Hydrothermal synthesis and structures of Ba3(NbO)2(PO4)4 and Co3(NbO)2(PO4)4(H2O)10

The new niobium phosphates Ba-3(NbO)(2)(PO4)(4) (1) and Co-3(NbO)(2)(PO4)(4)(H2O)(10) (2) have been synthesized in single crystal form by hydrothermal reactions at 250 degreesC and 170 degreesC respectively. The crystal structures have been determined from X-ray diffraction data. Both compounds contain NbP2O9 complex chains as a fundamental structural unit. The chains are similar to those of the known compound K3NbP2O9 and structurally may be considered similar to a slice of the Zr(HPO4)(2) layer in alpha -zirconium phosphate. In compound 1 the chains are separated and are held together by Ba-O bonds while in 2 the chains are linked by CoO6 octahedra to form a framework structure.