Chemical Synthesis And Characterization Of Rare Earth Doped Bismuth Titanate Nanopowders

In recent years, functional material bismuth titanate (Bi4Ti3O12) won the wideattention for its excellent ferroelectric and photoelectric properties in ferroelectricstorage, optical storage, variable frequency technology, energy harvesting,piezoelectric sensor and optical degradation. In this thesis, different wet chemicalpreparation process were used to synthesis well crystallinity of rare earth dopingbismuth titanate powders. Through X-ray diffraction (XRD), transmission electronmicroscope (TEM), scanning electron microscope (TEM), energy spectrum (EDS)and Fourier infrared spectrum (FITR)to examin the crystallinity, grain structure, sizeand morphology of these nanopowders. And then had analysized results of thecompared characterizations. The main content of this thesis are as follows:1. Through sol-gel-hydrothermal method, we have synthesized the Nd dopedbismuth titanate (Bi3.15Nd0.85Ti3O12, BNdT) nanopowders. The results show thatNd3+had successfully replaced the Bi3+in the lattice of Bi4Ti3O12and formed flakynanoparticles. Research results show that to synthesis those powders with thesol-gel-hydrothermal method, the lowest synthesis temperature is160℃, with aminimum of16h reaction time, and the best concentration of NaOH for2-3mol/L.We also found the density of BNdT ceramic chip which synthesized fromsol-gel-hydrothermal method is as high as95.2%, it is far higher than the sol-gelmethod (90.6%).2.Through sol-gel-hydrothermal method, we have synthesized the Gd dopedbismuth titanate (Bi3.6Gd0.4Ti3O12, BGdT) nanopowders. The results show that themaximum number of doped Gd3+is0.4(Bi4-xGdxTi3O12, x=0.4). Variouscharacterization results show that in the hydrothermal process, the reactiontemperature, reaction time and the mineralizer NaOH concentration of target productsof the crystallinity and microstructure has important influence, sol-gel-hydrothermalof Gd doped bismuth titanate powders were prepared by the lowest synthesistemperature is180℃, with a minimum of24h reaction time, the best concentrationof NaOH for3mol/L. 3. Through sol-gel-hydrothermal method, we have synthesized the La dopedbismuth titanate (Bi3.25La0.75Ti3O12, BLT) nanopowders. The result show that underthe temperature of160℃，we had successful synthesis of the BLT of a globularstructure with500nm in diameter which composed of nanosheet.The edge size of thenanosheet is200-300nm, and its thickness is about50nm. its minimum responsetime is16h and the best concentration of NaOH is2mol/L.4. Through solvothermal method, this method is on the basis of thehydrothermal method which join the right amount of ethylene glycol methyl ether assolvent to synthesis the BLT nano powders. Under the temperature of140℃, We hadsuccessfully synthesized good crystallinity of the thin sheet BLT crystals. Ethyleneglycol methyl ether not only can inhibit the hydrolysis of precursors, and in thehydrothermal process, as its low dielectric constant and surface tension, ethyleneglycol methyl ether can promote the process of crystal. With the compared result ofthe XRD, SEM, FITR and EDS characterization analysis showed that to synthesis theBLT powders with the solvothermal method, the shortest synthesis time is16hour,andthe best concentration of NaOH for3mol/L.