Pyro- and dielectric properties as well as modelling

热解和介电特性以及建模

• 批准号: 310975945
• 负责人: Professor Dr. Dirk Carl Meyer
• 金额: --
• 依托单位: Institut für Geologie, Mineralogie und Geophysik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2016
• 资助国家: 德国
• 起止时间: 2015-12-31 至 2019-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/310975945?language=en
• 关键词: Pyro; dielectric; properties; well; modelling

The here described project at the Institute of Experimental Physics at TU Bergakademie Freiberg is part of a package proposal that will be carried out together with the groups of Mineralogy at TU Bergakademie Freiberg and Crystal Physics at Ruhr-Universität Bochum. The objective of the collaboration is the formulation of correlations between structure and electromechanical properties of rare-earth oxoborate crystals (short RCOB). These are not only of fundamental interest but play a key role for potential applications of these materials as high-temperature piezoelectrics for temperatures up to approx. 1000 °C. The monoclinic symmetry of the RCOB materials implies more degrees of freedom for the anisotropy of properties and, with that, for the correlation between structure and properties than in higher symmetric crystals. The discontinuities in the temperature-dependent development of different properties observed in own preliminary work indicate possible structural instabilities. Numerous substitution possibilities on the differently coordinated cation positions result in a large, until now only scarcely characterized, chemical variability. For some representatives the possibility of growing large single crystals from the melt has already been verified.The project requested here will cover the electrical characterization and the ab initio modelling. Focus of the investigations will be the relations between chemism, structural parameters and electrical properties (conductivity, permittivity, pyroelectric coefficient) of the RCOB materials. For this it needs to be clarified, if the discontinuities of temperature-dependent specific heat and thermal expansion observed in preliminary work also express in electrical parameters. In this case, transition temperatures will be determined and related with structural changes. The correlation of electrical parameters with explicit structural features is the main objective.Theoretical properties obtained from ab initio modelling will verify measured ones and identify systematic connections between different kinds of crystals. Furthermore, statements regarding stability and material properties regarding substitution, disorder and mixed occupation will be made theoretically to confirm the experimental work of the project partners. Altogether, a complete picture of possible structural changes will be constructed to simultaneously allow predictions on properties relevant for applications of the RCOB materials.

这里描述的项目在工业大学实验物理研究所弗赖贝格是一个一揽子计划的一部分，将进行与集团的矿物学在工业大学弗赖贝格和晶体物理在鲁尔大学波鸿。合作的目的是制定稀土氧硼酸盐晶体（简称RCOB）的结构和机电性能之间的相关性。这些不仅是基本的利益，但这些材料作为高温压电材料的潜在应用发挥了关键作用的温度高达约。1000 °C。RCOB材料的单斜对称性意味着性能的各向异性以及结构与性能之间的相关性比更高对称性的晶体具有更多的自由度。在自己的初步工作中观察到的不同性质的温度依赖性发展的不连续性表明可能的结构不稳定性。在不同配位阳离子位置上的许多取代可能性导致大的化学可变性，直到现在几乎没有表征。对于一些代表来说，从熔体中生长大单晶的可能性已经得到了验证。这里要求的项目将包括电学特性和从头算建模。研究的重点将是RCOB材料的化学性质、结构参数和电学性质（电导率、介电常数、热释电系数）之间的关系。为此，需要澄清的是，如果在初步工作中观察到的温度依赖性比热和热膨胀的不连续性也表示在电气参数。在这种情况下，转变温度将被确定并与结构变化相关。电参数与明确的结构特征的相关性是主要目标。从从头计算模型获得的理论特性将验证测量值，并确定不同种类的晶体之间的系统连接。此外，还将从理论上阐述关于替代、无序和混合占据的稳定性和材料特性，以确认项目合作伙伴的实验工作。总而言之，一个完整的图片可能的结构变化将被构建，同时允许预测的RCOB材料的应用相关的属性。