Ceramics-Silikáty 48, (2) 41 - 48 (2004)

In this third paper of a series on the effective elastic properties of alumina-zirconia composite ceramics the calculation of the effective elastic moduli of polycrystalline alumina (corundum, i.e. trigonal α-Al₂O₃) and tetragonal zirconia (t-ZrO₂) from monocrystal data is recalled. The values estimated via the Voigt-Reuss-Hill average are compared with the most reliable published values. Standard formulae and theorems of elasticity theory and micromechanics are used as consistency tests for calculated and measured values. For dense polycrystalline α- Al₂O₃ the most reliable values calculated from monocrystal data are 402.7 GPa for the tensile modulus, 163.4 GPa for the shear modulus, 250.9 GPa for the bulk modulus and 0.23 for the Poisson ratio. In this case all the calculated values are in reasonable agreement with the measured values, taking into account the relatively large statistical errors of the latter. For dense polycrystalline zirconia values calculated from monocrystal data are 201.1 GPa for the tensile modulus, 78.7 GPa for the shear modulus, 150.6 GPa for the bulk modulus and 0.28 for the Poisson ratio. There is a discrepancy between calculated and measured values, especially for the bulk modulus, the measured values of which are approx. 180 ± 10 GPa and the Poisson ratio, the measured values of which are approx. 0.31. Possible reasons of this discrepancy are discussed.