Sintering of alumina ceramics reinforced with a bioactive glass of 3CaO.P₂O₅-SiO₂-MgO system

Abstract

Alumina-based ceramics, Al2O3, exhibit a combination of properties which favor its use as biomaterial, specifically as structural dental prosthesis. Its most important properties as biomaterial are its elevated hardness, chemical stability and biocompatibility. Usually, Al2O3 is processed by solid-state sintering at a temperature of about 1600 oC, but it is very difficult to eliminate the porosity due to its diffusional characteristics. The objective of this work was the development and characterization of sintered Al2O3 ceramics, densified with a transient liquid phase formed by a bioactive 3CaO.P2O5-SiO2-MgO glass. Powder mixtures of 90 wt.% Al2O3 and 10 wt.% bioglass were milled, compacted and sintered at 1200 oC to 1450 oC. Comparatively, monolithic Al2O3 samples were sintered at 1600 oC/120 min. The sintered specimens were characterized by relative density, crystalline phases, microstructure and mechanical properties. The results indicate that the specimen sintered at 1450 oC/120 min present the best properties. Under this sintering condition, a relative density of 95% was reached, besides hardness higher than 9 GPa and fracture toughness of 6.2 MPa.m1/2. XRD analysis indicate alumina (\αAl2O3), whitlockite (3CaO.P2O5) and diopsite [3(Ca,Mg)O.P2O5], as crystalline phases. Comparatively, monolithic sintered Al2O3 samples presented 92% of relative density with 17.4 GPa and 3.8 MPa.m1/2 of hardness and fracture toughness respectively.