The effect of alpha-lithium aluminate incorporation on the properties of bovine bone-derived hydroxyapatite

The aim of the present paper was to investigate the effect of alpha-lithium aluminate (α-LiAlO₂) incorporation (1, 3, and 5 wt%) on the properties (grain morphology, activation energy for grain growth, decomposition behavior, shrinkage, densification, hardness, fracture toughness, brittleness index, compressive strength, and in vitro bioactivity) of bovine hydroxyapatite (BHA) sintered between 900 and 1300 °C. BHA without α-LiAlO₂ incorporation exhibited the shrinkage of 12.02 ± 0.52%, density of 2.86 ± 0.47 g/cm³, relative density of 90.77 ± 1.51%, porosity of 1.12 ± 0.75%, hardness of 4.19 GPa ± 0.31, fracture toughness of 0.99 ± 0.13 MPam^1/2, brittleness index of 4.24 ± 0.31 μ^−1/2, and compressive strength of 115.75 ± 4.27 MPa, when it was sintered at 1300 °C. It decomposed to beta- and alpha-tricalcium phosphate (β- and α-TCP) as 4.7%, in totally. The activation energy for grain growth of pure BHA was calculated as 77.9 kcal/mol, as 57.61, 59.95, and 71.64 kcal/mol for 1, 3, and 5 wt% α-LiAlO₂ incorporated BHAs, respectively. The highest properties for α-LiAlO₂ incorporated BHAs were obtained at the sintering temperature of 1200 °C at amount of 5 wt% α-LiAlO₂. For this composite, the density of 2.87 g/cm³, fracture toughness of 1.95 ± 0.18 MPam^1/2, compressive strength of 218.33 ± 14.02 MPa, and brittleness index of 1.96 ± 0.21 μ^−1/2 were obtained. As a result of the in vitro bioactivity test, the bioactivation for this composite became clearly visible in 14 days. The results show that the incorporation of 5 wt% α-LiAlO₂ into BHA contributes to increasing the sinterability and properties of BHA without decreasing its bioactivity.