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41Author    Tetsuo Asaji, Tomohiro IshizakaRequires cookie*
 Title    Effect of Deuteration on Ammonium Motion and Structural Phase Transition Studied by Nuclear Quadrupole Resonance  
 Abstract    35 C1 NQR measurements revealed two phase transitions at 14.5 K and 70 K in NH4ICI4. By deuteration of the ammonium ions, the respective transition temperature increased to 27 K and 74 K. In the lowest-temperature phase of NH4ICI4, by the deuteration a remarkable change of the temperature dependence of the 35 C1 NQR frequencies was observed. The NQR spin-lattice relaxation-time minimum, ascribable to the modulation effect of the electric field gradient (EFG) due to a motion of the ammonium ions, was observed at 7 K and 11 K in NH4ICI4 and ND4ICI4, respectively. The activation energy of the ammonium motion and the fluctuation fraction q /q of the EFG were determined to be 0.32 kJ moP 1 and 1.3xlO~ 3 for NH4ICI4, and 0.30 kJ mol -1 and 0.88xl0~ 3 for ND4ICI4. The experimental result suggests that the inter-ionic interaction between the ammonium ion and the ICl^ complex anion is weakened by the deuteration. However, the frequency shift observed in the lowest-temperature phase is much larger in ND4ICI4 than in NH4ICI4. This suggests that the lattice distortion in NH4ICI4 is suppressed to a great deal by the tunneling rotation of NH4 ions. The effective inter-ionic interaction responsible for the lattice distortion, the transition temperature and the enhancement of tunneling of NH4 as compared with ND4 is discussed for NH4ICI4 as well as for previously reported NH4AUCI4 and ct-N^HgCb. 
  Reference    Z. Naturforsch. 55a, 83—89 (2000); received August 26 1999 
  Published    2000 
  Keywords    Isotope Effect, Tunneling, Phase Transition, Ammonium, NQR 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0083.pdf 
 Identifier    ZNA-2000-55a-0083 
 Volume    55 
42Author    Y. M. Seo, S. K. Song, J. PelzpRequires cookie*
 Title    Impurity Effects on the Local Structure in the Mixed Hexachlorometallate (A 2 BC1 6 : A = K, Rb, B = Sn, Re, and Pb) Studied by the Chlorine NQR  
 Abstract    Chlorine NQR was studied for the isostructural hexachlorometallate mixed system. The study shows that Isomorphic hexachlorometallate solid solutions exhibit often impurity induced local structural order because of their relatively clear local site symmetry. This is manifested in the formation of a few satellite lines near the original resonance line and results from the random distribution of impurities on the lattice sites of the corresponding counterpart ions. Using the point charge model and a simple binomial function for the occupation probability of the guest ions on the host lattice sites, the position and the line intensity could be determined, the results of which are in good agreement with the NQR-observation. The temperature region of lattice dynamics in the crystal seems to shift in proportion to the impurity content. This fact explains the gradual change of the transition temperature in the mixed crystal between two starting materials. 
  Reference    Z. Naturforsch. 55a, 207—211 (2000); received August 23 1999 
  Published    2000 
  Keywords    NQR, Hexahalmetallates, Phase Transition, Mixed Crystals 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0207.pdf 
 Identifier    ZNA-2000-55a-0207 
 Volume    55 
43Author    Hideta Ishihara, Keizo Horiuchi, ThorstenM. Gesing, Shi-Qi Dou, J.-Christian Buhl, Hiromitsu TeraoRequires cookie*
 Title    I NQR and Crystal Structure Studies of [N(CH 3 ) 4 ] 2 CdI 4  
 Abstract    The temperature dependence of 127 1 NQR and DSC as well as the crystal structure at room temperature of the title compound were determined. This compound shows a first-order phase transition of an order-disorder type at 245 K. Eight 127 I(i^i: m = ±5 <-+ ±|) NQR lines of 79. corresponding eight 127 I(^ 2 : m = ±| <-» • ±|) NQR lines were observed at liquid nitrogen temperature. Three 127 I(^i) NQR lines wfth an intensity ratio of 1:1:2 in the order of decreasing frequency were observed just above the transition point and two NQR lines except for the middle-frequency line disappeared around room temperature. This temperature behavior of NQR lines is very similar to that observed in [N(CH 3)4] 2 Hgl4. Another first-order phase transition takes place at 527 K. The structure of the room-temperature phase was redetermined: orthorhombic, Pnma, Z = 4, a = 1342.8(3), b = 975.7(2), c = 1696.5(3) pm. The NQR result of three lines with an intensity ratio of 1:1:2 is in agreement with this structure. The thermal displacement parameters of atoms in both cations and anions are large. 
  Reference    Z. Naturforsch. 55a, 225—229 (2000); received October 13 1999 
  Published    2000 
  Keywords    NQR, DSC, Crystal Structure, Phase Transition 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0225.pdf 
 Identifier    ZNA-2000-55a-0225 
 Volume    55 
44Author    Maciej Bujak, Jacek ZaleskiRequires cookie*
 Title    Structure and Phase Transition in (C 2 H 5 NH 3 ) 3 Sb 2 CI 9 (C 2 H 5 NH 3 )SbCl 4 ; X-ray, DSC and Dielectric Studies  
 Abstract    The structure of (C 2 H 5 NH 3) 3 Sb 2 Cl 9 • (C 2 H 5 NH 3)SbCl 4 at 295 K has been determined. The crystals are orthorhombic, space group Pna2! (a -16.925(3), b = 24.703(5), c = 7.956(2) A, V = 3326.4(12) A 3 , Z = 4, d c = 2.018, d m = 2.01(1) Mg m -3). They consist of an anionic sublattice composed of two different polymeric zig-zag chains. One is built of Sb 2 Cl 9 3-units (corner sharing octahedra) and the other one is made of corner sharing SbCl^ 2-square pyramids. In the cavites between the polyanionic chains four non-equivalent ethylammonium cations are located. Three of them are disordered. The cations are connected to the anions by weak N-H...C1 hydrogen bonds. A first order phase transition of the order-disorder type was found at 274 K. It was studied by DSC, dielectric and X-ray diffraction methods. The mechanism of the phase transition is attributed to the ordering of at least one of the ethylammonium cations. 
  Reference    Z. Naturforsch. 55a, 526—532 (2000); received January 10 2000 
  Published    2000 
  Keywords    Ethylamine, Chloroantimonate(III), Structure, Phase Transition 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0526.pdf 
 Identifier    ZNA-2000-55a-0526 
 Volume    55 
45Author    A. Wiirflinger, M. SandmannRequires cookie*
 Title    Thermodynamic Measurements on w-Hexadecane (C 16 H 34 ) and /z-Heptadecane (C 17 H 36 ) at Elevated Pressures  
 Abstract    Specific volumes of/7-hexadecane (H-Ci 6 H 34) and n-heptadecane (fl-C 17 H 36) are presented for tem-peratures between 298 and 348 K and pressures up to 280 MPa. The melting curve for /7-C j6 H 34 was determined with differential thermal analysis. ThepVTdata are established for the liquid, solid and (in the case of J?-C| 7 H 36) rotator phases. Forn-C 16 H 34 the density immediately below the freezing temper-ature is larger than for n-Ci 7 H 36 immediately below the rotational transition temperature. Changes of volume, enthalpy, and entropy along the phase transitions are reported. The volume change of melting decreases distinctly with increasing pressure, whereas the volume change at the rotational transition is much less pressure-dependent. Enthalpy and entropy changes have been calculated with the aid of the Clausius-Clapeyron equation. 
  Reference    Z. Naturforsch. 55a, 533—538 (2000); received February 16 2000 
  Published    2000 
  Keywords    Hexadecane, Heptadecane, DTA, /?V7, High Pressure, Phase Transitions 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0533.pdf 
 Identifier    ZNA-2000-55a-0533 
 Volume    55 
46Author    M. F. Mostafa, S. S. ArafatRequires cookie*
 Title    Dielectric Dispersion of New Ferroelectric Cobalt Halide Dimers: Bis-ethanolammonium-hexahalocobaltate, (C 2 H 8 NO) 2 Co 2 X 6 , X = CI/Br  
 Abstract    The AC conductivity in the frequency range 5.0 Hz -10.0 kHz, the magnetic susceptibility in a field of 14.7 and 17.810 4 A/m, and differential thermal analysis at 78 K up to room temperature for bis-(ethanolammonium)Co 2 X 6 ,X = CI and Br are reported. The bromide dimer undergoes an order-disorder transition at 302 K and a displacive type ferroelectric transition at T ~ 220 K. The chloride dimer shows two transitions, the first being in a displacive ferroelectric one at T ~ 210 K showing critical slowing down. The second phase transition, occuring at 282 K, is found to be inactive in the electric measurements. PACS: #76. 74 
  Reference    Z. Naturforsch. 55a, 595—604 (2000); received February 29 2000 
  Published    2000 
  Keywords    Dielectric Permittivity, Phase Transition, Ferroelctric Transition 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0595.pdf 
 Identifier    ZNA-2000-55a-0595 
 Volume    55 
47Author    Z. Czapla, S. Dacko, B. KosturekRequires cookie*
 Title    Ferroelectricity and Phase Transitions in Pyridinium Periodate Single Crystal  
 Abstract    Single crystals of pyridinium periodate were grown, and their physical properties were studied. Anomalies of the electric permittivity and birefringence were observed at T CL = 321 K and T C2 = 211 K. These observations gave evidences for the existence of three phases denoted as I, II, and III. Hysteresis loops were observed both in phase II and III. Pyroelectric measurements showed two anomalies at T CL and T C2 . The anomaly at T CL is related to the transition between a para-and ferroelectric phase, and the anomaly at T cl to the transition between two ferroelectric phases. 
  Reference    Z. Naturforsch. 55a, 891—894 (2000); received August 8 2000 
  Published    2000 
  Keywords    Phase Transitions, Ferroelecticity, Dielectric Properties, Birefringence 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0891.pdf 
 Identifier    ZNA-2000-55a-0891 
 Volume    55 
48Author    Albert Würflinger, M. Massalska-Arodż3, S. Urbanb, W. Weissflogc, S. EmstcRequires cookie*
 Title    Thermodynamic Measurements on the Binary System Bis{[2,2-di(w- hexyloxycarbonyl)ethenyl]phenyl} Biphenyl-4,4'-dicarboxylate and 4-w-Octyloxyphenyl 4-/i-Pentyloxybenzoate at Elevated Pressures  
 Abstract    Thermodynamic measurements have been carried out on the binary system of a swallow-tailed liquid crystal A = bis{[2,2-di(n-hexyloxycarbonyl)ethenyl]phenyl} biphenyl-4,4'-dicarboxylate (4DS6) and B = 4-n-octyloxyphenyl 4-rc-pentyloxybenzoate (5 0 /0 8). A filled smectic A phase is induced in the concentration range 0.11 < xA < 0.75. The maximum of the SmA-N transition temperature (365 K) is observed for xA = 0.33. Dilatometric measurements show that the packing density in the filled phases is increased. High-pressure DTA is employed in order to investigate the coexistence range of the liquid crystalline phases and the slopes of the transition lines. The slopes of the melting curves for the mixtures are significantly smaller than those for the pure components. The slopes for the smectic -nematic -isotropic transitions are considerably larger. The coexistence range for the (smectic + nematic) phases does not seem to be pressure-limited, rather it increases with pressure. 
  Reference    Z. Naturforsch. 56a, 658—662 (2001); received July 18 2001 
  Published    2001 
  Keywords    Phase Transitions, DTA, High Pressure, Swallow-tailed Liquid Crystals 
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 TEI-XML for    default:Reihe_A/56/ZNA-2001-56a-0658.pdf 
 Identifier    ZNA-2001-56a-0658 
 Volume    56 
49Author    Requires cookie*
 Title    Spectroscopic Behaviour of Quasi-One-Dimensional Linear Chains in MgPt(CN)4 * 7 H ,0 Single Crystals  
 Abstract    H a r t m u t Y e r s i n a n d G ü n t e r G l i e m a n n In stitu t In the direction of the crystallographic c-axis MgPt(CN)4 • 7 H 20 has a relatively low P t-P t-distance (3.15 A at 300 °K). Thus the optical behaviour shows inter-molecular interactions. Single crystal polarized emission and absorption spectra were measured between 300 °K and 5 °K. In this tem perature range the emission peaks shift to the red by about 1,100 cm-1. This is attributed to a decrease in Pt-Pt-distance. MgPt(CN)4 • 7 H 20 undergoes phase transitions at about 166 °K and 60 °K. To interprete the solid state emission and absorption behaviour the Davydov theory is applied. The two lowest excited bands of electronic origin are assigned to the symmetries r ^ f k) and r ^ u(k) in the double group Dgh. 
  Reference    (Z. Naturforsch. 30b, 183—190 [1975]; received December 27 1974) 
  Published    1975 
  Keywords    Electronic Spectra, Phase Transitions, Davydov Splitting 
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 TEI-XML for    default:Reihe_B/30/ZNB-1975-30b-0183.pdf 
 Identifier    ZNB-1975-30b-0183 
 Volume    30 
50Author    Otto Cullmann, Heinz-Walter Hinterkeuser, Hans-Uwe SchusterRequires cookie*
 Title    Hans  
 Abstract    The ternary compound /M^ZnGe was prepared and its structure determined from powder and single crystal data. The compound crystallizes in a modified NaßAs type structure, space group PlTm 1-Djjd-The cell parameters are: a = 432.6 pm, c — 1647.0 pm, c/a= 3.83. A phase transition between a-and /S-L^ZnGe was found and the reaction of the elements lithium, zinc and germanium to a-Li2ZnGe was followed by differential thermal analysis. The temperatures and the enthalpies of transition and fusion were determined. Vorbemerkung 
  Reference    Z. Naturforsch. 36b, 917—921 (1981); eingegangen am 20. Mai 1981 
  Published    1981 
  Keywords    Ternary Intermetallic Compounds, Crystal Structure, Phase Transition 
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 TEI-XML for    default:Reihe_B/36/ZNB-1981-36b-0917.pdf 
 Identifier    ZNB-1981-36b-0917 
 Volume    36 
51Author    Wolfgang Hönle, Arndt Simon, Gabriele GerlachRequires cookie*
 Title    Darstellung, Kristallstruktur und Eigenschaften von ß-Ga 2 Br 4 Preparation, Crystal Structure and Properties of y3-Ga 2 Br 4  
 Abstract    The compounds Ga 2 Br 4 (a+ß) have been prepared by reacting GaBr 3 with Ga metal without a solvent or in a hydrocarbon medium. a-Ga 2 Br 4 is isotypic with Ga 2 Cl 4 , and /3-Ga 2 Br 4 with Ga 2 I 4 . Both forms have to be formulated as Ga + (GaBr 4)~ according to their crystal structures. The first order phase transition a—*ß has been investigated by means of DTA and temperature dependent X-ray powder photographs. The crystal structure of /3-Ga 2 Br 4 has been refined with single crystal data (R3c; a = 2163.4(8) pm; c = 869.2(4) pm; Z = 18; R = 0.037). Main building units are GaBr 4 " tetrahedra (d(Ga —Br) = 232.9 pm), connected in three dimensions by capped trigonal prisms (6+2+1) around Ga + . The crystal chemical relationships between y3-Ga 2 Br 4 and Ga 2 I 4 are discussed. 
  Reference    Z. Naturforsch. 42b, 546 (1987); eingegangen am 13. November 1986 
  Published    1987 
  Keywords    Phase Transition, DTA Investigation, Crystal Structure 
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 TEI-XML for    default:Reihe_B/42/ZNB-1987-42b-0546.pdf 
 Identifier    ZNB-1987-42b-0546 
 Volume    42 
52Author    H. Einz, Jürgen Beister, K. Arl Syassen, Jürgen KleinRequires cookie*
 Title    Phase Transition of N a3As under Pressure  
 Abstract    We have investigated the high pressure behaviour of N a3As by powder X-ray diffraction. At 3.6 G Pa the material undergoes a reversible phase transition from the N a3As structure (P 6 3/ mmc, a = 487.4(8) pm, c = 851.5(20) pm, Z = 2, at 3.6 G Pa) to the Li3Bi structure type (Fm 3m , a = 683.5(15) pm, Z = 4, at 3.6 GaP). The equation of states is given for the pressure range up to 26 GPa. Results are discussed with respect to structural properties of related A3BV-compounds. 
  Reference    Z. Naturforsch. 45b, 1388—1392 (1990); received M arch 7 1990 
  Published    1990 
  Keywords    High Pressure, Crystal Structure, Phase Transition 
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 TEI-XML for    default:Reihe_B/45/ZNB-1990-45b-1388.pdf 
 Identifier    ZNB-1990-45b-1388 
 Volume    45 
53Author    Hideta Ishihara, Keizo Horiuchi, V. G. Krishnan, Ingrid Svoboda, Hartmut FuessRequires cookie*
 Title    Isolated versus Condensed Anion Structure VI: X-ray Structure Analysis and 81 Br NQR of Guanidinium Pentabromodicadmate(II), [C(NH 2 ) 3 ]Cd 2 Br 5 , fns-Hydrazinium Pentabromocadmate(II), [H 2 NNH 3 ] 3 CdBr 5 , and fo's-Hydrazinium Tetrabromocadmate(II)-Tetra Hydrate, [H 2 NNH 3 ] 2 CdBr 4 -4H 2 0  
 Abstract    The structure of the condensed bromocadmate anions in [C(NH 2) 3 ]Cd 2 Br 5 (1) and [H 2 NNH 3 ] 3 CdBr 5 (2) were studied at room temperature by X-ray diffraction. (1) crystallizes with double-chains bridged by Br atoms (orthorhombic, Pmmn, Z= 2, a = 1394.0(5), b = 394.5(1), c = 1086.9(5) pm). This chain structure was not described previously. (1) shows three 8 'Br NQR lines at temperatures between 77 and 323 K. Structural phase transitions take place at 283 K and at 535 K. (2) crystallizes with Br bridged zigzag-chains (monoclinic, P2[, Z=2,a = 943.1(1), b = 778.8(2), c = 942.0(2) pm, ß = 102.10(2)°) and shows a first-order phase transition around 304 K with a large thermal hysteresis. Below the transition point five 81 Br NQR lines are observed at temperatures between 122 and 304 K, and above the transition point four 81 Br NQR lines at tem-peratures between 288 and 353 K. Two 81 Br NQR lines are observed in [H 2 NNH 3 ] 2 CdBr 4 -4H 2 0 (3) at temperatures between 77 and around 320 K with positive temperature coefficients. 
  Reference    Z. Naturforsch. 55a, 390—396 (2000); received November 19 1999 
  Published    2000 
  Keywords    NQR, DSC, Crystal Structure, Phase Transition, Bromocadmate 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0390.pdf 
 Identifier    ZNA-2000-55a-0390 
 Volume    55 
54Author    Marcos Luján, Frank Kubel, Hans SchmidRequires cookie*
 Title    Crystal Growth, Room Temperature Crystal Structure and Phase Transitions of K M nP04  
 Abstract    Single crystals of K M nP 04 grown in a KC1 flux show ferroelastic domains. The structure was determ ined on an optically controlled single domain crystal by X-ray diffraction methods. The cell is triclinic with dimensions a = 5.4813(5), b = 8.627(1), c = 8.887(1), in A, a = 87.73(1)°, ß = 89.10(1)°, y = 88.01(1)°, VM = 419.6(1) A 3 and Z = 4. The structure is closely related to the stuffed /3-tridymite type. DTA experiments between room tem perature and 1000 °C and polarized light microscopy observations showed four phase transitions: at 165, 330, 353 and 707 °C. 
  Reference    Z. Naturforsch. 50b, 1210—1214 (1995); received February 20 1995 
  Published    1995 
  Keywords    Manganese Potassium Orthophosphate, Crystal Structure, Crystal Growth, Phase Transitions 
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 TEI-XML for    default:Reihe_B/50/ZNB-1995-50b-1210.pdf 
 Identifier    ZNB-1995-50b-1210 
 Volume    50 
55Author    S. Mazzuca, L. SportelliRequires cookie*
 Title    Thermal Behaviour of Lymphocyte Membrane: ESR Investigation  
 Abstract    The order parameter, S, of the plasma membrane of in toto human peripheral blood lym­ phocytes was obtained by electron spin resonance spectroscopy in the temperature range 25-41 C. This membrane is completely in the liquid crystalline state above 31 C. In presence of the antigen ETB from Staphylococcus aureus at the concentration of 4 (ig/3 * 107 cells an overall decrease of the order parameter for this membrane is observed. The decrease of 5 is followed by an upwards shift at about 35 C of the temperature of the liquid crystalline state. 
  Reference    Z. Naturforsch. 45c, 1060—1062 (1990); received April 6 1990 
  Published    1990 
  Keywords    Plasma Membrane, Lymphocyte, Phase Transition, Staphylococcal Enterotoxin B, Spin Labeling 
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 TEI-XML for    default:Reihe_C/45/ZNC-1990-45c-1060.pdf 
 Identifier    ZNC-1990-45c-1060 
 Volume    45 
56Author    Z. NaturforschRequires cookie*
 Title    An ESR Study of Structural Phase Transitions o f(N H ,)2Pb|C u(N 02)6|  
 Abstract    T etsuo Asaji, Laxm an S hrikrishna P ra b h u m irash i *, and D aiy u N ak a m u ra The structural changes o f (N H 4) 2P b [C u (N 0 2)6] crystals during the phase transitions at 316, 287, and 95 K were studied by means o f a single crystal ESR technique. Anisotropic g values [9 > 9±) were obtained in the lowest temperature phase IV, whereas the ESR spectra recorded in the intermediate phases III and II, in which the crystal is known to be tetragonally compressed along the c axis, could be interpreted by use o f effective g values [g (c) < g (_L c)]. In the highest temperature phase I an isotropic g value was obtained. The phases I, II, and III o f the present complex can be assumed to be very similar to the corresponding phases observed above ~ 250 K for the com pounds R2P b [C u (N 0 2) 6] with R = K, Rb, Cs, and Tl. However, the lowest temperature phase transition transforms the phase III with an antiferrodistortive order o f the elongated [C u (N 0 2)6]4_ octahedra into the phase IV with a ferrodistortive one. This occurs only for the complex with R = N H 4 and is very unusual. The results o f the 14N N Q R experiments already reported for the phases III and IV could be well explained by the present newly proposed model. 
  Reference    Z. Naturforsch. 41a, 1154—1158 (1986); received May 3 1986 
  Published    1986 
  Keywords    Magnetic Resonance (ESR, N Q R ), Phase Transition, Crystal Structure 
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 TEI-XML for    default:Reihe_A/41/ZNA-1986-41a-1154.pdf 
 Identifier    ZNA-1986-41a-1154 
 Volume    41 
57Author    G. Schmitz, H. Klein, D. WoermannRequires cookie*
 Title    Spinodal Decomposition in a Polystyren/ Cyclohexane Solution of Critical Composition  
 Abstract    Results of experiments are reported demonstrating spi-noidal decomposition in a critical mixture of polystyrene and cyclohexane. If time and length are properly scaled using data obtained from static and dynamic light scattering exper­ iments, the time evolution of the "spinodal ring" is repre­ sented to a good approximation by an empirical equation proposed by Snyder and Meakin which describes spinodal decomposition for various types of systems. 
  Reference    Z. Naturforsch. 43a, 825—827 (1988); received June 24 1988 
  Published    1988 
  Keywords    Phase transition, spinodal decomposition, criti­ cal phenomena, polymer solution 
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 TEI-XML for    default:Reihe_A/43/ZNA-1988-43a-0825_n.pdf 
 Identifier    ZNA-1988-43a-0825_n 
 Volume    43 
58Author    Taro Eguchi, Koichi Mano, Nobuo NakamuraRequires cookie*
 Abstract    p p lic a tio n o f M a x im u m E n tro p y M e th o d (M E M) f o r P r e c is e D e te r m in a tio n o f N Q R F re q u e n c ie s The maximum entropy method (MEM) is applied to the analysis of the closely spaced nuclear quadrupole resonance spectra of 35C1 in hexachlorobenzene and 14N in frarts-azobenzene. The superiority of the MEM to usual FFT spectra is discussed with respect to the precision of frequency measurements and the noise characteristics in broad and noisy NQR spectra. 
  Reference    Z. Naturforsch. 44a, 15—18 (1989); received November 3 1988 
  Published    1989 
  Keywords    Maximum Entropy Method, Nuclear Quadrupole Resonance, Phase Transition, Spec­ tral Analysis 
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 TEI-XML for    default:Reihe_A/44/ZNA-1989-44a-0015.pdf 
 Identifier    ZNA-1989-44a-0015 
 Volume    44 
59Author    Koji Yamada, Takashi Matsui, Tomoko Tsuritani, Tsutomu Okuda, Sumio IchibaRequires cookie*
 Title    I-NQR, 119 Sn Mössbauer Effect, and Electrical Conductivity of MSnI 3 (M = K, NH 4 , Rb, Cs, and CH 3 NH 3 )  
 Abstract    In a series of MSnI 3 compounds (M = K, NH 4 , Rb, Cs, CH 3 NH 3) two types of coordination around the central Sn(II) were found by 127 I-NQR and powder X-ray diffraction techniques. They are square pyramidal (for M = NH 4 , Rb) and octahedral (for M = CH 3 NH 3). CsSnI 3 , on the other hand, showed a drastic structural change of the anion at 425 K from a square pyramid to a regular octahedron. Associated with this phase transition, the electrical conductivity increased from 4xlO~ 3 Scm _1 to about 10 2 S cm" 1 . This metallic modification was characterized by 127 I-NQR and 119 Sn Mössbauer spectroscopy. 
  Reference    Z. Naturforsch. 45a, 307—312 (1990); received August 24 1989 in revised form October 28 1989 
  Published    1990 
  Keywords    NQR, Mössbauer effect, Perovskite compound, Phase transition, Electrical conductivity 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0307.pdf 
 Identifier    ZNA-1990-45a-0307 
 Volume    45 
60Author    V. P. Tarasov, G. A. Kirakosyan, K. E. German, Acad Sei, UssrRequires cookie*
 Title    Anomalous Temperature Dependence of the "Tc Quadrupole Coupling and Disordering of Cesium Positions in CsTc0 4  
 Abstract    A "Tc and 133 Cs solid-state NMR study of polycrystalline CsTc04 at a field of 7.04 T and temperatures from 90 to 430 K revealed first-order quadrupole effects. "Tc quadrupole coupling constant, Cq, shows anomalous positive temperature coefficients and decreases from 2.0 MHz at 430 K to 0.45 MHz at 90 K. The asymmetry parameter, rj ("Tc), is zero at 430 K and at 210 K. The high-temperature minimum of rj is associated with a phase transition from orthorhombic to tetrag-onal and the second minimum reflects an orientational change of the principal axes q xx and q yy of the EFG-tensor. The 133 Cs NMR spectra are characterised by a superposition of the two powder multiplets from the first-order couplings which arise from magnetically and crystallographically nonequivalent cesium sites, Cs (1) and Cs (2); the population ratio of Cs (2) and Cs (1), p2/p1, varies from 2.0 at 120 K to 6.5 at 373 K. The nonequivalence and population changes are attributed to the temperature change of the crystal field potential in the vicinity of the cations. 
  Reference    Z. Naturforsch. 47a, 325—329 (1992); received July 26 1991 
  Published    1992 
  Keywords    Technetium, Cesium, Solid State NMR, Quadrupole Effects, Phase Transitions 
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 TEI-XML for    default:Reihe_A/47/ZNA-1992-47a-0325.pdf 
 Identifier    ZNA-1992-47a-0325 
 Volume    47