Morphology,Structure And Properties Of Bismuth-based Oxide Particles

Bismuth-based oxides,a large family of functional ceramics,have drawn much attraction in photocatalysis,piezoelectricity,superconductivity and magnetic fields owing to their excellent visible-light excitation,favorable charge carriers mobility,high resonant frequency stability and non-toxic characteritics.In this work,CuBi₂O₄,Bi₂₅FeO₃₉ and Bi₁₂MnO₂₀ microcrystals were prepared through a hydrothermal method with strong alkali environment.Their composition,microstructures were fully studied,with emphasis on different properties.The main conclusions are as follows:Growth evolutions of urchin-like CuBi₂O₄ microspheres assembled by nanorods are revealed according to various reaction time.The nanorods are orderly grown along[001]crystal direction with rectangular cross-sections and a broad diameter distribution ranging of 100-350 nm.The microspheres were formed by radiated growth of nanorods which split along cleavage planes due to high internal stresses.The as-prepared CuBi₂O₄ exhibited a strong optical absorption in wavelength of300-630 nm.Under visible light,an improved degradation efficiency of 89.6%to Rhodamine B（Rh B）was determined with the aid of H₂O₂.As for Bi₂₅FeO₃₉ microcrystals,where their hierarchical morphologies could be designed from tetrahedron to orchid and marigold by the increment of pH values and reaction time.A good thermal stability up to 1000°C was revealed by DSC-TG with two endothermal peaks corresponding to decompositing（817°C）and melting（958°C）.A magnetic transition between ferromagnetism and paramagnetism around36.3 K was distinguished from thermomagnetic curves as well as hysteresis loops at 5K 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 0.37μA/cm².Finally,one-dimensional Bi₁₂MnO₂₀ microcrystals were obtained with the help of surfactant.Compared with Bi₁₂MnO₂₀ microspheres,microrods have stronger dielectric loss,which origined from the interfacial and orientational polarization.At the optimum absorbent thickness,the reflection loss achieves a minimum value of–13.1 d B around 15.6 GHz for Bi₁₂MnO₂₀ microrods.The effective absorption of Bi₁₂MnO₂₀ should be responsible for its dielectric loss together with electromagnetic impedance matching.