Single crystals of Ca4SiN4 were found in the product prepared by heating Ba, Ca, Si, NaN3, and Na at 900 C. Ca 4SiN4 [space group P21/c (No. 14), Z = 4, a = 9.1905(4) Å, b = 5.9775(3) Å, c = 11.0138(7) Å, β = 116.4054(17) ] is isotypic with Ca4GeN4 and K 4SiO4. Isolated [SiN4]8- tetrahedra were identified in the structure by single-crystal X-ray diffraction. After reheating the product at 900 C, a new polymorph of Ca5Si 2N6 crystallized. The space group of the polymorph [C2/m (No. 12), Z = 4, a = 6.2712(5) Å, b = 10.0175(8) Å, c = 12.0287(8) Å, β = 99.303(2) ] is different from C2/c previously reported for Ca5Si2N6, while both polymorphs are composed of Ca2+ and edge-sharing double tetrahedra [Si2N 6]10-.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Inorganic Chemistry