The crystal structure of δ-yttrium pyrosilicate, δ-Y2Si2O7

The single crystal structure of the high temperature phase, δ-Y2Si2O7, has been established by X-ray diffraction. Crystal data: Y2Si2O7, M=346.0; orthorhombic, Pnam, a=13.655(5), b=5.016(3), c=8.139(3) A; V=557.5 A3, Dx=4.121 g cm-3, Z=4. λ(Mo-Kα)=0.71069 A, μ(Mo-Kα)=21.2 mm-1, F(000)=648 electrons, room temperature; R=0.077 for 294 reflections. The structure proves to be similar to that proposed in the space group Pna2, for Gd2Si2O7 by Smolin and Shepelev. The present work suggests that the space group Pnam provides an adequate representation of this structure type in the case of Y2Si2O7. (orig.)