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 structure of the fully ordered α-Na(3)Ti(2)(PO(4))(3) NASICON compound was elucidated using high-quality single-crystal data. The cation/vacancy distribution forms a homogeneous 3D arrangement and could represent the absolute cationic ordering available in the full Na(3)M(2)(PO(4))(3) series, as verified for M = Fe. For M = Ti, the reversible α → γ transition was observed at 85 °C, leading to the standard disordered R ̅3c γ model. Through JPDF analysis, the most probable Na(+) zigzag M(2)-M(1) diffusion scheme was directly deduced using our accurate crystallographic data.