High sensitivity to the electric field of both the phase transition temperature and the electrocaloric effect in ferroelectric NH4HSeO4

https://doi.org/10.1016/j.ssc.2024.115747

The effect of an electric field on thermal and dielectric properties as well as electrocaloric response in the ferroelectric NH₄HSeO₄ has been studied using a universal multifunctional adiabatic calorimeter. The phase transition temperature between the ferroelectric and incommensurate phases is found to be highly sensitive to the electric field, dT₂/dE ≈ 1.6 K/(kV/cm), at a low electric field strength. The intensive electrocaloric effect at E = 1.35 kV/cm observed by direct measurements, ΔT_AD ≈ 0.045 K, as well as determined indirectly by analyzing the entropy-temperature-electric field phase diagram, ΔT_AD ≈ 0.03 K, is quite large compared to the effects in other ferroelectrics.