| Bismuth ferrite is a typical single-phase multi-ferric ternary oxide functional material with high ferroelectric Curie point,G-type antiferromagnetic point at room temperature,and a narrow band gap.Therefore,it shows great potential in the application of electronic devices and new catalysts,and it has also been a research hotspot.It is of great scientific significance and application value to carry out research on the controllable preparation of the micro-nano structure of bismuth ferrite compounds and to explore the relationship between micro-structure and propertiesIn this paper,the micro-structures of bismuth ferrite with different morphologies were successfully prepared by hydrothermal method.The phases of the samples were analyzed by XRD.The micro-structures and the crystal growth of the prepared samples were analyzed by SEM and TEM,respectively.On this basis,the photocatalysis of dyes by prepared bismuth ferrite samples and its magnetic properties at room temperature were studied in this paper and the following innovative results were obtained:(1)The pellet-like bismuth ferrite powders were prepared using dilute nitric acid as an auxiliary agent under the conditions of iron nitrate(Fe(NO3)3·9H2O)as iron source,bismuth nitrate(Bi(NO3)3·5H2O)as the source of bismuth and NaOH as mineralizer.Through the optimization of experimental conditions,the optimal experimental conditions were controled as follow:at%(Bi):at%(Fe)=1:2;the concentration of diluted HNO3 is 1M;the concentration of NaOH is 4M;the hydrothermal temperature is 200?,and hydrothermal time is 12h.The size of prepared bismuth ferrite particle is about 2?m,the thickness of the sample is about 800 nm.All of the particles show smooth surface and a uniform morphology.(2)Based on the study of the morphology and phase changes of the final products adjusted by different hydrothermal conditions,the phase transition mechanism of perovskite phase ferrite is proposed.At the beginning of the reaction,bismuth nitrate and sodium hydroxide react to form BiONO3,NaNO3.Further BiONO3 and sodium hydroxide are further reacted to form(Bi6O6)6+,while iron ions react with OH-in sodium hydroxide to form Fe(OH)3,and then Fe(OH)3 continues to react with excess OH-to form Fe(OH)4-,and finally,(Bi6O6)6+reacts with Fe(OH)4-to form a perovskite phase BiFeO3.We can reasonably conclude that the formation of the phases of the ferrite is closely related to the concentration of the base.(3)Photocatalytic degradation of methylene blue solution(5 mg/L)showed that bismuth ferrite had good photocatalytic performance.The photocatalytic degradation efficiency of BFO(BiFeO3 and Bi2Fe4O9)samples with the mineralizer concentration of 4M was the highest,which was 93.8%.The efficiency of the degradation was the worst when the concentration of the mineralizer was 6M,it was 83.7%.The magnetic properties of BFO(BiFeO3 and Bi2Fe4O9)samples were also tested.The results show that BiFeO3 powder and Bi2Fe4O9 powder both show weak ferromagnetism at room temperature.(4)Using ammonia as a precipitant,iron nitrate(Fe(NO3)3·9H2O as iron source,bismuth nitrate(Bi(NO3)3·5H2O)as a cerium source,NaOH as a mineralizer,200? hydrothermal The pure photographic Bi2Fe4O9 powder was successfully prepared in the reaction for 12 h.The nanosheet has a size of about 200-300 nm and a thickness of about 30 nm.The sample can degrade the 5 mg/L methylene blue solution to 0.18 mg/L within 120 min of visible light irradiation,and the degradation efficiency is 96.22%,indicating that the prepared Bi2Fe4O9 sample has good visible light catalysis effect. |
PDF Full Text Request