Verslag Materialica 1999 en Euromat 1999 te München

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Red emission from Mn2+ on a tetrhedral site in MgSiN2

Solubility and photoluminescence properties of Mn2+ in MgSiN2 host lattice are reported in this paper. X-ray diffraction (XRD) analysis shows that Mn2+ ions can be totally incorporated into MgSiN2 host lattice, forming a complete solid solution with MnSiN2. Mn2+ on a tetrahedral site exhibits a red emission band in the wavelength range of 550–750 nm in MgSiN2. The long-wavelength emission of Mn2+ despite tetrahedral coordination in MgSiN2 is attributed to the effect of strong crystal field experienced by Mn2+ in a nitrogen coordination environment. Also there exists energy transfer between MgSiN2 host lattice and Mn2+ activator. The potential applications of this phosphor have been pointed out

Photoluminescence Properties of Novel Red-Emitting Mn2+-Activated MZnOS (M = Ca, Ba) Phosphors

Photoluminescence properties of novel red-emitting Mn2+-activated MZnOS (M = Ca, Ba) phosphors were investigated. Mn2+-activated MZnOS phosphors show a single symmetric narrow red emission band in the wavelength range of 550-700 nm due to the 4T1(4G) ¿ 6A1(6S) transition of Mn2+. Peak centers are at about 614 nm for M = Ca and 634 nm for M = Ba, regardless of the excitation wavelength and Mn2+ doping concentration. A comparison is made between the luminescence properties of Mn2+ in the Ca versus Ba compound. A similarity between them is that both Mn2+-activated CaZnOS and BaZnOS can be efficiently excited under host lattice excitation in the wavelength range of 250-350 nm due to efficient energy transfer between the host lattice (MZnOS) and activator (Mn2+). An unexpected difference is that Mn2+-activated CaZnOS can also be efficiently excited under the excitation of Mn2+ itself (d-d transitions) in the wavelength range of 350-500 nm. This difference is ascribed to different crystal structures, different coordination environments, and point symmetries for Mn in these two compounds. The potential applications of these phosphors are pointed out. Among them, Mn2+-activated CaZnOS shows great potential for application as an alternative red-emitting LED conversion phosphor due to its high absorption and strong excitation bands in the wavelength range of 350-500 n

Photoluminescence properties of Eu2+-activated sialon S-phase BaAlSi5O2N7

Within the scope of the search of potential LED conversion phosphors, the photoluminescence properties of Eu2+-activated BaAlSi5O2N7 sialon S-phase have been investigated. It shows a broad emission band in the wavelength range of 400–650 nm with maxima from 483 to 500 nm with increasing the Eu2+ concentration. This short-wavelength emission of Eu2+ despite nitrogen-rich coordination is attributed to lowering of the crystal field strength as a result of long distance between Eu and (N, O) anions. Due to the very rigid T12X18-4 network, T = (Si, Al) and X = (N, O), in the crystal structure of MAlSi5O2N7 (M = Sr, Ba), it is supposed that each Eu ion will create its own preferred local coordination irrespective of the occupation of the other sites by Ba or Sr ions in the MAlSi5O2N7 host lattice, which results in resembling luminescence properties for Eu2+-doped in BaAlSi5O2N7 and SrAlSi5O2N7

Preparation and photoluminescence properties of Mn2+-activated M2Si5N8 (M = Ca, Sr, Ba) phosphors

Mn2+-doped M2Si5N8 (M=Ca, Sr, Ba) phosphors have been prepared by a solid-state reaction method at high temperature and their photoluminescence properties were investigated. The Mn2+-activated M2Si5N8 phosphors exhibit narrow emission bands in the wavelength range of 500–700 nm with peak center at about 599, 606 and 567 nm for M=Ca, Sr, Ba, respectively, due to the 4T1(4G)¿6A1(6S) transition of Mn2+. The long-wavelength emission of Mn2+ ion in the host of M2Si5N8 is attributed to the effect of a strong crystal-field of Mn2+ in the nitrogen coordination environment. Also it is observed that there exists energy transfer between M2Si5N8 host lattice and activator (Mn2+). The potential applications of these phosphors have been pointed out

Preparation, characterization and luminescence properties of porous Si3N4 ceramics with Eu2O3 as sintering additive

Porous Si3N4 ceramics with photoluminescence properties were prepared by pressureless sintering using a-Si3N4 powder as raw material and Eu2O3 as sintering additive. Chemical composition, phase formation, microstructure and photoluminescence properties of porous Si3N4 ceramics were studied by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence measurements (PL/PLE). The results show that single Eu2O3 additive promotes a¿ß transformation but not significant densification. A broad band emission center at 570 nm assigned to Eu2+ is observed, Eu3+ in Eu2O3 is (partially) converted to Eu2+ by reaction with Si3N4, which results in a lower ß aspect ratio and ß-content compared to the other Ln (Ln=lanthanide) oxide additives

Preparation, characterization and luminescence properties of porous Si3N4 ceramics with Eu2O3 as sintering additive

Porous Si3N4 ceramics with photoluminescence properties were prepared by pressureless sintering using a-Si3N4 powder as raw material and Eu2O3 as sintering additive. Chemical composition, phase formation, microstructure and photoluminescence properties of porous Si3N4 ceramics were studied by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence measurements (PL/PLE). The results show that single Eu2O3 additive promotes a¿ß transformation but not significant densification. A broad band emission center at 570 nm assigned to Eu2+ is observed, Eu3+ in Eu2O3 is (partially) converted to Eu2+ by reaction with Si3N4, which results in a lower ß aspect ratio and ß-content compared to the other Ln (Ln=lanthanide) oxide additives

Luminescence properties of Eu2+ - activated alkaline-earth silicon-oxynitride MSi2O2-deltaN2+2/3delta (M = Ca, Sr, Ba) : A promising class of novel LED conversion phosphors

The luminescence properties of Eu2+-activated alk.-earth Si-oxynitrides were studied. In the BaO-SiO2-Si3N4 system, a new BaSi2O2N2 compd. was obtained having the monoclinic structure with lattice parameters a 14.070(4), b 7.276(2), c 13.181(3) .ANG., b 107.74(6)°. All MSi2O2-dN2+2/3d:Eu2+ (M = Ca, Sr, Ba) materials can be efficiently excited in the UV to visible region (370-460 nm), making them attractive as conversion phosphors for LED applications. A blue-green emission at 490-500 is obsd. for BaSi2O2N2:Eu2+, yellow emission at 560 nm for CaSi2O2-dN2+2/3d:Eu2+ (d » 0), and a green-yellow emission peaking from 530 to 570 nm for SrSi2O2-dN2+2/3d:Eu2+ (d » 1), the position depending on the exact value of d. BaSi2O2N2:Eu2+ is the most promising conversion phosphor for white-light LEDs due to its high conversion efficiency for blue light from InGaN-based LEDs related to its very small Stokes shift

Luminescence properties of Eu2+ - activated alkaline-earth silicon-oxynitride MSi2O2-deltaN2+2/3delta (M = Ca, Sr, Ba) : A promising class of novel LED conversion phosphors

The luminescence properties of Eu2+-activated alk.-earth Si-oxynitrides were studied. In the BaO-SiO2-Si3N4 system, a new BaSi2O2N2 compd. was obtained having the monoclinic structure with lattice parameters a 14.070(4), b 7.276(2), c 13.181(3) .ANG., b 107.74(6)°. All MSi2O2-dN2+2/3d:Eu2+ (M = Ca, Sr, Ba) materials can be efficiently excited in the UV to visible region (370-460 nm), making them attractive as conversion phosphors for LED applications. A blue-green emission at 490-500 is obsd. for BaSi2O2N2:Eu2+, yellow emission at 560 nm for CaSi2O2-dN2+2/3d:Eu2+ (d » 0), and a green-yellow emission peaking from 530 to 570 nm for SrSi2O2-dN2+2/3d:Eu2+ (d » 1), the position depending on the exact value of d. BaSi2O2N2:Eu2+ is the most promising conversion phosphor for white-light LEDs due to its high conversion efficiency for blue light from InGaN-based LEDs related to its very small Stokes shift