The Preparation And Photoluminescence Properties Of Three Kinds Of Rare-earth Sc Compounds

Controlled synthesis of nano-/micro-crystals with diverse phases,morphologies and dimensionalities have been attracting prodigiouss interests for their promising applications such as catalysis,luminescence,and biological monitoring.Among them,inorganic fluoride materials have more prominent advantages in optical applications because of their low phonon energy and high transparency which give rise to a decrease in the nonradiative relaxation compared with other oxide or sulfide materials.In addition,orthophosphates（Ln PO₄）have excellent characteristics due to their low solubility in water,high chemical/thermal stability and high refractive index.Owing to the rigid three-dimensional lattice,phosphates are regarded as perfect materials for charge stabilization.These properties make them become promising candidates for a variety of applications in down-/up-conversion luminescence,magnets,lasers,and bio-labeling.However,Sc-based fluorides or orthophosphates have been overlooked,and few reports about Sc-based sodium fluorides or orthophosphates have been investigated to date.It’s well known that Scelement has the smallest rare earth ionic radius and unique electron configurations which result in distinct optical properties different from those of Y³⁺/Ln³⁺-based fluoride or phosphatic materials.The Ln³⁺ doping is regard as a novel route to control the growth process of nano-/micro-materials and change phase,size,morphology,dimensionality and physical and chemical properties.Hydrothermal or solvothermal method is a simple and convenient method to synthesis fluoride or phosphatic materials.The main research contents of this paper are as following:（1）We have successfully prepared monodisperse ScF₃ and NaScF₄ nano-/micro-crystals by a simple solvothermal method.In our experiment,we change reaction time,surfactant,the molar ratio of Na/F/（Sc+Ln）,the volume ratio of H₂O/EG and Ln³⁺ doping to control the synthesis of products.We find that the prepared products doped with 1%Ln³⁺（Ln=La-Lu,except Pm）or diverse concentrations of Lu³⁺（1% 60%）present different phases,morphlogies and sizes.The possible formation mechanism for the products with diverse morphologies is proposed: both different kinds of Ln³⁺ and diverse contents of Lu³⁺ give rise to various diffusion rates of F-;The chemical potential of the crystal facet changes with the number of F-on the crystal surface,and the corresponding growth rates in different directions transform,which finally result in a variety of crystal morphologies.Besides,the prepared products including ScF₃:5% Eu³⁺,NaScF₄:1% Ln³⁺（Ln=Ce,Er,Sm）and ScF₃:30% Yb³⁺/1% Er³⁺ displayed colorful UC/DC luminescent properties,which enables them to become promising candidates for lighting and display applications.（2）We have successfully synthesized ScPO₄·2H₂O and ScPO₄·2H₂O:Ln³⁺（Ln = Ce,Eu,Tb,Lu）nano-/micro-crystals via a simple hydrothermal method without any surfactant at a mild temperature.The p H value,reaction time,reaction temperature,additive and the doping of rare earth ion have crucial roles in modifying the morphologies of ScPO₄·2H₂O and ScPO₄·2H₂O:Ln³⁺（Ln = Ce,Eu,Tb,Lu）samples.In particular,Ln³⁺ doping,has no effect on the phase of the ScPO₄·2H₂O:Ln³⁺,but it greatly changes the morphologies of ScPO₄·2H₂O:Ln³⁺ which transform from hexagonal plates to broken micro-plates,four angle stars,diamonds and butterfly-shaped.Moreover,the samples of ScPO₄·2H₂O: Ln³⁺（Ln = Ce,Tb）nano-/micro-crystals present intense blue and green emissions,respectively.The PL emission intensity of ScPO₄·2H₂O: 3% Tb³⁺ hexagonal plates（p H = 5）is the most strongest because of the large anisotropic geometry.ScPO₄:Ln³⁺ crystals will become promising candidates for a variety of applications in down-/up-conversion luminescence,magnets,lasers,and bio-labeling.