Portal de Periódicos da CAPES

Kinetics of decomposition in ionic solids: neutron scattering study of the system AgBr-NaBr

2000; IOP Publishing; Volume: 13; Issue: 2 Linguagem: Inglês

10.1088/0953-8984/13/2/301

1361-648X

G. Eckold,

Chemical Thermodynamics and Molecular Structure

The kinetics of decomposition in the quasibinary ionic system AgBr-NaBr has been studied by time-resolved neutron diffraction and small-angle scattering. The temperature regimes for nucleation and for spinodal decomposition are clearly distinguished. The coherent critical point is estimated as 458±5 K which is about 100 K below the maximum of the chemical binodal. Even at low temperatures the chemical demixing is completed within some 100 s resulting in a metastable state which is characterized by coherency strains and internal stresses of the order of 0.3 GPa. The mechanical relaxation of the lattice takes place on a much longer timescale after the correlation length of the decomposition pattern is increased to some critical value larger than 40 nm.