New Members of the (Ba8Co6O18)ALPHA(Ba8Co8O24)BETA Polysomatic Series

The accurate control of both stoichiometry and synthesis conditions has allowed the stabilization of new Ba–Co oxides with onedimensional structures related to the 2H-ABO3 hexagonal perovskite. Ba26Co23O69, Ba44Co39O117, and Ba28Co25O75 are new members of the (Ba8Co6O18)(Ba8Co8O24)BETA polysomatic orthorhombic series whose structural features have been characterized by electron diffraction and high-resolution electron microscopy. These polysomes are described as the ordered intergrowth between structural slabs of one-half unit cell of the o-Ba8Co7O21 and one Ba8Co8O24 2H-block in different ratios.