R. Rottger et al., AN X-RAY-DIFFRACTION STUDY ON THE KINETICS OF THE CATION REDISTRIBUTION IN THE SPINEL NIAL2O4, Berichte der Bunsengesellschaft fur Physikalische Chemie, 101(8), 1997, pp. 1083-1089
Citations number
16
Categorie Soggetti
Chemistry Physical
Journal title
Berichte der Bunsengesellschaft fur Physikalische Chemie
A study of the relaxation kinetics in the partially inverse NiAl2O4 sp
inel after temperature jumps T-1 --> T-2 is reported. The change of th
e lattice parameter was measured by high temperature X-ray diffraction
at T-2 (695-760 degrees C) using NiAl2O4 powder samples equilibrated
with NiO in air. For the temperature range of T-1 under study (1100-14
50 degrees C), the kinetics can be well described by an equation which
is formally equivalent to a third-order rate law. Changes of the diff
raction line widths occur during the relaxation which are due to elast
ic stresses, strongly dependent on the initial temperature T-1. Compar
ison with recent results from optical spectroscopy indicates that the
process observed by lattice parameter measurements is not the homogene
ous exchange reaction between the two cation sublattices. The nature o
f the various relaxation phenomena occurring on different time scales
is discussed taking concentration inhomogeneities of structure element
s and elastic stress fields on different length scales into account.