High fidelity direct measurement of local electrocaloric effect by scanning thermal microscopy

Abstract

Electrocaloric effect (ECE) has great potential in solid-state cooling. However, the lack of reliable measurement method, especially at the local scale, hinders its materials optimization and structure design. In this paper, a high fidelity local measurement of ECE response with temperature sensitivity as high as ~8 mK has been developed based on scanning thermal microscopy (SThM) experiment and finite element model based quantitative analysis. With such high sensitivity, we have probed a multilayer capacitors (MLC) made of doped barium titanate, demonstrating significant effect of Joule heating that interferes the ECE measurement. An approach to correct the Joule heating has been proposed, with which we have identified the intrinsic ECE response, showing peak response near ferroelectric phase transition. Local mapping in ECE temperature response has also been acquired, revealing substantial spatial variation due to different heat exchange with exterior environment, leading to smaller temperature change experimentally measured in comparison to intrinsic ECE response. This demonstrates the importance of localized ECE measurement under direct method. The developed direct measurement method points to an alternative, reliable and high fidelity pathway for investigating ECE at local scale.