The recent development and use of Calcium Phosphate (CaP) based products as orthopaedic implants has increased the need for the development of a greater understanding of the starting materials inherent properties. Chemical composition and crystal phase greatly influence the final product’s behaviour in the body. By gaining a deeper understanding of these properties, greater control in making tailor-made products can be achieved.

Calcium Phosphate based powders of varying CaO: P2O5 ratios were prepared by cold isostatic pressing into compact discs (13 mm diameter x 3.6 mm height) and subsequently sintered at temperatures ranging between 200 to 1140 degrees Celsius for a period of 8 hours. The starting powders had CaO:P2O5 ratios ranging from 1.165 to 1.22. Each composition was analysed for microstructural and associated crystal phase modifications with varying sintering temperatures, by scanning electron microscopy (SEM) and X-ray diffraction (XRD).

All compositions were shown by XRD to have an initial starting composition of Hydroxyapatite (HA) and Dicalcium Phosphate Anhydrous (DCPA). With increasing sintering temperatures, it was found that the initial composition readily transformed to beta-tricalcium phosphate(B-TCP) for all of the CaO:P2O5 ratios. However, it was found that the higher CaO:P2O5 ratio materials tended to retain residual HA. Sintering of all powders was found to have a densification effect on the microstructure of these compositions.

The sintering behaviour of calcium phosphates is extremely dependent on the CaO:P2O5 ratio of the material, influencing both the crystal as well as microstructural properties of the sintered components. This in-turn will have a strong influence on the behaviour of this biomaterial when placed in-vivo.