Preparation And Energy Storage Properties Of PbZrO₃ Based Antiferroelectric Films

Dielectric materials typically display high charge-discharge rates and excellent fatigue resistance,which are the key properties for pulsed power devices.However,compared with batteries and electrochemical capacitors,the energy storage density of dielectric energy storage devices is relatively low,thus limiting their application in the field of energy storage.In order to realize a wide range of applications of dielectric capacitors,it is imperative to improve their energy storage density.In particular,antiferroelectric materials,as a typical dielectric material,have been gradually stressed in the field of high-density energy storage because they can possess a higher energy storage density during the antiferroelectric-ferroelectric?AFE-FE?phase transition.However,the current antiferroelectric materials still possess the disadvantage of poor electric breakdown strength and high energy loss,which make them not suitable for application.In this thesis,the PbZrO₃?PZO?-based antiferroelectric films were prepared by chemical solution deposition?CSD?.The microstructure,electrical properties and energy storage performance of the PZO-based antiferroelectric films were improved by means of the incorporation of gold nanoparticles,Ca²⁺-doping and constructing a pyrochlore nanocrystalline structure,and the mechanisms of modification were discussed in detail.The main contents are showed as follows:1.Enhancement of energy storage density in antiferroelectric PZO films via the incorporation of gold nanoparticlesAntiferroelectric Au-PZO nanocomposite thin films were prepared on Pt?111?/Ti/SiO₂/Si substrates by CSD,and the effects of Au concentration on microstructures,electric properties and energy storage performance were investigated.The results showed that Au nanoparticles with local electric field around them were distributed uniformly in the perovskite PZO matrix with 1 mol%Au,making the maximum polarization significantly improved.In addition,the addition of Au nanoparticles made the field-induced phase transition of PZO antiferroelectric films diffusive.Therefore,the recoverable energy density and efficiency were 10.8 J/cm³ and 60%at 600 kV/cm,which are 42%and 25%higher than that of the pure PZO films respectively.The results demonstrate that adding an appropriate amount of noble metal nanoparticles in antiferroelectric thin films is an effective method to improve the energy storage performance.2.High energy storage performance in Ca-doped PZO antiferroelectric filmsIon doping is one of the effective and simple methods to improve energy storage performance of materials,but the type and quantity of ions selected and the mechanisms for performance improvement still remain to be further studied.In this work,antiferroelectric Pb1-xCaxZrO₃?PCZ?thin films with different concentrations of Ca²⁺were prepared by CSD,and the effects of Ca²⁺ concentration on the microstructures,electric properties and energy storage performance were investigated.The results showed that with the increase of Ca²⁺concentration,the stability of antiferroelectric phase of PCZ films increased gradually,which conforms to the theory of tolerance factor.In addition,the densification of the PCZ films increased significantly with the increase of Ca²⁺ concentration,which is conducive to improving the electric breakdown strength.The optimal Ca²⁺ concentration in the PCZ thin films is x=0.12 for electric and energy storage performance.The recoverable energy storage density and efficiency are 50.2 J/cm³ and 83.1%at 2800 kV/cm respectively,which are 261%and 44.8%higher than those of the PZO films,respectively.Our results demonstrate that doping an appropriate amount of Ca²⁺ions in antiferroelectric thin films is an effective way to improve their energy storage performance.3.Ultrahigh energy storage properties of?PbCa?ZrO₃ antiferroelectric thin films via constructing pyrochlore nanocrystalline structureAntiferroelectric Pb_0.88Ca_0.12ZrO₃?PCZ?thin films were prepared via CSD and annealed using rapid thermal annealing.The microstructures of PCZ thin films were controlled via annealing temperature,and the effects of microstructures on electric properties and energy storage performance were systematically studied.Our results indicate that PCZ thin films annealed at 550? crystallized into a nanocrystalline structure of the pyrochlore phase basically,while also displaying the highest recoverable energy density and efficiency?91.3 J/cm³ and 85.3%?.We attribute the ultrahigh energy storage properties mainly to dramatic improvements in the electric breakdown strength caused by the dense nanocrystalline structure.The findings reported herein help to elucidate the relationship between energy storage performance and thin-film microstructure,thereby providing an effective way for improving the energy storage performance of antiferroelectric thin films.