12020-58-5Relevant articles and documents
EuCN2 - The first, but not quite unexpected ternary rare earth metal cyanamide
Reckeweg, Olaf,DiSalvo, Francis J.
, p. 177 - 179 (2003)
Red-orange, transparent single crystals of EuCN2 (Pnma (62), a = 1232.41(9), b = 395.26(3) and c = 539.43(4) pm, Z = 4) are obtained by the reaction of EuN, C and NaN3 in arc-welded Ta ampoules at 1300 K. The first ternary rare earth metal cyanamide is isotypic to α-SrCN2 and shows the characteristic frequencies for the CN22- unit in the optical spectra (νs = 1244; νas = 1969 and 2087; δ = 655/666 cm-1).
Preparation of high performance CaAlSiN3:Eu2+ phosphors with the aid of BaF2 flux
Hu, Wei-Wei,Cai, Chao,Zhu, Qiang-Qiang,Xu, Xin,Hao, Lu-Yuan,Agathopoulos, Simeon
, p. 226 - 231 (2014)
A strong red-emitting Eu2+ activated CaAlSiN3 phosphor was successfully prepared by a pressureless low temperature solid-state reaction method with the aid of fluxes, namely BaF2, CaF 2, NH4F, and H3BO3. The experimental results showed that the addition of BaF2 flux effectively reduced the temperature of formation of CaAlSiN3:Eu2+ by about 100 K and suppressed the volatilization of the raw materials, suggesting that BaF2 flux modifies the mechanism of formation of CaAlSiN 3:Eu2+. The powder of the CaAlSiN3:Eu 2+ phosphor produced with 6 wt% BaF2 flux had an enhanced emission intensity, which was a result of the high crystallinity, the absence of secondary phases, the narrow particle-size distribution, and the clean surfaces of the particles in the final product.
Magnetic characteristics of some lanthanide nitrides
Schumacher, David P.,Wallace
, p. 1563 - 1567 (1966)
Magnetic susceptibilities (χ) of Y, La, Ce, Nd, Sm, Yb, Lu, and their nitrides were determined over a temperature range extending from 2 to 300°K. Y, La, and Lu and their nitrides are Pauli paramagnets. SmN orders antiferromagnetically below 13°K. NdN exhibits ferromagnetic ordering below 35°K. Its magnetic moment in the ferromagnetic state at 2°K is 2.15 μB, as contrasted with 3.3 μB for the free Nd3+ ion. The reduction is ascribed to crystal field quenching. From the measured moment an over-all splitting of the ground state Nd3+ ion multiplet is estimated to be 234°K. The effective moment of Nd in paramagnetic NdN is in good agreement with that expected for the free ion. YbN exhibits Curie-Weiss behavior at >100°K with a moment in fair agreement with that expected for the Yb3+ ion. However, the magnitude of χ for YbN and the low-temperature deviation from Curie-Weiss behavior are not understood. Results for Yb indicate 34% Yb3+ and 66% Yb2+. The CeN results indicate a mixture of Ce3+ and Ce4+ with the latter strongly predominating at low temperatures. In accordance with theoretical expectations no magnetic ordering is observed for CeN and YbN at temperatures down to 2°K.
Preparation, structure and photoluminescence properties of Eu2+ and Ce3+-doped SrYSi4N7
Li,Fang,De With,Hintzen
, p. 4687 - 4694 (2004)
Undoped and Eu2+ or Ce3+-doped SrYSi 4N7 were synthesized by solid-state reaction method at 1400-1660 °C under nitrogen/hydrogen atmosphere. The crystal structure was refined from the X-ray powder diffraction data by the Rietveld method. SrYSi4N7 and EuYSi4N7, being isotypic with the family of compounds MYbSi4N7 (M=Sr, Eu, Ba) and BaYSi4N7, crystallize with the hexagonal symmetry: space group P63mc (No. 186), Z=2, a=6.0160 (1) A, c=9.7894 (1) A, V=306.83(3) A3; and a=6.0123 (1) A, c=9.7869 (1) A, V=306.37(1) A3, respectively. Photoluminescence properties have been studied for Sr1-xEu xYSi4N7 (x=0-1) and SrY1- xCexSi4N7 (x=0-0.03) at room temperature. Eu2+-doped SrYSi4N7 shows a broad yellow emission band peaking around 548-570 nm, while Ce3+-doped SrYSi4N7 exhibits a blue emission band with a maximum at about 450 nm. SrYSi4N7:Eu2+ can be very well excited by 390 nm radiation, which makes this material attractive as conversion phosphor for LED lighting applications. Emission spectra of Sr1- xEuxSi4N7 as function of Eu 2+ concentration (λexc=390nm). With increasing Eu2+ concentration the emission band shows a red-shift from 548 to 570 nm.
Magnesium nitride chemistry
Reckeweg, Olaf,Molstad, Jay C.,Disalvo, Francis J.
, p. 134 - 142 (2001)
Experiments in the system RE-Mg-N (RE = La, Ce, Gd) have been done to explore the possible synthesis of nitrides using Mg as reactive melt and to extend the number of known nitride compounds containing Mg. Since these experiments produce only binary nitrides, we explored the use of mixed Na/Mg melts and discovered the quarternary nitrides BaMg3.33Nb0.67N4 (1), BaMg3.33Ta0.67N4 (2) and Eu4TaMgN5 (3), which were characterized by single crystal structure analysis. The BaMg3.33M0.67N4 compounds are isotypic to UCr4C4 (filled MoNi4 type) and crystallize in the space group I4/m (#87) with the lattice parameters a = 856.40(12) and c = 353.90(7) pm for (1), and a = 859.61(8) and c = 354.21(5) for (2). (3) crystallizes in a new structure type in the acentric orthorhombic space group Pna21 (#33) with the lattice parameters a = 1265.5(3), b = 1015.9(2) and c = 692.5(1) pm.
Vibrational spectra and magnetic properties of Eu3[BN 2]2 and LiEu4[BN2]3
Somer, Mehmet,Guel, Cem,Muellmann, Ralf,Mosel, Bernd D.,Kremer, Reinhard K.,Poettgen, Rainer
, p. 389 - 393 (2004)
Eu3[BN2]2 and LiEu4[BN 2]3 were synthesized from a stoichiometric mixture of EuN, BN, europium metal and Li3N, EuN and BN (ratio: 1:4:3) in sealed niobium ampoules at 1475 and 1275 K, respectively. Temperature dependent susceptibility measurements of Eu3[BN2]2 and LiEu4[BN2]3 show Curie-Weiss behavior with experimental magnetic moments of 8.03(5) and 8.5(1) μB/Eu atom, respectively, compatible with divalent europium. Both nitridoborates order ferromagnetically at TC = 32.0(5) K (Eu3[BN2]2) and 22.0(5) K (LiEu4[BN2]3). The saturation magnetizations of 5.73(5) μB/Eu atom at 5 K and 7 T for Eu 3[BN2]2 and 4.2 μB/Eu atom at 5 K and 2 T for LiEu4(BN2)3 are smaller than the maximum value of 7 μB. 151Eu Moessbauer data of Eu3[BN2]2 at 4.2 K show an isomer shift of -11.4(1) mm/s and an experimental line width of 3.1(2) mm/s. Full magnetic hyperfine field splitting with 26.2(3) T at the europium nuclei is detected. Vibrational spectra of Eu3[BN2]2 are interpreted on the basis of discrete [BN2]3- units with symmetry D∞h by taking into account the existence of two crystallographically independent [BN2]3- anions and their dynamic coupling in the unit cell (factor group splitting).
Crystal structure and luminescence properties of SrxCa1 - xAlSiN3:Eu2+ mixed nitride phosphors
Watanabe, Hiromu,Kijima, Naoto
, p. 434 - 439 (2009)
This study was performed to characterize the crystal structure and luminescence properties of Eu2+-doped SrxCa1 - xAlSiN3 (0.2 ≤ x ≤ 1) red phosphor. Structural refinement was carried out using the Rietveld meth
Preparation and characteristics of various rare earth nitrides
Imamura,Imahashi,Zaimi,Sakata
, p. 636 - 639 (2008)
Active nanocrystalline nitrides of EuN and YbN with high surface areas were successfully prepared by the thermal decomposition of the rare earth amides (Eu(NH2)2, Yb(NH2)2 and Yb(NH2)3). For the preparation of CeN, PrN and NdN, the direct reaction of the rare earth metals with ammonia was extensively studied to determine optimal conditions. In the reaction of rare earth metals with ammonia, hydrides besides the nitrides were competitively formed. The reaction conditions such as temperatures and ratios of ammonia to rare earth metal were crucial in preferential formation of nitride. The nanocrystalline YbN and EuN readily absorbed large amounts of ammonia even at room temperature upon contact with ammonia (13.3 kPa). The absorbed ammonia existed in at least two forms on/in the nitride; the one was surface-adsorbed ammonia and the other ammonia absorbed in the nitride in a decomposed state. The properties of ammonia absorbed by the nitride were further evaluated by temperature-programmed desorption (TPD), FT-IR and XRD techniques.
Photoluminescence properties of rare-earth activated BaSi7N10
Li,Delsing,Metslaar,de With,Hintzen
, p. 28 - 33 (2009)
The photoluminescence properties of Eu2+-, Ce3+- and Tb3+-activated BaSi7N10 have been studied. The transitions of f ? d of the Eu2+ and Ce3+ ions occur at relatively high energi
Reactions of alkaline earth metals and nitrogen in sealed niobium ampoules: The formation of MgZn2 type intermetallic phases in the presence of nitrogen and the new compound Ba5[NbN4]N
Reckeweg, Olaf,Lind, Cora,Simon, Arndt,Disalvo, Francis J.
, p. 98 - 105 (2004)
Reactions between alkaline earth metals or their corresponding nitrides and NaN3 as nitrogen donor in cleaned sealed Nb ampoules at different temperatures yields known phases, 'β-Ca3N2' and single crystals in the form of transparent, orange plates of Ba 5[NbN4]N. The crystal structure of this new compound was determined by means of single crystal X-ray diffraction (C2/m (no. 12), a = 1231.7(3), b = 1094.6(2), c = 853.8(2) pm,β = 113.65(3) and Z = 4). At temperatures ≥ 1000°C, the available nitrogen apparently reacts with the Nb container walls and intermetallic phases are formed. The crystal structures of AeMg2 (MgZn2 type with Ae = Ca, Yb, Sr, Eu and Ba) were re-determined by X-ray single crystal structure analyses on crystals obtained in such reactions to ascertain the presence or absence of nitrogen in structural voids. The structures of the ternary nitride and intermetallic phases are described and compared to known compounds.
Luminescence properties of red-emitting M2Si5N8:Eu2+ (M = Ca, Sr, Ba) LED conversion phosphors
Li,van Steen,van Krevel,Botty,Delsing,DiSalvo,de With,Hintzen
, p. 273 - 279 (2006)
The influence of the type of the alkaline-earth ion and the Eu2+ concentration on the luminescence properties of Eu2+-doped M2Si5N8 (M = Ca, Sr, Ba) has been investigated. XRD analysis shows that Eu2+-doped Ca2Si5N8 forms a limited solid solution with a maximum solubility of about 7 mol% having a monoclinic lattice. The Eu2+ ion can be totally incorporated into Sr2Si5N8 and Ba2Si5N8 forming complete solid solutions with orthorhombic lattices. M2Si5N8:Eu2+ (M = Ca, Sr) shows typical broad band emission in orange to red spectral range (600-680 nm) depending on the type of M and the europium concentration. Ba2Si5N8:Eu2+ shows yellow to red emission with maxima from 580 to 680 nm with increasing Eu2+ content. The long-wavelength excitation and emission is attributed to the effect of a high covalency and a large crystal-field splitting on the 5d band of Eu2+ in the nitrogen environment. With increasing the europium concentration, the emission band shows a red-shift for all M2Si5N8:Eu2+ compounds due to changing Stokes shift and the reabsorption by Eu2+. The conversion (i.e. quantum) efficiency increases going from Ca to Ba and Sr under excitation at 465 nm. In particular, Sr2Si5N8:Eu2+ with a quantum efficiency of 75-80% and a thermal quenching of only a few percent at 150 °C, demonstrates to be a highly promising red-emitting conversion phosphor for white-LED applications.
Superstructure formation in SrBa8[BN2]6 and EuBa8[BN2]6
Seidel, Stefan,Dierkes, Tobias,Jüstel, Thomas,Benndorf, Christopher,Eckert, Hellmut,P?ttgen, Rainer
, p. 12078 - 12086 (2016/08/05)
X-ray pure samples of SrBa8[BN2]6 and EuBa8[BN2]6 were synthesized from appropriate amounts of binary nitrides (Sr3N2, Ba3N2 and BN in sealed niobium ampoules and EuN, Ba3N2 and BN in BN crucibles, respectively) at temperatures up to 1370 K. The structure of SrBa8[BN2]6 was refined from single crystal X-ray diffractometer data: Fd3m, a = 1595.1(1) pm, wR(F2) = 0.0515, 387 F2 values and 21 variables. EuBa8[BN2]6 has a lattice parameter of 1595.00(9) pm. Both nitridoborates adopt a new 2 × 2 × 2 superstructure variant of the LiCa4[BN2]3 type, realized through ordering of vacancies and Sr2+ and Eu2+ cations, respectively. The structures of SrBa8[BN2]6 and LiCa4[BN2]3 are related by a group-subgroup scheme. The Sr2+/vacancy ordering leads to an asymmetric coordination (1 × Sr2+ and 8 × Ba2+ in a distorted, mono-capped square prism) for the [BN2]3- units with B-N distances of 132 and 136 pm. Vibrational spectra of SrBa8[BN2]6 and EuBa8[BN2]6 confirm the discrete linear [BN2]3- units and 11B solid state MAS NMR spectra are compatible with single crystallographic sites for the boron atoms. In EuBa8[BN2]6 the spectra are profoundly influenced by interactions of the 11B nuclei with the unpaired electrons of the paramagnetic Eu2+ ions.
