Powder X-ray diffraction studies of hydroxyapatite and β-TCP mixtures processed by high energy dry milling

Abstract Samples of sintered biphasic calcium phosphates hydroxyapatite – Ca 10 (PO 4 ) 6 (OH) 2 and β-tricalcium phosphate – Ca 3 (PO 4 ) 2 subjected to high energy dry milling for different durations are studied by powder X-ray diffraction analysis. The Rietveld method as implemented in the FullProf program was applied in order to determine the quantities of the resulting crystalline phases and amorphous substance at each stage of the mechanical treatment. Microstructural analysis using appropriate size and strain models was performed in order to handle the distinct anisotropy observed in certain crystallographic directions for the hydroxyapatite and the results are presented in terms of crystallite size and strain evolution of the involved compounds. An interesting phenomenon of crystalline domains size enlargement of the hydroxyapatite phase upon prolonged milling duration was registered and discussed in the light of the up-to-date views and theories on crystal growth of nanocrystalline materials.