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1Author    G. Chiodelli, V. Campari-Viganò, G. Massarotti, FlorRequires cookie*
 Abstract    The electrical behaviour of La2_JtSrJ.Cu04_v solid solutions (with x = 0, x = 0.025, x = 0.05, and x = 0.15) at temperatures between 10 and 900 K and under different oxygen partial pressure pQl — 1 -M0~6 atm) has been investigated. The samples prepared and measured under an 0 2 flux (i.e~, with y = 0) show a superconducting transition with Tc = 46, 29. 37 K for x = 0. 0.05 and"0.15, respectively. The samples with x = 0.025, y = 0, and x = 0, y = t= 0 exhibit no sign of superconductivity. In the temperature range 100-900 K. La2Cu04 is semiconducting, whereas the electrical resistivity is independent of temperature for the x =0.025 sample, and the x = 0.05 and x = 0.15 are metallic. 
  Reference    Z. Naturforsch. 44a, 26—28 (1989); received September 19 1988 
  Published    1989 
  Keywords    Superconductors, electrical properties, defects 
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 TEI-XML for    default:Reihe_A/44/ZNA-1989-44a-0026.pdf 
 Identifier    ZNA-1989-44a-0026 
 Volume    44 
2Author    G. Chiodelli, G. Campari-Viganò, G. FlorRequires cookie*
 Title    Y B a 2C  
 Abstract    u 30 7 _ x : T r a n s p o r t P r o p e r tie s an d D e fe c ts a t H ig h T e m p e r a tu r e Electrical resistivity measurements were carried out on polycrystalline YBa2Cu,07_ v at temper­ atures 300 < T < 1023 K and oxygen partial pressures 5 ■ 10"7 < p0l < 1 atm. The samples, equili­ brated in the range from 5 10~4 to 1 atm, show metallic behaviour, the one equilibrated at p0, = 2 • 10"5 shows a transition between metallic and semiconducting behaviour at 920 K, and that equilibrated at p0i — 5-10" shows semiconducting behaviour: for the latter the relevant resistivity is due to the oxygen-ion migration. The isotherms log a vs. log (in the temperature range from 723 to 1023 K) show slopes of about 1/6 at 723 K (orthorhombic phase) and about 1/2 at 1023 K (tetragonal phase). These results are discussed in terms of appropriate defect models. 
  Reference    Z. Naturforsch. 44a, 1167—1171 (1989); received September 28 1989 
  Published    1989 
  Keywords    Superconductors, electrical properties, defects 
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 TEI-XML for    default:Reihe_A/44/ZNA-1989-44a-1167.pdf 
 Identifier    ZNA-1989-44a-1167 
 Volume    44 
3Author    C. B. Azzoni, G. B. Parravicini, G. Samoggia, P. Ferloni, F. ParmigianiRequires cookie*
 Title    Electrical Instability in CuOj_ x : Possible Correlations with the CuO-based High Temperature Superconductors  
 Abstract    Physical properties of stoichiometric and non stoichiometric CuO are reported. The electrical conductivity has been measured on CuO pellets, sintered with the usual procedure for the prepara-tion of Y Ba-Cu O superconductors and then deoxygenated under a nitrogen flow. It is shown that oxygen deficient CuO pellets present abrupt and large resistivity drops as the temperature decreases below 230-200 K. Possible correlations between the electrical instability of oxygen defi-cient CuO and the high temperature superconductivity problem are discussed. 
  Reference    Z. Naturforsch. 45a, 790—794 (1990); received February 20 1990 
  Published    1990 
  Keywords    Cupric oxide, Superconductors, Electrical conductivity 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-0790.pdf 
 Identifier    ZNA-1990-45a-0790 
 Volume    45 
4Author    G. Spinolo, U. Anselmi-Tamburini, M. Arimondi, P. Ghigna, G. FlorRequires cookie*
 Abstract    O x y g e n N o n -S to ic h io m e try , C a tio n M o le c u la r ity a n d X -r a y D if f r a c tio n D e te rm in a tio n s "BaCu02" is the key intermediate in the synthesis of the Ba2YCu30 7_5 superconductor. Its very complex crystal structure is able to accommodate a large change in oxygen content. Oxygen non-stoichiometry of "BaCu02" materials with 1:1 and 88:90 (Ba:Cu) molecularity has been investigated by polythermal X-ray powder diffraction coupled with isobaric-isothermal gravimetry determinations under different temperature and oxygen partial pressure conditions [300 < T< 820 °C, 1 > P (02) > 3 • 10 ~3 atm]. The 1:1 composition does not give well reproducible results, thus suggesting its polyphasic nature, at least in part of the investigated range. The results for the 88:90 = 0.98 (Ba:Cu) composi­ tion are well reproducible and show that the material is single phase. Ba0 ggCuOj 98 + 6 is oxygen over-stoichiometric in the whole investigated [T, i>(02)] range, with a maximum value S~0.21. A Rietveld X-ray profile fitting is in agreement with previous single-crystal data. The trend of < 5 vs. jP(02) is consistent with the presence of oxygen interstitial defects on (possibly different) crystallo­ graphic sites. 
  Reference    Z. Naturforsch. 50a, 1050—1058 (1995); received October 12 1995 
  Published    1995 
  Keywords    BaCuO, Superconductors, Oxygen non-stoichiometry 
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 TEI-XML for    default:Reihe_A/50/ZNA-1995-50a-1050.pdf 
 Identifier    ZNA-1995-50a-1050 
 Volume    50 
5Author    H. Endres, H. J. Keller, R. Swietlik, D. Schweitzer, K. Angermund, C. KrügerRequires cookie*
 Title    X-Ray Investigations of the Low-Temperature Phases of the Organic Metals a-and /KBEDT-TTF)2I3  
 Abstract    The structure of single crystals of the organic metals a-and /?-(BEDT-TTF)2I3* was determined at 100 K, well below the phase transitions indicated by resistivity and thermopower measurements as well as by differential therm al analysis. In the a-phase no unusual change of the room temperature unit cell but a slight variation in the triiodide network and especially a more pronounced dim erization in one of the two donor stacks have been found. The /?-phase develops a superstructure with a unit cell volume three times as large as that at room temperature and with pronounced distortions of the I 3-ions. 
  Reference    Z. Naturforsch. 41a, 1319—1324 (1986); received July 31 1986 
  Published    1986 
  Keywords    Low-Tem perature Structure, Organic Conductors, Superconductors 
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 TEI-XML for    default:Reihe_A/41/ZNA-1986-41a-1319.pdf 
 Identifier    ZNA-1986-41a-1319 
 Volume    41 
6Author    G. Chiodelli, U. Anselmi-Tamburini, M. Arimondi, G. Spinolo, G. FlorRequires cookie*
 Abstract    I . T r a n s p o r t P r o p e r tie s a n d N a t u r e o f D e fe c ts The charge transport properties of "BaCu02" with 88:90 (Ba :Cu) cation ratio were characterized by thermopower, electrical conductivity and ionic transport number measurements in a wide range of temperature and oxygen partial pressure conditions. The nature of carriers is always represented by small polarons due to self-trapping of the electronic holes generated by the oxygen non-stoichiometry equilibrium. Some anomalies in carrier mobility as a function of temperature are shown not to be related to incomplete ionization of oxygen atoms on interstitial sites 
  Reference    Z. Naturforsch. 50a, 1059—1066 (1995); received October 12 1995 
  Published    1995 
  Keywords    BaCu02, Superconductors, Small polarons, Oxygen non-stoichiometry 
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 TEI-XML for    default:Reihe_A/50/ZNA-1995-50a-1059.pdf 
 Identifier    ZNA-1995-50a-1059 
 Volume    50 
7Author    YaA. Ossipyan, N. S. Sidorov, V. I. Kulakov, V. L. Matukhin, A. I. Pogoreltsev, V. N. Anashkin, I. A. Safin, L. E. MatukhinaRequires cookie*
 Title    NQR Studies of Halogen Treated 1-2-3 System  
 Abstract    NQR spectra of copper in polycrystalline samples of iodine treated RBa 2 Cu 3 O y (R = Y, Gd) were studied. The results of all the experiments show evidence for the modifications occurring in the oxygen sublattice in treated compounds. 
  Reference    Z. Naturforsch. 53a, 542—545 (1998); received March 24 1998 
  Published    1998 
  Keywords    NQR-spectra, Superconductors, Treatment, Halogens, Diffusion 
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 TEI-XML for    default:Reihe_A/53/ZNA-1998-53a-0542.pdf 
 Identifier    ZNA-1998-53a-0542 
 Volume    53 
8Author    J. G. Correia, J. P. Araújo, J. G. Marques, A. R. Ramos, A. A. Melo, J. C. SoaresRequires cookie*
 Title    Electron-Gamma PAC: New Possibilities for NQI Studies  
 Abstract    The application of hyperfine interaction techniques to problems in solid state physics has been stead-ily growing over the last decade with the use of radioactive ion beam facilities such as ISOLDE at CERN. New applications of the e~-y Perturbed Angular Correlation (PAC) technique are underway at ISOLDE using probe nuclei with highly converted cascades. In this paper we present the motivation for extend-ing PAC experiments to elements/isotopes not usable with the conventional y-y PAC technique. Examples will be shown where the long-lived 73 As/ 73 Ge, the short lived 127 Ba/ 127 Cs and the 197m Hg/ l97 Hg decay cascades are applied to measurements of nuclear quadrupole interactions in materials. 
  Reference    Z. Naturforsch. 55a, 3—14 (2000); received September 11 1999 
  Published    2000 
  Keywords    Nuclear Techniques, Hyperfine Fields, Semiconductors, Superconductors 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0003.pdf 
 Identifier    ZNA-2000-55a-0003 
 Volume    55 
9Author    H. Yoshida, H. Nishihara, S. Yokota, M. Ohyanagi, T. NakaokiRequires cookie*
 Title    Field-Swept NMR Spectra of n B in Pyrex Glass and 93 Nb in NbN Perturbed by Quadrupole Interaction  
 Abstract    NMR experiments of "B by both field-swept and high-resolution NMR are reported to probe the electric field gradient at boron sites and its distribution in Pyrex glass. Both spectra are successfully interpreted with the same set of parameters. It is stressed that field-swept NMR experiments to observe total powder spectrum can be helpful to get information on electric field gradients and asymmetry pa-rameters if there exist many nonequivalent sites of atoms, since satellite transitions are affected by the larger first-order quadrupole effect. Field-swept NMR of 93 Nb in superconducting NbN powder, pre-pared by self-propagating high-temperature synthesis, is also reported. A very broad field-swept spec-trum disturbed by quadrupole interaction has been observed. The spectrum is simulated by assuming distributions in electric field gradient and Knight shift at Nb sites. It is stressed that a combination of experiments at separated frequencies is important 
  Reference    Z. Naturforsch. 53a, 309—313 (1998); received January 26 1998 
  Published    1998 
  Keywords    NMR, Pyrex, Glass, n B, NbN, Superconductor, 93 Nb 
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 TEI-XML for    default:Reihe_A/53/ZNA-1998-53a-0309.pdf 
 Identifier    ZNA-1998-53a-0309 
 Volume    53 
10Author    P. Ghigna, G. Chiodelli, U. Anselmi-Tamburini, G. Spinolo, G. FlorRequires cookie*
 Title    Homogeneity Range, Hole Concentration, and Electrical Properties of the Bi 2 Sr3_ x Ca x Cu 2 0 8+3 ,(l ^ x g 2) Superconductors  
 Abstract    The homogeneity range of Bi-Sr-Ca-Cu oxides with two-layers ("2212") structure has been investigated with X-ray powder diffraction and electron microprobe determination on materials with nominal Bi 2 Sr 3 _ Jt Ca x Cu 2 0 8+) , (x = 1-h2 in 0.1 steps) composition and being prepared at two different oxygen partial pressures. The results show Bi over-stoichiometry and a wide range of Sr/Ca substitution. DC resistivity measurements indicate that the hole concentration is controlled by both oxygen non-stoichiometry and cation molecularity. It is shown that a single phenomenological relation between hole concentration and electrical properties can explain in a consistent way the complex behaviour of the whole set of materials with different oxygen non-stoichiometry and cation molec-ularity. 
  Reference    Z. Naturforsch. 48a, 1214—1218 (1993); received October 26 1993 
  Published    1993 
  Keywords    Bi 2 Sr 2 CaCu 2 O s, Superconductors, Oxygen non-stoichiometry, Cation molecularity 
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 TEI-XML for    default:Reihe_A/48/ZNA-1993-48a-1214.pdf 
 Identifier    ZNA-1993-48a-1214 
 Volume    48