Synthesis And Morphology Evaluating Of Low Dimension Rare Earth Compound Materials

Rare earth (lanthanum, gadolinium and yttrium) hydroxides, ammonium yttrium oxalate and neodymium carbonates were synthesized by the hydration of rare earth oxides, the precipitation of yttrium with ammonium oxalate and the hydrothermal crystallization of neodymium carbonate respectively. Their morphologies and property were evaluated using XRD, SEM, TEM, PL and elemental analysis technologies. The main achievements include:[1] The hydration of La₂O₃,Gd₂O₃ and Y₂O₃ showed great difference due to their differences in basicity, ionic radius, and crystal structure. It was found that the La₂O₃ was hydrated to form rodlike La(OH)₃ with diameter 2-3μm,length 5-8μm at mild conditions (billing water temperature and ambient pressure) directly. Gd₂O₃ can also be hydrated to form Gd(OH)₃ under hydrothermal condition. However, Gd(OH)₃ with unusual fluffy dough sticks morphology was formed after hydrothermal treating its oxide with longer time or in NaOH solution. Y₂O₃ could not be hydrated in normal water. Sword-like Y(OH)₃ was obtained by the hydrothermal reaction in basic solution with prolonging time. Upon heating these hydroxides transformed into oxides with no evident morphology change, indicating that the rare earth oxides materials with special morphology could be prepared via their intermediate hydroxide.[2] Hexagonal tube-like Y(OH)₃ with inner diameter about 50nm,external diameter 100-200nm was prepared by hydrothermal treating Y₂O₃ in NaOH solution with additive of PVA or PEG.. The tube particles show smooth surface and disperse well. The relative elongation (ratio of the length of the long to the diameter) increased with the addition of surfactants, especially for the addition of PVA. It was the anisotropic crystal structure of La(OH)₃, Gd(OH)₃ and Y(OH)₃ that resulted in the formation of these hydroxides with one dimension crystal growth characteristics. The addition of surfactants should be favorable for the crystal growth along the surface horizontal direction due to the selection adsorption of surfactants on the crystal plane. However, the crystal growth from the middle position of a bar was slow down due to the limit of material diffusion, which resulted in the formation of tube morphology.[3] The excitation spectrum of Y₂O₃:Eu shows an unusual strong excitation peak at 226nm except for the charge transfer band at around 240nm, which might be...