Understanding the Doping Chemistry of High Oxidation States in Scheelite CaWO4 by Hydrothermal Conditions
Understanding the Doping Chemistry of High Oxidation States in Scheelite CaWO4 by Hydrothermal Conditions
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通过水热条件了解白钨矿 CaWO4 中高氧化态的掺杂化学
DOI：
10.1021/acs.inorgchem.1c02450
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发表时间：
2021
影响因子：
4.6
通讯作者：
Liping Li
中科院分区：
文献类型：
--
作者：
Guichen Gao;Zhibin Geng;Guangshe Li;Zhe Tan;Yantong Lu;Zhipeng Fan;Qiao Wang;Liping Li
掺杂化学已经成为调整材料性能以满足不同应用的最有效手段之一。尤其是对于白钨矿类型的CaWO4来说，高氧化态掺杂是极其重要的，因为人们可能会扩大白钨矿家族，并进一步为核取证创造新的应用和/或有用的光谱特征。然而，与白钨矿类型CaWO4的高价掺杂相关的化学成分还远未被了解。本文采用水热法和固相法合成了一系列白钨矿基材料(Ca1-x-y-zEuxKy-z)WO4(-代表钙离子中心的阳离子空位)，并进行了对比研究。对于固相法制备的块体，高氧化态的Eu3+占据CaWO4的钙位，然后以几乎相等的摩尔量掺杂低氧化态的K+。因此，Eu3+的局域对称性由原来的S4点群对称性变为C2v点群对称性。与块体情况不同的是，水热条件下制备的纳米级Eu3+在CaWO4中有两个不同的位置，其量高于低氧化态的K+，即使使用KOH作为矿化剂，也产生了一定数量的阳离子空位。因此，首次证明了(Ca1-x-y-zEuxKy-z)WO4的5D0→7F0的明显分裂发射。本工作揭示的高氧化态掺杂化学不仅解释了稀土离子修饰白钨矿结构中常见的光谱变化，而且为通过溶液化学路线设计和合成新型功能氧化物指明了一个新的方向。
Doping chemistry has become one of the most effective means of tuning materials’ properties for diverse applications. In particular for scheelite-type CaWO4, high-oxidation-state doping is extremely important, since one may expand the scheelite family and further create prospective candidates for novel applications and/or useful spectral signatures for nuclear forensics. However, the chemistry associated with high-valence doping in scheelite-type CaWO4is far from understanding. In this work, a series of scheelite-based materials (Ca1–x–y–zEuxKy□z)WO4(□ represents the cation vacancy of the Ca2+site) were synthesized by hydrothermal conditions and solid-state methods and comparatively studied. For the bulk prepared by the solid-state method, occupation of high-oxidation-state Eu3+at the Ca2+sites of CaWO4is followed by doping of the low-oxidation-state K+at a nearly equivalent molar amount. The Eu3+local symmetry is thus varied from the originalS4point group symmetry toC2vpoint group symmetry. Surprisingly different from the cases in bulk, for the nanoscale counterparts prepared by hydrothermal conditions, the high-oxidation-state Eu3+was incorporated in CaWO4at two distinct sites, and its amount is higher than that of the low-oxidation-state K+even though KOH was used as a mineralizer, creating a certain amount of cation vacancies. Consequently, an apparent split emission of5D0→7F0was first demonstrated for (Ca1–x–y–zEuxKy□z)WO4. The doping chemistry of high oxidation states uncovered in this work not only provides an explanation for the commonly observed spectral changes in rare-earth-ion-modified scheelite structures, but also points out an advanced direction that can guide the design and synthesis of novel functional oxides by solution chemistry routes.