Effects of uniaxial compressive stress on the electrocaloric effect of ferroelectric ceramics

The effects of uniaxial compressive stress on the electrocaloric effect (ECE) of ferroelectric ceramics are studied by Landau-Ginzburg-Devonshire (LGD) thermodynamic approach, direct method, and indirect techniques. Soft lead zirconate titanate ceramics is used as a model material. The direct measurement results are given by an infrared camera combined with a set of specially designed testing setup. It is demonstrated that ECE can be significantly tuned by uniaxial compressive stress. The direct measurement results are essentially in agreement with the LGD theory calculated results, while significant discrepancies between direct and indirect methods are observed. These results are explained by the complex domain switching and possible phase transition behavior under the coupled thermo-electro-mechanical field. In addition, with compressive stress of 50 MPa, direct measurement shows that an improvement of 66.7% in cooling capacity can be achieved at 375 K, which demonstrates that the application of compressive stress is an effective approach for enhancing ECE in ferroelectric ceramics. Our results not only provide insights into the effects of uniaxial compressive stress on ECE, but also offer more opportunities for the design of electrocaloric materials and devices.