Ropuszyńska-Robak P, Tomaszewski P E, Kępiński L, Macalik L
Wrocław University of Economics, Faculty of Engineering and Economy, Department of Bioorganic Chemistry Komandorska 118/120 53-345 Wrocław Poland.
Institute of Low Temperature and Structure Research, Polish Academy of Sciences Okólna 2 50-422 Wrocław Poland
RSC Adv. 2018 Jan 10;8(5):2632-2641. doi: 10.1039/c7ra10706d. eCollection 2018 Jan 9.
The Pechini and microwave-assisted hydrothermal syntheses of nanocrystalline Er and Tm co-doped MY(WO), where M = Li, Na, K, double tungstates are reported. The obtained samples were characterized using standard X-ray powder diffraction (XRD) technique, Rietveld method, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and IR spectroscopy. The smallest crystallites (about 13 nm) could be obtained for the sodium samples synthesized by both the Pechini (for the resin calcined at 550 °C) and hydrothermal methods (synthesis at 230 °C). The average particle size of nanocrystalline powders increases with increasing temperature. It was found that nanocrystals retain the bulk structure with tetragonal and monoclinic symmetry for the sodium and potassium analogues, respectively. In contrast to this behaviour, LiY(WO) undergoes a size-induced structural transformation from monoclinic (space group 2/) to tetragonal (space group 4/) symmetry. IR spectra of the synthesized sodium and potassium compounds are very similar to their bulk counterparts. IR spectra of the lithium analogues show, however, abrupt changes when the calcination temperature increases to 850 °C or higher. This behaviour is consistent with the size-induced phase transition in this compound.
报道了采用佩琴尼法和微波辅助水热法合成纳米晶铒和铥共掺杂的MY(WO)（其中M = Li、Na、K）双钨酸盐。使用标准X射线粉末衍射（XRD）技术、里特韦尔德法、透射电子显微镜（TEM）、扫描电子显微镜（SEM）和红外光谱对所得样品进行了表征。通过佩琴尼法（对于在550℃煅烧的树脂）和水热法（在230℃合成）合成的钠样品可获得最小的微晶（约13nm）。纳米晶粉末的平均粒径随温度升高而增大。发现纳米晶体分别保留了钠和钾类似物的四方和单斜对称的块状结构。与此行为相反，LiY(WO)经历了从单斜（空间群2/）到四方（空间群4/）对称的尺寸诱导结构转变。合成的钠和钾化合物的红外光谱与其块状对应物非常相似。然而，锂类似物的红外光谱在煅烧温度升至850℃或更高时显示出突然变化。这种行为与该化合物中的尺寸诱导相变一致。
