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High‐temperature mass spectrometric study of the vaporization processes and thermodynamic properties in the Gd 2 O 3 ‐Y 2 O 3 ‐HfO 2 system
Author(s) -
Kablov Eugene N.,
Stolyarova Valentina L.,
Lopatin Sergey I.,
Vorozhtcov Viktor A.,
Karachevtsev Fedor N.,
Folomeikin Yuriy I.
Publication year - 2017
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.7892
Subject(s) - vaporization , chemistry , analytical chemistry (journal) , mass spectrometry , vapor pressure , organic chemistry , chromatography
Rationale The refractory properties of the Gd 2 O 3 ‐Y 2 O 3 ‐HfO 2 system are considered promising for the production of many high‐temperature materials, e.g., thermal barrier coatings and casting molds for gas turbine engine blades. At high temperatures, components of the Gd 2 O 3 ‐Y 2 O 3 ‐HfO 2 system may vaporize selectively and this may significantly change the physicochemical properties of the materials. Therefore, information on vaporization processes and thermodynamic properties of the Gd 2 O 3 ‐Y 2 O 3 ‐HfO 2 system is of great importance. Methods The vaporization processes and thermodynamic properties of the Gd 2 O 3 ‐Y 2 O 3 ‐HfO 2 system were studied using high‐temperature Knudsen effusion mass spectrometry with a MS‐1301 mass spectrometer. Vaporization was carried out using a tungsten twin effusion cell containing the samples under study and pure Gd 2 O 3 as a reference substance. Electron ionization at an energy of 25 eV was employed in the present study. Results It was shown that at a temperature of 2500 K the vapor over the samples in the Gd 2 O 3 ‐Y 2 O 3 ‐HfO 2 system consisted of the GdO, YO and O vapor species. The Gd 2 O 3 and Y 2 O 3 activities in the samples in the Gd 2 O 3 ‐Y 2 O 3 ‐HfO 2 system as well as their vaporization rates were derived from the partial pressures of the vapor species. Using these data the HfO 2 activities, the Gibbs energy of mixing and the excess Gibbs energy in this system were calculated at 2500 K. Conclusions The thermodynamic properties of the Gd 2 O 3 ‐Y 2 O 3 ‐HfO 2 system, i.e., the component activities in the samples and the excess Gibbs energy, obtained in the present study at 2500 K, exhibited negative deviations from ideal behavior. The concentration dependence of excess Gibbs energy of the Gd 2 O 3 ‐Y 2 O 3 ‐HfO 2 system was approximated with an empirical equation. Copyright © 2017 John Wiley & Sons, Ltd.