Towards multicaloric effect with ferroelectrics

Abstract

Utilizing thermal changes in solid state materials strategically offers caloric-based alternatives to replace current vapor-compression technology. To make full use of multiple forms of the entropy and achieve higher efficiency for designs of cooling devices, the multicaloric effect appears as a cutting-edge concept encouraging researchers to search for multicaloric materials with outstanding caloric properties. Here we report the multicaloric effect in BaTiO 3 single crystals driven simultaneously by mechanical and electric fields and described via a thermodynamic phenomenological model. It is found that the multicaloric behavior is mainly dominated by the mechanical field rather than the electric field, since the paraelectric-toferroelectric transition is more sensitive to mechanical field than to electric field. The use of uniaxial stress competes favorably with pressure due to its much higher caloric strength and negligible elastic thermal change. It is revealed that multicaloric response can be significantly larger than just the sum of mechanocaloric and electrocaloric effects in temperature regions far above the Curie temperature but cannot exceed this limit near the Curie temperature. Our results also show the advantage of the multicaloric effect over the mechanically-mediated electrocaloric effect or electrically-mediated mechanocaloric effect. Our findings therefore highlight the importance of ferroelectric materials to develop multicaloric cooling.2

Unveiling Electrocaloric Potential of Antiferroelectrics with Phase Competition

“…[28] Surprisingly, our findings reveal that the critical factor is not which branch we keep but rather the parts of the loop that we must omit. [28] Surprisingly, our findings reveal that the critical factor is not which branch we keep but rather the parts of the loop that we must omit.…”

“…Values of up to 2.5°C at 88°C under an applied electric field of 90 kV cm −1 were predicted in Pb(Nb,Zr,Sn,Ti)O 3 using the indirect approach based on the numerical integration of the Maxwell relations and up to 1.1 K under the field of 5 kV mm −1 from direct measurements. At the same time the applicability of the indirect approach to study the ECE in ferroics is under never-ceasing debate, [2,28] especially for the case of AFEs. [19].…”

“…[18] Enhancement of the ECE in the vicinity of the AFE-FE phase transition was reported in the earlier experimental study of ref. [28] In particular, the presence of the electric hysteresis associated with the first-order nature of the electric-field-induced phase switching in many AFEs and FEs leads to the uncertainty regarding the application of the indirect approach. At the same time the applicability of the indirect approach to study the ECE in ferroics is under never-ceasing debate, [2,28] especially for the case of AFEs.…”

“…[19]. Given that nearly 87% of studies are completed using the indirect approach, [28] these are important questions to address. [28] In particular, the presence of the electric hysteresis associated with the first-order nature of the electric-field-induced phase switching in many AFEs and FEs leads to the uncertainty regarding the application of the indirect approach.…”

Multicaloric effect: An outlook

“…For materials in which αe > 0, αm > 0, d e /s e > 0 and d m /s m > 0, it can be shown that a heating effect (∆T > 0) is achieved for adiabatic polarization / magnetization, and a cooling effect (∆T < 0) for an adiabatic depolarization / demagnetization, respectively. Since its first publication in 2012, the multicaloric effect has generated increased interest and numerous studies of caloric and multicaloric effects have been reported [17][18][19][20][21][22][23][24][25][26][27]. However, a true experimental demonstration of the multicaloric effect has not been reported yet.…”