Fabrication and Luminescence Properties of One-Dimensional CaMoO4: Ln(3+) (Ln = Eu, Tb, Dy) Nanofibers via Electrospinning Process

One-dimensional CaMoo(4):Ln(3+) (Ln = Eu, Tb, Dy) nanofibers have been prepared by a combination method of sol-gel and electrospinning process. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), photoluminescence (PL), and low voltage cathodoluminescence (CL) as well as kinetic decays were used to characterize the resulting samples. SEM and TEM analyses indicate that the obtained precursor fibers have a uniform size, and the as-formed CaMoO4:Ln(3+) nanofibers consist of nanoparticles. Under ultraviolet excitation, the CaMoO4 samples exhibit a blue-green emission band with a maximum at 500 nm originating from the MoO42- groups. Due to an efficient energy transfer from molybdate groups to dopants, CaMoO4:Ln(3+) phosphors show their strong characteristic emission under ultraviolet excitation and low-voltage electron beam excitation.

Growth of highly crystalline CaMoO4 : Tb3+ phosphor layers on spherical SiO2 particles via sol-gel process: Structural characterization and luminescent properties

Highly crystalline CaMoO4:Tb3+ phosphor layers were grown on monodisperse SiO2 particles through a simple sol-gel method, resulting in formation of core-shell structured SiO2@CaMoO4:Tb3+ submicrospheres. The resulting SiO2@CaMoO4: Tb3+ core-shell particles were fully characterized by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectra (EDS), transmission electron microscopy (TEM), photoluminescence (PL), low-voltage cathodoluminescence (CL), and kinetic decays. The XRD results demonstrate that the CaMoO4:Tb3+ layers begin to crystallize on the SiO2 spheres after annealing at 400 degrees C and the crystallinity increases with raising the annealing temperature. SEM and TEM analysis indicates that the obtained submicrospheres have a uniform size distribution and obvious core-shell structure. SiO2@CaMoO4:Tb3+ submicrospheres show strong green emission under short ultraviolet (260 nm) and low-voltage electron beam (1-3 kV) excitation, and the emission spectra are dominated by a D-5(4) -F-7(5) transition of Tb3+(544 nm, green) from the CaMoO4:Tb3+ shells.

Improved optical photoluminescence by charge compensation in the phosphor system CaMoO4: Eu3+

It has been found that charge compensated CaMoO4:Eu3+ phosphors show greatly enhanced red emission under 393 and 467 nm-excitation, compared with CaMoO4:Eu3+ without charge compensation. Two approaches to charge compensation, (a) 2Ca(2+) -> EU3+ + M+, where M+ is a monovalent cation like Li+, Na+ and K+ acting as a charge compensator; (b) 3Ca(2+) -> 2EU(3+) + vacancy, are investigated. The influence of sintering temperature and Eu3+ concentration on the luminescent property of phosphor samples is also discussed.

新的白光LED灯用不同光色发射荧光体的研究

凡是与某种发光二极管（LED）匹配能够产生白光发射的荧光体均可称作白光LED荧光体，通过这种匹配构筑起来的白光发射体系（或器件），简称作白光LED。白光LED是一种新的固态光源，具有环保、节能等诸多优点。目前已实用化的白光LED只有蓝光LED＋YAG:Ce荧光粉，但其显色性差，不能满足通常的照明要求。因此，寻找并研究可以与UVLED、蓝光LED匹配的、能产生高效的各种光色发射的新的荧光体具有重要的理论和现实意义。 本工作利用高温固相法合成了四个白光LED灯用多光色发射荧光新体系。研究成果如下： 1. 合成出一种新的白光LED灯用荧光体－黄橙光发射的Eu2+掺杂的高温相氯硅酸钙荧光体，HTP-Ca3SiO4Cl2:Eu2+。该荧光体与近紫外LED匹配产生暖白光发射。晶体结构解析表明，HTP-Ca3SiO4Cl2属单斜晶系。 2. 研究发现Eu2+离子掺杂的低温相氯硅酸钙荧光体可用作白光LED灯用绿色荧光体，LTP-Ca3SiO4Cl2:Eu2+。实验结果证明与已报道的硫化物、氮化物LED灯用绿色荧光体相比，该荧光体具有合成条件相对温和、简便、无污染等优点。 3. 合成出一种新的白光LED灯用蓝绿光发射荧光体－Eu2+掺杂的硅酸锂钙，Li2CaSiO4:Eu2+。该荧光体的激发光谱从紫外延伸到可见区，和已报道的氯磷酸盐、铝酸盐LED灯用蓝光发射荧光体相比，具有更广泛的应用性。 4. 找到了一种可明显改善CaMoO4:Eu3+发光特性途径，通过碱金属离子和空穴进行电荷补偿可以使CaMoO4:Eu3+的红光发射强度提高3倍左右，使其有可能应用作白光LED红光发射组分。

Uniform AMoO(4):Ln (A = Sr2+, Ba2+; Ln = Eu3+, Tb3+) submicron particles: Solvothermal synthesis and luminescent properties

Rare-earth ions (Eu3+, Tb3+) doped AMoO(4) (A = Sr, Ba) particles with uniform morphologies were successfully prepared through a facile solvothermal process using ethylene glycol (EG) as protecting agent. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS), Fourier transform infrared spectroscopy (FT-IR), photoluminescence (PL) spectra and the kinetic decays were performed to characterize these samples. The XRD results reveal that all the doped samples are of high purity and crystallinity and assigned to the tetragonal scheelite-type structure of the AMoO(4) phase. It has been shown that the as-synthesized SrMoO4:Ln and BaMoO4:Ln samples show respective uniform pea nut-like and oval morphologies with narrowsize distribution. The possible growth process of the AMoO(4):Ln has been investigated in detail. The EG/H2O volume ratio, reaction temperature and time have obvious effect on themorphologies and sizes of the as-synthesized products.