Zur Bildung der Phase K3SiF7 durch thermische Zersetzung von K2[SiF6]

Kolditz, Lothar; Wilde, W.; Bentrup, Ursula

doi:10.1002/zfch.19830230703

Cited by 7 publications

(3 citation statements)

References 5 publications

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“…After the α–β KHF 2 phase transition, a broader endothermic peak between 220 and 280 °C is observed in the DTA curve of Figure d. This is ascribed to the melting and thermal decomposition of β-KHF 2 at temperatures between 220 °C (disappearance of diffraction peaks in XRPD, Figure a) and 239 °C (end of mass loss in TGA curve, Figure c). As soon as thermal decomposition of KHF 2 starts, K 3 SiF 7 is formed by following endothermic processes , in which KHF 2 acts as the KF source. Note that occurs at lower temperatures than the reported 280 °C for pure KHF 2 .…”

Section: Resultsmentioning

confidence: 95%

Red Mn⁴⁺-Doped Fluoride Phosphors: Why Purity Matters

Verstraete

Sijbom

Joos

et al. 2018

ACS Appl. Mater. Interfaces

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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 Mn-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 KSiF:Mn are revealed. Both crystalline impurities such as KHF and ionic impurities such as Mn are found to affect the phosphor performance. While Mn mainly influences the optical absorption behavior, KHF can affect both the optical performance and chemical stability of the phosphor. Moisture leads to decomposition of KHF, 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 KHF, facilitating the hydrolysis of [MnF] 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%.

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Section: Resultsmentioning

confidence: 95%

Red Mn⁴⁺-Doped Fluoride Phosphors: Why Purity Matters

Verstraete

Sijbom

Joos

et al. 2018

ACS Appl. Mater. Interfaces

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“…They confirmed by X-ray diffraction (XRD) analysis that the compound can crystallize with the space group Pnma. Although instructions for the synthesis and powder diffraction data of KNaSiF 6 were published, 23,24 its crystal structure was not known until Fischer-Krämer's report. More recently, Garavelli et al 25 have found "heklaite" that forms a fine-grained mass of micron-to submicron-sized crystals among fumarolic encrustations on the Hekla volcano, Iceland.…”

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confidence: 99%

Synthesis and Properties of Hetero-Dialkaline Hexafluorosilicate Red Phosphor KNaSiF₆:Mn⁴⁺

Adachi

Abe

Kasa

et al. 2011

J. Electrochem. Soc.

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In this study, we demonstrate the synthesis of the hetero-dialkaline hexafluorosilicate red phosphor KNaSiF 6 :Mn 4+ by etching Si wafers in a HF/KMnO 4 /NaMnO 4 • H 2 O mixed solution. The X-ray diffraction analysis indicates that the synthesized phosphor has an orthorhombic structure with the space group D 16 2h − Pnma. The luminescence properties of the phosphor are studied by photoluminescence (PL) analysis, PL excitation spectroscopy, and luminescence lifetime measurements, and are found to be intermediate of those of homo-dialkaline K 2 SiF 6 :Mn 4+ and Na 2 SiF 6 :Mn 4+ red phosphors.

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“…As expected, increasing temperature stabilized K 3 SiF 7 relative to K 2 SiF 6 . [50][51][52] Analysis of the decomposition products of CsH(tfa) 2 was significantly more challenging due to the extremely hygroscopic nature of Cs 3 SiF 7 . 53 Unlike K 3 SiF 7 , which decomposed after several hours under our experimental conditions (≈20-25% relative humidity), Cs 3 SiF 7 decomposed within minutes.…”

Section: Paper Dalton Transactionsmentioning

confidence: 99%