| Thin film dielectric capacitors play an important role in modern pulsed power electronic devices due to their ultra-fast charging/discharging speed.Moreover,the thin film forms can also promote the dielectric capacitor devices toward miniaturization and integration.In recent years,the investigations on the energy storage performance of dielectric capacitors have become more and more abundant,and many excellent performances have been obtained.However,there are still some problems to be solved urgently.Firstly,the energy storage density is still low for application.Secondly,the energy storage efficiency needs further improvement.Thirdly,optimizing the stabilities of dielectric capacitors,for example,the thermal stability and fatigue endurance.Fourthly,improving the understanding of energy storage characteristics-complex structure.Thus,it is still the research focus for further optimizing the energy storage properties of studied materials and developing for new energy storage materials and technologies.Aurivillius phase compounds are a kind of typical ferroelectric materials.By analyzing their structure and regulating the films preparation processes,we obtained excellent energy storage properties in Aurivillius phase compounds.Firstly,we prepared Bi3.25La0.75Ti3O12(BLT)thin films.By designing the annealing temperature,the grain size of BLT thin films can be obviously controlled.As a result,the BLT thin films annealed at lower temperature show slender polarization(P)-electric field(E)loops,which can be attributed to the clamping effects by grain boundaries.A high recoverable energy storage density Ure=44.7 J/cm3and efficiency ?=78.4%can be obtained for the 650?-annealed BLT thin film.At-the same time,the sample also shows excellent fatigue endurance up to 4×108 cycles and good thermal stability from room temperature to 140?.Secondly,for improve the energy storage performance of BLT-based thin films,we fabricate the multilayer BLT/BiFeO3(BF)thin films.On the one hand,BF has large ferroelectric polarization,which can effectively enhance the polarization in the multilayer thin films.On the other hand,for the multilayer thin films,the interface can hinder the development of electric trees in the thin film and enhance the breakdown field.Thus,we fabricated bilayer and trilayer BLT/BF thin films.The effects of BF thickness and the numbers of interfaces on energy storage are system investigated.As a result,we obtained a ultrahigh Ure=65.5 J/cm3 and ?=74.2%in the BLT/BF/BLT thin film.Moreover,the thin film also has outstanding fatigue endurance and good thermal stability.Thirdly,we deposited BaTiO3(BT)-BLT thin films for further improve the energy storage performance of BLT-based thin films.The addition of Bi-based materials into BT thin film can obviously enhance the growth kinetic of BT and thus reduce the defects concentration as well as improve film densification.In the prepared(1-x)BT-xBLT thin films,the BT can endure high breakdown field and BLT can contribute large polarization value.Thus,an ultrahigh Ure=61.1 J/cm3 and ?=84.2%are simultaneously achieved in the 0.6BT-0.4BLT thin film at room temperature.Additionally,excellent fatigue endurance after 6×109 cycles and good thermal stability up to 150? are observed.Fourthly,we explore another material in the Aurivillius phase,i.e.A2Bi4TisO18(A=Ba and Sr)thin films,which possess relatively large ferroelectric polarization,excellent fatigue endurance as well as high resistance.We deposited A2Bi4Ti5O18(A=Ba and Sr)thin films and study the energy storage properties.A high Ure=37.1 J/cm3and ultrahigh ?=91.5%are obtained.More importantly,the A 2Bi4TisOis(A=Ba and Sr)thin films show good thermal stability under the extra wide working temperature range from-100?-180?. |
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