Crystal Structure of Silicon Pyrophosphate (Form I) from Powder Diffraction Data

✍ Scribed by D.M. Poojary; R.B. Borade; F.L. Campbell III; A. Clearfield

• Publisher: Elsevier Science
• Year: 1994
• Tongue: English
• Weight: 320 KB
• Volume: 112
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.1994.1273

✦ Synopsis

The crystal structure of silicon pyrophosphate (Form I) was solved from (X)-ray powder data and refined by the Rietveld method. The crystals belong to the hexagonal space group (P \boldsymbol{6}{3}) with (a=) 4.7158(3) (\AA) and (c=11.917(1) \AA). There are two (\mathrm{SiP}{2} \mathrm{O}{7}) units in the unit cell. Both the (\mathbf{P}) atoms and the (\mathrm{Si}) atom are located on threefold axes. The silicon atoms are situated in the (a b) plane at (z=0) and (\frac{1}{2}). One of the (\mathrm{P}) atoms of the pyrophosphate group is located slightly above the plane at (z=0) while the other is slightly below the plane at (z=\frac{1}{2}). Thus, the structure resembles the layer structure of (\alpha)-zirconium phosphate. The layers in the present case, however, are held together by the (\mathrm{P}-\mathrm{O}-\mathrm{P}) bonds. The relationship between this structure and those of the other pyrophosphates and the layered (M\left(\mathrm{HPO}{4}\right)_{2}) phases is discussed. 1994 Academic Press, Inc.