晶粒尺寸对铁电材料多场耦合特性的影响

发布时间：2018-09-03 16:24

【摘要】：铁电多晶材料具有优良的多场耦合性能,故被广泛应用于传感器、存储器、能量转换器等功能器件中。铁电多晶材料中晶粒尺寸不仅影响晶粒内部的畴结构分布,而且对其多场耦合性能的影响也很大。本文利用实空间下的相场模型,研究了晶粒尺寸对铁电多晶材料内部微结构、力电耦合特性、电卡效应以及对铁电铁磁复合材料磁电耦合效应的影响。首先,本文研究了晶粒尺寸对铁电多晶材料的铁电性、介电性和压电性的影响。研究结果表明,铁电多晶体中的剩余极化,矫顽场和介电常数随晶粒尺寸的增加而单调递增;压电系数则随晶粒尺寸的增加而先增加后降低。同时,论文从晶粒内部微结构角度对随晶粒尺寸非单调变化的压电特性进行了分析,给出其随晶粒尺寸变化的内在机理。其次,研究了晶粒尺寸对铁电多晶材料电卡效应的影响。结果表明,在一定的温度和尺寸范围内,铁电材料的最大绝热温变值随晶粒尺寸增加而逐渐增加。与此同时,最大绝热温变处对应的温度随晶粒尺寸减小而降低,从而可以在更接近室温的条件下获得较大的绝热温变。对于含不同晶粒尺寸的铁电材料,结合相变温度点附近的晶粒内部畴结构,从微结构角度对绝热温变随晶粒尺寸变化的现象进行解释。最后,基于实空间下铁电铁磁复合材料的相场模型,研究了晶粒尺寸对磁电复合材料中磁电耦合系数的影响,并结合铁电铁磁两相材料晶粒内部的畴结构进行机理分析。结果表明,磁电耦合系数随晶粒尺寸的增加而先增加后逐渐降低。只有在适当的晶粒尺寸范围内,磁电耦合系数才会大大增加。论文的研究结论为选取合适的晶粒尺寸以获得多晶铁电材料优异的多场耦合性能提供了一定的理论基础。
[Abstract]:Ferroelectric polycrystalline materials are widely used in sensors, memory devices, energy converters and other devices because of their excellent multi-field coupling properties. The grain size in ferroelectric polycrystalline materials not only affects the domain structure distribution in the grains, but also has a great influence on their multi-field coupling properties. The effects of grain size on the microstructure, mechanical-electrical coupling properties, electric-card effect and magnetoelectric coupling effect of ferroelectric polycrystalline materials were investigated. Firstly, the effects of grain size on the ferroelectric, dielectric and piezoelectric properties of ferroelectric polycrystalline materials were studied. The coercive field and dielectric constant monotonically increase with the increase of grain size, while the piezoelectric coefficient increases first and then decreases with the increase of grain size. At the same time, the piezoelectric characteristics with non-monotonic change of grain size are analyzed from the angle of grain internal microstructure, and the internal mechanism of the change with grain size is given. Secondly, the grain size is studied. The results show that the maximum adiabatic temperature change of ferroelectric materials increases with the increase of grain size in a certain range of temperature and size, and the corresponding temperature decreases with the decrease of grain size, so that the maximum adiabatic temperature change can be obtained at room temperature. For ferroelectric materials with different grain sizes, the change of adiabatic temperature with grain size is explained from the point of view of microstructure by combining with the domain structure in the grain near the transformation temperature point. Finally, based on the phase field model of ferroelectric ferromagnetic composites in real space, the effect of grain size on magnetoelectric composites is studied. The results show that the magnetoelectric coupling coefficient increases first and then decreases gradually with the increase of grain size. The magnetoelectric coupling coefficient will increase greatly only in the proper grain size range. It provides a theoretical basis for selecting appropriate grain size to obtain excellent Multifield Coupling Properties of polycrystalline ferroelectric materials.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM221

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