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Mechanism of La 2 CuO 4 Solid‐State Powder Reaction by Quantitative XRD and Impedance Spectroscopy
Author(s) -
Cooper Elizabeth A.,
Mason Thomas O.
Publication year - 1995
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1995.tb08406.x
Subject(s) - activation energy , diffusion , kinetics , dielectric spectroscopy , reaction mechanism , rate equation , powder diffraction , chemical kinetics , copper , spectroscopy , materials science , analytical chemistry (journal) , conductivity , reaction rate , order of reaction , chemistry , thermodynamics , crystallography , reaction rate constant , physics , electrode , metallurgy , catalysis , biochemistry , quantum mechanics , chromatography , electrochemistry
Reaction kinetics for CuO + La 2 O 3 → La 2 CuO 4 were quantified by X‐ray diffraction on quenched samples reacted in air. The rate was successfully modeled by the Valensi‐Carter equation, taking into account the particle size distribution. Kinetics followed diffusion‐limited rather than reaction‐limited behavior; the activation energy was 265 kJ/mol. Conductivity‐time behavior from in situ impedance spectra confirmed the reaction model; CuO rapidly coats the La 2 O 3 particles and produces an La 2 CuO 4 diffusion barrier. This is consistent with the basic assumptions of the Valensi‐Carter equation. It is believed that copper diffusion controls the rate of reaction.