Sulphate-substituted tricalcium phosphate β-TCP: Effect of SO42− insertion and microwave conditions

Abstract

In the present work, we have successfully synthesized pure β-TCP and sulphate substituted β-TCP by a wet chemical method derived microwave irradiation technique. XRD and FTIR results showed that the insertion of the SO42− group at PO43− sites, without microwave treatment, decreases the crystallinity of β-TCP samples and promotes the growth of calcium pyrophosphate β-CPP as a secondary phase. Our results also showed that wet chemical preparation combined with microwave treatment for TCPS-M led to a decrease in peak intensity, crystallite size average, as well as the peak broadening, confirming the decrease in degree of crystallinity. The average crystallite size of samples decreases from 46 to 21 nm. Besides, we noted a slight shift of XRD peaks towards a lower diffraction angle, which could be explained by the replacement of PO43− ions, with a smaller anionic radius of 0.238 nm, by SO42− ions with larger anionic radius of 0.258 nm. The FTIR analysis revealed the presence carbonate groups and the formation of β-CPP as a secondary phase for sulphate substituted β-TCP, confirming the XRD results. The Ca/P molar ratios were calculated using the ICP/AES technique. Furthermore, the SEM micrograph of SO42− substituted β-TCP demonstrates the deposition of β-CPP on β-TCP surface, supporting the XRD and FTIR results. These results emphasize that microwave irradiation and insertion of SO42− in the β-TCP matrix affect the degree of crystallinity and increase structural disorder.