Study On The Synthesis Bi_3.25La_0.75Ti₃O₁₂(BLT) Nanotubes And Nano Wires

Polycrystalline Bi_3.25La_0.75Ti₃O₁₂ (BLT) nanotubes and nanorods were synthesized in Anodic Aluminum oxide membrane (AAO) by dipping BLT sol precursor into the AAO membrane and solvent evaporation induced deposition of BLT sol, respectively. Effect of different solvent on preparing BLT sol and influencing factors during synthesizing BLT nanotubes and nanorods and mechanism of synthesizing BLT nanotubes were investigated by TG-DTA, X-Ray diffraction (XRD), Scaning electron microscopy (SEM), Transmission electron microscopy (TEM), and High resolution transmission electron microscopy (HRTEM) techniques.The results indicated that using 4BiNO₃(OH)2?BiO(OH), La(NO3)3?6H2O and Ti(C4H9O)4 as starting materials, stable BLT sol can be prepared with solvent of acetic acid and Ethylene glycol, acetic acid and ethylene glycol monomethyl ether, acetic acid and acetylacetone, repectively. The volume of acetic acid used in preparing BLT sol should be adjusted to a proper quantity for its dual effects on the metal ions in the sol. The concentration, conglutination and surface tension of BLT sol can be adjusted by changing the volume quantity of Ethylene glycol, ethylene glycol monomethyl ether and acetylacetone used in the sols, however, their volume should be lagger than acetic acid used in the sols to insure a stable sol. Pure perovskite BLT can be synthesized after calcining the gel that comes from sol with acetic acid and ethylene glycol monomethyl ether as solvent at 400°C for 1h and 750°C for 0.5h and then quenching to room temperature, and the gel that come from sol with acetic acid and acetylacetone as solvent at 400°C for 1h and 700°C for 0.5h.When template dipping method is used to synthesize BLT nanotubes, deposition came form interaction of positively charged sol particles against the negatively charged nano-tunnel wall of the template and the deposition on the nano-tunnel wall will increase with time at the early stage of the dipping process, but it will not increase all the time. Deposition on the tunnel wall will increase efficiently with more dipping times, and this will lead to a thicker wall of BLT nanotubes. However, with more dipping times a thick film will form on the template surface which jam the open end of the tunnel and make it difficult for the sol to dipping into the template.BLT nanorods can be synthesized by using a solvent evaporation induced deposition method, which makes the sol particles to deposit from one end of the template to the other. Electrophoresis deposition of BLT sol will lead the separation of different metal ions, and it is impossible to synthesize BLT nanotubes or nanorods with an accurate stoichiometric proportion.BLT nanotubes synthesized by dipping sol precursor method are just replica of AAO template tunnel and they have a wall thickness of 20～50nm, diameter of 200～300nm. BLT nanorods synthesized by solvent evaporation induced deposition method are stacks of polycrystalline BLT particles, and their diameters are about 200nm.