New layered copper oxide: LaSrCuAlO₅

Square-pyramidal coordination of copper and Cu-O planes are common structural features in many of the high T_c oxide superconductors that support this state. These poorly screened (highly ionic) compounds have occupied Cu-O dpπ bonding orbitals and empty Cu-O dpσ anti-bonding orbital partners. The combination of four and six coordination leads to similar layered structures and Cu-O σ and π bonding. Our recent efforts preparing quaternary oxides with strongly basic counter cations, small tetrahedrally coordinated cations and copper have led to a new series of layered copper oxides.