High-temperature X-ray diffraction and specific heat studies on GdAlO3, Gd3Al5O12 and Gd4Al2O9

Up-Date of a Thermodynamic Database of the ZrO2-Gd2O3-Y2O3-Al2O3 System for TBC Applications

“…New heat capacity data were used to describe Gd 4 Al 2 O 9 and Gd 3 Al 5 O 12 phases. New data on heat capacity of the GdAlO 3 [13] and Gd 2 Zr 2 O 7 [14] phases appeared to be in reasonable agreement with data used in Ref 15. The use of new data for lattice stabilities, compounds and solid solutions resulted in changes both in binary Gd 2 O 3 -Al 2 O 3 and ternary ZrO 2 -Gd 2 O 3 -Al 2 O 3 systems: the melting character of Gd 4 Al 2 O 9 phase changed to congruent and the type of invariant reaction between Gd 4 Al 2 O 9 , fluorite, Gd 2 O 3 _B and liquid phase changed to transition U type.…”

“…[35][36][37][38] Also, the eutectoid reaction F = M + Pyr mentioned above can not be investigated experimentally due to kinetic reasons. Recently, heat capacity measurements for the GdAlO 3 (GdAP), Gd 4 Al 2 O 9 (GdAM) and Gd 3 Al 5 O 12 (GdAG) phases have been published by Chaudhury et al [13] The comparison of these new measurements with the data of Kolitsch [39] for the GdAP phase revealed very good agreement with the data used in work of Lakiza et al [15] and therefore these data were not changed. The present description takes into account the C P data of Chaudhury et al [13] for the GdAM and GdAG phases.…”

“…Recently, heat capacity measurements for the GdAlO 3 (GdAP), Gd 4 Al 2 O 9 (GdAM) and Gd 3 Al 5 O 12 (GdAG) phases have been published by Chaudhury et al [13] The comparison of these new measurements with the data of Kolitsch [39] for the GdAP phase revealed very good agreement with the data used in work of Lakiza et al [15] and therefore these data were not changed. The present description takes into account the C P data of Chaudhury et al [13] for the GdAM and GdAG phases. The calculated phase diagram of the Gd 2 O 3 -Al 2 O 3 system along with experimental data is presented in Fig.…”

“…It should be mentioned that in the previously accepted thermodynamic description of the Gd 2 O 3 -Al 2 O 3 system of Lakiza et al, [15] the character of the Gd 4 Al 2 O 9 (GdAM phase) melting was incongruent. Due to the change in the parameters of oxides and taking into account new heat capacity measurements, [13] the character of melting of the GdAM phase changed to congruent. It should be mentioned that it is still under discussion in the literature if the GdAM phase melts Section I: Basic and Applied Research congruently or by a peritectic reaction.…”

“…Since the time of publication, new data on the thermodynamics of transformations in the ZrO 2 , [11] Gd 2 O 3 and Y 2 O 3 [12] have been published. Additionally new heat capacity measurements for the GdAlO 3 , Gd 4 Al 2 O 9 and Gd 3 Al 5 O 12 phases have been performed by Chaudhury et al [13] and of the Gd 2 Zr 2 O 7 , pyrochlore by Liu et al [14] In the previous work of Lakiza et al, [15] the heat capacities of the Gd 4 Al 2 O 9 and Gd 3 Al 5 O 12 phases were described according to the Neumann-Kopp rule and therefore new data should be included into the database. The heat capacity of the Gd 2 Zr 2 O 7 and GdAlO 3 phases used in work of Lakiza et al [15] needs to be compared with more recent data.…”