Giant electrocaloric effect of free-standing Pb0.85La0.1(Zr0.65Ti0.35)O3 thick films fabricated by the self-lift-off screen printing method

Abstract

Free-standing Pb0.85La0.1(Zr0.65Ti0.35)O3 (PLZT) ceramic thick films have been prepared via a facile and low-cost self-separating screen printing method for electrocaloric cooling, and the relation among the fabrication processes, phase composition, microstructure, dielectric characteristics, ferroelectric properties and electrocaloric effect (ECE) has been systematically investigated. Compared to the conventional ceramic thick films supported by substrates, the free-standing feature enables the EC cooling of the free-standing PLZT thick films to be fully used for cooling down different thermal loads rather than be futilely absorbed by the substrates. Furthermore, without the mechanical restriction of the substrates, the free-standing PLZT thick films can freely shrink during the high-temperature densification process, leading to their high density and favorable microstructures. Additionally, by introducing an adequate amount of excess PbO, the pyrochlore phase can be removed from the samples to yield high-purity perovskite PLZTs. With the comprehensive improvement in phase composition, microstructure and the elimination of mechanical strain between the active materials and substrates, the free-standing PLZT thick films exhibited an optimized ECE including changes of temperature and entropy of 1.95°C and 2.09Jkg−1K−1, which are almost 3 times that of the samples deposited on the Al2O3 substrates without excess PbO. This work would contribute to the development of ferroelectric ceramics, especially thick films, for practical EC cooling.