Thermodynamic Assessment of Phase Equilibria in the SrO-Al₂O₃ System

Abstract

Thermodynamic modeling of phase equilibria with the subsequent construction of the phase diagram of the SrO–Al2O3 system has been carried out. To calculate the activities of the oxide melt in the course of this work, we used the approximation of the theory of subregular ionic solutions, with the most optimal values of the energy parameters Q1112 = –104 349: Q1122 = –217 689; Q1222 = –104 436 J/mole. The results obtained for the liquidus line in this work are in good agreement with the literature experimental data. In the course of the calculation, the values of the equilibrium constants for the formation of strontium aluminates from the components of the oxide melt were estimated.

Mass spectrometric study and modeling of the thermodynamic properties of SrO–Al2O3 melts at high temperatures

“…All compounds were considered as single phase. It was found 16 that 3SrO·Al 2 O 3 and SrO·Al 2 O 3 compounds melted congruently at temperatures of 2063 and 2284 K, respectively, while 4SrO·Al 2 O 3 , SrO·2Al 2 O 3 , and SrO·6Al 2 O 3 had incongruent melting patterns. The 4SrO·Al 2 O 3 compound was calculated as a stable one down to the lowest temperature of the modeling.…”

“…Melting temperature of SrO is 2930 K 17 and that of Al 2 O 3 is 2327 K. 17 However, in modeling of the phase diagram of this system, these compounds were considered as metastable and were not included in the optimization since they had insufficient proofs of stability or were close in composition to the compounds that were reliably identified. [14][15][16] The optimization of the phase equilibria in the SrO-Al 2 O 3 system in studies [14][15][16] sometimes led to different conclusions on melting patterns of strontium aluminates. Ye et al 14 studied the SrO-Al 2 O 3 system using the CALPHAD approach 18 for the first time.…”

“…Makrovets et al 16 used the theory of subregular ionic solutions for thermodynamic assessment of the phase equilibria in the SrO-Al 2 O 3 system. All compounds were considered as single phase.…”

“…All compounds were considered as single phase. It was found 16 Optimization of the phase diagram of the SrO-Al 2 O 3 system was also carried out in the NUCLEA database 19,20 based on the experimental results by Massazza 6 and Ganits et al 9 It was found that Thermodynamic properties of the SrO-Al 2 O 3 system were reported in a number of studies. [21][22][23][24] Ueda et al 21 from the oxides at a temperature of 1723 K using a chemical equilibrium technique by equilibrating the corresponding strontiumaluminum oxide with molten copper in an atmosphere with controlled oxygen partial pressure.…”

“…It is to be mentioned that, according to the phase diagram of the SrO-Al 2 O 3 system, [14][15][16] sample 1 should correspond to the SrOÁ2Al 2 O 3 compound. However, it has been reported 13 In addition to SEM images, EPMA of the surface composition was carried out to confirm the contents of the components in the samples determined by X-ray fluorescence analysis.…”