Energy Effect And Regulation Mechanism Of Bi_Ti₃O₁₂ Matrix Ferroelectric Thin Films

Compared with ceramic capacitors,thin film capacitors are more in line with the development requirements of miniaturization and integration of electronic devices in today's society.As an important part of some energy storage devices,they have great application prospects.In addition,the volumetric photovoltaic effects of its asymmetric systems are of great interest due to the large open circuit voltages observed.In order to solve this problem,this paper used chemical sol-gel method to prepare Bi₄Ti₃O₁₂-based ferroelectric thin films.By introducing layered structure and doping rare earth elements into the Bi₄Ti₃O₁₂to obtain small size easily reversible polar nanoregions and small band gap,thus obtaining an excellent energy storage performance and ferroelectric photovoltaic effect.This paper mainly includes the following research contents:1.By introducting rare-eaeth elements Pr³⁺into the K_0.5Na_0.5NbO₃Bi_4-xPr_xTi₃O₁₂system have increased the energy storage effect of thin films.As a representative material in the Aurivillius phase structure family,BT has(Bi₂O₂)²⁺the insulating layer,so that it plays the role of a space charge pool to hinder the accumulation of oxygen vacancies on the domain walls,reduces the pinning effect of the domain walls,and therefore obtain higher breakdown field strength of thin films.The piezoelectric material K_0.5Na_0.5NbO₃was chosen to be inserted into BT because its addition can break the long-range order of BT's ferroelectricity.Moreover,with the introduction of Pr³⁺,the disorder of the A-site ions increases,and the energy storage efficiency is greatly improved by the transformation from ferroelectric to relaxation ferroelectric.This rare earth doping provides a new strategy for regulating the energy storage performance of multilayer perovskite relaxor ferroelectric thin films.2.By introducing BaTiO₃and CaTiO₃into the Bi₄Ti₃O₁₂thin film,the energy storage performance is further improved,resulting in a higher energy storage density under low electric field.Since CT is a ciselectric substance,the addition of CT not only improves the intrinsic breakdown strength of the film,but also greatly improves the energy storage efficiency of the film.We obtained a high energy storage density of 47.6 J/cm³and a high efficiency of 70.4%in the Ba CaBi₄Ti₅O₁₈film.Notably,the film exhibits excellent temperature stability over the relatively wide temperature range(-15°C-150°C).This strategy of introducing a paraelectrics into a ferroelectric body provides a simple method for the design of pulsed power capacitors.3.Since researchers found that BiFeO₃films exhibit photoelectric voltages higher than the band gap,the study of ferroelectric photovoltaic properties has received more and more attention.In this paper,rare earth elements Er,Ce and Y were selected to conduct single-doped and co-doped Bi₅FeTi₃O₁₅films to improve its electrical properties and photovoltaic performance.It is worth noting that in terms of improving photovoltaic effect,non-compensating doping(Ce⁴⁺)shows greater advantages than compensating doping(Er³⁺and Y³⁺),which is reflected in the reduction of band gap and the enhancement of ferroelectric polarization.This is because the doped rare earth ions not only increase the scattering cross section,but also in the Ce⁴⁺doped and fully doped BTFO films,the vast majority of electrons are carried,and the band gap photons near the visible region are excited from the ground state to the conduction band,which improves the photovoltaic effect.