Mechanical properties of PSZ-reinforced biphasic calcium phosphate bone substitute sintered in a conventional furnace and by microwave irradiation

Abstract The aim of this study was to compare the mechanical properties of partially stabilized nanozirconia (PSZ)‒reinforced biphasic calcium phosphate (BCP) bone substitutes sintered in an electric furnace and by microwave irradiation. The BCP powder was mixed with different amounts (0–3 vol%) of PSZ and formed using an isostatic press. The green bodies were then sintered at 1200 °C through two different techniques: traditional sintering process using an electric furnace and rapid sintering process by a microwave oven. The phase composition and microstructure of the samples were analyzed using X-ray diffractometry, scanning electron microscopy and energy dispersive X-ray spectroscopy. The fracture toughness (K Ic ) and compressive strength of the samples were also determined. The maximum K Ic and compressive strength values of 2.33 MPa m 0.5 and 170 MPa were obtained for those BCP bodies reinforced with 1 vol% of PSZ, in the electric furnace. In the case of microwave irradiation, the maximum K Ic value (1.88 MPa m 0.5 ) was also achieved by employing 1 vol% of PSZ. Moreover, the presence of PSZ nanoparticles caused phase transformation of hydroxyapatite into β -tricalcium phosphate. Although density of the samples was enhanced due to the higher energy efficiency of microwave irradiation, this process encouraged β to α phase transformation of tricalcium phosphate and hence decreased the K Ic .