The influence of silicon dioxide on the stability of the phase composition and mechanical properties of alumina-toughened zirconia-based ceramics

The influence of SiO$_{2}$ impurity (with a concentration varying from 0 to 10 mol.%) on the stability of tetragonal ZrO$_2$ ($t$-ZrO$_{2}$) and on a set of micro- and macromechanical properties of calcia-stabilized ($C_{\mathrm{CaO}}$ = 6.5 mol.%) alumina-toughened ($C_{\mathrm{Al}_2\mathrm{O}_3}$ = 5.8 mol.%) zirconia-based ceramics (ATZ ceramics) has been studied. It has been found that the introduction of SiO$_{2}$ ($C_{\mathrm{SiO}_{2}}$ = 5 mol.%) raises fracture toughness $K_c$ by nearly twofold (from 7.05 to 12.43 MPa m$^{1/2}$), slightly decreases hardness $H$ (from 12.75 to 10.9 GPa), and improves ultimate compression strength $\sigma_S$ (from 2.44 to 2.73 GPa) and ductility (compression strain $\varepsilon$ grows from 5.3 to 7.3%) of ATZ ceramics. It has been shown that the above improvements were achieved by means of a reduction in $t$-ZrO$_2$ stability.