| Ferroelectric materials with layered perovskite structure can produce various thermoelectric effects under the influence of external conditions.The combination of different electrical properties or several properties makes ferroelectric materials have great potential applications in aerospace,integrated circuits,optoelectronics information technology,energy and other fields.SrmBi4Tim+3O3m+3?SBTim?ferroelectric materials represented by Sr2Bi4Ti5O18?SBTi?have excellent properties,such as non-fatigue,high remanent polarization,low coercive field strength and leakage current.Because of those properties the Srm Bi4Tim+3O3m+3?SBTim?ferroelectric materialshave become the main materials for non-volatile ferroelectric memory?NVFRAM?.However,its lower Curie temperature and relatively low piezoelectric coefficient limit its application.BiFeO3?BFO?is a typical lead-free multiferroic environment-friendly material with excellent ferroelectric properties and ferromagnetic properties.However,due to charge compensation,a large number of oxygen vacancies are generated,which leads to a higher leakage current density of the film and a higher electrical conductivity.What's more,it's difficult to synthesize single-phase BFO.Therefore,it has become a research hotspot to modify ferroelectric materials by various means such as doping substitution,forming a solid solution structure,and optimizing the preparation process.In this paper,sol-gel method was used to synthesize SBTi and BFOat room temperature to prepare xBiFeO3-?1-x?Sr2Bi4Ti5O18?SBFTi-x,x=00.4?series films,and the content of BiFeO3on the structural properties of the film was studied.The effect of the content of BFO on the structural properties of the film was studied experimentally.At the same time,the process parameters of the film preparation were changed and the process parameters were optimized.It is found that with the increase of BFO content,the remanent polarization of the film sample increases first and then decreases.When the content of BFO is 0.1,the maximum remanent polarization is 2Pr=40.3?C/cm2,and the leakage current density is also the smallest.The conduction of leakage current of thin film samples under low electric field is mainly ohmic conduction mechanism or ohmic conduction coexist with space-limited charge conduction mechanism.When the content of BFO is 0.1,the maximum remanent polarization is 2Pr=40.3?C/cm2,and the leakage current density is also the smallest,which is J=2.2×10-6A/cm2.Leakage current conduction mechanism of thin film sample is mainly ohmic conduction mechanism under low electric field.When the annealing temperature is 575°C,the crystallinity of the film is the best,and the maximum remanent polarization is 2Pr=48.7?C/cm2.At this time,the coercive field and leakage current density are also small,which is 4.1×10-7A/cm2.After fitting the leakage current curve,it was found that the internal conductive mechanism of the thin film is Ohmic conduction at low electric field and space charge limited current conduction at high electric field.As the temperature rises,the dielectric constant of the film sample becomes larger.When the test frequency reaches a stable range,the changes in dielectric constant and dielectric loss tend to be stable and have good stability.The bilayer film samples of SBTi and BFO have also been prepared,and SBTihas been used as a transition layer.It is found that the film samples are crystallized and the crystal grains are dense.For the BFO film,the ab axis of the grain appeared preferential.The presence of the SBTi buffer layer reduces the leakage current density of the double-layered film.When the transition layer is 4,the leakage current density is the smallest. |
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