Morphology evolution of NaTaO_3 submicrometer single-crystals: from cubes to quasi-spheres

NaTaO_3微晶从立方体到准球形的形貌转变（英文）

Surface structure control of functional nano-/micro-crystallites has attracted great attention because many important physicochemical properties depend on their surface. Guided by the supersaturation-dependent surface structure evolution strategy we proposed recently, NaTaO3 submicrometer crystals with morphologies of cubes, corner truncated cubes, edge and corner truncated cubes, and quasi-spheres can be synthesized by changing the volume ratio of ethylene glycol to water and the amount of NaOH in the composite solvent. Under low supersaturation condition, NaTaO3 cubic crystals with low energy {100} facets were obtained. As the supersaturation increases, the corners and edges of NaTaO3 cubic crystals, which possess higher surface energy, were gradually truncated. Surprisingly, quasi-sphere crystallites formed under extremely high supersaturation condition, which is difficult to be explained by the classical crystal growth theories. By analyzing the formation work of two-dimension crystal nuclei, we concluded that the crystal growth tend to be isotropic at extremely high supersaturation, which well explained the formation of the quasi-sphere crystallites.

表面结构决定了晶体材料的许多重要的物理化学性质.可控制备具有特定表面结构的微纳米晶体,从而实现对晶体材料性能的改善,引起了广泛的关注.本课题组近期相关的研究表明,晶体生长体系中,生长单元的过饱和度决定了晶体的表面结构.基于已有研究结果,本文通过调节混合溶剂体系中乙二醇和水的相对体积比及Na OH的用量,改变晶体生长体系中生长单元的过饱和度,合成了亚微米尺寸的Na Ta O3立方体、削角立方体、削角削棱立方体和准球体.低过饱和度条件下,形成的Na Ta O3颗粒是低能{100}晶面裸露的立方体;随过饱和度的增加,立方体的角和棱逐渐削去,裸露表面能更高的晶面;极高过饱和度条件下,则形成准球体Na Ta O3颗粒.这种准球体的形成难以用经典的晶体生长理论加以解释.通过研究同样受过饱和度影响的二维晶核生成功(Whkl),发现在极高的过饱和度的条件下,晶体生长趋于各向同性,合理地解释了准球体的形成机制.