Two step sintering of a novel calcium magnesium silicate bioceramic: Sintering parameters and mechanical characterization

Two-step sintering (TSS) was applied to control the grain growth during sintering of a novel calcium magnesium silicate (Ca3MgSi2O8 – Merwinite) bioceramic. Sol–gel derived nanopowders with the mean particle size of about 90 nm were sintered under different TSS regimes to investigate the effect of sintering parameters on densification behavior and grain growth suppression. Results showed that sintering of merwinite nanopowder under optimum TSS condition (T1 = 1300 °C, T2 = 1250 °C) yielded fully dense bodies with finest microstructure. Merwinite compacts held at T2 = 1250 °C for 20 h had the average grain size of 633 nm while the relative density of about 98% was achieved. Mechanical testing was performed to investigate the effect of grain growth suppression on the hardness and fracture toughness. Comparison of mechanical data for samples sintered under two sintering regimes, including TSS and normal sintering (NS), showed TSS process resulted in significant enhancement of fracture toughness from 1.77 to 2.68 MPa m1/2.