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Gao G, Geng Z, Li G, Tan Z, Lu Y, Fan Z, Wang Q, Li L. Understanding the Doping Chemistry of High Oxidation States in Scheelite CaWO 4 by Hydrothermal Conditions. Inorg Chem 2021; 60:16558-16569. [PMID: 34668700 DOI: 10.1021/acs.inorgchem.1c02450] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
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 CaWO4 is 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 CaWO4 is followed by doping of the low-oxidation-state K+ at a nearly equivalent molar amount. The Eu3+ local symmetry is thus varied from the original S4 point group symmetry to C2v point 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 CaWO4 at 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 of 5D0 → 7F0 was 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.
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Affiliation(s)
- Guichen Gao
- State Key Lab of Inorganic Syntheses and Preparative Chemistry, College of Chemistry, Jilin University, Chuangchun 130012, P. R. China
| | - Zhibin Geng
- State Key Lab of Inorganic Syntheses and Preparative Chemistry, College of Chemistry, Jilin University, Chuangchun 130012, P. R. China
| | - Guangshe Li
- State Key Lab of Inorganic Syntheses and Preparative Chemistry, College of Chemistry, Jilin University, Chuangchun 130012, P. R. China
| | - Zhe Tan
- State Key Lab of Inorganic Syntheses and Preparative Chemistry, College of Chemistry, Jilin University, Chuangchun 130012, P. R. China
| | - Yantong Lu
- State Key Lab of Inorganic Syntheses and Preparative Chemistry, College of Chemistry, Jilin University, Chuangchun 130012, P. R. China
| | - Zhipeng Fan
- State Key Lab of Inorganic Syntheses and Preparative Chemistry, College of Chemistry, Jilin University, Chuangchun 130012, P. R. China
| | - Qiao Wang
- State Key Lab of Inorganic Syntheses and Preparative Chemistry, College of Chemistry, Jilin University, Chuangchun 130012, P. R. China
| | - Liping Li
- State Key Lab of Inorganic Syntheses and Preparative Chemistry, College of Chemistry, Jilin University, Chuangchun 130012, P. R. China
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