Synthesis of K2XF6:Mn4+ (X=Ti, Si and Ge) red phosphors for white LED applications with low-concentration of HF

Wang, Zhengliang; Zhou, Yayun; Yang, Zhiyu; Liu, Yong; Yang, Hui; Tan, Huiying; Zhang, Qiuhan; Zhou, Qiang

doi:10.1016/j.optmat.2015.09.023

Cited by 55 publications

(14 citation statements)

References 25 publications

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“…The K 2 NaAlF 6 :Mn 4+ particles prepared with our co-precipitation method have a more uniform shape and size than the K 2 NaAlF 6 :Mn 4+ particles prepared by Zhu et al via cation exchange [19]. Moreover, the K 2 NaAlF 6 :Mn 4+ (0.9%) phosphor shown in Figure 2c,d exhibits particle size and shape distributions that are superior to the size and shape distributions of other reported Mn 4+ -doped fluoride phosphors [10,24,32,33,34,35,36,37]. …”

Section: Resultsmentioning

confidence: 84%

Co-Precipitation Synthesis and Optical Properties of Mn4+-Doped Hexafluoroaluminate w-LED Phosphors

2017

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Mn4+-activated hexafluoroaluminates are promising red-emitting phosphors for white light emitting diodes (w-LEDs). Here, we report the synthesis of Na3AlF6:Mn4+, K3AlF6:Mn4+ and K2NaAlF6:Mn4+ phosphors through a simple two-step co-precipitation method. Highly monodisperse large (~20 μm) smoothed-octahedron shaped crystallites are obtained for K2NaAlF6:Mn4+. The large size, regular shape and small size distribution are favorable for application in w-LEDs. All Mn4+-doped hexafluoroaluminates show bright red Mn4+ luminescence under blue light excitation. We compare the optical properties of Na3AlF6:Mn4+, K3AlF6:Mn4+ and K2NaAlF6:Mn4+ at room temperature and 4 K. The luminescence measurements reveal that multiple Mn4+ sites exist in M3AlF6:Mn4+ (M = Na, K), which is explained by the charge compensation that is required for Mn4+ on Al3+ sites. Thermal cycling experiments show that the site distribution changes after annealing. Finally, we investigate thermal quenching and show that the luminescence quenching temperature is high, around 460–490 K, which makes these Mn4+-doped hexafluoroaluminates interesting red phosphors for w-LEDs. The new insights reported on the synthesis and optical properties of Mn4+ in the chemically and thermally stable hexafluoroaluminates can contribute to the optimization of red-emitting Mn4+ phosphors for w-LEDs.

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Section: Resultsmentioning

confidence: 84%

Co-Precipitation Synthesis and Optical Properties of Mn4+-Doped Hexafluoroaluminate w-LED Phosphors

2017

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“…Due to the small bandwidth and the good spectral position, the class of manganese-doped fluorides gained a lot of attention. A whole series of hexafluorides A 2 MF 6 :Mn 4+ (A = K, Na, Cs; M = Si, Ge, Zr, Ti) was prepared since the discovery of K 2 SiF 6 :Mn 4+ by Adachi and co-workers. ,− Usually, these kind of phosphors are prepared via wet chemical etching processes in aqueous HF solutions. ,,, Due to high security measures, which are mandatory during the application of HF in industrial processes, HF-free synthesis methods are in high demand. The first “HF-free” synthesis of K 2 SiF 6 :Mn 4+ was published by Wang and co-workers in 2006 .…”

Section: Introductionmentioning

confidence: 99%

HF-Free Synthesis of Li₂SiF₆:Mn⁴⁺: A Red-Emitting Phosphor

et al. 2019

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Li2SiF6:Mn4+ was synthesized via a new HF-free synthesis route by a high-pressure/high-temperature doping experiment at 5.5 GPa and 750 °C. It is proven that the phosphor cannot be synthesized by the common wet-chemical precipitation route in aqueous HF. The sample was characterized by powder X-ray diffraction, EDX, and luminescence spectroscopy. At room temperature, Li2SiF6:Mn4+ exhibits seven emission lines with the strongest line at λmax ≈ 630 nm and a dominant wavelength of λdom ≈ 618 nm. The CIE coordinates are 0.688 and 0.312 for x and y, respectively. The compound shows a luminous efficacy of radiation (LER) of 218 lm Wopt –1, which exceeds the LER of current state-of-the-art red LED phosphor K2SiF6:Mn4+ by 7% due to a blue-shift of the emission. It reveals excellent thermal quenching behavior up to 125 °C.

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“…In contrast, transition metal Mn 4+ activated fluoride phosphors possess narrow-band red emission around ∼630 nm and broad excitation band at ∼460 nm (with a bandwidth of ∼50 nm), as well as milder synthesis conditions, showing more promise for warm W-LED applications . For these characteristics, considerable attention has been focused on this field and various Mn 4+ -doped fluoride red phosphors such as A 2 BF 6 :Mn 4+ (A = NH 4 , Na, K, Rb, Cs; A 2 = Ba, Zn; B = Si, Ge, Ti, Zr) and H 3 XF 6 :Mn 4+ (H = Li, Na, K; X = Al, Ga) have been developed. ,− By using a suitable synthesis route, nearly a 100% high internal quantum efficiency (IQE) has been achieved in fluoride phosphor K 2 TiF 6 :Mn 4+ . However, since the Mn 4+ emission belongs to a spin-forbidden transition ( 2 E g → 4 A 2 ), it is still a fundamental challenge to synthesize these Mn 4+ -related fluoride phosphors with external quantum efficiency (EQE) higher than 60%, which is crucial for practical applications. ,, The ultrahigh IQE value and relatively low EQE in these Mn 4+ -doped fluoride are due to the lower absorption efficiency (AE) of Mn 4+ (usually, AE < 60%).…”

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Highly Efficient and Stable Narrow-Band Red Phosphor Cs₂SiF₆:Mn⁴⁺ for High-Power Warm White LED Applications

et al. 2017

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Due to the unique narrow-band red emission and broadband blue light excitation, as well as milder synthesis conditions, Mn 4+ ion activated fluoride red phosphors show great promise for white light emitting diode (W-LED) applications. However, as the Mn 4+ emission belongs to a spin-forbidden transition ( 2 E g → 4 A 2 ), it is a fundamental challenge to synthesize these phosphors with a high external quantum efficiency (EQE) above 60%. Herein, a highly efficient and thermally stable red fluoride phosphor, Cs 2 SiF 6 :Mn 4+ , with a high internal quantum efficiency (IQE) of 89% and ultrahigh EQE of 71% is demonstrated. Furthermore, nearly 95% of the room-temperature IQE and EQE are maintained at 150 °C. The static and dynamic spectral measurements, as well as density functional theory (DFT) calculations, show that the excellent performance of Cs 2 SiF 6 :Mn 4+ is due to the Mn 4+ ions being evenly distributed in the host lattice Cs 2 SiF 6 . By employing Cs 2 SiF 6 :Mn 4+ as a red light component, stable 10 W high-power warm W-LEDs with a luminous efficiency of ∼110 lm/W could be obtained. These findings indicate that red phosphor Cs 2 SiF 6 :Mn 4+ may be a highly suitable candidate for fabricating high-performance high-power warm white LEDs.

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Synthesis of K2XF6:Mn4+ (X=Ti, Si and Ge) red phosphors for white LED applications with low-concentration of HF

Cited by 55 publications

References 25 publications

Co-Precipitation Synthesis and Optical Properties of Mn4+-Doped Hexafluoroaluminate w-LED Phosphors

Co-Precipitation Synthesis and Optical Properties of Mn4+-Doped Hexafluoroaluminate w-LED Phosphors

HF-Free Synthesis of Li₂SiF₆:Mn⁴⁺: A Red-Emitting Phosphor

Highly Efficient and Stable Narrow-Band Red Phosphor Cs₂SiF₆:Mn⁴⁺ for High-Power Warm White LED Applications

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Synthesis of K2XF6:Mn4+ (X=Ti, Si and Ge) red phosphors for white LED applications with low-concentration of HF

Cited by 55 publications

References 25 publications

Co-Precipitation Synthesis and Optical Properties of Mn4+-Doped Hexafluoroaluminate w-LED Phosphors

Co-Precipitation Synthesis and Optical Properties of Mn4+-Doped Hexafluoroaluminate w-LED Phosphors

HF-Free Synthesis of Li2SiF6:Mn4+: A Red-Emitting Phosphor

Highly Efficient and Stable Narrow-Band Red Phosphor Cs2SiF6:Mn4+ for High-Power Warm White LED Applications

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Product

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HF-Free Synthesis of Li₂SiF₆:Mn⁴⁺: A Red-Emitting Phosphor

Highly Efficient and Stable Narrow-Band Red Phosphor Cs₂SiF₆:Mn⁴⁺ for High-Power Warm White LED Applications