Volodymyr Svitlyk, Stephan Weiss, Gaston Garbarino, René Hübner, Andreas Worbs, Nina Huittinen, Christoph Hennig
{"title":"Phase composition and stability of Gd2−x Th x Zr2O7 under extreme conditions","authors":"Volodymyr Svitlyk, Stephan Weiss, Gaston Garbarino, René Hübner, Andreas Worbs, Nina Huittinen, Christoph Hennig","doi":"10.1515/zkri-2024-0066","DOIUrl":null,"url":null,"abstract":"Introduction of Th into synthetic disordered fluorite-type Gd<jats:sub>2</jats:sub>Zr<jats:sub>2</jats:sub>O<jats:sub>7</jats:sub> induces a transition to an ordered pyrochlore-type phase at a Th concentration of 10 % at the Gd site (Gd<jats:sub>1.8</jats:sub>Th<jats:sub>0.2</jats:sub>Zr<jats:sub>2</jats:sub>O<jats:sub>7</jats:sub> composition). The degree of order of the fluorite-type phase reaches 50 % for a Th concentration of 25 % (Gd<jats:sub>1.5</jats:sub>Th<jats:sub>0.5</jats:sub>Zr<jats:sub>2</jats:sub>O<jats:sub>7</jats:sub> composition). Upon application of high pressure, the Gd<jats:sub>2</jats:sub>Zr<jats:sub>2</jats:sub>O<jats:sub>7</jats:sub> phase retains the fluorite-type structure until 33 GPa (<jats:italic>K</jats:italic> <jats:sub>0</jats:sub> = 167(1) GPa), where it undergoes reversible amorphization. The Gd<jats:sub>1.7</jats:sub>Th<jats:sub>0.3</jats:sub>Zr<jats:sub>2</jats:sub>O<jats:sub>7</jats:sub> phase was found to be stable up to at least a pressure of 25 GPa (<jats:italic>K</jats:italic> <jats:sub>0</jats:sub> = 169(3) GPa). Upon heating to <jats:italic>T</jats:italic> <jats:sub>max</jats:sub> of 1135 K, the Gd<jats:sub>2</jats:sub>Zr<jats:sub>2</jats:sub>O<jats:sub>7</jats:sub> phase retains its disordered fluorite-type structural arrangement (<jats:italic>α</jats:italic> = 3.03 × 10<jats:sup>−5</jats:sup> K<jats:sup>−1</jats:sup>). The excellent stability of the Gd<jats:sub>2−<jats:italic>x</jats:italic> </jats:sub>Th<jats:sub> <jats:italic>x</jats:italic> </jats:sub>Zr<jats:sub>2</jats:sub>O<jats:sub>7</jats:sub> phases under extreme conditions of temperature and pressure makes Gd<jats:sub>2</jats:sub>Zr<jats:sub>2</jats:sub>O<jats:sub>7</jats:sub> a promising candidate as a host matrix for radioactive elements for safe long-term underground storage of nuclear waste.","PeriodicalId":23855,"journal":{"name":"Zeitschrift für Kristallographie - Crystalline Materials","volume":"20 1","pages":""},"PeriodicalIF":0.0000,"publicationDate":"2024-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Zeitschrift für Kristallographie - Crystalline Materials","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.1515/zkri-2024-0066","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
引用次数: 0
Abstract
Introduction of Th into synthetic disordered fluorite-type Gd2Zr2O7 induces a transition to an ordered pyrochlore-type phase at a Th concentration of 10 % at the Gd site (Gd1.8Th0.2Zr2O7 composition). The degree of order of the fluorite-type phase reaches 50 % for a Th concentration of 25 % (Gd1.5Th0.5Zr2O7 composition). Upon application of high pressure, the Gd2Zr2O7 phase retains the fluorite-type structure until 33 GPa (K0 = 167(1) GPa), where it undergoes reversible amorphization. The Gd1.7Th0.3Zr2O7 phase was found to be stable up to at least a pressure of 25 GPa (K0 = 169(3) GPa). Upon heating to Tmax of 1135 K, the Gd2Zr2O7 phase retains its disordered fluorite-type structural arrangement (α = 3.03 × 10−5 K−1). The excellent stability of the Gd2−xThxZr2O7 phases under extreme conditions of temperature and pressure makes Gd2Zr2O7 a promising candidate as a host matrix for radioactive elements for safe long-term underground storage of nuclear waste.