Crystal growth of Ti nO 2n−1 with large n by chemical transport reaction

Abstract

Single crystals of Ti n O 2 n−1 (16⩽ n⩽20) were obtained as a single phase by chemical transport from a hot zone to a cold zone in a closed tube using NH 4Cl as a transport agent. The single crystals of titanium oxide deposited at the cold zone were always higher in oxidation state than the source materials which were oxidized at the hot zone in the beginning of chemical transport. Mass spectrometric analysis of the gas species in the closed transport tube revealed that a great deal of hydrogen gas, some water vapor and hydrogen chloride gas played important roles in the chemical transport reaction. The main reaction of chemical transport may be: 1 n Ti nO 2n-1 + 4 HCl = TiCl 4 + (2n− 1) n H 2O + 1 n H 2 . The phase relations between the oxidized source materials and the single crystals were discussed from the standpoint of equilibrium with H 2 + H 2O gas mixture.