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Thermodynamic Properties of Nd 1+ x Ba 2– x Cu 3 O y Compounds and Their Application for Optimizing the Synthesis of Superconducting Materials
Author(s) -
Zelenina Ludmila N.,
Chusova Tamara P.,
Matskevich Nata I.,
Naumov Victor N.,
Stenin Yuri G.,
Krabbes Gernot
Publication year - 2009
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.200800745
Subject(s) - chemistry , heat capacity , calorimetry , enthalpy , atmospheric temperature range , gibbs free energy , adiabatic process , thermodynamics , standard enthalpy of formation , standard molar entropy , standard enthalpy change of formation , analytical chemistry (journal) , physics , organic chemistry
The standard enthalpies of formation from oxides of Nd 1+ x Ba 2– x Cu 3 O y , where x = 0–0.8 and y = 6.65–7.24, were determined by using dissolution enthalpies of these compounds measured by solution calorimetry. The temperature dependence of the heat capacity of NdBa 2 Cu 3 O 6.87 wasmeasured over the range 5–320 K by adiabatic calorimetry. The absolute entropy, S° ( T ), the enthalpy of heating, H° ( T K) – H° (0 K), and the reduced Gibbs energy, Φ ° ( T ) = S° ( T ) – [ H° ( T ) – H° ( 0 )]/ T , were calculated by using the temperature dependence of C p in the interval 0–320 K. The heat capacity and absolute entropy of NdBa 2 Cu 3 O 6.87 over the temperature range 320–1380 K were estimated by methods of quantum chemistry with use of the temperature dependence of C p at low temperatures. A thermodynamic simulation was performed on the basis of the obtained data, and the conditions for synthesis of the NdBa 2 Cu 3 O 6.9 phase were determined.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)