Die neuen Schichtsilicate Ba 3 Si 6 O 9 N 4 und Eu 3 Si 6 O 9 N 4

The New Layer‐Silicates Ba 3 Si 6 O 9 N 4 and Eu 3 Si 6 O 9 N 4 The new oxonitridosilicate Ba 3 Si 6 O 9 N 4 has been synthesized in a radiofrequency furnace starting from BaCO 3 , amorphous SiO 2 and Si 3 N 4 . The reaction temperature was at about 1370 °C. The structure of the colorless compound has been determined by single‐crystal X‐ray diffraction analysis (Ba 3 Si 6 O 9 N 4 , space group P 3 (no. 143), a = 724.9(1) pm, c = 678.4(2) pm, V = 308.69(9)· 10 6 pm 3 , Z = 1, R 1 = 0.0309, 1312 independent reflections, 68 refined parameters). The compound is built up of corner sharing SiO 2 N 2 tetrahedra forming corrugated layers between which the Ba 2+ ions are located. Substitution of barium by europium leads to the isotypic compound Eu 3 Si 6 O 9 N 4 . Because no single‐crystals could be obtained, a Rietveld refinement of the powder diffractogram was conducted for the structure refinement (Eu 3 Si 6 O 9 N 4 , space group P 3 (no. 143), a = 711.49(1) pm, c = 656.64(2) pm, V = 287.866(8) ·10 6 pm 3 , R p = 0.0379, R F 2 = 0.0638). The 29 Si MAS‐NMR spectrum of Ba 3 Si 6 O 9 N 4 shows two resonances at −64.1 and −66.0 ppm confirming two different crystallographic Si sites.