Abstract
Spinodal decomposition with a reversible transformation between single and multiple phases takes place below a critical temperature in the system of vanadium-titanium oxide. To enhance chemical homogeneity, a sol-gel method using a mixture of ammonium vanadate and titanium isopropoxide is applied. Changes in the lattice parameter of single-phase state are analyzed by X-ray diffraction. The spinodal line, determined by annealing V0.7Ti0.3O2 at different temperatures in argon, has a critical temperature of 802K at a composition of 35 mol % Ti. Transmission electron micrographs reveal the spinodally decomposed samples have the lamella structures consisted of V-rich and Ti-rich layers with a wavelength of 20-48 nm, and the samples with nucleation & growth form the rod-like phase within the matrix. The metal-insulator transition takes place at reduced temperatures of 318-341K and a decrease in the metal-insulator transition temperature is observed with increasing amount of Ti4+ for the spinodally decomposed samples.