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Structural and Optical Properties of Tunable Warm-White Light-Emitting ZrO2:Dy3+Eu3+ Nanocrystals

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Author to whom correspondence should be addressed. e-mail: chlu@ntu.edu.tw

Abstract

A series of Dy3+–Eu3+-codoped ZrO2 nanocrystals with tetragonal and cubic symmetry was synthesized via a wet chemical reaction. When the Eu3+-doping content was fixed, the crystal structure could be stabilized from the mixed phase to single cubic phase by simply adjusting the content of Dy3+. The cubic ZrO2:Dy3+–Eu3+ nanoparticles exhibited spherical and nonagglomerated morphology. The effective phonon energy of cubic ZrO2:5%Dy3+–5%Eu3+ was calculated to be 445 cm−1, which is lower than the previously reported results. Extensive luminescence studies of ZrO2:Dy3+–Eu3+ as a function of Dy3+ content demonstrated that the dopant concentration and its site symmetry play an important role in the emissive properties. Under 352 nm excitation, the increment of Dy3+ concentration in ZrO2:Dy3+–Eu3+ led to an increase in orange (590 nm) and red (610 nm) emissions of Eu3+ ions, which are attributed to the 5D07FJ(J = 1, 2) transitions of Eu3+ ions. This increment is possibly due to the efficient energy transfer (ET) 4F9/2:Dy3+5D0:Eu3+. The phosphors can generates light from yellow through near white and eventually to warm white by properly tuning the concentration of Dy3+ ions through the ET and change in site symmetry. These phosphors may be promising as warm-white-/yellow-emitting phosphors.

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