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首页> 外文期刊>Journal of Crystal Growth >Microemulsion mediated synthesis of nanocrystalline (K_x,Na_(1-x))NbO_3 powders
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Microemulsion mediated synthesis of nanocrystalline (K_x,Na_(1-x))NbO_3 powders

机译：微乳液介导的纳米晶（K_x，Na_（1-x））NbO_3粉末的合成

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摘要

The present study reports on the synthesis of nanocrystalline (K_x,Na_(1-x))NbO_3 powders prepared via microemulsion mediated hydrolytic decomposition of mixed alkoxide solutions. Compositions with different K/Na ratios ranging between the two end members KNbO_3 and NaNbO_3 have been synthesized and characterized with respect to stoichiometry, purity, crystalline structure, particle size and powder morphology using X-ray diffraction, Raman spectroscopy and inductively coupled plasma with optical emission spectroscopy. Both raw as well as calcined powders were investigated. For the technically relevant and piezoelectric most active composition (K_(0.50),Na_(0.50))NbO_3 the results are presented and discussed in comparison to micron-sized and submicron-sized powders, that have been prepared by solid state reaction for reference. The study of the crystallographic structure of these reference powders by XRD and Raman spectroscopy confirms the size induced phase transition between the thermodynamically stable monoclinic modification for large particles towards a new triclinic polymorph, which has been reported for nano-powders of this composition by us previously. As possible origin for this phenomenon, internal OH~- groups, variations in K-/Na-site occupancy and mechanical stresses arising from the large surface curvature of the nanocrystalline powders are addressed.
机译：本研究报道了通过微乳液介导的混合醇盐溶液的水解分解制备的纳米晶体（K_x，Na_（1-x））NbO_3粉末的合成。合成了在两个末端成员KNbO_3和NaNbO_3之间具有不同K / Na比的组合物，并使用X射线衍射，拉曼光谱和带光学感应耦合等离子体的化学计量，纯度，晶体结构，粒度和粉末形态进行了表征。发射光谱。研究了生粉和煅烧粉。对于技术上相关且压电性最高的活性成分（K_（0.50），Na_（0.50））NbO_3，与通过固态反应制备的微米级和亚微米级粉末进行了比较，以供参考。通过XRD和拉曼光谱对这些参比粉末的晶体结构进行的研究证实了大颗粒的热力学稳定的单斜晶变体向新的三斜晶型之间发生了尺寸诱导的相变，我们先前已经报道了这种组合物的纳米粉体。解决这种现象的可能原因是，内部的OH〜-基团，K- / Na-位占有率的变化以及由纳米晶体粉末的大表面曲率引起的机械应力。

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