Research On The Microstructure,Electrical And Photoelectric Properties Of Bismuth Sodium Titanate And Bismuth Ferrite Based Ceramics

In recent years,the solar eneygy which is clean and pollution-free has been favored by humans to solve the energy depletion.Perovskite ferroelectric semiconductor materials have strong light absorption and photocurrent generation capabilities,which have attracted widespread attention in recent years.Bi_0.5Na_0.5TiO₃（BNT）-based ceramics and Bi FeO₃（BFO）-based ceramics are the research hotspots of lead-free functional ceramics.However,their development in the field of photoelectric is limited by the width of band gap,therefor,doping is an important method to solve this problem.The microstructure,electrical properties especially the optical properties of La₂Mo₂O₉,MnO₂and Sr_0.7Bi_0.2TiO₃dopped into BNT-based and BFO-based ceramics were systematically studied in this work.The（1-x）Bi_0.5Na_0.5TiO₃-xLa₂Mo₂O₉（x=0,0.3%,0.5%,0.7%,0.9%）ceramics were successfully prepared by traditional solid phase synthesis method.The XRD and Raman spectra showed that the structure of the ceramics changed from rhombohedral structure（x=0）to the coexistence of rhombohedral and pseudo cubic structures（x=0.9%）.With the enhancement of doping amount,the maximum polarization(P_max)of the ceramics decreased firstly and then increased,the minimum value of 39.66μC/cm²for P_maxcould be obtained in x=0.7%ceramics.With the increase of doping amount,the photocurrent density of the ceramics increased firstly and then decreased;when x=0.7%,the maximum photocurrent density before poling was 33.90 n A/cm²,and the photocurrent density after poling at 10 k V/cm was 71.06 n A/cm².The 0.993Bi_0.5Na_0.5TiO₃-0.7%La₂Mo₂O₉+xMnO₂（x=0、0.2%、0.4%、0.6%、0.8%、1%）ceramics were successfully prepared by traditional solid phase synthesis method.The XRD and Raman spectra showed that the structure of the ceramics changed from a rhombohedral structure（x=0）to pseudo cubic structure（x=1%）.XPS analysis showed that the valence of Mn ions have changed,Mn²⁺and Mn⁴⁺generated an intermediate state between the conduction band and the valence band,which reduced the band gap values.As the amount of doping increases,P_maxdecreased from 40.51μC/cm²to 17.33μC/cm².With the enhancement of doping amount,the light absorption intensity of ceramics increased greatly.When x=1%,the light absorption intensity exceeded 80%in the range of visible light.The optical band gap value of ceramics decreased with the increase of the doping amount.The minimum value of 1.18 e V for band gap could be obtained in x=0.7%ceramics.The maximum photocurrent density was 147.982 n A/cm²at x=1%,and the open circuit voltage was 2.12 V.At this time,the corresponding power was 0.314μW/cm².Then the photocurrent value was 552 n A/cm²after polarization at 10 k V/cm,which was an obvious increase,and the open circuit voltage was 2.16 V,the corresponding power was1.192μW/cm².（1-x）BiFeO₃-0.3BaTiO₃-xSr_0.7Bi_0.2TiO₃+0.5%MnO₂（x=0、0.03、0.06、0.09、0.12、0.15、0.2、0.3）ceramics were successfully prepared by traditional solid phase synthesis method.XRD spectra showed that the structure of the ceramics have changed from rhombohedral structure to pseudo cubic structure.Under 60 k V/cm,P_maxand P_rgradually decreased with the increase of the doping amount,the minimum value of 0.38μC/cm²for the remanent polarization could be obtained in x=0.3 ceramics.The light absorption intensity of ceramics remained at a high level at 0?x?0.09,which exceeded 90%in the visible light range,and then slightly decreased at 0.15?x?0.3.When 0?x?0.15 the photocurrent density of ceramics were maintained a low level;the maximum value of12.73 n A/cm²for photocurrent density could be obtained in x=0.2 ceramics,and the corresponding maximum power was 71.92n W/cm²;when x=0.3,the maximum photocurrent density dropped slightly,which was 9.79 nA/cm².