Tetragonal—Monoclinic Phase Transition Enthalpy and Temperature of ZrO₂‐CeO₂ Solid Solutions

Abstract

DSC (differential scanning calorimeter) measurements were performed to investigate the tetragonal‐monoclinic (t‐m) transition enthalpy of the compositionally homogeneous ZrO2‐X mol% CeO2 solid solution of X= 0, 4, 8, and 12. The transition enthalpy decreases linearly with an increase of CeO2 content. The m → t transition enthalpy on heating agreed well with the inverse t → m one obtained during cooling. With increasing X, the DSC peak broadens and the transition temperature distribution of each sample increases, while the thermal hysteresis is almost independent of X.

Phase diagrams and thermodynamics of rare-earth-doped zirconia ceramics

“…For thermodynamic studies, the equilibrium temperature (T 0 , where the Gibbs energies of monoclinic and tetragonal phases are identical) is undoubtedly important. Due to the experimental difficulty in the direct measurement of the T 0 temperature, it is customary to calculate it empirically by the equation [11] (1) or (2) The high-temperature cubic fluorite-type structure can be stabilized to lower temperatures by doping with certain amounts of RE elements, so that the destructive tetragonal ↔ monoclinic transition can be avoided. Nevertheless, in some composition range, even the cubic phase is not quenchable due to a diffusionless transformation from cubic to another kind of tetragonal phase T' [12,13].…”

TEM Observation of Reaction at the Interface between Yttria-Doped Ceria and Yttria-Stabilized Zirconia

“…Other oxide-doped CeO -ZrO systems are expected to follow this basic phase transition behavior, though the stability of each fluorite phase is influenced by the kind of dopants. Yoshimura et al (5)(6)(7)(8) have explained phase equilibria in the system ZrO -CeO and established metastable-stable phase diagrams. The transport properties of oxide ion strongly depend on the mixing of cerium and zirconium ions as well as dopant concentration of aliovalent cations such as Ca or Y (9, 10).…”

Phase transformation studies on YSZ doped with alumina. Part 2: Yttria segregation

“…6(c)) increased for longer annealing times at 800 • C. It has been found previously that with increasing the Y 2 O 3 concentration, the intensity ratio (I 4 /I 6 ) decreases. This explains the lower oxygen displacement at higher concentrations of Y 2 O 3 [4]. The variation of I 4 /I 6 ratio could be due to the deficiency of yttria and/or alumina in YSZ.…”

“…Fig. 1 depicts to the ZrO 2 -Y 2 O 3 phase diagram together with T0-lines proposed by Yashima et al [4]. Numerous phase diagrams correspond to YSZ could be found in the literature [5][6][7].…”

“…Stabilizing the high temperature phases at room temperate results in an enhancement in the density of the oxygen vacancies and enrichment in the oxygen-ion conductivity. Higher ionic conductivity facilitates to exploit this stabilized zirconia as an electrolytic material [4,8]. Y-TZP is an O 2− ion-conducting material at temperatures above 300 • C. The conductivity requirement for the electrolyte determines the operating temperature of the gas sensors to be about 1000 • C. Hence, the stability and phase transformations of the YSZ electrolyte at 1000 • C are of great importance.…”