Cation Interdiffusion and Phase Stability in Polycrystalline Tetragonal Ceria–Zirconia–Hafnia Solid Solution

Abstract

H a k o z a k i , Fukuoka 81 2, Japan Zr-Hf interdiffusions were carried out at 1350" to 1520°C for p o l y c r y s t a l l i n e t e t r a g o n a l s o l i d s o l u t i o n s of l4CeO2.86(Zrl-,Hf,)O2 with X = 0.02 and 0.10. Lattice and grain-boundary interdiffusion parameters were calculated from the concentration distributions by using Oishi and Ichimura's equation. Lattice interdiffusion coefficients were described by D = 3.0 X 1w exp[-623 (kJ/mol)/RT] cmz/s and grain-boundary interdiffusion parameters by SD' = 0.29 exp[-506 (kJ/mol)/RT] cm3/s. The cation diffusivity was lower than the anion diffusivity. The results were compared with diffusivities in the fluorite-cubic solid solution. The critical grain radii for stabilization of the tetragonal phase in Ce02-doped ZrOz were 11 and 6 pm for the solutions with 2 and 10 mol% HfOz substitution, respectively, both of which are much greater than in the Yz03-doped Zr02 solid solution. [

Sintering Kinetics of Plasma-Sprayed Zirconia TBCs

“…The parameters describing the geometry have been obtained experimentally, using mercury intrusion porosimetry and measurements on scanning electron microscope (SEM) micrographs. The surface diffusivity and activation energy are those reported for tetragonal ZrO 2 -3mol%Y 2 O 3 [11], while grain boundary diffusivities are for tetragonal 14CeO 2 -86(Zr 1-x Hf x )O 2 , with x=0.02 and 0.10 [12]. Ω is the volume of the unit cell, calculated from lattice parameters obtained by X-ray diffraction (XRD).…”

Effect of starting powders on the sintering of nanostructured ZrO2ceramics by colloidal processing

“…In the bicomponent sample, the tetragonal solid solution is formed at a higher temperature. Burger et al [30] demonstrated that this transformation occurs very slowly, because it depends on the diffusion rate of yttria, and the cation diffusion rate in yttria and zirconia is very low [41,42]. The experimental results presented by Burger et al showed that the diffusion-controlled phase transformation plays an important role in the densification behavior and in the inhibition of grain growth.…”

High-strain-rate superplasticity in oxide ceramics

“…In an extreme case of L5e, instantaneous de-bonding may occur along grain boundaries or interfaces. Using the diffusion data for Ce-doped tetragonal ZrO 2 [31] and an average dihedral angle of 1201, for which s is 0.45, and assuming that n ¼ 3 and s ¼ 30 MPa, we can calculate the critical case (b), for which d c ¼ 3e ¼ 3L. The results of this calculation are shown in Fig.…”