Zaifa Yang

Preparation and photoluminescence properties of Dy3+-doped Ba3Lu(PO4)3 phosphors

Ba3Lu(PO4)3:Dy3+ phosphors were successfully synthesized by conventional solid state reaction and its photoluminescence properties were investigated by X-ray diffraction (XRD), photoluminescence spectra and diffuse reflectance spectra, respectively. Results showed that the phosphor could be excited by the ultraviolet visible light in the region from 320 to 460 nm, and it showed two dominant emission bands peaking at 484 nm (blue light) and 575 nm (yellow light) which originated from the transitions of 4F9/2→6H15/2 and 4F9/2→6H13/2 of Dy3+, respectively. According to Dexters theory, the concentration quenching mechanism occurred via the electric dipole-dipole interaction. The lifetime values of Dy3+ ions at different concentrations (x=0.01, 0.03, 0.05, 0.08 and 0.10) were determined to be about 0.8556, 0.7595, 0.6864, 0.6059 and 0.5456 ms.

Characterization and luminescence properties of Sr3Gd(PO4)3: Sm3+ orange–red phosphor

Abstract. Reddish-orange emitting phosphors, Sr3Gd(PO4)3:  Sm3+, were successfully synthesized by a conventional solid-state reaction. The crystal structure of the phosphors was characterized by x-ray diffraction. The excitation spectra and emission spectra were utilized to characterize the luminescence properties of the as-prepared phosphors. The results show that the phosphor consisted of some sharp emission peaks of Sm3+ ions centered at 564, 600, 647, and 707 nm, respectively. The critical distance of Sr3Gd0.93(PO4)3: 0.07Sm3+ was calculated to be 19.18  Å and the lifetime value of the sample was 1.63 ms. The band gap of Sr3Gd(PO4)3 was estimated to be about 2.74 eV from the diffuse reflection spectrum. The optimum doping concentration is 7 mol. % and the quenching occurs via dipole–dipole interaction according to Dexter’s theory. The Commission Internationale de L’Eclairage value of Sr3Gd(PO4)3:  Sm3+ phosphors presented that it has high color purity. These results indicated that the Sr3Gd(PO4)3:  Sm3+ may be a promising reddish-orange emitting phosphor for cost-effective near ultraviolet white light-emitting diodes.

Synthesis and luminescence properties of Ba_3Lu(PO_4)_3:Sm^3+ phosphor for white light-emitting diodes

A series of Ba₃Lu(PO₄)₃:Sm³⁺ phosphors were prepared by traditional high temperature solid-state reaction methods. The site-preferred occupancy of Sm³⁺ in Ba₃Lu(PO₄)₃ and the luminescence properties of Ba₃Lu(PO₄)₃:Sm³⁺ were studied combined with X-ray diffraction, photoluminescence excitation (PLE) spectra, and emission (PL) spectra as well as temperature-dependent PL and decay curves. The PL intensity is improved with increasing Sm³⁺ content and the optimal dopant content is 0.05. The temperature-dependent PL spectra indicate that the emission intensity decreases with the temperature because of the enhancement of the non-radiative transition. The results indicate that these reddish-orange emitting phosphors could be for potential applications in w-LEDs.

Hydrothermal synthesis and luminescence properties of KLa(MoO4)2:Eu3+ phosphor

Abstract. KLa(MoO4)2:Eu3+ phosphors were prepared by the hydrothermal method. The after tuning of synthesis time and the ratio of the ethylene glycol to water ratio made the phosphor present different morphologies, including peanut-like shape and spheres. The samples were characterized by x-ray diffraction (XRD), scanning electron microscope (SEM), diffuse reflectance spectrum, and fluorescence spectrum. Under the excitation of 397 nm near-ultraviolet, the typical red emission produced by Eu3+ ions can be observed. And the phosphors show strong red light around 612 nm, attributed to D50→F72 transition of Eu3+ ion. The luminescence properties of the as-prepared phosphors were studied based on changing the synthesis condition. It is found that the synthesis time and the changing of the ratio of ethylene glycol to water play the crucial role in the formation of morphology. The optimum dopant concentration of Eu3+ ions in KLa(MoO4)2:Eu3+ is around 7 mol. %. Moreover, the fluorescence decay curve and thermal stability of luminescence were also investigated in detail. The Commission International de I’Eclairage coordinates of KLa(MoO4)2:0.07Eu3+ located in the red reddish region. All the results suggest that KLa(MoO4)2:0.07Eu3+ might be a promising reddish-orange emitting phosphor used in white light-emitting diodes (w-LED).

Electronic and mechanical properties of C/Si phases with sp2 and sp3 hybridization: A first-principles study

A first-principles approach is utilized to systematically investigate the electronic and mechanical properties of SiC3/Si3C phases with sp2 and sp3 hybridization. In the SiC3 phases, electronic states around the Fermi level mainly originate from the C-2p orbitals, whereas in the case of Si3C phases, it is the C-2p and Si-3p orbitals. Cm-SiC3 and Cmc21-SiC3 show metallic properties arising from sp2-hybridized components. P4¯m2-Si3C exhibits good ductility and metallic properties due to the formation of conductive sublattices as a result of the distribution of valence electrons in three-dimensional C and Si frameworks. Furthermore, the semiconducting P4¯m2-SiC3 phase is a superhard material with a remarkable hardness of 47.14 GPa. In general, SiC3 phases exhibit higher brittleness due to sp3-hybridized C atoms while Si3C phases are more ductile.A first-principles approach is utilized to systematically investigate the electronic and mechanical properties of SiC3/Si3C phases with sp2 and sp3 hybridization. In the SiC3 phases, electronic states around the Fermi level mainly originate from the C-2p orbitals, whereas in the case of Si3C phases, it is the C-2p and Si-3p orbitals. Cm-SiC3 and Cmc21-SiC3 show metallic properties arising from sp2-hybridized components. P4¯m2-Si3C exhibits good ductility and metallic properties due to the formation of conductive sublattices as a result of the distribution of valence electrons in three-dimensional C and Si frameworks. Furthermore, the semiconducting P4¯m2-SiC3 phase is a superhard material with a remarkable hardness of 47.14 GPa. In general, SiC3 phases exhibit higher brittleness due to sp3-hybridized C atoms while Si3C phases are more ductile.

Synthesis and Luminescence Properties of Ba 3 Lu(PO 4 ) 3 :Sm 3+

Novel Ba3Lu(PO4)3:Sm3+ phosphors were prepared by solid-state reaction. The results of X-ray diffraction, photoluminescence spectra and decay time spectra suggest that it might be a promising reddish-orange emitting phosphor used in w-LEDs.