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Red Mn4+-doped fluoride phosphors : why purity matters

Reinert Verstraete UGent, Heleen Sijbom UGent, Jonas Joos UGent, Katleen Korthout UGent, Dirk Poelman UGent, Christophe Detavernier UGent and Philippe Smet UGent (2018) ACS APPLIED MATERIALS & INTERFACES. 10(22). p.18845-18856
abstract
Traditional light sources, e.g., incandescent and fluorescent lamps, are currently being replaced by white light-emitting diodes (wLEDs) because of their improved efficiency, prolonged lifetime, and environmental friendliness. Much effort has recently been spent to the development of Mn4+-doped fluoride phosphors that can enhance the color gamut in displays and improve the color rendering index, luminous efficacy of the radiation, and correlated color temperature of wLEDs used for lighting. Purity, stability, and degradation of fluoride phosphors are, however, rarely discussed. Nevertheless, the typical wet chemical synthesis routes (involving hydrogen fluoride (HF)) and the large variety of possible Mn valence states often lead to impurities that drastically influence the performance and stability of these phosphors. In this article, the origins and consequences of impurities formed during synthesis and aging of K2SiF6:Mn4+ are revealed. Both crystalline impurities such as KHF2 and ionic impurities such as Mn3+ are found to affect the phosphor performance. While Mn3+ mainly influences the optical absorption behavior, KHF2 can affect both the optical performance and chemical stability of the phosphor. Moisture leads to decomposition of KHF2, forming HF and amorphous hydrated potassium fluoride. As a consequence of hydrate formation, significant amounts of water can be absorbed in impure phosphor powders containing KHF2, facilitating the hydrolysis of [MnF6]2− complexes and affecting the optical absorption of the phosphors. Strategies are discussed to identify impurities and to achieve pure and stable phosphors with internal quantum efficiencies of more than 90%.
Please use this url to cite or link to this publication:
author
organization
year
type
journalArticle (original)
publication status
published
subject
keyword
fluoride phosphors, stability, purity, transition-metal dopants, LEDs, LIGHT-EMITTING-DIODES, WARM-WHITE LEDS, THERMAL-DECOMPOSITION, PHOTOLUMINESCENCE PROPERTIES, LUMINESCENCE PROPERTIES, SYNCHROTRON-RADIATION, CONVERSION PHOSPHORS, K2SIF6MN4+ PHOSPHOR, OPTICAL-PROPERTIES, CRYSTAL-STRUCTURE
journal title
ACS APPLIED MATERIALS & INTERFACES
ACS Appl. Mater. Interfaces
editor
Kirk Schanze
volume
10
issue
22
pages
18845 - 18856
Web of Science type
Article
Web of Science id
000434895500045
ISSN
1944-8244
DOI
10.1021/acsami.8b01269
project
Center for nano- and biophotonics (NB-Photonics)
language
English
UGent publication?
yes
classification
A1
copyright statement
I have retained and own the full copyright for this publication
id
8564420
handle
http://hdl.handle.net/1854/LU-8564420
date created
2018-06-06 12:40:06
date last changed
2018-06-27 13:28:09
@article{8564420,
  abstract     = {Traditional light sources, e.g., incandescent and fluorescent lamps, are currently being replaced by white light-emitting diodes (wLEDs) because of their improved efficiency, prolonged lifetime, and environmental friendliness. Much effort has recently been spent to the development of Mn4+-doped fluoride phosphors that can enhance the color gamut in displays and improve the color rendering index, luminous efficacy of the radiation, and correlated color temperature of wLEDs used for lighting. Purity, stability, and degradation of fluoride phosphors are, however, rarely discussed. Nevertheless, the typical wet chemical synthesis routes (involving hydrogen fluoride (HF)) and the large variety of possible Mn valence states often lead to impurities that drastically influence the performance and stability of these phosphors. In this article, the origins and consequences of impurities formed during synthesis and aging of K2SiF6:Mn4+ are revealed. Both crystalline impurities such as KHF2 and ionic impurities such as Mn3+ are found to affect the phosphor performance. While Mn3+ mainly influences the optical absorption behavior, KHF2 can affect both the optical performance and chemical stability of the phosphor. Moisture leads to decomposition of KHF2, forming HF and amorphous hydrated potassium fluoride. As a consequence of hydrate formation, significant amounts of water can be absorbed in impure phosphor powders containing KHF2, facilitating the hydrolysis of [MnF6]2\ensuremath{-} complexes and affecting the optical absorption of the phosphors. Strategies are discussed to identify impurities and to achieve pure and stable phosphors with internal quantum efficiencies of more than 90\%.},
  author       = {Verstraete, Reinert and Sijbom, Heleen and Joos, Jonas and Korthout, Katleen and Poelman, Dirk and Detavernier, Christophe and Smet, Philippe},
  editor       = {Schanze, Kirk},
  issn         = {1944-8244},
  journal      = {ACS APPLIED MATERIALS \& INTERFACES},
  keyword      = {fluoride phosphors,stability,purity,transition-metal dopants,LEDs,LIGHT-EMITTING-DIODES,WARM-WHITE LEDS,THERMAL-DECOMPOSITION,PHOTOLUMINESCENCE PROPERTIES,LUMINESCENCE PROPERTIES,SYNCHROTRON-RADIATION,CONVERSION PHOSPHORS,K2SIF6MN4+ PHOSPHOR,OPTICAL-PROPERTIES,CRYSTAL-STRUCTURE},
  language     = {eng},
  number       = {22},
  pages        = {18845--18856},
  title        = {Red Mn4+-doped fluoride phosphors : why purity matters},
  url          = {http://dx.doi.org/10.1021/acsami.8b01269},
  volume       = {10},
  year         = {2018},
}

Chicago
Verstraete, Reinert, Heleen Sijbom, Jonas Joos, Katleen Korthout, Dirk Poelman, Christophe Detavernier, and Philippe Smet. 2018. “Red Mn4+-doped Fluoride Phosphors : Why Purity Matters.” Ed. Kirk Schanze. Acs Applied Materials & Interfaces 10 (22): 18845–18856.
APA
Verstraete, R., Sijbom, H., Joos, J., Korthout, K., Poelman, D., Detavernier, C., & Smet, P. (2018). Red Mn4+-doped fluoride phosphors : why purity matters. (K. Schanze, Ed.)ACS APPLIED MATERIALS & INTERFACES, 10(22), 18845–18856.
Vancouver
1.
Verstraete R, Sijbom H, Joos J, Korthout K, Poelman D, Detavernier C, et al. Red Mn4+-doped fluoride phosphors : why purity matters. Schanze K, editor. ACS APPLIED MATERIALS & INTERFACES. 2018;10(22):18845–56.
MLA
Verstraete, Reinert, Heleen Sijbom, Jonas Joos, et al. “Red Mn4+-doped Fluoride Phosphors : Why Purity Matters.” Ed. Kirk Schanze. ACS APPLIED MATERIALS & INTERFACES 10.22 (2018): 18845–18856. Print.