Phase Equilibrium in the System La-Ni-O at 1100℃

概要

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Phase equilibrium in La-Ni-O system was established at 1100℃ at the oxygen partial pressure ranging from -log(Po_2/atm) = 0 to 12.00, and a phase diagram for the corresponding La_2O_3, -Ni- Ni_2O_3 system at 1100℃ was constructed. Stable La_2O_3, Ni, NiO, La_2NiO_4, and La_6Ni_5O_15 phases were found in the La-Ni-O system. La_2Ni_2O_5, LaNiO_2 LaNiO_3, La_3Ni_2O_7, La_4Ni_3O_<10>, La_5Ni_40_<13> were not found under the present experimental conditions. Nonstoichiometric ranges were found in both La_2NiO_4 and La_6Ni_5O_<15> phases, with the composition of La_2NiO_4 represented as functions of log (Po_2/atm), No/N_<La2NiO4>=-2.932 × 10^<-4> (log Po_2)^2 + 1.056 × 10^<-2>log Po_2 + 0.1318, and with the composition of La_6Ni_5O_<15> represented as functions of log (Po_2/atm), No/N_<La6.Ni5O15>= 0.0641 log Po_2 + 0.480, respectively. Activity of the components in a solid solution was calculated from these equations. Lattice constants of La_2NiO_4 quenched at two different oxygen partial pressures were determined. The standard Gibbs energy changes of the reactions, Ni + La_2O_3 + 1/2 O_2 = La_2NiO_4 and NiO + 3 La_2NiO_4 + 1/2 O_2 = La_6Ni_5O_<15> appearing in the phase diagrams were calculated to be -133.8 and -20.1kJmol^<-1>, respectively.
新潟工科大学の論文
2006-12-25