Spinodally decomposed nanostructures in a TiO₂–VO₂ crystal

We have prepared a single crystal of Ti 0.4 V 0.6 O 2 which forms a solid solution crystallizing in the rutile structure at high temperatures and undergoes phase separation due to the spinodal decomposition when cooled to room temperature. The spinodally decomposed crystal consists of a self-assembled, mega stack of alternate Ti-and Vrich layers with an approximate period of 33 nm along the c axis. The unidirectional microstructure causes a large anisotropy in resistivity and a small one in thermal conductivity. A sharp metal-insulator transition as well as a structural transition to a monoclinic structure is observed in the thin V-rich layers.