Abstract
This work successfully verified that the addition of a flux (NH4F, NH4Cl, and H3BO3) during synthesis has an impact on the crystallite size and quantum efficiency of submicron-sized particles of CaMgSi2O6:Eu2+ phosphors. The addition of NH4F or NH4Cl increased the crystallite size in the submicron-sized particles, yielding an increase in emission intensity and quantum efficiency. On the other hand, the use of the H3BO3 flux crystallized a secondary phase, SiO2, and changed the lattice parameters, which degraded the luminescent properties. In addition, an excessive amount of NH4Cl was examined, resulting in nucleation of a secondary phase, CaSiO3, which changed the lattice parameters with no improvement in luminescent properties. These results demonstrate that the addition of a flux could be a method to improve the quantum efficiency of submicron-sized particles composed of nanocrystallites; however, a judicious choice of the flux composition and amount has to be carefully considered.
Highlights
Powder phosphors produced by the conventional solid-state reaction method have been widely researched for application in near UV-emitting LEDs [1,2]
The crystallite size and quantum efficiency of blue-emitting Ca0.94 Eu0.06 MgSi2 O6 submicrometersized phosphors prepared by the co-precipitation method were altered with the addition of a flux, NH4 F, NH4 Cl, or H3 BO3
A direct correlation between crystallite sizes of the materials produced with NH4 F or NH4 Cl fluxes and their corresponding quantum efficiencies was verified
Summary
Powder phosphors produced by the conventional solid-state reaction method have been widely researched for application in near UV-emitting LEDs (nUV-LEDs) [1,2] This method produces micron-sized powders that have higher quantum efficiencies than smaller-sized powders [3,4], whereas chemical synthesis methods produce submicron-sized powders composed of nanocrystallites. In the remote configuration, the packing density of the large particles is low, which generates substantial light scattering [5]. To overcome this issue, phosphors with a small, narrow particle size distribution are required. If the particle radii are
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