Chemically pure β-tricalcium phosphate powders: Evidence of two crystal structures
Bastien Le Gars Santoni, Luzia Niggli, Gabrielle A. Sblendorio, Duncan T. L. Alexander, C. Stähli, Paul Bowen, N. Döbelin, Marc Bohner
Abstract
The question whether β‐tricalcium phosphate (β‐TCP) can form a solid solution with β-calcium pyrophosphate (β-CPP) and/or hydroxyapatite (HA) has still not been solved. For this reason, wet-chemically synthesized β-TCP powders with only 20 ppm Sr (among 43 tested elements) and with different HA and β-CPP contents, or in other words Ca/P molar ratios, were used. The graphical relationship between these various Ca/P molar ratios determined by X-ray diffraction and by inductively-coupled plasma mass spectrometry showed no discontinuity, indicating the absence of a solid solution between β‐TCP and β-CPP or HA. Analysis of the β‐TCP lattice parameters as a function of the Ca/P molar ratio revealed a discontinuity at a Ca/P molar ratio of 1.500 and a maximum microstrain. These results indicated that at least two β‐TCP structures co-existed, with variable mixing ratios depending on the Ca/P molar ratio, and with a distinct jump at a Ca/P molar ratio of 1.500.