Crystal structures of the R1.33 Ni3 Ga8 (R = Tb, Ho, Er, Tm, Lu) compounds

The existence of five new ternary compounds with Gd1.33Pt3Al8-type structure (Pearson symbol hR 51, space group R- 3 m ) was established by means of X-ray powder diffraction and energy-dispersive X-ray spectroscopy: Tb1.33Ni3Ga8 (& acy; = 4.2056(1), & scy; = 37.8913(9) & Aring;), Ho1.33Ni3Ga8 (& acy; = 4.19666(9), & scy; = 37.7882(9) & Aring;), Er1.33Ni3Ga8 (a = 4.19290(8), c = 37.7446(8) & Aring;), Tm1.33Ni3Ga8 (a = 4.18819(7), c = 37.6980(7) & Aring;), and Lu1.33Ni3Ga8 (a = 4.1826(1), c = 37.647(1) & Aring;). The structures of the ternary R 1.33 Ni 3 Ga 8 compounds belong to a family of linearintergrowth structures with the general formula R 0.67 T n M 2 n + m and are built from atom layers of the composition R 0.67 Ga ( R 0.67 M ), separated by single or double NiGa2 slabs (TM2). The layers containing the rare-earth metal atoms are characterized by a disordered distribution of rare-earth metal atoms and Ga-atom triangles.