Effect of quartz particle size on the strength of triaxial porcelain

The effect of the quartz component on strength, σ f , and fracture toughness, K Ic, of a triaxial porcelain was studied by varying the size distribution of the quartz particles. Both σ f and K Ic were found to increase and then to pass over a maximum as the quartz distribution became finer. Improvements in σ f and K Ic of more than a factor of 2 were achieved. The flaw size that controlled failure was shown to equal the maximum quartz particle size in the material containing the coarsest quartz component and to be a constant independent of the quartz size in the other materials. The toughness increase was attributed to microcrack toughening of the glass matrix, the microcracks being formed by thermal mismatch stresses between the quartz particles and the glass matrix on cooling from the sintering temperature.