Structural Characterization of the Metal-Compound Nanosize Tricalcium Phosphate Prepared by Sol–Gel Method

The metal compound of nanosize tricalcium phosphate, which is based on lime mineral and phosphoric acid, prepared by the sol–gel method, is investigated. The functional group of tricalcium phosphate is confirmed from the FTIR spectrum results, in which a hydroxyl functional group (-OH) tends to disappear at the temperature of 800°C and 1000°C. With both deficiency optimum number of –OH (3564 cm-1) and increase of the functional groups of PO4 3- (567 cm-1 and 601 cm-1) as asymmetry bending and PO4 3- (1039 cm-1, 962 cm-1, and 900 cm-1) as asymmetry stretching vibration modes, the metal compound is formed as tricalcium phosphate (TCP). The crystallographic plane orientations for metastable a-TCP are (001), and for rhombohedral b-TCP, they are (002) and (200), that is found from the XRD results. However, the crystallographic plane orientation for hexagonal a¢-TCP is still unformed due to its temperature unreached. Inhomogeneous crystallites of the metal-compound nanosize tricalcium phosphate are confirmed in the relating parameters of crystallite sizes, strains, and dislocations, whereas the crystallinity increases when their temperature increases and is occurred at 800°C and 1000°C with numbers of @ 72% and @ 77%, respectively. The thermal characterisation is obtained by the specific heat capacity, the fusion and crystallization enthalpies, and weight loss calculated from results of differential scanning calorimetry–thermogravimetric (DSC–TG) and differential thermogravimetric (DTG) analyses.