Large electrocaloric effects in oxide multilayer capacitors over a wide temperature range

Heat pumps based on magnetocaloric and electrocaloric working bodies-in which entropic phase transitions are driven by changes of magnetic and electric field, respectively-use displaceable fluids to establish relatively large temperature spans between loads to be cooled and heat sinks^1,2. However, the performance of prototypes is limited because practical magnetocaloric working bodies driven by permanent magnets^3-5 and electrocaloric working bodies driven by voltage^6-16 display temperature changes of less than 3 kelvin. Here we show that high-quality multilayer capacitors of PbSc_0.5Ta_0.5O₃ display large electrocaloric effects over a wide range of starting temperatures when the first-order ferroelectric phase transition is driven supercritically (as verified by Landau theory) above the Curie temperature of 290 kelvin by electric fields of 29.0 volts per micrometre. Changes of temperature in the large central area of the capacitor peak at 5.5 kelvin near room temperature and exceed 3 kelvin for starting temperatures that span 176 kelvin (complete thermalization would reduce these values from 5.5 to 3.3 kelvin and from 176 to 73 kelvin). If magnetocaloric working bodies were to be replaced with multilayer capacitors of PbSc_0.5Ta_0.5O₃, then the established design principles behind magnetocaloric heat pumps could be repurposed for better performance without bulky and expensive permanent magnets.