Determination of Precise Unit‐Cell Parameters of the α‐Tricalcium Phosphate Ca 3 (PO 4 ) 2 Through High‐Resolution Synchrotron Powder Diffraction

Unit‐cell parameters of the α‐tricalcium phosphate [TCP; Ca 3 (PO 4 ) 2 ] were investigated using high‐resolution synchrotron powder diffraction and the Rietveld method. The diffraction experiment was conducted at 29°C at the BL‐15XU experimental station of SPring‐8, Japan. Precise unit‐cell parameters of the α‐TCP were obtained; a =12.87271 (9), b =27.28034(8), c =15.21275(12) Å, α=γ=90°, and β=126.2078(4)°. The calculated density of α‐TCP (2.8677 g/cm 3 ) is smaller than that of β‐TCP, indicating the “looser” structure of α‐TCP.