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'Oxygen non stoichiometry' in keywords
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1995 (2)
1993 (1)
1Author    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 
2Author    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 
3Author    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