Crystal symmetry of La₃Cu₂VO₉ and La₄Cu₃MoO₁₂ derived from the YA1O₃ hexagonal structure by transmission electron microscopy

La₄Cu₃MoO₁₂ and La₃Cu₂VO₉, homeotypes of YA1O₃, an ABO₃ hexagonal phase, have been investigated using a variety of transmission electron microscopy techniques. Both compounds possess the same hexagonal subcell but exhibit different supercells. The unit cell parameters and symmetry have been determined using selected area and convergent beam electron diffraction techniques. For La₃Cu₂VO₉, electron energy loss spectroscopy and energy dispersive X-ray spectroscopy were used to determine the oxidation-state of vanadium and the cation stoichiometry, respectively, which conforms to La₃Cu₂VO₉. This paper highlights the need for multitechnique approaches to complex oxide structures.