Large electrocaloric effects in single-crystal ammonium sulfate.

Electrocaloric (EC) effects are typically studied near phase transitions in ceramic and polymer materials. Here, we investigate EC effects in an inorganic salt, namely ammonium sulfate (NH4)2SO4, with an order-disorder transition whose onset occurs at 223 K on cooling. For a single crystal thinned to 50 μm, we use a Maxwell relation to find a large isothermal entropy change of 30 J K(-1) kg(-1) in response to a field change of 400 kV cm(-1) The Clausius-Clapeyron equation implies a corresponding adiabatic temperature change of 4.5 K.This article is part of the themed issue 'Taking the temperature of phase transitions in cool materials'.