REVO₄, REBO₃ And REPO₄ (RE=Rare Earth Element) Nanomaterials Constructed Via Solid Phase Hydrothermal Route And Their Fluorescence Properties

Rare earth oxysalts have been widely investigated and applied as one series important functional materials. It has been a hot topic field how to product their nanostructure materials.The dissertation is devoted to quest for and establish a facile, eco-friend, low-cost mild approach to metal oxysalt nano-material, which is named as solid phase hydrothermal (S-HT) or oxides-hydrothermal method (O-HT). This method the most essentially differ from the classical hydrothermal method as follow: the former directly utilizes insoluble/slight-soluble oxides as precursors, and the latter uses soluble rare earth salt as reagent. Compared with the latter, the 0-HT method exhibits many advantages, such as no side-products, facile operation, low cost, special crystal structure and morphology, and the prefect crystallization.The series of REVO₄ (RE= La, Nd, Sm, Y) and rare earth ion doped REVO₄ nanomaterials are facilely fabricated by the O-HT route directly used insoluble V₂O₅ and RE₂O₃ as precursors under appropriate conditions. It is original to accomplish the hydrothermal synthesis reaction among common insoluble reagents in water system and substantiates the feasibility of the O-HT route. The influences of many factors included temperature, time, additives, pH value of the system on products are investigated. The pure rodlike monoclinic (m-) and tetragonal phase (t-) LaVO₄ nanocrystals also are controllably constructed via the oxides-hydrothermal approach. It is found that FTIR spectra can be used as a simple means to detect crystal phase of LaVO₄. The self-mill hydrolysis crystallized mechanism (SMHCM) and dissolution-precipitation mechanism controlled by additives are hypothesized to interpret the rare earth orthovanadate nanomaterials obtained and controlling phase transition in 0-HT system. The fluorescence properties of YVO₄ and Eu³⁺ doped LaVO₄ nanomaterials are investigated.Based on above result, By O-HT approach, the REBO₃ (RE= La, Nd, Sm, Dy, Gd, Er, Y) and some ion doped REBO₃ nanomaterials are firstly obtained by mixing stoichiometric rare earth oxide Ln₂O₃ and boric oxide B₂O₃ into proper deionized water in a surfactant-free system, and the formation conditions of the nanomaterials are investigated. Pseudo-vaterite NdBO₃ and its self-assembled layer-by-layer (SALBL) nanopancakes (the thickness ca.50nm with the size ca. 10-13μm) are originally obtained via the O-HT route. The influences of treatment time, temperature, filling ratio, and pH value of solution on the hexagonal NdBO₃ nanopancakes, the thermal stability and irreversible phase transition properties, and the formation factors of pseudo-vaterite NdBO₃ crystal in O-HT system are investigated. The relationship between ionic radium and crystal growth of hexagonal REBO₃ nanomaterials are discussed. The preparing condition of pure ErBO₃ and YBO₃ nanomaterials are ascertained in the O-HT routes. It is firstly found that the crystal growth rate can be modified by different ions doped processes. The fluorescence properties of Sm³⁺ and Dy³⁺ doped LaBO₃ nanorods are investigated. And the two-step reaction mechanism is found and confirmed.The O-HT route is extended to prepare rare earth phosphates. Many REPO₄ (RE= La, Nd, Sm, Tb, Gd, Dy, Er, Y,) nanorods (the diameter ca. 20-30 nm with the aspect ca. 400-500) or nanoparticles are initially synthesized by mixing RE₂O₃ and P₂O₅ or H₃PO₄ via pH-free and additive-free oxides-hydrothermal process. The effects of time, temperature, P/La molar ratio on the products additive and solvent for LaPO₄ nanorods, and some factor for other lanthanum orthophosphate are investigated thoroughly. It is firstly demonstrated that the P/ La ratio (>1) can not influent the composition but the sizes and morphologies of products in the inspected O-HT system. It firstly confirmed that additives and solvent significantly influent the size and shapes of the LaPO₄ nanomaterials. It is firstly exhibited the phase transition growth mechanism of the REPO₄ (RE=La—Dy) nanomaterials in O-HT system.In summary, the O-HT route exhibits important applicable value in nanosciences and nanotechnologies, and great industizal prespect in future.