Crystal structures of the Al–Ti–Pt τ₅ and τ₆ phases solved by zonal precession electron diffraction

Highlights: • Applying Direct Methods to the PED zonal data atomic structure of two intermetallides designated as τ₅ and τ₆ was solved. • The τ₅-phase (FeCr-type, P4₂/mnm, a = 9.702 and c = 5.023 Å) can be described by the formula Al₂Ti₅Pt₃. • The τ₆-phase (P2₁3, a = 6.8477 Å) can be described by the formula Al₃Ti₅Pt₂. • Due to deviation from the stoichiometry, the τ₆-phase can be related to a defect variant of the Au₄Al-type structure. - Abstract: The earlier reported Al–Ti–Pt phases τ₅ and τ₆ were studied using Precession Electron Diffraction (PED) and Convergent Beam Electron Diffraction (CBED). Their atomic models were proposed applying Direct Methods to the PED zonal data. The τ₅-phase (FeCr-type, P4₂/mnm, a = 9.702 and c = 5.023 Å) can be described by the formula Al₂Ti₅Pt₃, positioning 18 Ti, eight Pt and four Al atoms at five unique atomic positions in the unit cell. The τ₆-phase (P2₁3, a = 6.8477 Å) can be described by the formula Al₃Ti₅Pt₂. Its unit cell consists of 20 atoms at 12b and two 4a atomic positions occupied by Ti, Pt and Al atoms, respectively. Due to deviation from the stoichiometry, the τ₆-phase can be related to a defect variant of the Au₄Al-type structure. The structures of the studied phases are presented as the stacking of coordination polyhedra