Stolyarova Valentina L, Vorozhtcov Viktor A, Lopatin Sergey I, Shugurov Sergey M, Shilov Andrey L, Karachevtsev Fedor N
Saint Petersburg State University, 7/9 Universitetskaya nab, Saint Petersburg, 199034, Russia.
Grebenshchikov Institute of Silicate Chemistry of the Russian Academy of Sciences, 2 Admiral Makarov nab, Saint Petersburg, 199034, Russia.
Rapid Commun Mass Spectrom. 2021 May 15;35(9):e9066. doi: 10.1002/rcm.9066.
Systems containing zirconia, hafnia, and rare earth oxides are indispensable in various areas of high-temperature technologies as a basis of ultra-high refractory ceramics. Exposure of these materials to high temperatures may result in unexpected selective vaporization of components or phase transitions in the condensed phase leading to changes in physicochemical properties. Consequently, reliable application of the ceramics based on systems such as Sm O -ZrO -HfO is impossible without data on its vaporization processes and thermodynamic properties, which may be used to predict the physicochemical characteristics of the ultra-high refractory ceramics.
Ceramics based on the Sm O -ZrO -HfO system were obtained by solid-state synthesis and characterized by X-ray fluorescence and X-ray phase analyses. The vaporization and thermodynamics of the system considered were examined by the high-temperature mass spectrometric method using a MS-1301 magnetic sector mass spectrometer with a tungsten twin effusion cell. Vapor species effusing from the cell were ionized by electrons with an energy of 25 eV.
The main vapor species over the Sm O -ZrO -HfO system were shown to be SmO, Sm, and O at a temperature of 2373 K, indicating selective vaporization of Sm O from the samples. The partial pressures of these vapor species and the Sm O activities were determined in the Sm O -ZrO -HfO system and allowed the excess Gibbs energies to be evaluated. These excess Gibbs energy values were compared with the results obtained by the semi-empirical and statistical thermodynamic approaches.
The data obtained in this study showed negative deviations from the ideal behavior in the Sm O -ZrO -HfO system at 2373 K. The results calculated according to the semi-empirical methods and statistical thermodynamic Generalized Lattice Theory of Associated Solutions were in agreement with each other. Thus, this evidenced the desirability of further experimental investigation of the Sm O -ZrO -HfO system by the high-temperature mass spectrometric method.
包含氧化锆、氧化铪和稀土氧化物的体系作为超高温耐火陶瓷的基础，在高温技术的各个领域中不可或缺。这些材料暴露于高温下可能会导致组分意外的选择性蒸发或凝聚相中的相变，从而导致物理化学性质发生变化。因此，如果没有关于其蒸发过程和热力学性质的数据，就不可能可靠地应用基于Sm₂O₃-ZrO₂-HfO₂等体系的陶瓷，而这些数据可用于预测超高温耐火陶瓷的物理化学特性。
通过固态合成获得了基于Sm₂O₃-ZrO₂-HfO₂体系的陶瓷，并通过X射线荧光和X射线相分析对其进行了表征。使用带有钨双喷吹池的MS-1301磁扇形质谱仪，通过高温质谱法研究了所考虑体系的蒸发和热力学。从池中喷出的蒸汽物种被能量为25 eV的电子电离。
在2373 K的温度下，Sm₂O₃-ZrO₂-HfO₂体系上的主要蒸汽物种被证明是SmO、Sm和O，这表明样品中Sm₂O₃发生了选择性蒸发。在Sm₂O₃-ZrO₂-HfO₂体系中测定了这些蒸汽物种的分压和Sm₂O₃的活度，并由此评估了过量吉布斯自由能。将这些过量吉布斯自由能值与通过半经验和统计热力学方法获得的结果进行了比较。
本研究获得的数据表明，Sm₂O₃-ZrO₂-HfO₂体系在2373 K时偏离理想行为呈现负偏差。根据半经验方法和统计热力学缔合溶液广义晶格理论计算的结果相互一致。因此，这证明了通过高温质谱法对Sm₂O₃-ZrO₂-HfO₂体系进行进一步实验研究的必要性。
