HSO₄ was studied. Strong difference in linear baric coefficients and as a result in intensive and extensive PCE associated with the different crystallographic axes was found. PCE giving the main contribution to the barocaloric effect were determined at both phase transitions. Rather strong effect of the lattice dilatation on the tuning of PCE was observed. Comparative analysis of PCE at the phase transitions in different materials showed that NH₄HSO₄ can be considered as a promising solid-state refrigerant. A hypothetical cooling cycle based on alternate using uniaxial pressure along two axes was considered.