14456-48-5Relevant articles and documents
Spectroscopy and upconversion mechanisms of CsCdBr3:Dy3+
Wermuth, Markus,Riedener, Toni,Guedel, Hans U.
, p. 4369 - 4376 (1998)
The upconversion luminescence of a Dy3+-doped system is presented and analyzed. CsCdBr3:x% Dy3+ (x = 0.2,1,5) was synthesized and grown as crystals using the Bridgman technique. Dy3+ ions preferentially enter this host as charge-compensated dimers. Due to the low-phonon energy the efficiency of multiphonon-relaxation processes is significantly reduced in this host compared to oxides and fluorides. Yellow-green upconversion luminescence originating from 4F9/2 can be induced upon excitation into 6F5/2 or 6F3/2 in the near infrared (NIR). Depending on the excitation wavelength, upconversion occurs by an energy-transfer or excited-state absorption mechanism. The two are distinguished by their temporal behavior after an excitation pulse. Analysis of the upconversion-luminescence transient of CsCdBr3:0.2% Dy3+ at 10 K leads to a rate constant Wt = 165 s-1 for the energy-transfer step. This is very small, and thus upconversion based on one excitation wavelength is inefficient. In addition, the intermediate NIR level 6F5/2 is significantly depopulated by multiphonon relaxation at room temperature.
Structural characterization of methanol substituted lanthanum halides
Boyle, Timothy J.,Ottley, Leigh Anna M.,Alam, Todd M.,Rodriguez, Mark A.,Yang, Pin,Mcintyre, Sarah K.
, p. 1784 - 1795 (2010/07/03)
The first study into the alcohol solvation of lanthanum halide [LaX3] derivatives as a means to lower the processing temperature for the production of the LaBr3 scintillators was undertaken using methanol (MeOH). Initially the de-hydration of {[La(μ-Br)(H2O)7](Br)2}2 (1) was investigated through the simple room temperature dissolution of 1 in MeOH. The mixed solvate monomeric [La(H2O)7(MeOH)2](Br)3 (2) compound was isolated where the La metal center retains its original 9-coordination through the binding of two additional MeOH solvents but necessitates the transfer of the innersphere Br to the outersphere. In an attempt to in situ dry the reaction mixture of 1 in MeOH over CaH2, crystals of [Ca(MeOH)6](Br)2 (3) were isolated. Compound 1 dissolved in MeOH at reflux temperatures led to the isolation of an unusual arrangement identified as the salt derivative {[LaBr2.75·5.25(MeOH)]+0.25 [LaBr3.25·4.75(MeOH)]-0.25} (4). The fully substituted species was ultimately isolated through the dissolution of dried LaBr3 in MeOH forming the 8-coordinated [LaBr3(MeOH)5] (5) complex. It was determined that the concentration of the crystallization solution directed the structure isolated (4 concentrated; 5 dilute) The other LaX3 derivatives were isolated as [(MeOH)4(Cl)2La(μ-Cl)]2 (6) and [La(MeOH)9](I)3·MeOH (7). Beryllium Dome XRD analysis indicated that the bulk material for 5 appear to have multiple solvated species, 6 is consistent with the single crystal, and 7 was too broad to elucidate structural aspects. Multinuclear NMR (139La) indicated that these compounds do not retain their structure in MeOD. TGA/DTA data revealed that the de-solvation temperatures of the MeOH derivatives 4-6 were slightly higher in comparison to their hydrated counterparts.
M3NS3 (M = La - Nd, Sm, Gd - Dy): Structure and magnetism of 3:1:3-type nitride sulfides of trivalent lanthanides
Lissner, Falk,Meyer, Monika,Kremer, Reinhard K.,Schleid, Thomas
, p. 1995 - 2002 (2008/10/09)
Nitride sulfides of the trivalent lanthanides with the composition M 3NS3 (M = La - Nd, Sm, Gd - Dy) can be prepared by the oxidation of the respective lanthanide metal with sulfur, sodium azide (NaN 3), and the corresponding lanthanide tribromide (MBr3) when an additional flux (NaBr) is used. Temperature ranges from 800 to 900 °C for the thermal treatment of the reaction mixtures in evacuated silica tubes secure the formation of bright to dark brown, transparent, lath shaped single-crystals. The orthorhombic crystal structure (Pnma, Z = 4) was determined from single-crystal X-ray diffraction data (La3NS3: a = 1215.13(5), b = 415.90(2), c = 1322.12(5) pm, Ce3NS3: a = 1206.28(4), b = 410.16(1), c = 1307.18(5) pm, Pr3NS3: a = 1205.45(7), b = 405.35(2), c = 1297.58(8) pm, Nd3NS3: a = 1207.82(5), b = 401.31(1), c = 1295.20(4) pm, Sm3NS3: a = 1201.58(6), b = 394.84(2), c = 1285.63(7) pm, Gd3NS3: a = 1197.17(7), b = 388.22(3), c = 1286.92(8) pm, Tb3NS3: a = 1191.62(7), b = 385.07(3), c = 1282.44(8) pm, and Dy3NS3: a = 1187.66(7), b = 382.55(3), c = 1276.77(8) pm). There are three crystallographically different M3+ cations present in coordination of both the N3- and the S2- anions. However, [NM 4]9+ tetrahedra connected via two common corners (c) to form linear chains ∞1{[N(M1)1/1 t(M2)1/1t(M3)2/2c] 6+} along [010] build up the main structural feature. A non-linear behaviour for the decreasing lattice constants of the pseudo-isotypic series from La3NS3 to Dy3NS3 concerning the a- and c-axes is observed along with the lanthanoid contraction caused by the diminishing coordination sphere of (M1)3+ (CN = 7) and (M3) 3+ (CN = 7) moving from the light to the heavier lanthanides. Curie-Weiss-type magnetic behaviour for Dy3NS3 with μeff = 10.3(1) μB for DyN1/3S corresponding to a 6H15/2 groundstate for Dy3+ at higher temperatures and antiferromagnetic ordering of the Dy3+ moments below 5 K is observed.
