Crystal Structure of a Modulated Composite Structure with Two Subsystems: Ba1.1064CoO3

The new phases of composition Ln1.33NaxMnxTi2-xO6 (Ln=Pr, x=0.66; Ln=Nd, x=0.66 and 0.55), derived from LnMnO3 by partial substitution of Mn3+ by Ti4+ and Na+, are reported. Powder neutron diffraction data were used to refine the crystal structures and to analyze the ferromagnetic interactions. These phases can be described as orthorhombic perovskites, space group Pbnm, in which A(Ln, Na) and B(Mn, Ti) cations are disordered at random. Conductivity results are attributed to an electronic contribution and the activation energies are relatively low, about 0.3 eV.