Effect of tetravalent dopants on Raman spectra of tetragonal zirconia

Abstract

Tetragonal zirconia solid solutions were prepared by the additions of ceria, titania, germania, and cassiterite into 2-mol%-Y2O3-stabilized t-ZrO2 (2Y-TZP), and the effect of the dopant size on the changes in the Raman spectra of t-ZrO2 was investigated. The frequencies of the Raman modes that mere associated with Zr-O bond stretching decreased as doping with the oversized cation (Ce4+) increased and increased linearly as doping with the undersized dopants (Ti4+, Ge4+, Sn4+) increased within the solubility limits of the dopants in 2Y-TZP. The frequency of the 640 cm(-1) Raman band decreased as the square root of the unit-cell volume increased, suggesting that the ionic size of dopants governs the Raman mode that is related to the short Zr-O bond between two Zr-O bonds in t-ZrO2 solid solutions. Although there was no consistent relationship between the change in the tetragonality of t-ZrO2 solid solutions and the tetravalent cation size, the intensity ratio of the Raman modes at 609 and 640 cm(-1) (I-609/I-640) decreased as the ionic size decreased.