Interface-Charge Induced Giant Electrocaloric Effect in Lead Free Ferroelectric Thin-Film Bilayers

Sagar E Shirsath; Claudio Cazorla; Teng Lu; Le Zhang; Yee Yan Tay; Xiaojie Lou; Yun Liu; Sean Li; Danyang Wang

doi:10.1021/acs.nanolett.9b04727

Interface-Charge Induced Giant Electrocaloric Effect in Lead Free Ferroelectric Thin-Film Bilayers

Nano Lett. 2020 Feb 12;20(2):1262-1271. doi: 10.1021/acs.nanolett.9b04727. Epub 2019 Dec 30.

Authors

Sagar E Shirsath¹, Claudio Cazorla¹, Teng Lu², Le Zhang¹, Yee Yan Tay³, Xiaojie Lou⁴, Yun Liu², Sean Li¹, Danyang Wang¹

Affiliations

¹ School of Materials Science and Engineering , University of New South Wales , Sydney , New South Wales 2052 , Australia.
² Research School of Chemistry , The Australian National University , Canberra , Australian Capital Territory 2601 , Australia.
³ Facility for Analysis, Characterization, Testing and Simulation and School of Materials Science and Engineering , Nanyang Technological University , 50 Nanyang Avenue , 639798 Singapore.
⁴ Multi-disciplinary Materials Research Centre, Frontier Institute of Science and Technology, and State Key Laboratory for Mechanical Behavior of Materials , Xi'an Jiaotong University , Xi'an 710049 , China.

PMID: 31877053
DOI: 10.1021/acs.nanolett.9b04727

Abstract

Conventional refrigeration methods based on compression-expansion cycles of greenhouse gases are environmentally threatening and cannot be miniaturized. Electrocaloric effects driven by electric fields are especially well suited for implementation of built-in cooling in portable electronic devices. However, most known electrocaloric materials present poor cooling performances near room temperature, contain toxic substances, and require high electric fields. Here, we show that lead-free ferroelectric thin-film bilayers composed of (Bi_0.5Na_0.5)TiO₃-BaTiO₃ (BNBT) and Ba(Zr_0.2Ti_0.8)O₃-(Ba_0.7Ca_0.3)TiO₃ (BCZT) display unprecedentedly large electrocaloric effects of ∼23 K near room temperature under moderate electric bias. The giant electrocaloric effect observed in BNBT/BCZT bilayers, which largely surpasses the sum of the individual caloric responses measured in BNBT and BCZT, is originated from the presence of compositional bound charges at their interface. Our discovery of interface charge-induced giant electrocaloric effects indicates that multilayered oxide heterostructures hold tremendous promise for developing highly efficient and scalable solid-state cooling applications.

Keywords: Lead-free ferroelectrics; electrocaloric effect; first-principles calculations; thin film bilayer.