Spinodal Decomposition in Solutions of Ternary Oxides

Abstract

A miscibility gap exists in the quasi‐binary solid solution Co2TiO4 – CoAl2O4 as verified by experimental investigations and theoretical calculations. The critical temperature is ca. 1700 K. Spinodal decomposition was observed in this two‐cation‐sublattice system, if the spinel solid solution had been undercooled into the region of the coherent spinodal at T = 973 K. Simultaneous ordering occurs in certain regions of the crystal. The growth‐rate of the spinodal wavelength λ varies linearly in time. This unusual quasi‐ripening process is discussed in relation to the characteristic features of diffusion in (semiconducting) oxides.