Details

Autor(en) / Beteiligte

• Sokolnicki, Jerzy

Titel

Rare earths (Ce, Eu, Tb) doped Y2Si2O7 phosphors for white LED

Ist Teil von

• Journal of luminescence, 2013-02, Vol.134, p.600-606

Ort / Verlag

Amsterdam: Elsevier B.V

Erscheinungsjahr

2013

Quelle

Access via ScienceDirect (Elsevier)

Beschreibungen/Notizen

• Nanocrystalline yttrium pyrosilicate Y2Si2O7 (YPS) singly, doubly or triply doped with Ce3+, Eu3+, Tb3+ was obtained by the reaction of nanostructured Y2O3:Ln3+ and colloidal SiO2 at high temperatures. X-ray diffraction analysis confirmed the formation of a single phase of α-YPS at 1200°C. Two series of YPS samples doped with Eu3+ or Eu3+/Tb3+ were obtained by applying the reducing atmosphere (75%N2+25%H2) at different temperatures. The luminescence and excitation spectra are reported. The singly Eu3+ doped YPS emit from both Eu3+ and Eu2+ ions, with the spectral position and width of the Eu2+ emission different in both series. The presence of Eu2+ in the samples was confirmed by electron paramagnetic resonance (EPR) spectra. A broadband emission of Eu2+ (380–650nm), combined with the red emission of Eu3+ is perceived by the naked eye as white light. Co-doping of YPS:Eu3+ with Tb3+ results in enhancement of the green component of the emission, and well-balanced white luminescence. The colour of this emission is tunable, and it is possible to get Commission International de I'Eclairage (CIE) chromaticity coordinates of (0.327, 0.327), colour-rendering index (CRI) of 85, and quantum efficiency (QE) of 71%. These phosphors are efficiently excited in the wavelength range of 300–420nm, which perfectly matches a near UV-emitting InGaN chip. It was shown that for triply (Ce3+, Eu3+ and Tb3+) doped samples the three emissions from the particular activators can be generated using one excitation wavelength. The white light resulting from the superposition of the blue (Ce3+), green (Tb3+) and red (Eu3+) emissions can be obtained by varying the concentration of the active ions and the treating atmosphere, i.e. reducing or oxidising. Eu2+ was not detected in the triply doped samples, and hence line emissions mostly exhibit CRI values equal to or below 30. ► Nanocrystalline Y2Si2O7 was obtained by the reaction of Y2O3:Ln3+ and colloidal silica at 1200°C. ► Eu3+ can be partially reduced to Eu2+ in the Y2Si2O7 host lattice. ► The Y2Si2O7:Eu2+, Eu3+, Tb3+ sample emits white light. ► CRI=85 and QE ∼70% can be reached for the white emission.