High‐temperature mass spectrometric study of the thermodynamic properties in the Sm₂O₃‐ZrO₂‐HfO₂ system

Abstract

Rationale The Sm2O3‐ZrO2‐HfO2 system is a promising base for the development of a wide spectrum of new refractory materials. Reliable data on thermodynamic properties in this system are of significant importance for planning the preparation and application of high‐temperature ceramics. Especially, they can be useful for calculation of the unknown phase equilibria in this system. Methods The thermodynamic properties of the Sm2O3‐ZrO2‐HfO2 system were studied by the high‐temperature mass spectrometric method. The samples in the system under consideration synthesized by the solid‐state method were vaporized from a tungsten twin effusion cell using a MS‐1301 magnetic sector mass spectrometer. Ionization of the vapor species effusing from the cell was carried out by electrons at an energy of 25 eV. Results It was shown that, at temperatures below 2500 K, the main vapor species over the ceramics based on the Sm2O3‐ZrO2‐HfO2 system were SmO, Sm, and O corresponding to vapor composition over pure Sm2O3. The SmO, Sm, and O partial vapor pressures over the samples and the Sm2O3 activities were obtained in the temperature range 2319–2530 K. This allowed the excess Gibbs energy values to be determined. For comparison, the excess Gibbs energies in the Sm2O3‐ZrO2‐HfO2 system were also calculated by the semi‐empirical Kohler, Toop, Redlich‐Kister, and Wilson methods and optimized by the statistical thermodynamic Generalized Lattice Theory of Associated Solutions (GLTAS). Conclusions The thermodynamic data calculated by the semi‐empirical approaches at 2423 K were shown to be lower than the experimental values. However, the Toop and Wilson methods were found to be useful for evaluation of the excess Gibbs energy values at the Sm2O3 mole fraction less and higher than 0.32, respectively. The self‐consistent thermodynamic description of the Sm2O3‐ZrO2‐HfO2 system was derived at high temperatures by optimization of the experimental results using the GLTAS.

Knudsen effusion mass spectrometry: Current and future approaches

“…[203][204][205][206][207][208][209] It should be mentioned that, although not included in the reviews discussed earlier, recent experimental data obtained using KEMS at high temperatures on oxide systems and materials for nuclear We next focus on the latest experimental data on the vaporization and thermodynamic properties of binary and multicomponent systems containing rare-earth and hafnium oxides. [197][198][199][219][220][221][222][223][224][225] In recent years, the composition of vapor, the temperature dependences of partial pressures of the vapor species, properties and relating physicochemical characteristics to structure.…”

“…It should be mentioned that, although not included in the reviews discussed earlier, recent experimental data obtained using KEMS at high temperatures on oxide systems and materials for nuclear applications such as the UO 2 ‐ZrO 2 , 67,210 Cs 2 O‐B 2 O 3 , 211 Cs 2 O‐MoO 3 , 212 and SrO‐Al 2 O 3 213,214 systems are available. Recent KEMS data on ceramics and glass ceramics with the special unique physicochemical properties such as the ZnO‐Nb 2 O 5 , 215 TiO 2 ‐Al 2 O 3 ‐SiO 2 , 216,217 and Al 2 O 3 ‐SiO 2 ‐ZrO 2 systems 218 as well as ultrahigh refractory ceramics based on the binary and multicomponent systems containing rare‐earth and hafnium oxides 219–221 have also been reported. It is necessary to emphasize that the thermodynamic properties obtained in all these systems were discussed within the framework of semiempirical and statistical thermodynamic approaches for modeling and prediction of thermodynamic properties of multicomponent systems based on the corresponding data on binary systems.…”

“…We next focus on the latest experimental data on the vaporization and thermodynamic properties of binary and multicomponent systems containing rare‐earth and hafnium oxides 197–199,219–225 . In recent years, the composition of vapor, the temperature dependences of partial pressures of the vapor species, and the thermodynamic properties of vaporization of the following individual pure rare‐earth oxides have been studied: Y 2 O 3 , La 2 O 3 , CeO 2 , Nd 2 O 3 , Sm 2 O 3 , Gd 2 O 3 , Yb 2 O 3 , and Lu 2 O 3 .…”

High temperature thermodynamic properties of ceramics based on hafnium and rare earth oxides

“…Перспективным направлением разработки материалов для использования в качестве высокоэффективных теплозащитных покрытий является исследование трехкомпонентных керамических материалов, содержащих оксиды редкоземельных элементов. В настоящей работе были исследованы системы Sm2O3-ZrO2-HfO2 и Gd2O3-ZrO2-HfO2 [7][8][9].…”

“…Основной целью проведенного исследования [7] являлось изучение термодинамических свойств системы Sm2O3-ZrO2-HfO2 методом высокотемпературной масс-спектрометрии и сравнение полученных результатов с данными, рассчитанными полуэмпирическими методами. Были рассмотрены семнадцать образцов, что позволило изучить широкий диапазон концентраций и диапазон температур , составляющий 2331-2530 К.…”