The Preparation And Investigation On The Energy-storage Performance Of PLZT-based Anti-ferroelectric Thick Films

(Pb1-3x/2Lax)(ZryTi1-y)O3(PLZT)is the typical antiferroelectric materials with ABO3 perovskite structure,which have phase transformation behavior when electric,temperature or stress fields are applied.In the phase transformation process,the dielectric,polarization and electrical conduction have the obvious change,and the electrical energy can be stored and released.In addition,the perovskite structure can be modulated and tailord,leading to a fact that PLZT exhibit a potential application in capacitors.Here,PLZT thick films were prepared,and the dielectric and energy storage behavior were investigated.In this dissertation,(Pb1-3x/2Lax)(ZryTi1-y)O3 antiferroelectric thick films were deposited on LaNiO3/Si(100)matrix by the sol-gel method.Crystallization phase structure of the thick films were investigated by X-ray diffractometer(XRD).Surface microstructure were studied with scanning electron microscopy(SEM).Dielectric properties were measured by LCR analyzer.Ferroelectric properties(P-E)and breakdown strength(BDS)of the thick films were tested by a Radiant Technology Ferroelectric tester.Based on the P-E loops,the energy storage density and efficiency were calculated.(Pb1-3x/2Lax)(ZryTi1-y)O3 thick films were prepared by the method which includes two thermal treatments and one annealing processes.The optimal technological conditions were obtained:the thermal treatment temperature Ti and T2 is 350 ℃ and 600 ℃ respectively,and the annealing temperature T is 700 ℃.In addition,for the sol added Polyvinyl Pyrrolidone(PVP),the optimal technological conditions conclude that the thermal treatment temperature T1 is 350 ℃,and the thermal treatment temperature T2 and the annealing temperature T is 700 ℃.The effect of thickness and compositional gradient on dielectric and energy storage behavior of PLZT thick films was investigated.It is found that thickness of thick films influences intensively their properties.With the increase of thickness,the BDS of PLZT decreases while the dielectric constant increases.In addition,compositional gradient is also a key influence factor for the energy storage properties of PLZT.Compared with the thick films with single component,the thick films with high component possess larger energy density of 12.4J/cm3,which increases 75%of the energy density for single component thick films.Therefore,tuning the energy storage behavior of antiferroelectric thick films can be achieved by controlling the compositional gradient.The effect of component on structure and energy storage behavior of Pbi-3x/2Lax(Zr,Sn,Ti)O3(PLZST)thick films was investigated.La3+ content has a great influence on the process of growth and phase transformation of the thick films.The addition of La3+ is helpful for(100)orientation growth,and it changes the structure of the thick films,leading to a transformation of tetragonal antiferroelectric-rhombohedral ferroelectric-cubic paraelectric.In addition,controlling the ratio of Zr/Ti,Zr/Sn and Sn/Ti can tune the phase transformation of ferroelectric-antiferroelectric.In a phase transformation process induced by temperature,the thick films with stable antiferroelectric phase at room temperature can exhibit the transformation of antiferroelectric-rhombohedral-paraelectric by tuning the applied electric filed.However,the thick films with weak antiferroelectric phase at room temperature just have a transformation of antiferroelectric-paraelectric.The effect of Mn4+ on the structure and energy storage behavior of PLZT thick films was investigated.Mn4+ doping improves the stability of antiferroelectric phase,and it can increase effectively energy density and efficiency.As the doping content is 1%,the PLZT thick film exhibits the optimal properties,which has high BDS of 1678.5kV/cm,energy density of 30.8 J/cm3 and efficiency of 69.6%.The effect of oxide buffer layers and ZrO2 covering layer on the dielectric and energy storage behavior of PLZT thick films was also investigated.It is found that buffer layers have great influence on the structure and growth orientation of PLZT thick films.The buffer layers increase the compactness of the surface,and they are helpful for the increase of grain size,leading to an improvement of dielectric properties.Particularly,ZnO is the most effective buffer layers to enhance the efficiency.With the increase of ZrO2 thickness,the grain size and compactness increases while the efficiency decreases,and the energy density hardly changes.Therefore,it is concluded that the suitable buffer layers can improve effectively the structure of thick films,leading to an enhancing in energy storage properties.