Phase transformation of sol-gel derived ZrO2-2RE2O3 (RE=Sm,Gd and Dy) spun fibres by ageing in humid atmosphere

Zirconia fibres doped with 2 equivalent mol% of RE2O3 (RE = Sm, Gd and Dy) were prepared by spinning of acetate derived sols followed by calcination of the gel fibres thus obtained at 900°-1300°C for 1 h. The oxide fibres were characterized by X-ray diffraction (XRD) analysis. The fibres containing only tetragonal (t) phase were aged under controlled humidity at 150°-300°C for 8 h and in addition at 200°C for 2 and 5 h. The aged samples were then characterized by XRD analysis. Dy3+-doped zirconia showed the maximum tendency to undergo phase transformation from tetragonal (t) to monoclinic (m) phase because of its increased tendency for hydrolysis