Enthalpies of formation of pyrochlore Tb2Hf2O7 and fluorite RE2O3·2HfO2 (RE = Dy-Lu) rare-earth hafnates

IF 3.8 3区材料科学 Q1 MATERIALS SCIENCE, CERAMICS

Journal of the American Ceramic Society Pub Date : 2025-04-30 DOI:10.1111/jace.20598

Irina A. Bajenova, Anton V. Guskov, Pavel G. Gagarin, Alexandra V. Khvan, Vladimir N. Guskov, Konstantin S. Gavrichev

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Abstract

The enthalpies of formation of heavy rare-earth hafnates Tb₂Hf₂O₇ (pyrochlore structure) and RE₂O₃^.2HfO₂ (RE = Dy-Lu) (defect fluorite structure) have been determined by the method of oxide melt drop-solution calorimetry. The data obtained for Tb₂Hf₂O₇ revealed that they are in trend with previously experimentally determined values for “light” RE hafnates. The formation enthalpies of fluorite structured compounds in general become more positive with the RE ionic radius contraction. The values of enthalpy of formation from oxides for the fluorite solid solutions obtained in the current study are sufficiently more negative than was predicted by the ab initio calculations. The calculation of the Gibbs energy dependencies as well as the contribution of both entropy and enthalpy factors allowed us to estimate the stability of the compounds in the high-temperature range.

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烧绿石Tb2Hf2O7和萤石RE2O3·2HfO2 （RE = Dy-Lu）稀土半酸盐的生成焓

用氧化物熔体滴液量热法测定了重稀土半酸盐Tb2Hf2O7（焦绿石结构）和RE2O3.2HfO2 (RE = Dy-Lu)（缺陷萤石结构）的生成焓。获得的Tb2Hf2O7的数据表明，它们与先前实验确定的“轻”稀土铪酸盐的值是一致的。萤石结构化合物的生成焓随着稀土离子半径的收缩而增大。在目前的研究中得到的萤石固溶体的氧化物生成焓值比从头计算预测的值要负得多。Gibbs能量依赖关系的计算以及熵和焓因子的贡献使我们能够估计化合物在高温范围内的稳定性。

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来源期刊

Journal of the American Ceramic Society 工程技术-材料科学：硅酸盐

CiteScore

7.50

自引率

7.70%

发文量

590

审稿时长

2.1 months

期刊介绍： The Journal of the American Ceramic Society contains records of original research that provide insight into or describe the science of ceramic and glass materials and composites based on ceramics and glasses. These papers include reports on discovery, characterization, and analysis of new inorganic, non-metallic materials; synthesis methods; phase relationships; processing approaches; microstructure-property relationships; and functionalities. Of great interest are works that support understanding founded on fundamental principles using experimental, theoretical, or computational methods or combinations of those approaches. All the published papers must be of enduring value and relevant to the science of ceramics and glasses or composites based on those materials. Papers on fundamental ceramic and glass science are welcome including those in the following areas: Enabling materials for grand challenges[...] Materials design, selection, synthesis and processing methods[...] Characterization of compositions, structures, defects, and properties along with new methods [...] Mechanisms, Theory, Modeling, and Simulation[...] JACerS accepts submissions of full-length Articles reporting original research, in-depth Feature Articles, Reviews of the state-of-the-art with compelling analysis, and Rapid Communications which are short papers with sufficient novelty or impact to justify swift publication.