The compound Ba4Nd3F17 was prepared by heating predried BaF2 and EuF3 (4:3) at 900 °C for 8 h in static vacuum. The polycrystalline sample obtained was characterized by Rietveld refinement of the observed powder diffraction data with the starting model of Ba4Y3F17. This compound crystallizes in a rhombohedral lattice with unit-cell parameters, a=11.2818(3) and c=20.7788(11) Å, Z=6, (Space group R 3, No. 148). The Rp, Rwp and Rexp factors were 9.5%, 12.9% and 10.9%, respectively.

The compound Ba4Eu3F17 was prepared by heating pre-dried BaF2 and EuF3 (4:3) at 800 °C for 8 h in static vacuum. The colorless polycrystalline product obtained was characterized by Rietveld refinement of the observed powder diffraction data with a starting model of Ba4Y3F17. The title compound Ba4Eu3F17 crystallizes in rhombohedral lattice with lattice parameters, a=11.1787(4) and c=20.5789(10) Å, Z=3 (Space group R 3, No. 148). The Ba4Eu3F17 structure can be described as an ordered anion-rich fluorite type structure with the formation of Eu6F37 clusters. There are two crystallographically distinct Ba (CN=10, 11) and one distinct Eu (CN=8). The typical Ba(1)–F, Ba(2)–F, and Eu–F bond lengths range from 2.56 to 2.83 Å, 2.54 to 3.25 Å, and 2.24 to 2.49 Å, respectively. The salient feature of the structure is that the EuF8 polyhedra share their corner to form a cubo-octahedron of fluoride ions. The cubic BaF8 polyhedra of BaF2 are modified to Ba(1)–F10 and Ba(2)–F11 polyhedra in this structure. The cubo-octahedron encloses extra fluorine F(8) inside it.