Synthesis And Characterisation Of Niobic And Tantalu Photocatalytic Composite Oxides

In this paper, we succeed in synthesizing the series of Bi_2-xLa_xAlNbO₇ (x=0-0.4), Bi₂Mn_xAl_1-xNbO₇ (x=0-1) and NaTaO₃ single phase polycrystalline samples by the solid-state reaction and concentrate our study on structures and photocatalytic activity of these compounds by X-ray diffraction, Fourier Transform Infrared, Differential Thermal Anylysis, Brunaure-Emmett-Teller Anylysis, Ultraviolet Visible DiffuseReflectance Spectra, and the measurement of photocatalytic activities. We also studied the influence of co-catalyst such as NiO_x and CoO on photocatalytic activity. Many new data and results of them were obtained here, which will help us to do the further reseaches, development and applications.The XRD patterns of Bi_2-xLa_xAlNbO₇(x=0-0.4) were assigned to be Bi₂AlNbO₇ phases with the pyrochlore 2 2 7 structure with space group Fd3m. The lattice vibration of M–O(M=Al,Nb), (La, Bi)–O′and (La, Bi)-O were observed in FT-IR spectra. It was interesting to note that Bi_2-xLa_xAlNbO₇(x=0-0.4) show photoabsorption in the visible light region(λ>420nm). The band gaps of Bi_2-xLa_xAlNbO₇ were almost the seem as Bi₂AlNbO₇ irrespective of the lanthanum metal cations at the A sites. This might attribute to the hybridization of unoccupied 4f levels of La with O2p and Nb4d. We studied the influence of amounts of NiOx co-catalyst on photocatalytic activity and found that the most optimum amount of the co-catalyst was around 0.2 wt% as Ni metal particles on the Bi_1.95La_0.06AlNbO₇ photocatalyst. The surface areas of Bi2-xLaxAlNbO7 were relatively small and increase slightly as the increasing of x. From the results of the present study, Bi_1.9La_0.2AlNbO₇ photocatalyst showed a relatively high activity among the solid solutions of Bi_2-xLa_xAlNbO₇.The XRD patterns of Bi₂MnxAl_1-xNbO₇ were also assigned to be Bi2AlNbO7 phases with the pyrochlore 2 2 7 structure with space group Fd3m. The Bi₂AlNbO₇ phases might covert to cubic Bi₂MnNbO₇ phase, with x increasing and the lattice parameters, the surface area also varied with x. It is interesting to noted that Bi_2-xLa_xAlNbO₇ showed strong photoabsorption in the visible light region(λ>420nm) and had absorption peaks in 700-850nm. The photocatalytic...