Polytypes of Cu₃TiO₄ and their Formation Reactions

Abstract

Polytypism has been observed among delafossite-type compounds; AgFe02, AgCoO₂ and AgCrO₂. This phenomenon was also observed in Cu3TiO₄. The crystal structure of Cu3TiO₄ (2 H) has been reported in the previous paper. A polytype-Cu3TiO₄ (3 R) has a trigonal lattice with the unit cell dimensions; a0=5.995 A and a=29.27°.
The 3 R-type of Cu3TiO₄ was synthesized by heating the mixture (3 mol Cu0+1 mol Ti02) at 1050° C in an oxygen stream for several hours followed by rapid quenching. The above two types usually coexist and their ratio depends on the oxygen pressure. At higher oxygen pressure and at lower one, Cu3TiO₄ (3 R) and Cu3TiO₄ (2 H) are mainly produced, respectively.