The assessment of thermodynamic parameters in the Al₂O₃‐Y₂O₃ system and phase relations in the Y‐Al‐O system

Abstract

Thermodynamic parameters for solid and liquid phases in the Al2O3‐Y2O3 system are assessed using new calorimetric measurement for the YAG (Y3Al5O12), YAP (YAlO3) and YAM (Y4Al2O9) phases. The calculated phase diagram of the Al2O3‐Y2O3 system is in reasonable agreement with experimental data. According to the calculations, the YAP phase melts congruently and is stable down to the low temperatures, while the YAM phase disproportionates to a mixture of YAP and Y2O3 phases at temperatures below 1385 K. The calculated entropy of the YAG phase 300.1 J/(mol · K) is between 2 experimentally determined values 284.8 and 349.1 J/(mol · K). However, the difference between calculated and experimental values exceeds uncertainty limits of adiabatic calorimetry data. The enthalpies of melting for the YAG and YAP phases calculated in this study are in reasonable agreement with DTA measurements. The calculated enthalpy of melting for the YAG phase is not consistent with estimates based on solution calorimetric data. New independent measurement of the standard entropy and enthalpy of melting are desirable for the YAG, YAM and YAP phases. The liquidus surface and isothermal section at 2000 K for ternary Al‐Y‐O system are calculated in this study.

The investigation of YAlO3–NdAlO3 system, synthesis and characterization

“…It was reported, however, that YAP is stable if annealed as long as 300 hours in air at 1200°C, and melts congruently at 1940°C 15 . This observation is in agreement with a recent assessment of the Al 2 O 3 -Y 2 O 3 system where YAP was found to be stable down to low temperatures 16 . YAP with limited amount of dopant can be grown as a single crystal by the Czochralski technique but obtaining it as crystalline powder by wet chemical method is very difficult 17,18 .…”

Thermodynamic considerations in the stability of binary oxides for alternative gate dielectrics in complementary metal–oxide–semiconductors

“…An important issue that arises with the proposed reaction mechanism and that should be addressed in further experimental studies are the very low p O 2 's that are predicted by reaction (14) that would be necessary for an initially stoichiometric high-k oxide to become oxygen deficient enough for the silicide reaction (10) (18) are G (17) o = -2.96 kJ/mol [19], and G (18) o = -135 kJ/mol [19,58], respectively. Thus there is a much greater driving force to form the Y-silicate than the Zr-silicate, if, for example, SiO 2 is present at the interface between Si and the high-k oxide.…”

Oxide nanoparticles in an Al-alloyed oxide dispersion strengthened steel: crystallographic structure and interface with ferrite matrix

“…They have been determined to be yttrium-aluminum oxides by Electron Energy Loss Spectroscopy (EELS) [16] and Electron Dispersive X-Ray Spectroscopy (EDS) [17][18][19]. But there are at least four different yttrium aluminum oxides known in the Y-Al-O system [20], namely Y4Al2O9 (yttrium-aluminum-monoclinic, YAM), YAlO3 (yttrium-aluminumhexagonal, YAH), YAlO3 (yttrium-aluminum-perovskite, YAP) and Y3Al5O12 (yttriumaluminum-garnet, YAG). These possible variants complicate the identification of the oxide nanoparticles in Al-alloyed ODS ferrtic steels and their relationships with the ferrite matrix [16,17,[21][22][23][24][25][26].…”