【摘要】 采用石墨还原法探索了CeO2-ZrO2二元体系在不同还原温度、还原时间条件下的物相组成及结构,借助X射线衍射、红外振动光谱等手段对还原样品进行了物相表征及结构分析。实验结果表明:通过石墨还原能在较低温度(Tred=1 050℃)、较短时间(t=24h)内合成纯相Ce2Zr2O7.97,较传统先还原(95%Ar+5%H2,Tred≥1 400℃,t>48h)后氧化(O2或空气气氛)工艺更简单经济;Ce2Zr2O7.97相能在1 050~1 300℃、24~72h还原条件下稳定存在并保留至室温而不发生相分解,其机制可能归因于石墨所形成的弱还原环境;Ce2Zr2O7.97相拥有与烧绿石Ce2Zr2O7相近的有序阳离子亚晶胞结构,但由于其氧空位(O3、O4、O11)被大部分氧离子所填充,导致该相结构对称性降低。本文提出的石墨还原法制备富氧相Ce2Zr2O7.97有望成为一种较传统制备工艺更简单经济的新方法,而Ce2Zr2O7.97相能在还原气氛中稳定存在,可为An2Zr2O7+x固化体的存放环境提供借鉴和参考。更多还原

【Abstract】 The phase composition and phase structure of CeO2-ZrO2binary system were studied via graphite reduction method under different reducing temperatures and time. The various reduced products were characterized by powder X-ray diffraction and infrared spectra.Experimental results show that Ce2Zr2O7.97phase can be synthesized successfully at a relative low temperature(Tred=1 050℃)and short time(t=24h)bygraphite reduction method,which is more simplified and economic than traditional reduction-reoxidation method with Ar-H2(5% V/V hydrogen in argon)reduction atmosphere.Ce2Zr2O7.97phases prepared in a temperature range of 1 050-1 300 ℃for 24-72h are stable and can be retained until room temperature without phase decomposition.The mechanism may be attributed to a weak reduction environment formed by graphite.Ce2Zr2O7.97phase with an ordered cation sub-unit cell structure is similar with pyrochlore Ce2Zr2O7,but the structure symmetry of Ce2Zr2O7.97phase is lower than that of pyrochlore Ce2Zr2O7due to the oxygen vacancy(O3,O4,O11)filled partially.Graphite reduction method is expected to become a new,simple and economical preparation method comparing with the traditional preparation process for Ce2Zr2O7.97.The Ce2Zr2O7.97 phase retained at room temperature in a weak reducing atmosphere can provide a reference for the storage environment of An2Zr2O7+x waste forms.更多还原