Neutron Diffraction Study of Tetragonal Zirconias containing Tetravalent Dopants

Abstract

In tetragonal zirconia, the cation is coordinated by two interpenetrating tetrahedra of oxygen ions, implying two different cation-oxygen bond lengths. Neutron powder diffraction was used to study tetragonal ZrO₂–2 mol% Y₂O₃ incorporating various amounts of the different tetravalent ions Ge, Ti, Sn and Ce. Precise and accurate values for the lattice parameters and the variable oxygen position parameter have been obtained, and from these the bond lengths derived. The results are compared with those from an earlier X-ray and Raman study on the same materials. Of interest are the confirmation of the increase in cell volume occurring when Zr is replaced by the smaller Sn ion, and the observation of departures from Vegard’s law in the case of substitution of Zr by Ti.