Tunable electrocaloric effect in lead scandium tantalate through calcium doping

Abstract

State-of-the-art electrocaloric cooling prototypes rely on the conventional electrocaloric effect of ferroelectric lead scandium tantalate (PbSc0.5Ta0.5O3, PST), which peaks near room temperature. Here, we demonstrate that A-site calcium doping in highly ordered PST modifies its phase transitions and enables precise tuning of the electrocaloric response. The transition temperature shifts down to 258 K and up to 319 K, depending on Ca concentration. Calorimetry under electric field, electrical polarization loops, and piezoresponse force microscopy reveal the emergence of an intermediate antiferroelectric phase stabilized for Ca $\ge$ 2\%. These results are supported by first-principles calculations. We observe a conventional electrocaloric effect for Ca $\le$ 2\% and an inverse electrocaloric effect at higher doping ($\ge$ 2\%). Under an applied field of 110 kV cm${}^{-1}$, Ca-doped PST exhibits an adiabatic temperature change of 2 K over a range from 263 K to 353 K. Such Ca-doped PST compounds could be used to expand the temperature range of PST below the freezing point of water. Our results offer a pathway to cascaded electrocaloric cooling devices with extended operating spans.

References in corpus (6)

• Restoring the density-gradient expansion for exchange in solids and surfaces
• Generalized gradient approximation for solids and their surfaces
• Implementation strategies in phonopy and phono3py
• First-principles study of the multi-mode anti-ferroelectric transition of PbZrO3
• Origin of the Large Negative Electrocaloric Effect in Antiferroelectric PbZrO3
• Quantitative correlation between structural (dis-)order and diffuseness of phase transition in lead scandium tantalate