CONTENTS 6524 4.2. Bond-Length Variations 6524 4.3. Bond-Angle Variations 6524 4.4. Variations of the A•••A Distances 6524 5. Concluding Remarks 6524 Author Information 6525 Corresponding Author 6525 Notes 6525 Biographies 6525 Acknowledgments 6526 References 6526

The crystal structure of the NASICON Na3V2(PO4)3 phase (NVP) has been investigated as a function of temperature. Combining laboratory and synchrotron X-ray powder diffraction with single crystal X-ray diffraction, we demonstrate the presence of four polymorphs of NVP from 30 to 225 °C. While the high temperature γ-NVP crystallizes in the classical rhombohedral cell (S.G. R3̅c, a = 8.73382(4) Å, c = 21.91438(17) Å), the low temperature α-NVP undergoes a monoclinic distortion (S.G. C2/c, a = 15.1244(6) Å, b = 8.7287(3) Å, c = 21.6143(8) Å, β = 90.163(2)°) together with an ordering of the Na atoms. In the middle temperature range, two incommensurate modulated structures (β- and β′-NVP) are also reported for the first time.