Single-Crystal X-Ray Diffraction Studies of Homologues in the Series nBa(Nb,Zr)O3+3mNbO with n=2, 3, 4, 5 and m=1

Single crystals of four homologues in the series nBa(Nb,Zr)O3+3mNbO, with n:m=2:1, 3:1, 4:1, and 5:1, were found in the reduced Ba–Nb–Zr–O system. Single-crystal X-ray diffraction data were collected for all the crystals. For all homologues the space group was found to be P4/mmm. The structures can be described as intergrowths of Ba(Nb,Zr)O3 perovskite and NbO slabs. The refined cell parameters and compositions of the 2:1, 3:1, and 4:1 homologues are a=4.1768(5) ? and c=12.269 (2) ? for Ba2Nb4.5(1)Zr0.5(1)O9, a=4.1769(5) ? and c=16.493(3) ? for Ba3+deltaNb4.8(2)-delta Zr1.2(2)O12-delta (delta= 0.098(4)), and a=4.1747(6) ? and c= 20.619(4) ? for Ba4+deltaNb5.1(4)-deltaZr1.9(4)O15-delta (delta=0.270(9)). The refined cell parameters of the 5:1 homologue are a=4.1727(3) ? and c=24.804(3) ?. Zr replaces Nb only in the NbO6 octahedra found in the perovskite slabs.