Synthesis, Rietveld Analysis and Solid State Raman Spectroscopy of K4SrSi3O9

Abstract

AbstractThe crystal structure of K4SrSi3O9 has been determined from laboratory X‐ray powder diffraction data using polycrystalline material prepared from solid state reactions. The compound crystallizes with 16 formula units in a cubic primitive unit cell (a = 16.16957(5) Å, V = 4227.62(2) Å3) and adopts space group $Pa{\bar 3}$. The structure belongs to the group of cyclosilicates and is isotypic with Na4CaSi3O9 and other similar silicates and germanates. It contains puckered twelve‐membered [Si12O36]‐rings centered on the ${\bar 3}\rm -axes$. The rings are connected by seven different M‐sites occupied by potassium or strontium atoms. Five of the seven crystallographically independent alkaline and alkaline earth cations are surrounded by six oxygen ligands in the form of distorted octahedra. The octahedra share opposite triangular faces, building non‐intersecting columns parallel to the body diagonals of the cubic unit cell. The arrangement of these rods corresponds to one of the cubic cylinder or rod packings. The remaining two potassium sites have more irregular coordination environments with eight next oxygen neighbors. Structural investigations are completed by solid state Raman spectroscopy.