High pressure hydrothermal synthesis of magnetic and electronic materials

高压水热合成磁性电子材料

• 批准号: 2446095
• 金额: --
• 依托单位: University of Liverpool
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2020
• 资助国家: 英国
• 起止时间: 2020 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2446095
• 关键词: pressure; hydrothermal; synthesis; magnetic; electronic

The versatile perovskite structure has shown to be useful within a wide range of areas including transparent conductors, photocatalysts, multiferroics and thermoelectrics. The ideal perovskite structure, ABX3, generally consists of a large metal cation (A) with a smaller metal cation (B) with an anion (X), often an oxide or halide. In the ideal structure, the B ion is found in a 6-fold octahedral coordination. Material properties are strongly related to the structure and the perovskite structure is tolerant to distortions such as octahedral tilting. By careful selection of elements and dopants, the intrinsic properties of the material can be finely tuned. Introducing magnetic cations to non-magnetic structures can induce magnetic behaviour into the previously non-magnetic material. When a sufficient amount of a magnetic dopant is added, exchange pathways can form to give a magnetic structure. Similarly, introducing aliovalent dopants into previously insulating or semiconducting materials can cause a transition into materials exhibiting more conductive behaviour. One extension of the perovskite structure is the double perovskite, where the A or B site contains multiple elements and forms an ordered arrangement of ions across the structure. Having two ordered sites where at least one element has unpaired d-electrons, interesting magnetic structures can form, leading to exotic behaviours.This project will look at two perovskite systems: stannate perovskites and iron double perovskites. For both systems, d-block dopants and aliovalent dopants will be used to induce both magnetic and conductive behaviour. In the iron double perovskite systems, ordering of the B sites will be targeted whereas for the stannate perovskites, the B site will be disordered and so an investigation into the substitution quantity will be performed. The structures will be analysed by X-ray diffraction and HAADF-STEM techniques. Compositional data will be found through ICP and EDX techniques, with XPS and XANES to characterise the oxidation states of the present elements. SQUID magnetometry will be used to characterise the magnetic behaviour and resistivity will be measured using a PPMS.

多才多艺的钙钛矿结构已被证明在包括透明导体、光催化剂、多铁性和热电性在内的广泛领域中都有应用。理想的钙钛矿结构ABX3通常由大的金属阳离子(A)和较小的金属阳离子(B)和阴离子(X)组成，通常是氧化物或卤化物。在理想结构中，B离子以6重八面体配位。材料性能与结构密切相关，钙钛矿结构对八面体倾斜等变形具有很强的耐受性。通过仔细选择元素和掺杂剂，可以精细地调整材料的内在性能。将磁性阳离子引入非磁性结构可以在先前的非磁性材料中诱导磁性行为。当添加足够量的磁性掺杂剂时，可以形成交换路径以获得磁性结构。同样，在以前的绝缘或半导体材料中引入等价掺杂可以导致向表现出更多导电行为的材料的转变。钙钛矿结构的一种延伸是双钙钛矿结构，其中A或B位包含多个元素，并在结构上形成离子的有序排列。有两个有序的位置，其中至少有一个元素具有未配对的d电子，可以形成有趣的磁性结构，导致奇怪的行为。这个项目将研究两个钙钛矿系统：锡酸盐钙钛矿和铁双钙钛矿。对于这两个系统，将使用d-嵌段掺杂剂和等价掺杂剂来诱导磁性和导电行为。在铁双钙钛矿系统中，B位的有序性将是目标，而对于锡酸盐钙钛矿系统，B位将是无序的，因此将对取代量进行调查。结构将用X射线衍射和HAADF-STEM技术进行分析。成分数据将通过电感耦合等离子体发射光谱和能谱分析技术获得，并用XPS和XANES表征当前元素的氧化状态。将使用SQUID磁测量来表征磁性行为，并将使用PPMS测量电阻率。