(Zn, Ti) Co-doped BiFeO₃ Ceramic And Spin-coated Film Preparation And Performance Research

Materials with two or more sequence parameters of iron?such as ferroelectricity,ferromagnetism,ferroelasticity,ferrovorticity,etc.?are called multiferroics.As a typical ferroelectric material,BiFeO₃?BFO?has both ferroelectric and G-type antiferromagnetic sequence.Because there are many physical effects in a system,and the mutual effects can regulate each other,it can be applied in many important fields.In recent years,the photovoltaic effect of ferroelectric materials has once again aroused people's interest in the films.Because BFO is a rare ferroelectric with a narrow band gap,it is not only ferroelectricity and ferromagnetism,but also has band gap matching with the appearance of visible light wave.BFO film has strong photovoltaic effect and can generate large open circuit voltage.This provides a great opportunity for visible degradation of organic pollutants,photocatalysis,and new solar cells and other related optical devices.However,because of the small synthesis temperature range of BiFeO₃ material,the volatilization of Bi and the valence state change of Fe lead to the large of leakage current.Therefore,the synthesis of high-quality BiFeO₃ materials is very different,which seriously restricts the application of BiFeO₃.In this paper,BiFeO₃ powders were successfully synthesized by sol-gelmethod,and BFZTO ceramics were prepared by three different preparation processes,and the ceramics were used to study structure?morphology?and physical properties.The BiZn_0.02Ti_0.02Fe_0.96O₃?BFZTO?ceramics prepared by the combination of cold isostatic pressing and conventional sintering were studied.Then,BiZn_0.02Ti_0.02Fe_0.96O₃thin films were prepared on the substrate of FTO/glass by using the method of spin coating,the structure and physical properties of this film were studied.Our main research work is as follows:?1?We have successfully prepared BFZTO ceramics by three different preparation processes,manual powder tableting combined with conventional sintering?MPT-CS?,the combination of cold isostatic pressing and conventional sintering?CIP-CS?,and spark plasma sintering?SPS?.The effects of Zn²⁺and Ti⁴⁺on Fe doping were investigated.By comparing the corresponding experimental results,it was found that all the ceramics prepared by different preparation processes were all rhombohedral phase,and the space group was R3c.After physical properties test,it was found that the electrical properties of ceramics samples prepared by CIP-CS was obviously improved,and the residual polarization P_r=1.18?C/cm²,it was three times higer than the other two preparation.The reason for the performance improvement is that the formation of defects complexes within the system reduces the free moving charge,and the increase of the number of grain boundaries hinders the domain wall turnover.The range of optical band gap is 1.72-1.98 eV,which provides a greater opportunity for the application of BiFeO₃ in the field of photocatalysis.?2?We prepared the BiZn_0.02Ti_0.02Fe_0.96O₃ powders by Sol-gel,and the BiZn_0.02Ti_0.02Fe_0.96O₃ ceramics by CIP.We studied the effects of the sntering temperature and holding time on BFZTO powders and ceramics.The results were that the under the condition of sintering temperature is 550?and the holding time is 2h can have a single phase powders.Compared to the correlative results of BiZn_0.02Ti_0.02Fe_0.96O₃ ceramics,it was found that the sintering temperature and holding time can effect the electrical and optical properties of BiZn_0.02Ti_0.02Fe_0.96O₃ ceramics,under the sintering condition of 800?/1h,the remnant polarization P_r=1.2?C/cm².?3?BiZn_0.02Ti_0.02Fe_0.96O₃ thin film was prepared on FTO/glass substrate by using spin coating method.By exploring and studying the concentration of sol?annealing temperature and annealing time of the thin film.The structure and physical properties of BFZTO thin film were studied.The innovation of this paper lies in the use of CIP preparation?Zn,Ti?co-doped BiFeO₃ ceramics,the analysis of its impact on the structure and physical properties.In addition,the physical properties of BFO ceramics were deeply analyzed.The defects complexes caused by ion doping not only reduced the leakage current density and enhanced the polarization intensity,but also controlled the optical band gap of BFO.The microscopic mechanism of improving the physical properties of BFZTO ceramics was described.