Obtaining Ceramic Materials from Hydroxyapatite Using Spark-Plasma Sintering

Hydroxyapatite was synthesized via sol-gel and solid-state reaction. Both compounds were investigated using high-temperature X-ray diffraction and differential scanning calorimetry. For sol-gel hydroxyapatite, we observed a phase transition, confirmed by character of changing of unit-cell parameters, thermal expansion coefficients and endothermic effect on DTA curve. In the process of obtaining ceramics using spark-plasma sintering both compounds manifested an unexpected shrinkage rate. All effects were explained on the basis of changings in crystal structure during distortion polymorphic transition.