New and Improved Electroceramics

这项大型的格兰特计划结合了谢菲尔德和利兹的专业知识，建立了一个主要的电子陶瓷研究中心。电陶瓷是一种先进材料，其性能和应用依赖于对晶体结构、化学成分、陶瓷微结构、掺杂和掺杂(或缺陷)分布的严格控制。在大多数情况下，属性取决于结构、加工和成分变量的复杂相互作用。它们在各种物理形式中都有应用，例如陶瓷圆盘、厚膜和薄膜，以及由陶瓷和金属电极的交替层(多达数百层)组成的多层器件。感兴趣的特殊性质可以是晶体的大块性质，例如，高水平的离子导电性、电子-离子混合导电性、铁氧体、热释电或亚铁磁性。或者，它可能具体地与多晶材料中的晶界(或表面层)以及组成上的微小差异有关，因此与块体和晶界(或表面层)之间的电学行为有关。这种异质或功能梯度陶瓷有许多应用，例如在压敏电阻和热敏电阻等电流限制器中的非欧姆器件。这项建议侧重于潜在的近期和长期应用的新的和改进的电子陶瓷。这项工作将由一个多学科团队进行，他们在材料发现、建模、加工和高级表征方面具有互补的技能。在英国，这种多方面的电瓷研究和开发方法并不存在于一所大学内，而在两所大学之间建立“枢纽”将使我们能够与世界上最好的大学竞争。提出了三项工作：一、新型和改进的块体材料：结构-性能关系，包括：(A)具有目标功能的新型钙钛矿型材料：铁电性、可逆电应变、压电性、磁电耦合和混合导电性；(B)开发基于硅晶石的新型低温共烧陶瓷；(C)掺杂BaTiO3中的氧非化学计量比和核壳现象；(D)基于层状岩盐结构的改进的锂电池正极。2.薄膜和厚膜形式的材料加工和开发，包括：(A)用于执行器和存储器应用的铁弹/铁电开关的BiFeO_3-PbTiO_3和BiMeO_3薄膜；(B)关于固体氧化物燃料电池结构的薄膜可行性研究；(C)基于新型铁电系统Ba2RETi2Nb_3O_(15)的厚膜和薄膜，以评估其潜在的器件应用；(D)开发掩蔽电沉积技术以沉积基于Pb(Zr，Ti)O_3-Pb(Ni，Nb)O_3(软压电体)和(La，Ca)MnO_3(磁致伸缩器)的平面磁电复合材料。块体材料和界面现象的模拟：(A)对(I)非均质陶瓷中的电流路径进行有限元模拟，(Ii)在晶体内和跨越单个晶界的局部探头测量，以及(Iii)多层器件；结果将用于模拟阻抗谱数据，并允许与实验数据进行比较和解释；(B)功能氧化物的模拟：点缺陷、电子能带结构计算和陶瓷中的质量扩散；这将支持关于新材料开发和掺杂剂在现有材料中的作用的实验方案。工作包I和II将得到利兹和谢菲尔德提供的一系列表征技术的支持，用于研究块状和界面现象。新的表征技术将被应用：像差校正的透射电子显微镜允许对界面和缺陷进行真正的原子尺度光谱；开尔文探针显微镜可以直接成像颗粒和跨晶界区域的功函数变化。

This Large Grant proposal combines the expertise of Sheffield and Leeds to establish a major electroceramics research hub. Electroceramics are advanced materials whose properties and applications depend on close control of crystal structure, chemical composition, ceramic microstructure, dopants and dopant (or defect) distribution. In most cases, properties depend on a complex interplay of structural, processing and compositional variables. They find applications in various physical forms, eg as ceramic discs, thick and thin films and multi-layer devices consisting of alternating layers (up to several hundred) of ceramic and metal electrodes. The particular property of interest may be a bulk property of the crystals, for example, high levels of ionic conductivity, mixed electronic-ionic conduction, ferro-, pyro- piezo-electricity or ferrimagnetism. Alternatively, it may relate specifically to the grain boundaries (or surface layers) in polycrystalline materials and to small differences in composition and therefore electrical behaviour between the bulk and grain boundary (or surface) regions. Such heterogeneous, or functionally-graded ceramics find many applications eg non-ohmic devices in current limiters such as varistors and thermistors. This proposal focuses on new and improved electroceramics for potential near- and long-term applications. The work will be carried out by a multidisciplinary team with complementary skills in materials discovery, modelling, processing and advanced characterisation. Such a multifaceted approach to electroceramics research and development does not exist in the UK within a single institution and the establishment of a 'hub' between the two universities will allow us to compete with the best in the world. Three work packages are proposed.I. New and improved bulk materials: structure-property relations, including: (a) novel perovskite-type materials with targeted functionality: ferroelectricity, reversible electro-strain, piezoelectricity, magneto-electric coupling and mixed conductivity; (b) development of new low temperature co-fired ceramics based on Sillenites; (c) oxygen nonstoichiometry and core-shell phenomena in doped BaTiO3; (d) development of improved lithium battery cathodes based on layered rock salt structures. II. Materials processing and development in thin and thick film form, including:(a) BiFeO3-PbTiO3 and BiMeO3 thin films for ferroelastic/ferroelectric switching for actuator and memory applications; (b) thin film feasibility studies on Solid Oxide Fuel Cell structures; (c) thick and thin films based on the novel ferroelectric system Ba2RETi2Nb3O15 to assess their potential device applications; (d) development of a masked Electrophoretic Deposition technique to deposit planar magnetoelectric composites based on Pb(Zr,Ti)O3-Pb(Ni,Nb)O3 (soft piezoelectric) and (La,Ca)MnO3 (magnetostrictor). III. Modelling of bulk materials and interfacial phenomena: (a) Development of Finite Element modelling of current pathways in (i) heterogeneous ceramics, (ii) local probe measurements within grains and across individual grain boundaries and (iii) multilayer devices; the results will be used to simulate Impedance Spectroscopy data and allow comparison with, and interpretation of, experimental data; (b) Modelling of functional oxides: point defects, electronic band structure calculations and mass diffusion in ceramics; this will underpin the experimental programmes on the development of new materials and the role of dopants in existing materials. Work packages I and II will be supported by a wide range of characterisation techniques available at Leeds and Sheffield for studying bulk and interfacial phenomena. New characterisation techniques will be applied: aberration-corrected TEM allows true atomic scale spectroscopy of interfaces and defects; Kelvin Probe Microscopy gives direct imaging of the work function variation in grain and across grain boundary regions.