Mn[sup 4+]-Activated Red Photoluminescence in K[sub 2]SiF[sub 6] Phosphor

Takahashi, Toru; Adachi, Sadao

doi:10.1149/1.2993159

Cited by 259 publications

(252 citation statements)

References 28 publications

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“…The K 2 SiF 6 :Mn 4+ red phosphor was synthesized by etching Si wafer in aqueous HF/KMnO 4 solution [14]. As expected, no Mn-related ESR signature is detected in Fig.…”

Section: Structural Propertiessupporting

confidence: 58%

Synthesis and photoluminescence spectroscopy of BaGeF6:Mn4+ red phosphor

Sekiguchi

Adachi

2015

Optical Materials

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“…The K 2 SiF 6 :Mn 4+ red phosphor was synthesized by etching Si wafer in aqueous HF/KMnO 4 solution [14]. As expected, no Mn-related ESR signature is detected in Fig.…”

Section: Structural Propertiessupporting

confidence: 58%

Synthesis and photoluminescence spectroscopy of BaGeF6:Mn4+ red phosphor

Sekiguchi

Adachi

2015

Optical Materials

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“…Therefore, the region for E > 0 meV (E < 0 meV) means that the light emission is due to the Stokes (anti-Stokes) emission process. 1 The PL spectra in Fig. 4 reveal the main peak features at | E| ∼ 30 meV (ν 6 ), ∼40 meV (ν 4 ), and ∼80 meV (ν 3 ).…”

Section: Resultsmentioning

confidence: 90%

“…[1][2][3][4] Such Mn 4+ -activated phosphors exhibit efficient red emission under blue (∼460 nm) or UV excitation (∼360 nm). Of course, searching for new red-emitting phosphors or those containing a red emission component is still an important approach to the realization of warm-white LED applications.…”

mentioning

confidence: 99%

Editors' Choice—Rb₂SiF₆:Mn⁴⁺and Rb₂TiF₆:Mn⁴⁺Red-Emitting Phosphors

Sakurai

Nakamura

Adachi

2016

ECS J. Solid State Sci. Technol.

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Rb-based hexafluoride red-emitting phosphors, Rb 2 SiF 6 :Mn 4+ and Rb 2 TiF 6 :Mn 4+ , were synthesized by the coprecipitation method. Optical microscopy observation, X-ray diffraction (XRD) measurement, photoluminescence (PL) analysis, PL excitation (PLE) spectroscopy, and luminescence decay characteristics measurements were used to study the structural and optical properties of the phosphors. The photographs of the bulk samples showed clear crystallographic habits originating from the cubic and trigonal symmetries of the Rb 2 SiF 6 and Rb 2 TiF 6 hosts, respectively, in agreement with the XRD results. The phosphors exhibited an intense narrow-band Mn 4+ ( 2 E g → 4 A 2g ) red emission with internal quantum efficiencies higher than 90% upon blue light excitation. The Franck−Condon analysis of the PLE data yielded the Mn 4+ intra-d-shell transitions to occur at ∼2.47 eV (∼2.34 eV) for the 4 A 2g → 4 T 2g transition and at ∼2.86 eV (∼2.83 eV) for the 4 A 2g → 4 T 1g transition in the Rb 2 SiF 6 :Mn 4+ (Rb 2 TiF 6 :Mn 4+ ) phosphor. Temperature dependence of the PL spectra from T = 20 to 500 K gave the quenching temperature values (T q 's) at which the PL intensity has fallen to half its maximum value to be T q ∼ 490 and ∼450 K for Rb 2 SiF 6 :Mn 4+ . To the best of our knowledge, only one paper has been published on Rb 2 TiF 6 reporting that it crystallizes in the trigonal structure with a = 0.5892 nm and a = 0.4795 nm. Our synthesized phosphors were examined by the X-ray diffraction (XRD) measurement, PL, PLE, and PL decay curve measurements. Temperature dependence of the PL properties was also examined from T = 20 to 500 K in 10-K increments. Efficient sharp red emissions with internal quantum efficiencies larger than 90% were observed from our phosphors that may promise improving a color rendering index of the conventional white-LED lamps.z E-mail: tnakamura@gunma-u.ac.jp; adachi@gunma-u.ac.jp ExperimentalThe rubidium hexafluorometallate phosphors were grown by the coprecipitation method. First, XO 2 (X = Si, Ti) and Rb 2 CO 3 in molar ratio of 1 : 1 were dissolved in an HF solution. Then, KMnO 4 powder was added in the HF solution at 300 K. This mixed solution was left in dark for a few days and resulted in a large single-crystalline phosphor growth (see Fig. 2 below). The resultant bulk single-crystalline phosphors were paper-filtered and dried in room ambient. They were grained in an agate mortar and then used for various measurements.The crystal structures of the synthesized phosphors were examined by performing an XRD analysis using a SmartLab X-ray diffractometer (Rigaku) with Cu Kα radiation at λ = 0.1542 nm. PL measurements were carried out using a single monochromator equipped with a charge-coupled device (Princeton Instruments PIXIS 100) in a CryoMini cryostat (Iwatani Industrial Gases) and a stainless cryostat (Technolo Kogyo) at T = 20 − 500 K in increments of 10 K. A He−Cd laser at λ ex = 325 nm (Kimmon IK3302R-E) was used as the excitation light source.PLE measurements were performed at 300 K...

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“…[73][74][75][76] However, the reactivity with water is a concern for the practical applications of fluorides in LED devices. 21 Oxides are chemically more stable than fluorides but the emission wavelengths of currently known Mn 4+ activated oxides are too far red-shifted for general lighting.…”

Section: 57mentioning

confidence: 99%

Using DFT Methods to Study Activators in Optical Materials

2015

ECS J. Solid State Sci. Technol.

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Density functional theory (DFT) calculations of various activators (ranging from transition metal ions, rare-earth ions, ns 2 ions, to self-trapped and dopant-bound excitons) in phosphors and scintillators are reviewed. As a single-particle ground-state theory, DFT calculations cannot reproduce the experimentally observed optical spectra, which involve transitions between multi-electronic states. However, DFT calculations can generally provide sufficiently accurate structural relaxation and distinguish different hybridization strengths between an activator and its ligands in different host compounds. This is important because the activator-ligand interaction often governs the trends in luminescence properties in phosphors and scintillators, which can be used to search for new materials. DFT calculations of the electronic structure of the host compound and the positions of the activator levels relative to the host band edges in scintillators are also important for finding optimal host-activator combinations for high light yields and fast scintillation response. Mn 4+ Luminescence of materials when excited by photons or ionizing radiation is the foundation for numerous technologies, such as energy efficient lighting (fluorescent lamps and white LEDs), laser, medical imaging, and nuclear materials detection.1-3 Efficient luminescence in semiconductors and insulators usually relies on the localization of excited electrons and holes at certain impurities, which act as luminescence centers (or activators). An activator can trap electrons and holes for efficient radiative recombination and is the essential component of a phosphor or scintillator material. The commonly used activators are typically multivalent ions, which can insert multiple electronic states inside the bandgap of the host material. 45 Good examples of the multivalent ions that can act as luminescent centers are rare-earth ions (e.g., Ce 3+ , Eu 2+ ), 6-11 transition metal ions (e.g., Cr 3+ , Mn 4+ ), [12][13][14][15][16][17] and ns 2 ions (ions with outer electron configuration of ns 2 , such as Tl + , Sn 2+ ). 18-20Energy efficiency is critically important for phosphors used for lighting. To suppress the energy loss through nonradiative recombination, a phosphor is excited by directly exciting activators, not the host (see Fig. 1a). The excitation energy is less than the bandgap energy of the host but is large enough to excite the activator. Since the excitation occurs locally at the activator, the chance for the excited activator to interact with nonradiative recombination centers, such as deep defects, is small. This is important for achieving high quantum efficiencies for phosphors. In scintillators used for detecting ionizing radiation, the radiation creates charge carriers in the valence and conduction bands of the host, which are subsequently trapped by activators, leading to radiative recombination (see Fig. 1b). In scintillators, a portion of the charge carriers need to travel a certain distance before being trapped by the activators, which ...

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Mn[sup 4+]-Activated Red Photoluminescence in K[sub 2]SiF[sub 6] Phosphor

Cited by 259 publications

References 28 publications

Synthesis and photoluminescence spectroscopy of BaGeF6:Mn4+ red phosphor

Synthesis and photoluminescence spectroscopy of BaGeF6:Mn4+ red phosphor

Editors' Choice—Rb₂SiF₆:Mn⁴⁺and Rb₂TiF₆:Mn⁴⁺Red-Emitting Phosphors

Using DFT Methods to Study Activators in Optical Materials

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Mn[sup 4+]-Activated Red Photoluminescence in K[sub 2]SiF[sub 6] Phosphor

Cited by 259 publications

References 28 publications

Synthesis and photoluminescence spectroscopy of BaGeF6:Mn4+ red phosphor

Synthesis and photoluminescence spectroscopy of BaGeF6:Mn4+ red phosphor

Editors' Choice—Rb2SiF6:Mn4+and Rb2TiF6:Mn4+Red-Emitting Phosphors

Using DFT Methods to Study Activators in Optical Materials

Contact Info

Product

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Editors' Choice—Rb₂SiF₆:Mn⁴⁺and Rb₂TiF₆:Mn⁴⁺Red-Emitting Phosphors