Synthesis And Luminesence Properties Of Rare Earthdoped CsGd[（Mo/w）O₄]₂ Phosphors

Rare earth-doped molybdates/tungstates is outstanding owing to their excellent chemical durability, thermal stability, rigid and tunable crystal structure and good optical properties. Thus, the composition, crystal structure, synthesis and spectroscopic properties of molybdates/tungstates-based phosphors have attracted great attention in recent years. In this study, CsGd(MoO4)2 is selected as the host material. A series of phosphors doped with Eu3+, Dy3+, Yb3+- Er3+ were synthesized and the crystal structure characters, spectroscopic properties and the relationship between them were studied. The research results can provide theoretical basis and experimental data for later exploration in molybdate-based phosphors.A series of red-emitting CsGd(MoO4)2: Eu3+ phosphors have been synthesized by conventional solid-state synthesis and microwave radiation method. The crystal structure and luminescent properties were analyzed by XRD, Rietveld refinement, SEM, fluorescence spectra, decay curves and some other tests. A detailed analysis of the structural properties indicates that the isostructural scheelite-type CsGd1-x Eux(MoO4)2 solid-solutions with monoclinic phase crystallize in space group P2/c exhibiting a layered structure. Considering the ion sizes and valence states, Eu3+ ions enter into the Gd3+ sites. Based on the Rietveld refinement results, the proportional increase of unit cell volume takes place upon substitution of Gd3+ by Eu3+. The phosphors can efficiently absorb nearUV/blue light, and show a strong red emission at 615 nm. The critical doping concentration of Eu3+ is determined to be 0.6 in order to realize the maximum emission intensity. In addition, samples with regular grain morphology and high uniformity were obtained by microwave radiation method. The temperature needed to produce pure phase covered a wide range and was lower than that of solid-state method.Dy3+ activated CsGd(MoO4)2-x(WO4)x phosphors have been prepared through solid-state reaction. The effect of WO42- doped into the host on the optical properties were studied. By integral fitting based on the emission spectra, the component of yellow emission increased and the component of blue emission decreased with the proportion of WO42- increasing.Yb3+-Er3+ co-doped CsGd(MoO4)2 phosphors with different Er3+ concentration have been also prepared. The results show that the phosphors can give intense green emission and weak red emission under the excitation of 980 nm laser. The optimum doping concentration of Er3+ is focused on 0.015. Energy transition process of up-conversion luminescence was explored in combination with the energy level diagram of Yb3+- Er3+. It proves that Yb3+ can sensitize Er3+. The emission spectra under different pump power were collected. By plotting the double logarithmic curve of the excitation power and the emission intensity, it is found that both the green and red emission correspond to the twophoton process.