Assessment of thermodynamic functions in the ZrO2–Sm2O3–Al2O3 system

Abstract

a b s t r a c tA thermodynamic database for the ZrO 2 -Sm 2 O 3 -Al 2 O 3 system is derived using CALPHAD approach taking into account experimental data on isothermal sections and liquidus surface. The compound energy formalism and two-sublattice partially ionic liquid model are applied for phase descriptions in the system. Thermodynamic parameters for the binary systems of ZrO 2 -Sm 2 O 3 and Sm 2 O 3 -Al 2 O 3 are assessed in this study based on phase equilibrium and calorimetric data for binary systems taking into account sub-solidus phase relations in the ternary system of ZrO 2 -Sm 2 O 3 -Al 2 O 3 . It is demonstrated that the phase equilibria between solid phases in the ternary ZrO 2 -Sm 2 O 3 -Al 2 O 3 system constrain thermodynamic parameters in the binary systems ZrO 2 -Sm 2 O 3 and Sm 2 O 3 -Al 2 O 3 . The ternary interaction parameter is assessed for the liquid phase using experimental data on the liquidus surface. Isothermal sections at 1523 and 1923 K, the liquidus surface and vertical sections are calculated and compared with available experimental data. The experimental data are generally well reproduced by calculations with exception that in contrast to experimental data a primary crystallisation field for pyrochlore was indicated in calculations. Additionally, differences between experimental and calculated liquidus surface phase diagram were found in the Sm 2 O 3 -rich corner. Because of these differences several inconsistencies were also found for vertical sections.

Mass spectrometric study of ceramics in the Sm2O3‐ZrO2‐HfO2 system at high temperatures

“…Nevertheless, the phase diagrams of the corresponding binary systems have been extensively examined. The Sm 2 O 3 ‐HfO 2 phase equilibria were studied experimentally, 27,28 while information on those in the Sm 2 O 3 ‐ZrO 2 system was not only obtained using various experimental methods, 29–32 but also optimized by the Calphad approach 32,33 . The main equilibrium phases in the systems mentioned were the solid solutions based on the Sm 2 O 3 , ZrO 2 , and HfO 2 polymorphic modifications and on the intermediate compounds with the pyrochlore structure, namely Sm 2 Hf 2 O 7 and Sm 2 Zr 2 O 7 .…”

“…However, valuable thermodynamic information has been obtained for the corresponding binary systems. In the Sm 2 O 3 ‐ZrO 2 system, the thermodynamic properties found previously corresponded mainly to the samarium zirconate compound, and they were reviewed by Wang et al 32 and Fabrichnaya and Seifert 33 . The physicochemical properties of samarium hafnate were also obtained using the drop calorimetric method, 42 laser flash analysis, and dilatometry 14 .…”

Thermal properties of La2O3-YSZ powder fabricated by heterogeneous precipitation

“…In order to reduce thermal conductivity and improve phase stability of the TBC, YSZ coatings have been modified by doping with rare oxides such as Al 2 O 3 , La 2 O 3 , Nd 2 O 3 , Er 2 O 3 , CeO 2 , and Sc 2 O 3 , providing coatings with low thermal conductivity and a high thermal cycle life [5][6][7][8][9]. Among the many rare oxides, La 2 O 3 , in particular, is highly effective in reducing the densification and thermal conductivity of YSZ [10].…”