Preparation And Electrical Properties Of Flexible Ferroelectric And Antiferroelectric Thin Films

An urgent requirement for flexible integrated circuits systems is increasing with the arrival of the Internet of Things?IoT?.Multifunctional capacitors have attracted widespread attention because they can efficiently integrate multiple functionalities into a single material for achieving“multipurpose”to further down-scale integrated circuits.Relaxor-ferroelectrics?RFEs?and antiferroelectrcs?AFEs?multifunctional capacitors have been extensively used in microactuator,infrared detectors,sensor,enegry storage capacitors and electrocaloric refrigeration devices,due to great superiority simultaneously in dielectric,piezoelectric,and pyroelectric properties together with a ferroelectric response.Although numerous efforts have made to give an improved enegry-storage performances and electrocaloric effect in RFEs or AFEs,there are still some tricky problems in practical application.There are some disadvantages that exist in enegry storage capacitors including low energy-storage density and energy-storage efficiency at present.Meanwhile,there are some disadvantages which exist in the electrocaloric materials including poor refrigeration capacity,refrigeration efficiency and difficult to refrigerate over a wide temperature range.In response to this,a novel bilayer-like thin film with the same chemical composition is designed to enhance energy-storage performance by controlling sputtering pressure.Because the single-layer materials that constitute the bilayer-like film have different phase structures and micro-morphologies,each single-layer thin films generate a different electrical response under an applied electric field.The bilayer-like thin film combines the complementary advantages of each single-layer thin films based on the electric field amplifying effect and interlayer coupling.Due to combination of high electric breakdown field and large polarization,an enhanced recoverable energy-storage density(W_rec)is achieved in bilayer-like thin film.The maximum W_recec of 39.35J/cm³is achieved in antiferroelectric bilayer-like Pb_0.99Nb_0.02(Zr_0.55Sn_0.40Ti_0.05)_0.98O₃(PNZST_BL)thin film,which is 70%higher than that of single-layer PNZST.The relaxor composition of Pb_0.91La_0.09(Zr_0.65Ti_0.35)_0.9775O₃?PLZT9/65/35?which close to morphotropic phase boundary?MPB?was selected as a research target.We studied systematically the microstructure,dielectric properties,polarization behavior,energy storage performance and electrocaloric effect of PLZT9/65/35 thick films.The results indicated that flexible PLZT9/65/35thick film possesses a superior W_recec of 40.2J/cm³,accompanied by a desirable breakdown field of1998kV/cm.Meanwhile,the thick film exhibits excellent stability of energy-storage performance,especially a broad operating temperature?30-180??,reduplicative charge-discharge cycles?1×10⁷cycles?under the simulated environment of practical application.It is most important that the flexible PLZT9/65/35 thin film shows a favorable stability of energy-storage performance endurance before and after repeated mechanical cycling 1200 times for a 3.5 mm tensile radius.We verified that the degree of phase transition diffuseness of PLZT9/65/35 thick film reaches up to 1.99 by the temperatuere-dependent dielectric properties.It indicates that the PLZT9/65/35 is a a typical RFEs.In addiation,the temperature corresponding to the maximum dielectric constant is only 80?in PLZT9/65/35 thick film.All of these are beneficial to the wide operating temperature range in electrocaloric effect near room temperature.A large reversible adiabatic temperature change??T?of 18.0?,accompanied by an excellent electrocaloric strength??T/?E?of 22.4 K cm/V and refrigerant capacity?RC?of 11.2J/cm³in the flexible PLZT 9/65/35 thick film are obtained by an indirect calculation method at 80?under the moderate applied electric field of850kV/cm.All of these results shed light on a flexible PLZT9/65/35 thick film capacitor that opens up a route to practical applications in microenergy-storage systems and on-chip thermal refrigeration of advanced electronics.