Crystal chemistry and structures of uranium-doped gadolinium zirconates

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• 作者：Daniel J. Gregg ; ^{daniel.gregg@ansto.gov.au} ; Yingjie Zhang ; Zhaoming Zhang ; Inna Karatchevtseva ; Mark G. Blackford ; Gerry Triani ; Gregory R. Lumpkin ; Eric R. Vance
• 刊名：Journal of Nuclear Materials
• 出版年：2013
• 出版时间：July, 2013
• 年：2013
• 卷：438
• 期：1-3
• 页码：144-153
• 全文大小：1890 K

文摘

A series of uranium-containing gadolinium zirconate samples have been fabricated at 1450 ¡ãC in oxidizing, inert and reducing atmospheres. X-ray diffraction, Raman spectroscopy and transmission electron microscopy have been utilized to confirm adoption of pyrochlore or defect fluorite structures. X-ray diffraction allowed determination of the bulk averaged structure while Raman spectroscopy and transmission electron microscopy were used to determine ordering at the microdomain scale. Diffuse reflectance, X-ray absorption near edge structure and X-ray photoelectron spectroscopies indicated a predominantly U⁶⁺ oxidation state for all the air-sintered samples, even when Ca²⁺ or A-site vacancies were incorporated to charge balance for U⁴⁺, a mixed U⁵⁺/U⁶⁺ oxidation state was found for samples sintered in argon, while a mixed U⁴⁺/U⁵⁺ oxidation state occurred for sintering under N₂-3.5 % H₂. This demonstrates a degree of uranium oxidation state control through sintering conditions, and the potential of using gadolinium zirconates as host materials for uranium in nuclear waste applications.