Surface characterization of chemically treated aluminium nitride powders

A method is designed to improve the luminescence of AlN-based phosphors by tuning the band structure and crystal structure due to alloying with GaN. The pure (Al,Ga)N:Eu phosphors were initially prepared by gas-phase reaction in an NH 3 atmosphere. GaN alloying was used to expand the crystal lattice of AlN due to Ga 3+ substituting for smaller Al 3+ ions, making dissolution of Eu 2+ easier. The dissolution of Ga in the AlN lattice was proven by the result of the Rietveld refinement and the increase in lattice parameters with increasing Ga content. To introduce other energy states mixing with the 5d states of Eu 2+ , Ga doping was also used to tune the band structure of AlN by acting on Eu 2+ ions. The theoretical result was analyzed using the Cambridge Sequential Total Energy Package (CASTEP). According to the calculated total and atom resolved partial density of states, it was observed that the Ga 5p states contribute a large portion to the corresponding Eu 2+ absorption band in (Al,Ga)N:Eu phosphors. As a consequence, an enhanced emission intensity at 470 nm and a high quantum efficiency for excitation at 330 nm was obtained despite of stronger thermal quenching of the (Al,Ga)N:Eu phosphors compared with AlN:Eu.

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“…As we know, the chemical stability of AlN powders against hydration is low. In water hydrolysis takes place according to the below reactions:

AlN + 2 {normalH}_{2} normalO \to AlOOH + N {normalH}_{3}

N {normalH}_{3} + {normalH}_{2} normalO \leftrightarrow normalN {normalH}_{4}^{+} + O H^{-}

AlOOH + {normalH}_{2} normalO \to Al (OH)_{3}

…”

Section: Resultsmentioning

confidence: 99%

Improved Blue‐Emitting AlN:Eu²⁺ Phosphors by Alloying with GaN

et al. 2015

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“…It clearly reveals the signals from Al 2p 3 = 2 , Al 2s, N 1s, O1s and Mn 2p, which indicates that Mn 2þ ions were successfully introduced into the AlN crystal lattice. The relatively stronger signal of oxygen could be resulted from the oxide layer of the phosphor powder13,14 as well as the starting material of MnO. The high-resolution XPS spectrum of Mn 2p for the AlN:3% Mn 2þ phosphor is presented inFig.…”

mentioning

confidence: 99%

Red-emittingAlN:Mn²⁺phosphors prepared by combustion synthesis

Shi

Zou

Jing

et al. 2015

Funct. Mater. Lett.

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Red-emitting Mn 2þ -doped AlN (AlN:Mn 2þ ) phosphors were successfully prepared by a highly effective combustion synthesis method. The phase purity, morphology, element-composition and luminescence properties of the synthesized phosphors were investigated. X-ray diffraction (XRD) results show that the Mn 2þ -doped into the AlN host did not induce a second phase and distort the structure significantly. Scanning electron microscopy (SEM) images display that the phosphors have an irregular shape with a particle size in the range of 1-5 μm. X-ray photoelectron spectroscopy (XPS) spectrum indicates that Mn ions are divalent state. The synthesized AlN:Mn 2þ phosphors exhibit a strong red emission centered at $ 600 nm, which is ascribe to the 4 T 1 ( 4 G)-6 A 1 ( 6 S) transition of Mn 2þ under ultraviolet excitation. The emission intensity reaches its maximum when Mn 2þ -doped concentration is 3 mol%.

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“…In a study of the adsorption on silicon nitride, sialon, and aluminum nitride surfaces, 14,15 similar N 2 peaks were observed. Located at 320°C at 60% RH (and perhaps already at 20% RH) it shifts to 470°C with a humidity increase to 95%.…”

Section: B Desorption Of H 2 O and Nmentioning

confidence: 84%

Adsorption of H₂O, H₂S, and N₂ on MnZn ferrite

2000

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MnZn ferrites show extensive subcritical crack growth. In this process water plays an important role. The fracture surfaces of MnZn ferrites with three different stoichiometries were investigated with adsorption isotherm measurements, temperature-programmed desorption, diffusive reflection infrared Fourier transform spectroscopy (DRIFT), low-energy ion spectroscopy (LEIS), and x-ray photoelectron spectroscopy (XPS). The XPS results confirmed the presence of Mn, Zn, Fe, and O atoms in the surface region, but LEIS indicated that the outer layer of the fracture surfaces contained no Zn atoms. DRIFT confirmed that hydroxyl groups were present on the fracture surfaces. Experiments with H 2 S, for which the XPS is more sensitive, indicated that at low coverage pairs of S atoms bridge a pair of Fe atoms. With increasing coverage the S bridge shifts to one Fe atom while at the highest coverage each Fe atom is bonded to one S atom. In experiments with N 2 the highest nitrogen absorption is found for the lowest oxygen concentration in the ferrite, which is probably related to the polarity of the surface. Both the adsorption and desorption tests indicated that N 2 had a larger adsorption affinity to MnZn ferrite surfaces than H 2 O. a) Present address:

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Surface characterization of chemically treated aluminium nitride powders

Cited by 36 publications

References 9 publications

Improved Blue‐Emitting AlN:Eu²⁺ Phosphors by Alloying with GaN

Improved Blue‐Emitting AlN:Eu²⁺ Phosphors by Alloying with GaN

Red-emittingAlN:Mn²⁺phosphors prepared by combustion synthesis

Adsorption of H₂O, H₂S, and N₂ on MnZn ferrite

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Surface characterization of chemically treated aluminium nitride powders

Cited by 36 publications

References 9 publications

Improved Blue‐Emitting AlN:Eu2+ Phosphors by Alloying with GaN

Improved Blue‐Emitting AlN:Eu2+ Phosphors by Alloying with GaN

Red-emittingAlN:Mn2+phosphors prepared by combustion synthesis

Adsorption of H2O, H2S, and N2 on MnZn ferrite

Contact Info

Product

Resources

About

Improved Blue‐Emitting AlN:Eu²⁺ Phosphors by Alloying with GaN

Improved Blue‐Emitting AlN:Eu²⁺ Phosphors by Alloying with GaN

Red-emittingAlN:Mn²⁺phosphors prepared by combustion synthesis

Adsorption of H₂O, H₂S, and N₂ on MnZn ferrite