Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Comparison between crystal field effects on the fluorescence spectra of crystalline SmP5O14 and vitreous (Sm2O3)0.248(P2 O5)0.752 (1999)
    Springer
    Journal of materials science 34 (1999), S. 2389-2400 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract To investigate how the local symmetry of the Sm3+ ion affects the fluorescence of a samarium metaphosphate glass of composition (Sm2O3)0.248(P2O5)0.752, the temperature and pressure dependences of its laser induced fluorescence spectrum are compared with those of a samarium pentaphosphate crystal (SmP5O14). Findings include: (i) The crystal field splitting of the energy levels responsible for fluorescence in SmP5O14 at room temperature is consistent with the local symmetry of oxygen atoms of the phosphate cage around the Sm3+ ions being quite close to cubic – in accord with crystal structure. At 12 K there is a systematic disappearance of the shortest wavelength lines of each fluorescence band attributable to a decreasing population of higher crystal field levels, which are occupied at ambient temperature. (ii) The (Sm2O3)0.248(P2O5)0.7520.248 glass fluorescence spectrum forms five bands, which can be related to that of the crystal but with inhomogeneous line broadening; the short wavelength edges sharpen at low temperatures, also attributable to a decreasing population of higher crystal field levels at lower temperatures. (iii) The shifts (dλ/dp) in the wavelengths of the fluorescence peaks of the SmP5O14 crystal induced by pressure up to 50 kbar in a diamond anvil cell are small but measurable at room temperature, being about +0.03 nm kbar−1 (+0.3 Å kbar−1). Application of pressures up to 50 kbar to the (Sm2O3)0.248(P2O5)0.752 glass did not alter the positions of the bands within the error in the fluorescence wavelength measurements. Neither the SmP5O14 crystal nor the metaphosphate glass showed any indication of undergoing a phase transition up to the highest pressure reached. A low frequency Raman mode has been observed, which softens with reducing temperature, indicating softening of the associated optical mode and suggesting that, like other RP5O14 crystals, SmP5O14 undergoes a ferroelastic phase transition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004502430642
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Komplexchemie P-reicher Phosphane und Silylphosphane. XII. Bildung und Struktur von Li(THF)2[η2-(tBu2P)2P], Li(TMEDA)[η2-(tBu2P)2P], Li(THF)2[η2-(iPr2P)2P], Li(THF)2[η2-(Et2N)2P—P—PtBu2], Li(THF)2[η2-(tBu2P—P—PiPr2] und (tBu2P)2P—SiMe3Professor Kurt Dehnicke zum 65. Geburtstag gewidmet (1996)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 622 (1996), S. 1564-1572 
    Details
    ISSN: 0044-2313
    Keywords: Li(THF)2[η2-(tBu2P)2P] ; Li(TMEDA)[η2-(tBu2P)2P] ; Li(THF)2[η2-(iPr2P)2P] ; Li(THF)2[η2-(Et2N)2P—P—PtBu2] ; Li(THF)2[η2-(tBu2P—P—PiPr2)] ; (tBu2P)2P—SiMe3 ; crystal structures ; 1H, 31P, 7Li-NMR spectra ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Formation and Structure of Li(THF)2[η2-(tBu2P)2P], Li(TMEDA)[η2-(tBu2P)2P], Li(THF)2[η2-(iPr2P)2P], Li(THF)2[η2-(Et2N)2P—P—PtBu2], Li(THF)2[η2-(tBu2P—P—PiPr2] and (tBu2P)2P—SiMe3The formation and crystal structures of the compounds (tBu2P)2P—SiMe3 1, Li(THF)2[η2-(tBu2P)2P] 2, Li(TMEDA)[η2-(tBu2P)2P] 3, Li(THF)2[η2-(iPr2P)2P] 4, Li(THF)2[η2-(Et2N)2P—P—PtBu2] 5 and Li(THF)2[η2-(tBu2P—P—PiPr2)] 6 are reported. Compounds 3-6 are formed by reacting the corresponding silylated triphosphanes with nBuLi: 2 and 3 result from (tBu2P)2P—SiMe3 1, 4 from (iPrP)2P—SiMe3, 5 from (Et2N)2P—P(SiMe3)—PtBu2 and 6 from tBu2P—P(SiMe3)—PiPr2. 1 crystallizes in the orthorhombic space group P212121 (no. 19) with a = 910.87(7) pm, b = 1132.5(1) pm, c = 2373.5(2) pm (determined at 90 K). The structure determination of 2 was performed at 293 K and 200 K, respectively. 2 crystallizes in the monoclinic space group P21/n (no. 14) with a = 1069.7(3) pm, b = 1802.5(3) pm, c = 1604.0(7) pm, β = 98.11(2)° (200 K); 3 also in P21/n (no. 14) with a = 904.3(2) pm, b = 1936.4(5) pm, c = 1653.2(3) pm, β = 94.52(1)° (200 K). 4 crystallizes monoclinically in C2/c (no. 15) with a = 1650.0(5) pm, b = 945.6(3) pm, c = 1779.8(5) pm, β = 108.81(2)° (200 K); 5 in P21/n (no. 14) with a = 939.4(5) pm, b = 1736.8(6) pm, c = 1943.3(7) pm, β = 98.17(4)° (200 K). All compounds contain Z = 4 molecules in the unit cell.The 1H, 31P and 7Li NMR spectra of 2-6 are discussed.
    Notes: Es wird über die Verbindungen (tBu2P)2P—SiMe3 1, Li(THF)2[η2-(tBu2P)2P] 2, Li(TMEDA) · [η2-(tBu2P)2P] 3, Li(THF)2[η2-(iPr2P)2P] 4, Li(THF)2[η2-(Et2N)2P—P—PtBu2] 5 und Li(THF)2[η2-(tBu2P—P—PiPr2)] 6 berichtet. Letztere bilden sich durch Umsetzung der entsprechenden silylierten Triphosphane mit nBuLi: 2 und 3 aus (tBu2P)2P—SiMe3 1, 4 aus (iPr2P)2P—SiMe3, 5 aus (Et2N)2—P · (SiMe3)—PtBu2, 6 aus tBu2P—P(SiMe3)—PiPr2.1 kristallisiert orthorhombisch in P212121 (Nr. 19) mit a = 910,87(7) pm, b = 1132,5(1) pm, c = 2373,5(2) pm (bei 90 K bestimmt). Die Strukturbestimmung von 2 erfolgte bei 293 K und 200 K. 2 kristallisiert monoklin in P21/n (Nr. 14) mit a = 1069,7(3) pm, b = 1802,5(3) pm, c = 1604,0(7) pm, β = 98,11(2)° (200 K), 3 ebenfalls in P21/n (Nr. 14) mit a = 904,3(2) pm, b = 1936,4(5) pm, c = 1653,2(3) pm, β = 94,52(1)° (200 K). 4 kristallisiert monoklin in C2/c (Nr. 15) mit a = 1650,0(5) pm, b = 945,6(3) pm, c = 1779,8(5) pm, β = 108,81(2)° (200K), 5 in P21/n (Nr. 14) mit a = 939,4(5) pm, b = 1736,8(6) pm, c = 1943,3(7) pm, β = 98,17(4)° (200 K). Alle fünf Verbindungen enthalten jeweils vier Formeleinheiten in der Elementarzelle.Es wird über die Untersuchung der 1H-, 31P- und 7Li-NMR-Spektren der Verbindungen 2-6 berichtet.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19966220920
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Neue Tetrapnictidometallate von Silicium, Germanium, Zinn und Tantal mit der Na6ZnO4-Struktur (1997)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 623 (1997), S. 205-211 
    Details
    ISSN: 0044-2313
    Keywords: Tetrapnictidometallates(IV) ; Tetrapnictidotantalates(V) ; Na6ZnO4 structure type ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: New Tetrapnictidometallates of Silicon, Germanium, Tin, and Tantalum with the Na6ZnO4 StructureThe tetrapnictidometallates(IV) Na3M3EIVX4 (M = Na/Ca, Na/Sr, Na/Eu; E = Si, Ge, Sn and X = P, As) were prepared from NaX, M′X (M′ = Ca, Sr, Eu) and elemental E in tantalum ampoules at temperature of 1270 K. The tetrapnictidotantalates(V) Na3(Na2Eu)TaP4 and Na3(Na2Eu)TaAs4 were formed by a reaction with the walls of the ampoule. All compounds crystallise hexagonal in the Na6ZnO4 structure type hP22 (P63mc; no. 186; Z = 2) with polar orientated tetrahedron anions [SiX4]8-, [GeX4]8-, [SnX4]8- and [TaX4]7-. The average bondlengths are: d̄(Si—P) = 230.4 pm; d̄(Si—As) = 239.9 pm; d̄(Ge—P) = 237.1 pm; (Ge—As) = 247.8 pm; d̄(Sn—P) = 252.3 pm; d̄(Sn—As) = 261.4 pm; d̄(Ta—P) = 238.3 pm; d̄(Ta—As) = 247.4 pm.
    Notes: Die Tetrapnictidometallate(IV) Na3M3EIVX4 (M = Na/Ca, Na/Sr, Na/Eu; E = Si, Ge, Sn und X = P, As) wurden aus NaX, M'X (M′ = Ca, Sr, Eu) und elementarem E (Tantalampullen, 1270 K) synthetisiert. Die Tetrapnictidotantalate(V) Na3(Na2Eu)TaP4 und Na3(Na2Eu)TaAs4 entstanden bei Wandreaktionen mit dem Ampullenmaterial. Alle Verbindungen kristallisieren hexagonal im Na6ZnO4-Strukturtyp hP22 (P63mc, Nr. 186, Z = 2) mit polar ausgerichteten Tetraederanionen [SiX4]8-, [GeX4]8-, [SnX4]8- und [TaX44]7-. Die mittleren Bindungslängen sind: d̄(Si—P) = 230.4 pm, d̄(Si—As) = 239.9 pm, d̄(Ge—P) = 237.1 pm, d̄(Ge—As) = 247.8 pm, d̄(Sn—P) = 252.3 pm, d̄(Sn—As) = 261.4 pm, d̄(Ta—P) = 238.3 pm, d̄(Ta—As) = 247.4 pm.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19976230134
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Die kubischen Phasen Na16(ARb6)Sb7, Verbindungen mit den Anionen A = Rb-, Na-, Au-, I-In memoriam Professor Wilhelm Klemm (1996)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 622 (1996), S. 112-122 
    Details
    ISSN: 0044-2313
    Keywords: Zintl phases with anionic Rb, Na, Au and I ; (ARb6)5+ octahedra ; Sr11Ir4 type ; Li3Bi defect variants ; electrostatic potentials ; volume increments ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The Cubic Phases Na16(ARb6)Sb7, Compounds with the Anions A = Rb-, Na-, Au-, I-The novel compounds Na16(ARb6)Sb7 have been synthesized from the elements in sealed Nb ampoules at 873 K (A = Rb) and 823 K (A = I, Na, Au). They form brittle cuboctahedra (silver metallic; A = Rb) and irregular polyhedra (silver metallic lustre; A = Na, I; golden metallic lustre; A = Au). They rapidly decompose in moist air to gray products. Their crystal structures have been determined by single crystal X-ray crystallography (A = Rb: a = 1565.8(2) pm; A = I: a = 1563.3(2) pm; A = Na: a = 1562.6(2) pm; A = Au: a = 1560.7(2) pm). They crystallize cubically in the space group Fm3m (no. 225) with Z = 4 formula units and are isotypic with Sc11Ir4. The compounds are ZINTL phases and their structures can be described as an eightfold defect variant of the Li3Bi type of structure (cF128-8; a = 2a′(Li3Bi)). The Sb atoms form a network of cuboctahedra, centered alternatingly by a SbNa8 cube or a ARb6 octahedron. Main structural features are the anions A- within the Rb6 octahedron. Supporting the existence of A- are the isotypical compounds with the more common anion forming elements (A = Au, I), as well as electrostatic potential considerations together with calculations of the volume increments. The semiconducting properties (Eg = 0.33 eV) of Na16(RbRb6)Sb7, as well as the diamagnetism χmol = -508 × 10-6 cm3 mol-1, are in accordance with those to be expected from the Zintl concept.
    Notes: Die neuartigen Verbindungen Na16(ARb6)Sb7 wurden aus den entsprechenden Elementen in verschweißten Nb-Ampullen bei 873 K (A = Rb) bzw. 823 K (A = I, Na, Au) dargestellt. Sie bilden spröde silberfarbene Kuboktaeder (A = Rb) bzw. unregelmäßige Polyeder (silberglänzend: A = Na, I; metallisch golden glänzend: A = Au). Die Verbindungen zersetzen sich schnell an feuchter Luft zu grauen Produkten. Die Kristallstrukturen wurden an Einkristallen bestimmt (A = Rb: a = 1565,8(2) pm; A = I: a = 1563,3(2) pm; A = Na: a = 1562,6(2) pm; A = Au: a = 1560,7(2) pm). Sie kristallisieren in der Raumgruppe Fm3m (Nr. 225) mit Z = 4 Formeleinheiten und sind isotyp zu Sc11Ir4. Die Verbindungen sind Zintl-Phasen, deren Strukturen als achtfache Defektvariante der Li3Bi-Struktur (cF128-8; a = 2a′ (Li3Bi)) beschrieben werden können. Die Sb-Atome bilden ein Netz von Kuboktaedern, die abwechselnd durch SbNa8-Würfel bzw. durch ARb6-Oktaeder zentriert werden. Wesentliches Strukturmerkmal sind die A--Anionen im Rb6-Oktaeder, deren Existenz durch die Darstellung der isotypen Verbindungen mit typischen Anionenbildnern (A = Au, I), durch elektrostatische Betrachtungen und Berechnungen der Volumeninkremente manifestiert wird. Im Einklang mit den nach dem Zintl-Konzept zu erwartenden elektronischen Eigenschaften ist Na16(RbRb6)Sb7 ein diamagnetischer Halbleiter mit Eg = 0,33 eV und χmol = -508 × 10-6 cm3 mol-1.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19966220117
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Sr13□NbAs11 and Eu13□NbAs11 - Defect Variants of the Ca14AlSb11 Structure with asymmetric [As3]7- anionsDedicated to Professor John D. Corbett on the Occasion of his 70th Birthday (1996)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 622 (1996), S. 518-524 
    Details
    ISSN: 0044-2313
    Keywords: Asymmetric [As3]7- anion ; Zintl phase ; defect Ca14AlSb11 structure ; tetraarsaniobate(V) anion ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Sr13□NbAs11 und Eu13□NbAs11, Defektvarianten der Ca14AlSb11-Struktur mit asymmetrischen [As3]7--AnionenDie neuen Verbindungen Sr13NbAs11 und Eu13NbAs11 wurden aus den Elementen Sr, Nb und As sowie den binären Komponenten SrAs und Eu5As4 synthetisiert (Niobampullen; 1173 - 1273 K). Die tetragonalen tI 200-Phasen sind Defektvarianten der Ca14AlSb11-Struktur (Raumgruppe I41/acd (Nr. 142); Sr13□NbAs11: a = 1649.8(2) und c = 2214.1(3); Eu13□NbAs11: a = 1632.9(8) und c = 2197.3(8) pm; Z = 8). Die Strukturen sind aufgebaut aus den Kationen Sr2+ und Eu2+, den Anionen [NbAs4]7- und As3- sowie dem linearen Polyanion [As3]7-. Das Polyanion (isoster mit I3-) ist asymmetrisch mit den Bindungslängen d(As—As) = 273.0 und 346.0 pm (Sr) bzw. d(As—As) = 274.7 und 335.6 pm (Eu). Die Bindungslängen in den tetraedrischen Anionen betragen d(Nb—As) = 250.8 bzw. 251.1 pm. Die gesamte strukturelle Anordnung entspricht derjenigen von Cu2O durch die Ausbildung zweier sich durchdringender Netzwerke. Dabei werden die O-Atome durch As4-Tetraeder ersetzt (zentriert durch Nb) und die Cu-Atome durch As6-Oktaeder (zentriert durch Sr bzw. Eu). Die zentralen As-Atome der Polyanionen verbinden die Netze miteinander. Beide As-Netze werden von den restlichen Kationen eingehüllt, welche Würfel, tetragonale Antiprismen und überkappte trigonale Prismen ausbilden.
    Notes: The novel compounds Sr13NbAs11 and Eu13NbAs11 have been synthesized from SrAs, Eu5As4, Sr, Nb and As in niobium ampoules at 1173-1273 K. The tetragonal tI 200 phases are defect variants of the Ca14AlSb11 structure (space group I41/acd (no. 142); Sr13□NbAs11: a = 1649.8(2) and c = 2214.1(3); Eu13□NbAs11: a = 1632.9(8) and c = 2197.3(8) pm; Z = 8). The structures are built from the cations Sr2+, and Eu2+, respectively, and from the anions [NbAs4]7-, As3-, and the linear polyanion [As3]7-. This polyanion (isosteric to I3-) is asymmetric with d(As—As) = 273.0 and 346.0 pm (Sr) and 274.7 and 335.6 pm (Eu), respectively. The bond lengths in the tetrahedral anions are d(Nb—As) = 250.8 and 251.1 pm. The complete structural arrangement is related to that of Cu2O by forming two interpenetrating networks. The oxygen atoms are substituted by niobium centered As4 tetrahedra, and the Cu atoms are substituted by As6 octahedra (centered by Sr, Eu). The central As atoms of the polyanions connect the nets. Both As networks are enveloped by the remaining cations forming cubes, tetragonal antiprisms and capped trigonal prisms.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19966220322
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...