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Lead-free PTCR-ceramics: charge transport and ceramic technology

无铅PTCR陶瓷：电荷传输和陶瓷技术

基本信息

批准号：
264514172
负责人：
Professor Dr. Jörg Töpfer
金额：
--
依托单位：
Fachbereich SciTec - Präzision - Optik - Materialien - Umwelt
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2014
资助国家：
德国
起止时间：
2013-12-31 至 2016-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/264514172?language=en
关键词：
Lead free PTCR ceramics charge

项目摘要

The aim of the project is to develop new lead-free functional ceramics with positive temperature coefficient of resistance (PTC thermistors). It is necessary to develop synthesis protocols as well as to study charge transport properties and mechanisms, the effect of dopants, the defect chemistry and the microstructure of this new class of materials. PTC thermistor ceramics are needed for efficient heating systems in the automotive industry.PTC thermistors are based on the PTC effects: if the temperature exceeds a certain critical temperature, the resistance of the material is increased by some orders of magnitude. After providing an operating voltage, the thermistor is heated to its critical temperature. The system is self-regulating: if heat is transported away from the thermistor, a low-resistance working point with high power consumption is maintained. As soon as the heat transport is reduced, the PTC thermistor changes in to its high-resistance state and limits the power consumption. Ceramics with PTC effect for heaters traditionally are made of Pb-substituted BaTiO3 with Curie temperatures in the range of 120-200°C. Ferroelectric insulating BaTiO3 is transferred into a semiconducting state by appropriate donor doping. The proposed project aims at investigating lead-free PTC thermistor materials based on the system (1-x)Bi0.5Na0.5TiO3--xBaTiO3 (BNBT) which show high Curie temperatures compare to BaTiO3. The main problem is to tailor optimum PTC characteristics through doping and microstructural design. Synthesis routes for the fabrication of homogeneously doped BNBT ceramics are needed. Optimum doping concentrations of donor and acceptors need to be identified as well as their mechanisms need to be clarified. The correlation between microstructure and properties of these PTC thermistors should be carefully looked at. Deviations from stoichiometry as well as the defect chemistry of the materials need to be measured and modeled. Th effect of dopant and point defect concentrations on the electrical properties of the material and especially on the grain and grain boundary regions needs to be understood.The proposal addresses engineering problems of preparation of a new generation of PTC ceramics and their property optimization as well as more basic problems of charge transport, defect chemistry and microstructure-properties correlations in lead-free PTC thermistors in the system BNBT.

该项目的目的是开发具有正电阻温度系数的新型无铅功能陶瓷(PTC热敏电阻)。有必要制定合成方案，研究电荷传输特性和机理、掺杂的影响、缺陷化学和这类新材料的微观结构。在汽车工业中，高效的加热系统需要PTC热敏陶瓷。PTC热敏电阻是基于PTC效应的：如果温度超过一定的临界温度，材料的电阻就会增加几个数量级。在提供工作电压后，热敏电阻被加热到其临界温度。该系统是自我调节的：如果热量从热敏电阻中转移出去，则会保持一个低电阻、高功耗的工作点。一旦热传输减少，PTC热敏电阻就会变为高阻状态，并限制功耗。具有PTC效应的电热陶瓷传统上是由居里温度在120-200℃的铅取代的钛酸钡陶瓷制成的，铁电绝缘钛酸钡通过适当的施主掺杂转变为半导体态。本项目旨在研究(1-x)Bi0.5Na0.5TiO3-xBaTiO3(BNBT)系无铅PTC热敏电阻材料，与BaTiO3相比，BNBT具有更高的居里温度。主要的问题是通过掺杂和微结构设计来定制最佳的PTC特性。制备均相掺杂的BNBT陶瓷的合成路线是必要的。需要确定施主和受主的最佳掺杂浓度以及它们的作用机理。应仔细研究这些PTC热敏电阻的微观结构和性能之间的关系。与化学计量的偏差以及材料的缺陷化学需要测量和建模。需要了解掺杂和点缺陷浓度对材料电学性能的影响，特别是对晶界和晶界区域的影响。该建议解决了新一代PTC陶瓷的制备及其性能优化的工程问题，以及BNBT系统中无铅PTC热敏电阻的电荷传输、缺陷化学和微结构-性能关联等更基本的问题。