Preparation Of Several Bismuth-based Functional Nano-materials And Their Properties

It has been well known that synthetic method gives a great effect on the properties of a material. Solid state method is a typical way to obtain materials. However, it has many defaults, such as high heat-treatment temperature, long reaction time, high energy consumption, and large particle size. So it is hard to meet the demands for novel materials,especially for nano-materials. Nowadays, nano-materials have attracted much attention because of their special properties, and it is vital to develop an effective synthesis method.In this paper, three kinds of functional nano-materials containing Bi³⁺ were prepared by co-precipitation method and low-temperature molten salt method. In addition, the properties of these materials were investigated. The main contents were summarized as follows:Part I: Ca₂Sb₂O₇:x Bi³⁺ phosphors were synthesized by co-precipitation method. Their structure and morphologies were characterized by XRD, SEM, XPS and FTIR. The results show that the shapes of the as-prepared Ca₂Sb₂O₇:x Bi³⁺ powders are sphere-like, and the diameters of particles are in the range of 20-40 nm. Under the excitation of UV light, the samples exhibit a strong broad emission band peaking at 441 nm. Furthermore, this emission band can be divided into two sub-bands centered at 432 and 456 nm, and they could be assigned to two different emission centers of Bi³⁺（4a） and Bi³⁺（4d）, respectively.Part II: A novel low-temperature flux method was applied to synthesis Na₃Bi（PO₄）₂powders. The optimal synthesis conditions were as follows: the temperature is 180 °C, the reaction time is 12 h, and the ratio is 1:4. Under the optimal conditions, Eu³⁺ ions were introduced into the Na₃Bi（PO₄）₂ system, then the morphologies and optical properties of phosphors were studied, and also their optical mechanism was discussed.Part III: A novel bismuth phosphate material has been successfully prepared by low-temperature flux method. Results show that nano-particles are pure and in good crystallization. The morphologies of the as-prepared Na Bi7P2O16 sample are plates with the width in nano-size. The band gap of was evaluated to be 3.44 e V. The photocatalyticperformance of was tested by the degradation of MO solution under the irradiation of UV light. The researches show that MO solution could be degraded into 3% after 30 min irradiation. In addition, after cycling for 5 times, the photocatalytic performance remains very high. The mechanism of photocatalysis was also studied.