EFFECT OF TETRAVALENT DOPANTS ON RAMAN-SPECTRA OF TETRAGONAL ZIRCONIA

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 t he Raman spectra of t-ZrO2 was investigated. The frequencies of the Ra man modes that mere associated with Zr-O bond stretching decreased as doping with the oversized cation (Ce4+) increased and increased linear ly as doping with the undersized dopants (Ti4+, Ge4+, Sn4+) increased within the solubility limits of the dopants in 2Y-TZP. The frequency o f the 640 cm(-1) Raman band decreased as the square root of the unit-c ell volume increased, suggesting that the ionic size of dopants govern s 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 r elationship between the change in the tetragonality of t-ZrO2 solid so lutions and the tetravalent cation size, the intensity ratio of the Ra man modes at 609 and 640 cm(-1) (I-609/I-640) decreased as the ionic s ize decreased.