Thermal, magnetic and photoelectrical behaviors of sillenite Bi25FeO39 microcrystals

Bi25FeO39 microcrystals were synthesized via a one-pot hydrothermal process without additives, where their hierarchical structures could be designed from tetrahedron to orchid and marigold by the increment of pH values and reaction time. For all types of as-prepared Bi25FeO39, a high crystallinity and purity was confirmed in XRD and XPS analysis. A good thermal stability up to 1000 degrees C was revealed by DSC-TG with two endothermal peaks corresponding to decompositing and melting. A magnetic transition between ferromagnetism and paramagnetism around 36.3 K was distinguished from thermomagnetic curves as well as hysteresis loops at 5 K and 300 K respectively. In contrast to tetrahedron and orchid shaped Bi25FeO39, marigold shaped Bi25FeO39 exhibited a higher magnetization up to 4.8 emu/g at 5 K and enhanced photocurrent density around 0.37 mu A/cm(2). The special crystal arrays and increased concentration of Fe should be responsible for it. This work paves an attractive way for facile preparation and potential applications of sillenite materials.

Automated summary

Bi25FeO39 microcrystals with hierarchical structures can be synthesized via hydrothermal process, showing high crystallinity and purity, as well as magnetic and photocurrent properties.