Density Dependence of Bending Strength and Vickers Hardness of Mullite-Silica and Zirconia Ceramics

Fired bodies were prepared from the clay mineral (kaolin and pyrophyllite) and Y2O3-stabilized zirconia powders. The bulk density (ρ) dependence of the bending strength (σ) and Vickers hardness (HV) were studied. The relation, σ∝HVn/m was obtained from the power law of σ∝ρn and HV∝ρm. Also, the relation, KIc∝σt, was proved. The fracture toughness (KIc) can be estimated easily from the measurement of σ. Moreover, an empirical equation χ=χ0exp(-ñP) was derived theoretically using the power law, where χ is a physical quantity related to the mechanical properties and P is the porosity.