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.

协作的目的是形成稀土氧化晶体的结构与机电特性之间的相关性（短RCOB）。这些不仅具有根本的兴趣，而且对于这些材料作为高温压电的潜在应用起着关键作用，可用于大约大约。 1000°C。 RCOB材料的单斜形对称性意味着对性质各向异性的自由度，而与较高的对称晶体相比，与结构和性质之间的相关性更大。在自身初步工作中观察到的不同特性的温度依赖性发展中的不连续性表明可能的结构不稳定性。在不同的协调阳离子位置上，许多取代导致很大，直到现在才几乎没有表征化学变异性。对于某些代表从熔体生长大型单晶的可能性的人已经得到验证。此处请求的项目将涵盖电气表征和从头算建模。研究的重点将是RCOB材料的化学主义，结构参数和电性能（电导率，介电常数，高电系数）之间的关系。为此，需要澄清，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在电气参数中表达。在这种情况下，将确定过渡温度并与结构变化相关。电参数与显式结构特征的相关性是主要的目标。从头算建模获得的理论特性将验证并确定不同种类的晶体之间的系统连接。此外，理论上将使有关替代，混乱和混合气体的稳定性和物质特性的陈述以确认项目伙伴的实验性工作。总体而言，将构建可能的结构变化的完整图片，以简单地允许对与RCOB材料应用相关的属性进行预测。