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Fluorine Phosphors for LEDs : K2SiF6:Mn4+

Reinert Verstraete (UGent) , Katleen Korthout (UGent) , Heleen Sijbom (UGent) , Philippe Smet (UGent) and Dirk Poelman (UGent)
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Abstract
White light-emitting diodes (wLEDs) are currently dominating the lighting and display market because of their high efficiency, long lifetime and environmental friendliness [1]. Narrow band red fluoride phosphors have recently gained interest to further improve the luminous efficacy and color rendering of wLEDs [2]. These fluoride phosphors incorporate Mn4+ as the activator for the luminescence. However, the broad range of possible Mn valence states proves to complicate both synthesis and stability of these materials, especially when they are stressed by heat and humidity. As a result, a mixed oxidation state of Mn4+ and Mn3+ exists in these materials. A XANES study on the Mn valence state in K2SiF6:Mn4+ [3] was performed. It was found that aqueous environments during the synthesis of the K2MnF6 precursor [4] or the K2SiF6:Mn4+ phosphor can lead to hydrated, Mn3+-containing impurity compounds such as K2MnF5•H2O or KMnF4•H2O. Hydrolysis and hydration processes cause water to be incorporated in the crystal structure, often replacing fluorine. Hence, the same hygroscopic behavior can be expected when K2MnF6 or K2SiF6:Mn4+ is in contact with air. However, careful elimination of the synthesis impurities drastically improves the chemical stability.

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Chicago
Verstraete, Reinert, Katleen Korthout, Heleen Sijbom, Philippe Smet, and Dirk Poelman. 2018. “Fluorine Phosphors for LEDs : K2SiF6:Mn4+.” In SyNew 2018, Abstracts.
APA
Verstraete, R., Korthout, K., Sijbom, H., Smet, P., & Poelman, D. (2018). Fluorine Phosphors for LEDs : K2SiF6:Mn4+. SyNew 2018, Abstracts. Presented at the SyNew 2018 : Dutch-Belgian Synchrotron/Neutron/FEL workshop and Symposium on Synchrotron Based Imaging and Spectroscopy.
Vancouver
1.
Verstraete R, Korthout K, Sijbom H, Smet P, Poelman D. Fluorine Phosphors for LEDs : K2SiF6:Mn4+. SyNew 2018, Abstracts. 2018.
MLA
Verstraete, Reinert, Katleen Korthout, Heleen Sijbom, et al. “Fluorine Phosphors for LEDs : K2SiF6:Mn4+.” SyNew 2018, Abstracts. 2018. Print.
@inproceedings{8557597,
  abstract     = {White light-emitting diodes (wLEDs) are currently dominating the lighting and display market because of their high efficiency, long lifetime and environmental friendliness [1]. Narrow band red fluoride phosphors have recently gained interest to further improve the luminous efficacy and color rendering of wLEDs [2].  These fluoride phosphors incorporate Mn4+ as the activator for the luminescence. However, the broad range of possible Mn valence states proves to complicate both synthesis and stability of these materials, especially when they are stressed by heat and humidity. As a result, a mixed oxidation state of Mn4+ and Mn3+ exists in these materials.
A XANES study on the Mn valence state in K2SiF6:Mn4+ [3] was performed. It was found that aqueous environments during the synthesis of the K2MnF6 precursor [4] or the K2SiF6:Mn4+ phosphor can lead to hydrated, Mn3+-containing impurity compounds such as K2MnF5{\textbullet}H2O or KMnF4{\textbullet}H2O. Hydrolysis and hydration processes cause water to be incorporated in the crystal structure, often replacing fluorine. Hence, the same hygroscopic behavior can be expected when K2MnF6 or K2SiF6:Mn4+ is in contact with air. However, careful elimination of the synthesis impurities drastically improves the chemical stability.},
  author       = {Verstraete, Reinert and Korthout, Katleen and Sijbom, Heleen and Smet, Philippe and Poelman, Dirk},
  booktitle    = {SyNew 2018, Abstracts},
  language     = {eng},
  location     = {Ghent, Belgium},
  title        = {Fluorine Phosphors for LEDs : K2SiF6:Mn4+},
  year         = {2018},
}