Effect of zirconia nanoparticles on ZrO2-Bearing Lithium-Silicate glass-ceramic composite obtained by spark plasma sintering

The present study evaluated the effect of the zirconia nanoparticles on the physical and mechanical properties of ZrO2-bearing Lithium Silicate (ZLS) glass-ceramics fabricated by SPS method. Flexural strength of the rectangular bar shapes, fracture toughness by indentation method, Vickers microhardness with a diamond pyramid indenter and, the relative density of the samples were measured. Statistical analysis was performed and Weibull failure probabilities were obtained. The results of flexural strength were analyzed with Weibull distribution analysis (95% confidence interval). According to Weibull analysis, glass-ceramic without zirconia nanoparticles had the highest Weibull modulus (m = 15.96), while composite with 20 wt % zirconia nanoparticles showed the lowest Weibull modulus (m = 1.59). The glass-ceramic without zirconia nanoparticles exposed a lower probability of failure and a higher strength than composites contain zirconia nanoparticles according to Weibull analysis. Addition of the 20 wt % ZrO2, encourage SiO2 crystals to be stable. Results showed the addition of zirconia causes to decrease in the physical and mechanical properties such as bending strength from 262.21 to 60.78 MPa and Vickers microhardness from 7.96 +/- 0.13 to 4.87 +/- 0.65 GPa during the addition of zirconia nanoparticles from 0 wt % to 20 wt %. According to the XRD patterns and FESEM images, with increasing zirconia from 0 to 20 wt %, relative density from 99.93 to 92.34%, and crystallinity from 59.5 to 25.9% decreased. Overall, in amounts greater than 10%, the fraction of SiO2 increased and the lithium metasilicate phase formed.