毕业论文移动版

摘要：晶体的形态是纯粹的科学好奇的主题，具有悠久的历史。雪晶是一个典型的例子，其形态特征被认为是“天空的字母”。晶体的形态在许多科学和工业领域中也具有重要的意义，因为形态在确定晶体的性质中起重要作用。形态控制目前是开发功能材料的关键问题，并且已经进行了许多努力来提高材料的特性。然而，大多数早期的作品侧重于稳定特定形式，而不是提供一种自由指导晶体形态的策略。具有完全可调形态的功能材料的直接制造仍然是一个挑战。由于晶体的各向异性特性，纳米/微结构的生长方向或暴露面的约束长期以来被认为是受欢迎的研究课题。在科学研究中，开发一种控制纳米级或微米级功能材料的生长方向或曝光面的技术是非常重要的，因为它在确定空间几何效应带来的电，磁和光学性质方面具有重要意义。

SmFeO3是正交结构的稀土铁氧体，属于钙钛矿结构，反铁磁奈尔温度在397℃左右,铁电居里温度也在397℃左右,它的出现让我们重新燃起了制备强磁电耦合单相多铁材料的希望。而且SmFeO3可以通过水热反应法制得，这就便于与我们对反应的参数进行调整，我们希望能通过一些方法来控制SmFeO3的形貌。实现钙钛矿氧化物形貌的可控生长是挑战性的，但这是有前途的独立的物理和化学性质研究和有可能的应用。

在本论文中，我们采用水热反应法，在240℃，72h的条件下，PPL内衬的反应釜中合成铁酸钐，并且加入PVA和NaOH来调控形貌，我们认为NaOH在水热法中不仅可以作为矿化剂，而且可以作为表面活性剂。我们知道，水热合成是一个复杂的过程。产物的尺寸和形态主要取决于晶体成核和晶体生长之间的竞争，它由固有晶体结构和前体溶液的化学势决定。加入不同浓度的NaOH就会导致SmFeO3的形貌发生变化，我们得到样品后或多或少的有些杂质，处理完杂质后对样品进行了SEM，XRD表征，分析样品发现其在NaOH浓度为2M-4M时呈现块状，在NaOH浓度为6M-8M时呈现金字塔尖状，在NaOH浓度为10M-12M时出现了棍状。

关键词：钙钛矿；水热反应；SmFeO3；形貌控制

Abstract：The morphology of crystals is a s purely scientific curiosity with a long history. Snow crystals are representative examples ,whose morphological characteristics were regarded as a “letter from the sky”. The morphology of crystals is also of significant interest in many fields of science and industry because morphologies play an important role in determining the property of crystals. Control of morphologies is currently a key issue in developing functional materials, and much effort has been undertaken for upgrading the characteristics of materials. However, most of the early works focused on the stability of a particular form, rather than providing a free guide crystal form strategy. Direct fabrication of functional materials with fully tunable morphology still remains a challenge.Constraint of the growth directions or exposed facets of nano-/microstructures has been long regarded as a popular research topic due to the various anisotropic properties of crystals.In scientific research, developing a technique of ontrolling the growth directions or exposed facets of functional materials on a nanometer- or micrometer-scale is of great importance because of its significance in determining the electrical, magnetic, and optical properties brought by a spatial geometry effect.

SmFeO3 is an orthorhombic rare earth ferrite, belongs to the perovskite structure, the antiferromagnetic Nair temperature is about 397 ℃, the ferroelectric Curie temperature   is also around 397 ℃,Its appearance so that we re-ignited the preparation of strong magnetic coupling single-phase multi-iron material hope. And SmFeO3 can be prepared by hydrothermal reaction, which makes it easy to adjust the parameters of our reaction, we hope that through some methods to control SmFeO3 morphology.With controllable growth of perovskite oxide for shape is challenging, but promising independent research on physical and chemical properties and possible applications. (责任编辑：qin)