| Title | [(C2H5)(4)N][U2O4(HCOO)(5)], an Ammonium Uranyl Formate Framework Showing Para- to Ferro-Electric Transition: Synthesis, Structures, and Properties |
| Authors | Zhu, Qianqian Shang, Ran Chen, Sa Liu, Chunli Wang, Zheming Gao, Song |
| Affiliation | Peking Univ, Beijing Natl Lab Mol Sci, Fundamental Sci Lab Radiochem & Radiat Chem, State Key Lab Rare Earth Mat Chem & Applicat,Coll, Beijing 100871, Peoples R China. |
| Keywords | METAL-ORGANIC FRAMEWORKS X-RAY-DIFFRACTION CRYSTAL-STRUCTURE WEAK FERROMAGNETISM DIELECTRIC ANOMALIES MAGNETIC-PROPERTIES BOND REARRANGEMENT PHASE-TRANSITIONS THERMAL-EXPANSION POROUS SOLIDS |
| Issue Date | 2014 |
| Publisher | inorganic chemistry |
| Citation | INORGANIC CHEMISTRY.2014,53,(16),8708-8716. |
| Abstract | We report an ammonium uranyl formate framework of formula [(C2H5)(4)N][U2O4(HCOO)(5)], prepared by using components of tetraethylammonium, uranyl, and formate. The compound possesses a layered structure of anionic uranyl-formate wavy sheets and intercalated (C2H5)(4)N+ cations. The sheet consists of pentagonal bipyramidal uranyl cations connected by equatorial anti-anti and anti-syn HCOO- bridges, and it has a topology of 3(3).4(3).5(4) made of edge-sharing square and triangle grids. The high-temperature (HT) phase belongs to the chiral but nonpolar tetragonal space group P (4) over bar2(1)m. In the structure, one HCOO- is 2-fold disordered, showing a flip motion between the two anti-syn orientations. On cooling, this flip motion slowed and finally froze, leading to a phase transition at similar to 200 K. The low-temperature (LT) structure is monoclinic and polar in space group P2(1); the cations shift, and the layers slide. Especially, the concerted and net shifts of the ammonium cations toward the -b direction, with respect to the anionic sheets, result in an estimated spontaneous polarization of 0.86 mu C cm(-2) in LT. The phase transition is thus para- to ferroelectric, in Aizu notation (4) over bar 2mF2, accompanied by significant, anisotropic dielectric anomalies, with a quite significant thermal hysteresis. Variable-temperature luminescent spectroscopy and differential scanning calorimetry confirmed the transition and provided further information. The structure-property relationship is established. |
| URI | http://hdl.handle.net/20.500.11897/210201 |
| ISSN | 0020-1669 |
| DOI | 10.1021/ic501336x |
| Indexed | SCI(E) |
| Appears in Collections: | å å¦ä¸ å å å·¥ç¨ å¦é ¢ 稀土材料化学与应用国家重点实验室 |
