High‐temperature mass spectrometric study of the vaporization processes and thermodynamic properties of samples in the Bi2O3‐P2O5‐SiO2 system

Vorozhtcov

et al. 2018

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Vaporization of ceramics based on the La O -Y O -HfO system at 2337 K led to selective transition of La O and Y O to the gaseous phase, with the La O vaporization rate being higher than that of Y O . The directions of composition changes of samples due to their vaporization at 2337 K were determined. In the solid solution of this system negative deviations from ideal behavior were found. The ability to estimate the excess Gibbs energies in the solid solution of the La O -Y O -HfO system by the Kohler method was shown.

Section: Resultssupporting

confidence: 80%

Section: Resultsmentioning

confidence: 99%

Vaporization and thermodynamics of ceramics based on the La₂O₃‐Y₂O₃‐HfO₂ system studied by the high‐temperature mass spectrometric method

Vorozhtcov

et al. 2018

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“…Secondly, information on the phase diagram of the Gd 2 O 3 ‐Y 2 O 3 ‐HfO 2 system was not found. However, the phase diagram is necessary since the semi‐empirical methods discussed can be applied correctly only to homogeneous liquid solutions or to glasses and glass‐forming melts, as was done, for instance, by others . Thirdly, the weaker negative deviations from ideality obtained in the present study than those predicted on the basis of the data for the corresponding binary systems may be because the semi‐empirical methods applied in this study assume independence of interactions between components in a binary system on the presence and content of a third component of a ternary system and, consequently, disregard three‐component interactions.…”

Section: Resultsmentioning

confidence: 85%

High‐temperature mass spectrometric study of the vaporization processes and thermodynamic properties in the Gd₂O₃‐Y₂O₃‐HfO₂ system

Лопатин

et al. 2017

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“…In the present study an attempt was made to calculate the excess Gibbs energies of the Y 2 O 3 ‐ZrO 2 ‐HfO 2 system based on the corresponding values in the constituting binary systems using the Kohler method:

normalΔ G^{E} = {[Δ {G_{YH}}^{E}]}_{\frac{x_{normalY 2 normalO 3}}{x_{HfO 2}}} {(x_{{normalY}_{2} {normalO}_{3}} + x_{Hf {normalO}_{2}})}^{2} + {[Δ {G_{YZ}}^{E}]}_{\frac{x_{normalY 2 normalO 3}}{x_{ZrO 2}}} {(x_{{normalY}_{2} {normalO}_{3}} + x_{Zr {normalO}_{2}})}^{2} + {[Δ {G_{ZH}}^{E}]}_{\frac{x_{ZrO 2}}{x_{HfO 2}}} {(x_{Zr {normalO}_{2}} + x_{Hf {normalO}_{2}})}^{2},

where

{[Δ {G_{YH}}^{E}]}_{\frac{x_{normalY 2 normalO 3}}{x_{HfO 2}}}

{[Δ {G_{YZ}}^{E}]}_{\frac{x_{normalY 2 normalO 3}}{x_{ZrO 2}}}

and

{[Δ {G_{ZH}}^{E}]}_{\frac{x_{ZrO 2}}{x_{HfO 2}}}

are the values of the excess Gibbs energies in the Y 2 O 3 ‐HfO 2 , Y 2 O 3 ‐ZrO 2 and ZrO 2 ‐HfO 2 systems, respectively, with the ratios of components in the binary systems being the same as in the ternary system. The applicability of the Kohler approach for this purpose was successfully demonstrated previously in the calculation of the thermodynamic properties in the Bi 2 O 3 ‐P 2 O 5 ‐SiO 2 , Gd 2 O 3 ‐Y 2 O 3 ‐HfO 2 and La 2 O 3 ‐Y 2 O 3 ‐HfO 2 systems at high temperatures …”

Section: Discussionmentioning

confidence: 68%

Vaporization and thermodynamics of ceramics in the Y₂O₃‐ZrO₂‐HfO₂ system

Vorozhtcov

et al. 2019

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Rationale:The Y 2 O 3 -ZrO 2 -HfO 2 system is a promising base for a wide range of high-temperature materials including ultra-high-temperature ceramics. At high temperatures of synthesis and application of these ceramics the components may vaporize selectively, leading to changes in chemical composition and exploitation properties of the materials. Therefore, study of the vaporization processes of ceramics based on the Y 2 O 3 -ZrO 2 -HfO 2 system is of great importance. The thermodynamic properties of the Y 2 O 3 -ZrO 2 -HfO 2 system obtained in the present study can be used for the prediction and modeling of the physicochemical properties of ultra-high-temperature ceramics.Methods: The present study was carried out by the high-temperature Knudsen effusion mass spectrometric method using the MS-1301 mass spectrometer, which was designed to study the physicochemical properties of non-volatile compounds.Vapor species effusing from the tungsten twin effusion cell, which was used for vaporization of the samples under study, were ionized by electron ionization with an ionization energy of 30 eV. Results: The gaseous phase over the samples of the Y 2 O 3 -ZrO 2 -HfO 2 system was shown to consist of the YO, ZrO, ZrO 2 , HfO and O vapor species at a temperature of 2660 K. The YO, ZrO, ZrO 2 , HfO and O partial vapor pressures were obtained in a wide concentration range by the complete isothermal vaporization method, which allowed determination of the activities of Y 2 O 3 , ZrO 2 and HfO 2 , Gibbs energies of mixing and excess Gibbs energies of the Y 2 O 3 -ZrO 2 -HfO 2 system at 2660 K. Conclusions: Negative deviations from the ideal behavior were shown in the solid solutions of the Y 2 O 3 -ZrO 2 -HfO 2 system at 2660 K. The excess Gibbs energies found in the present study were approximated using the Redlich-Kister representation. The possibility of application of the Kohler method to estimate the excess Gibbs energies of the Y 2 O 3 -ZrO 2 -HfO 2 system was considered.