Sharp-Line Fluorescence, Electron Paramagnetic Resonance, and Thermoluminescence of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow><mml:mi mathvariant="normal">Mn</mml:mi></mml:mrow><mml:mrow><mml:mn>4</mml:mn><mml:mo>+</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math>in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>α</mml:mi></mml:math>-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mm

Geschwind, S.; Kisliuk, P.; Klein, Melvin P.; Remeika, J. P.; Wood, D. L.

doi:10.1103/physrev.126.1684

Cited by 171 publications

(50 citation statements)

References 12 publications

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“…The freshly dried sample exhibits a Mn band at 21 700-22 000 cm -1 , partly covered by strong but unresolved charge-transfer bands at 35 000-40 000 cm -1 (not shown). 18 In the near-infrared region, overtones of the acetate precursor (2ν of the C-H vibration) are observed at 5820 and 5940 cm -1 . 22 Moreover, the first overtone (2ν) of molecularly adsorbed water (6800 cm -1 ) can be seen, accompanied by a combination band (ν + δ) at 5200 cm -1 .…”

Section: Methodsmentioning

confidence: 99%

“…30 Therefore, the band observed at 20 000-22 500 cm -1 in all the other spectra can be assigned only to the 5 T 2g r 5 E g transition in Mn 3+ /Al 2 O 3 19,31 and/or the 4 T 2 r 4 A 2 transition in Mn 4+ / Al 2 O 3 . 18 The DRS spectrum of the dried, uncalcined catalyst ( Figure 1a) shows this band, indicating that oxidation of the Mn 2+ ion of the precursor already proceeds during drying, and not only during calcination. However, the band becomes more intense during calcination, as more Mn 2+ ions are oxidized to higher oxidation states.…”

Section: Oxidation State and Coordination Manganese Speciesmentioning

confidence: 99%

“…14,18,[24][25][26][32][33][34] Wichterlová et al 34 report an ESR signal of Mn 2+ in a distorted tetrahedron at g ) 4.27. Literature data presented in Table 2 suggest the coordination of the Mn 2+ ions observed in the recorded ESR spectra to be most reasonably described as axially distorted octahedral.…”

Section: Oxidation State and Coordination Manganese Speciesmentioning

confidence: 99%

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Characterization of Al₂O₃-Supported Manganese Oxides by Electron Spin Resonance and Diffuse Reflectance Spectroscopy

Kijlstra¹,

Poels²,

Bliek³

et al. 1997

J. Phys. Chem. B

144

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Alumina-supported manganese oxides, used as catalysts for the selective catalytic reduction of NO, were characterized by combined electron spin resonance and diffuse reflectance spectroscopies. Upon impregnation of the acetate precursor solution, the [Mn(H 2 O) 6 ] 2+ complex interacts strongly with surface hydroxyls of the γ-Al 2 O 3 . Evidence was obtained that this anchoring reaction proceeds at a Mn/OH ) 1/2 ratio up to 4.5 wt % Mn loading, leading to a highly dispersed oxidic manganese layer. At higher loadings, the precursor complex is deposited on the surface concurrently. Upon drying at 383 K, part of the manganese is oxidized to higher oxidation states (Mn 3+ and Mn 4+ ), while a further increase in (average) oxidation state takes place upon calcination at 573 K. After calcination, the manganese species are present as a mixture of Mn 2+ , Mn 3+ , and Mn 4+ . At low loadings (<1 wt %), approximately equal amounts of these three oxidation states are present, whereas Mn 3+ becomes the predominant species at higher loadings. ESR reveals that at low loadings, almost all the manganese is present as isolated species, while at 4.5 wt % Mn loading, still more than 70% of the manganese is isolated. The decrease of the fraction of isolated manganese species at higher loadings is accompanied by a decreased selectivity toward N 2 production in the selective catalytic reduction of NO. The fraction Mn 2+ is present in an axially distorted octahedral coordination.

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Section: Methodsmentioning

confidence: 99%

Section: Oxidation State and Coordination Manganese Speciesmentioning

confidence: 99%

Section: Oxidation State and Coordination Manganese Speciesmentioning

confidence: 99%

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Characterization of Al₂O₃-Supported Manganese Oxides by Electron Spin Resonance and Diffuse Reflectance Spectroscopy

Kijlstra¹,

Poels²,

Bliek³

et al. 1997

J. Phys. Chem. B

144

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“…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][7][8][9][10][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][19][20] Energy efficiency is critically important for phosphors used for lighting.…”

mentioning

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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“…In past decades, a large number of theoretical and experimental investigations have been reported on the EMR spectra and spin-Hamiltonian parameters of iron group ions in Al 2 O 3 [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. In Al 2 O 3 host crystal, Al 3+ is located at octahedral trigonal symmetry site surrounded by six O 2− ions.…”

Section: Introductionmentioning

confidence: 99%

Spin-Spin and Spin-Other-Orbit Interactions of Spin-Hamiltonian Parameters for 3d²⁽⁸⁾Ions in Al₂O₃Crystals

et al. 2011

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By considering weaker magnetic interactions (including spin-spin and spin-other-orbit interactions) in Hamiltonian, the spin-Hamiltonian parameters, including the zero-field splitting parameter D and g factors (g , g ⊥ ) for 3d 2(8) ions in Al2O3 crystals have been investigated. The results show that the contributions to D, g and g ⊥ from the spin-orbit interaction are dominant. The contributions from weaker magnetic interactions to D decrease (increase) with increasing charge of impurity ions for 3d 2 (3d 8 ) ions.

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Sharp-Line Fluorescence, Electron Paramagnetic Resonance, and Thermoluminescence ofMn4+inα-

Cited by 171 publications

References 12 publications

Characterization of Al₂O₃-Supported Manganese Oxides by Electron Spin Resonance and Diffuse Reflectance Spectroscopy

Characterization of Al₂O₃-Supported Manganese Oxides by Electron Spin Resonance and Diffuse Reflectance Spectroscopy

Using DFT Methods to Study Activators in Optical Materials

Spin-Spin and Spin-Other-Orbit Interactions of Spin-Hamiltonian Parameters for 3d²⁽⁸⁾Ions in Al₂O₃Crystals

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Sharp-Line Fluorescence, Electron Paramagnetic Resonance, and Thermoluminescence ofMn4+inα-

Cited by 171 publications

References 12 publications

Characterization of Al2O3-Supported Manganese Oxides by Electron Spin Resonance and Diffuse Reflectance Spectroscopy

Characterization of Al2O3-Supported Manganese Oxides by Electron Spin Resonance and Diffuse Reflectance Spectroscopy

Using DFT Methods to Study Activators in Optical Materials

Spin-Spin and Spin-Other-Orbit Interactions of Spin-Hamiltonian Parameters for 3d2(8)Ions in Al2O3Crystals

Contact Info

Product

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About

Characterization of Al₂O₃-Supported Manganese Oxides by Electron Spin Resonance and Diffuse Reflectance Spectroscopy

Characterization of Al₂O₃-Supported Manganese Oxides by Electron Spin Resonance and Diffuse Reflectance Spectroscopy

Spin-Spin and Spin-Other-Orbit Interactions of Spin-Hamiltonian Parameters for 3d²⁽⁸⁾Ions in Al₂O₃Crystals