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首页> 外文期刊>RSC Advances >Alkali metal impact on structural and phonon properties of Er3+ and Tm3+ co-doped MY(WO4)2 (M = Li, Na, K) nanocrystals
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Alkali metal impact on structural and phonon properties of Er3+ and Tm3+ co-doped MY(WO4)2 (M = Li, Na, K) nanocrystals

机译：碱金属对Er 3 + 和Tm 3 + 共掺杂MY（WO 4 ） 2 <的结构和声子性能的影响/ sub>（M = Li，Na，K）纳米晶体

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摘要

The Pechini and microwave-assisted hydrothermal syntheses of nanocrystalline Er3+ and Tm3+ co-doped MY(WO4)2, 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(WO4)2 undergoes a size-induced structural transformation from monoclinic (space group P2/n) to tetragonal (space group I41/a) 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.
机译：纳米晶Er 3 + 和Tm 3 + 的Pechini和微波辅助水热合成共掺杂MY（ WO 4 ） 2 ，其中M = Li，Na，K，双钨酸盐。使用标准X射线粉末衍射（XRD）技术，Rietveld方法，透射电子显微镜（TEM），扫描电子显微镜（SEM）和IR光谱对获得的样品进行表征。通过Pechini（对于在550°C下煅烧的树脂）和水热法（在230°C下合成）合成的钠样品，可以获得最小的微晶（约13 nm）。纳米晶体粉末的平均粒度随温度升高而增加。发现纳米晶体分别保留钠和钾类似物的四方和单斜对称的整体结构。与此行为相反，LiY（WO 4 ） 2 从单斜晶系经历尺寸诱导的结构转变（空间组 P 2 / n ）到四边形（空间组 I 4 1 / a ）对称。合成的钠和钾化合物的红外光谱与它们的大部分相似。然而，锂类似物的红外光谱显示，当煅烧温度升至850°C或更高时，突变会突然改变。此行为与该化合物中尺寸诱导的相变一致。

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