Effect of uniaxial stress on energy harvesting, storage and electrocaloric performance of BZT ceramics

Abstract

In this work, a systematic approach of waste (thermal/mechanical) energy harvesting and storage potential is studied in Ba_0.85Zr_0.15TiO₃ (BZT) ceramics. The effect of stress on energy storage density (harvesting/storage) and electrocaloric performance is also studied. For this purpose, polarization–electric field hysteresis loops were recorded at various temperatures and uniaxial compressive stress. The Olsen cycle and electro-mechanical cycle are used for direct waste heat or mechanical energy to electrical energy conversion. A thermal energy-harvesting density of 42 kJ/m³ per cycle was obtained when the Olsen cycle was operated between 296–343 K and 0.25–1.5 MV/m. The electro-mechanical cycle-based energy harvesting is estimated as 78 kJ/m³ under the applied stress of 5–160 MPa and the electric field of 0.25–1.5 MV/m. The energy storage density is found as 39 kJ/m³ at zero stress field and 343 K, which increases to 53 kJ/m³ under the biased stress of 80 MPa in a wide operating temperature range of 296–328 K. It is observed that the high energy storage is a result of the reduction of the hysteresis loss. The electrocaloric temperature is found as 0.16 K and 0.18 K under the 0 and 80 MPa stress fields, respectively. Overall, the reported findings will enrich our understanding of the stress effect on BZT materials, which offers high performance for energy harvesting and storage-based applications. Moreover, this work can be also helpful in improving the energy storage density and electrocaloric effect via stress confinement.