Bi0.5Na0.5TiO3基多元无铅铁电材料的设计、合成及热释电性能研究

Electro-caloric (EC) effect in ferroelectric materials is of great interest in the past decade because of the increasing demand on cooling solution for micro- and nano-electronic devices which have high-power and high-density heat-generating components. Although lead-based ferroelectrics show excellent EC behaviors, it is desirable that environmentally friendly lead-free ferroelectrics can be used for EC coolers in microelectronic devices. It is known that Bi0.5Na0.5TiO3 is one of the most important lead-free materials with excellent ferroelectric properties. However, the large coercive field, low depoling temperature, and high conductivity during poling may hinder the practical application as EC materials.. In this project, some additions (e.g., BaTiO3, BiFeO3, Na2Ti6O3, etc.) will be introdcted to the Bi0.5Na0.5TiO3 microstructure to prepare Bi0.5Na0.5TiO3 based multiferroelectric ceramics and thin-films by using the improved citrate method and the improved sol-gel spin coating method, respectively. The purposed materials with different compositions and structures will be designed and prepared by controlling the synthesis factors. Furthermore, the relation between the microstructure and the electro-caloric behaviors will be investigated through the analytic results, such as the in situ dynamic mechanical analysis, the high voltage differential scanning calorimetry, and the thermodynamics results. . The main expected research result of the project is the formation of the electro-caloric effect mechanism of the Bi0.5Na0.5TiO3 based multiferroelectric materials. Meanwhile, The lead-free ferroelectric material with excellent electro-caloric behavior will be selected for the practical application as EC coolers.

随着我国对环境保护的日益重视和越来越多微型电子设备的出现，研发环保、高效的无铅热释电铁电冷却材料成为迫切性课题。Bi0.5Na0.5TiO3被认为是最具吸引力的材料体系之一，但是单纯的Bi0.5Na0.5TiO3矫顽场大，在铁电相区电导率高，难以极化。. 本项目拟分别利用柠檬酸络合法和溶胶-凝胶旋涂法设计并制备BaTiO3、BiFeO3、Na2Ti6O3等组分改性的Bi0.5Na0.5TiO3基多元陶瓷/薄膜材料，通过调控不同合成条件，制备不同结构和组成的目标材料，在运用多种分析表征技术基础上，采用动态机械热分析、高压差显扫描量热分析等原位技术及热力学计算，研究其热释电性能与结构之间的关系，探寻其作用机制。. 本项目主要预期成果是探寻出Bi0.5Na0.5TiO3基多元材料热释电性能与其相结构转变之间的关系，为微电子设备冷却器材料的开发和应用提供理论支持。

随着各种精密电子设备的陆续面世、可供利用的矿石资源的日趋枯竭以及人类生存环境的持续恶化，研究性能优异的无铅热释电铁电冷却材料、新型储能及污染水净化材料，并大力开发生物燃料对于优化能源结构、改善环境质量并实现可持续发展具有重要的科学意义。本研究团队在积极推进本项目开展的同时，在本项目基金的支持下，还围绕杂多酸基多孔固体酸材料以及石墨烯气凝胶（GA）基功能材料的组装及性能开展了一系列工作。具体工作如下：. （1）采用柠檬酸络合法制备了一系列Bi0.5Na0.5TiO3-BaTiO3（BNT-BT）材料以及BiFeO3（BF）改性的BNT-BT-BF、Bi0.5K0.5TiO3（BKT）改性的 BNT-BKT材料；采用水热合成法制备了Ba0.75Sr0.25TiO3（BST）及BT纳米线，进而与聚（偏氟乙烯-三氟乙烯）[P(VDF-TrFE)]复合为共聚物复合膜BST-P(VDF-TrFE)、BT-P(VDF，对所制材料进行了较详尽的表征，并考察了其热电性能。. （2）分别采用水热法及近室温敞开体系法制备了数类单纯及铝掺杂六方相介孔分子筛（SBA-15、MCM-41）和立方相介孔分子筛（MCM-48），以其及GA为载体、采用浸渍法制备了一系列磷钨杂多酸（HPW）和硅钨杂多酸（HSiW）基多孔催化剂。性能评价结果证明，该类催化剂在油酸甲酯化及乙酰丙酸酯化反应中呈现出不错的催化性能，为合成生物燃料提供了一类可行性较强的新型催化剂。. （3）采用水热还原自组装并结合冷冻干燥、焙烧工艺制备了SiO2、TiO2、Fe2O3、Fe3O4掺杂GA三维复合材料。所制材料具有高比表面、高孔隙率、便于离子和电子的快速迁移等特性，作为锂离子电池负极材料呈现出较高的比容量、良好的循环稳定性能及倍率性能，有望成为应用前景较好的新型锂离子电池电极材料。. （4）采用直接水热还原自组装结合冷冻干燥工艺制备了一系列TiO2掺杂GA三维多孔复合材料，同时采用冰晶模板法结合焙烧工艺制备了一系列介孔TiO2掺杂还原氧化石墨烯（rGO）多孔复合材料，这两类材料对有机染料（RhB等）呈现出良好的吸附性能和可见光光催化活性，为有机染料废水的有效处理提供了可能。