Synthesis And Luminescence Properties Of Rare Earth Ions Activated Tungstate/Molybdate Materials With Multicolor Emissions

Rare earth ions activated tungstate/molybdate luminescent materials have been found potential applications in fields of lighting,displays,and biomedicine due to their long decay lifetime,good luminescence efficiency and light stability.The luminescence intensity can be tuned by controlling the morphology and particle size of the materials.In this work,the tungstate/molybdate luminescent nano/micromaterials with diverse morphologies have been synthesized by hydrothermal method,and the phase,structure,morphology,and luminescence properties have been investigated in detail.Well-defined sodium lanthanum molybdate [NaLa?MoO₄?₂] microcrystals with a variety of morphologies?microspheres,ellipsoids,microspindles,microflowers,etc.?have been fabricated via a mild and controllable solvothermal method.The whole process was carried out without any organic surfactant,template,or catalyst.The morphology and size of the NaLa?MoO₄?₂ particles can be tuned in a controlled manner by altering the pH value of the initial solution,reaction temperature,and composition of solvent.Upon ultraviolet?UV?or near infrared?NIR?excitation,the as-synthesized NaLa?MoO₄?₂:Ln3+ phosphors exhibit intense characteristic down-conversion or up-conversion luminescence,respectively.The dependence of NaLa?MoO₄?₂:Ln3+ luminescence intensity on different particle sizes and morphologies has been also investigated.The facile synthesis strategy may be extended to the synthesis of other well-defined lanthanide molybdate materials.The rare earth ions doped hollow spherical CaMoO₄/CaF₂ composite luminescent materials were prepared by hydrothermal method.XRD and EDX results show that the sample is composed of the CaMoO₄/CaF₂ composite.From the SEM images,we can seen that the sample exhibits good dispersion and uniformity.The morphology and particle size of the samples can be tuned by changing the reaction temperature or the molar ratio of the reactants.The activator ions doped samples exhibit good luminescence properties,which confirms that the composite can be applied as candidate of phosphor host.Compared with the single component rare earth luminescent material,the as-obtained composite materials may exhibitstronger luminescence and find a broader applications.The rare earth ions doped CaWO₄ hollow spheres with excellent luminescence properties have been synthesized by a simple hydrothermal route.SEM and TEM images indicate that the sample shows evident hollow spherical structure.During the synthesis process,CaF₂ microspheres were firstly synthesized by a hydrothermal process.Subsequently,CaWO₄ hollow spheres were obtained by a hydrothermal conversion route.Upon ultraviolet?UV?or near infrared?NIR?excitation,the as-synthesized CaWO₄:Ln3+ phosphors exhibit intense characteristic down-conversion or up-conversion luminescence,respectively.The as-synthesized materials may be potentially applied in fields of optical displays,optoelectronic devices,and light emitting diodes?LEDs?.