Cryogenic refrigeration utilizing the electrocaloric effect in pyroelectric lithium sulfate monohydrate

Abstract

A cryogenic refrigeration cycle based on the (linear) electrocaloric effect in single crystals of lithium sulfate monohydrate (LSM) is proposed. The phenomenology of the electrocaloric effect is developed and expressions for the low-temperature heat capacity and pyroelectric coefficient are derived. A Carnot cycle consisting of two isothermal and two isentropic steps is proposed and extensions are made to multi-stage refrigerators. Refrigerators operating with a high-temperature reservoir at 1.25 K have a maximum refrigeration capacity of 3.84 μJ per cycle per cm3 of working material (maximum electric field = 100 kV cm-1). However, the minimum temperature achievable with one-stage of refrigeration is 0.875 K and with three-stages, 0.047 K. Three-stage refrigerators operating with 1 K reservoirs can theoretically reach temperatures less than 1 mK.