Anisotropy of the Electrocaloric Effect in Lead‐Free Relaxor Ferroelectrics

Abstract

The highly anisotropic electrocaloric effect, evidenced by both direct measurements and a descriptive theoretical model in lead‐free relaxor ferroelectric Sr0.75Ba0.25Nb2O6 single crystals, can be exploited by producing low‐cost grain‐oriented ceramics. Combined with the broad‐temperature‐range cooling regime provided by their polar nanoregions, these materials may be the key to future cost‐ and energy‐efficient solid‐state refrigeration.

Direct and indirect measurements on electrocaloric effect: Recent developments and perspectives

“…In turn, electrocaloric effect is always characterized by an isotropic DT with a homogeneous distribution along the sample in the literature except for very few studies. 138 151 and different crystal orientations. 152 In addition, extrinsic variation of electrocaloric effect (approximately 0.2 K) due to specific geometry in multilayer capacitors was observed between the metallic terminals and electrocaloric active ceramic regions in multilayer capacitors.…”

“…149 This result corresponds to about 50% of the average value in the sample, which is larger than the previous ones on anisotropy and inhomogeneity of electrocaloric cooling. 138,151,152 Let us briefly recall that current interest in design of electrocaloric prototypes is mainly based on multilayer capacitors. The multilayer capacitors consist of around 200 ceramic layers each of thickness about 10 lm separated by interdigitated inner electrodes with a thickness of several lm.…”

A novel sol–gel route to synthesize (Sr0.5Ba0.5)Nb2O6 ceramics with enhanced electrocaloric effect

“…This effect is considered as a promising cooling technology because of its high-efficiency and environment-friendly working system. [1][2][3] In the 21st century, a massive ECE was detected in PbZr 0:95 Ti 0:05 O 3 and P(VDF-TrFE) thin films, successively. 4,5 To date, related studies have been conducted on numerous ferroelectric films, [6][7][8] polymers, 9,10 and ceramics.…”

Upper limit of the electrocaloric peak in lead-free ferroelectric relaxor ceramics

“…1,2 This phenomenon is the electrocaloric effect (ECE). [3][4][5][6][7] Lead-free relaxor ferroelectrics with high dielectric strength 8 are suitable candidates for solid state refrigeration, due to the extra contribution of their polar nano-regions (PNRs); however, their ECE must be increased. One approach is to operate close to critical points (CPs) where energy barriers for switching between different phases are reduced.…”