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Two different hydroxyapatites with the particle sizes of 3.9 and 1.69 μm were chosen. Slurries with initial hydroxyapatite concentration of 15 vol% were prepared. Different cooling rates from 2 to 14°C/min were utilized. The specimens were sintered at different temperatures of 1250–1350°C. The phase composition (by X‐Ray Diffraction), microstructure (by Scanning Electron Microscopy), mechanical characteristics, and the porosity of sintered samples were assessed. The porosity of the sintered samples was in range of ~57–83%, and the compressive strength varied from ~1.7 to 15 MPa. The mechanical strength of the scaffolds increased as a function of cooling rate and sintering temperature.

The most important characteristic of biomaterial as bone-repairing material, in addition to biocompatibility and appropriate porosity, is providing mechanical strength complying with injured tissue. In the present work, slurry with 15 vol% HA prepared from calcinated hydroxyapatite. The prepared slurry freeze casted unidirectionally with the cooling rate of 8°C/min from the ambient temperature. Then, green bodies freeze-dried for 72h following with sintering at different temperatures of 1250-1350°C with intervals of 25°C. The results showed that lamella space and porosity decreases with temperature while compressive strength and shrinkage goes up. Total porosity has a range of 75-83% while has a compressive strength of ~2-8 MPa. The sintered sample at 1350°C, with 75% porosity, which has a ~ 8 MPa compressive strength, chose to be the optimum. Also, some dendritic branch like structure and bridges can be seen on the internal walls of lamellae which can improve mechanical properties. These features may improve adhesion and growth of osseous cells.

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Scaffolds have to meet exacting physical, chemical, and biological criteria to function successfully, and those criteria vary with the type of tissue being repaired. In the present work, slurry with different initial content of 7.5-22.5 vol% HA prepared from calcinated hydroxyapatite. The prepared slurries freeze casted unidirectionally with the different cooling rate of 2-14°C/min with intervals of 3°C/min from the ambient temperature. Then, green bodies freeze-dried for 72h following with sintering at temperatures of 1350°C. The results showed that compressive strength goes up with cooling rate and initial content. Total porosity has a range of 66-88% while has a compressive strength of ~0.4-18 MPa. Porosity size has a value of 20-200 μm by initial content and cooling rate. Based on strength and porosity, the specimen with initial content and cooling rate of 15 vol% and 5°C/min, respectively, chose to be the optimum. This specimen has a compressive strength and porosity size of 5.26 MPa and 88 μm, respectively. The compressive strength value of the mentioned lamellar HA scaffolds was in the range of the values reported for human proximal tibia.