Solution combustion synthesis of bioceramic calcium phosphates by single and mixed fuels—A comparative study

Calcium phosphate based bioceramics have been synthesized by a modified combustion synthetic route using both citric acid and succinic acid separately and in mixture as fuels and nitrate and nitric acid as oxidants. Calcium nitrate and diammonium hydrogen phosphate were used as calcium and phosphate sources. The effects of citric acid to succinic acid ratio on the phase formation have been investigated. The precursors and the calcined products have been characterized by powder X-ray diffraction, Fourier-transform infrared spectroscopy and scanning electron microscopy. Succinic acid has been used as a fuel for the first time to synthesize hydroxyapatite. Hydroxyapatite phase is formed when either citric acid or succinic acid is used as a fuel and β-tricalcium phosphate phase is formed when a mixture of citric acid and succinic acid is used as a fuel as revealed by powder X-ray diffraction. The average crystallite size of the synthesized powder determined by Debye–Scherrer formula is found to be in the range of 55–65 nm. Surface morphology of the samples was imaged using scanning electron microscope. Chemical analysis shows that the Ca:P ratio in synthesized ceramics is 1.67. Results are discussed in terms of the phases present in the precursors formed during single and mixed fuel approaches and also its carbonate content present in hydroxyapatite products.