Effect of lanthanum oxide additive on the sinterability, physical/mechanical and bioactivity properties of hydroxyapatite-alpha alumina composite

Journal of the Australian Ceramic Society, cilt.1, sa.1, ss.1-14, 2019 (SCI İndekslerine Giren Dergi)

The aimof this study was to evaluate the effect of lanthanumoxide (La2O3) additive on the microstructural, physical, mechanical,

and in vitro bioactivity properties of hydroxyapatite (HA)-alpha alumina (α-Al2O3) composite. The monolithic HA as well as

composites of HA-5 wt% α-Al2O3 and HA-5 wt% Al2O3-(0.5 wt%, 1.5 wt%, and 2.5 wt%) La2O3 were uniaxially pelleted at

350 MPa with a size of ∅11 and 11 mm2 and sintered at the temperatures ranging from 1100 to 1300 °C for 4 h. The highest

mechanical strength values of 130.20 ± 6.22 MPa, 60.27 ± 9.93 MPa, and 0.96 ± 0.05 MPa m1/2 for compressive strength

(σcompressive), three-point bending strength (σthree-point bending), and fracture toughness (Kıc) were obtained for monolithic HA,

respectively. While the decomposition (transformation of HA to secondary phases such as beta-tricalcium phosphate (β-TCP),

alpha-tricalcium phosphate (α-TCP), and calcium oxide (CaO)) ratio was about 5.7% for monolithic HA, it attained to 27.4% for

HA-5wt% α-Al2O3 composite. However, addition of La2O3 to HA-5 wt% α-Al2O3 composite contributed to decreasing of

decomposition from 27.4 to 22.0%. The mechanical strength values of σcompressive of 214 ± 32.50 MPa, σthree-point bending of 75.70

± 2.40MPa, and Kıc of 1.95 ± 0.10 MPa m1/2 were obtained for HA-5wt% α-Al2O3 composite. SEM images exhibited that α-

Al2O3 led to decreasing the in vitro bioactivity ofHA. However, La2O3 additive contributed to improvement of the mechanical as

well as bioactivity properties of HA-5 wt% α-Al2O3 composite. HA-5 wt% α-Al2O3-0.5 wt% La2O3 composite can be used as a

bioceramic in human body, because it has enough mechanical properties as well as its desirable in vitro bioactivity.