Their dielectric loss is about 10 - 2 , and figure of merit ( fom ) is less than 300 . recently , cross etc . found that lead strontium titanate ( pst ) has bigger tunability and lower loss , besides this , pst is a perovskite ferroelectric material which has good solid solution 就微波可调介电材料而言，目前研究较多、性能较好的主要是钛酸锶钡( bst )及其掺杂系列，其可调性一般在50左右，介电损耗在10 ~ ( - 2 )量级上，综合反映材料可调性的优值一般在300以下。
The thesis mainly investigated the bati _ 4o _ 9 ( bt _ 4 ) , which has the lowest dielectric loss in ba - ti system , and ( ba , sr ) tio _ 3 , the a position substitute compound of batio _ 3 . the dielectric properties of bt _ 4 / bst with different preparation way and different elements doping were investigated . a archimedes method , xrd , sem , impedance analyzer , network analyzer and hakki - coleman method were used to investigate the density , phase formation , microstructure , dielectric properties and doping mechanisms 本论文以在ba - ti系中具有最低介电损耗的bati _ 4o _ 9 ( bt _ 4 )高频介质陶瓷和batio _ 3a位sr取代而得的( ba , sr ) tio _ 3 ( bst )高频介质陶瓷作为研究对象,对不同粉体制备方法制备的bt _ 4 / bst高频电介质材料进行不同元素的掺杂,运用阿基米德方法, x射线衍射分析仪,扫描电子显微镜和阻抗分析仪,网络分析仪, hakki - coleman法等方法手段和测试仪器测试烧成样品的密度,相组成情况,微观结构和介电性能,探讨造成介电性能起伏的形成机理。
The first part of this thesis includes the following information : ( 1 ) the significance of materials and the progress in every fields of material science in recent years ; ( 2 ) the history of magnetic material and the classification of magnetic material ; ( 3 ) the emergency and the classification of organic magnetic materials as well as the significant progress in the field of ferrocene polymeric magnet recently ; ( 4 ) introducing die development and the status quo of dielectric polymer and discussing the four parameters which are used to characterize the dielectric beheaviour of material , these parameters mclude dielectric constants dielectric loss ^ electric conductivity and breakdown strength 本文在开头部分简单讲述了以下内容了： ( 1 )材料的重要性以及近些年来材料业各个领域的发展； ( 2 )磁性材料的发展史以及磁性材料的分类； ( 3 )有机磁性材料的出现、有机磁性材料的分类和近些年来有机金属磁性材料尤其是二茂铁高分子磁体领域所取得的重要进展； ( 4 )高分子介电材料的发展与现状，对表征材料介电性能的四个重要参数即介电常数、介电损耗、电导率和击穿强度做了比较详尽的论述。
It is shown that good performance on millimeter - wave and centimeter - wave can be achieved respectively by electric loss and magnetic loss , then through improving the impedance matching between layers compatible absorbability will be obtained on the whole by double - layer structure letting the centimeter - wave absorbing layer be the inner layer and the millimeter - wave absorbing layer the outer layer 理论分析和实验结果表明，先分别以电损耗和磁损耗为主，采用单层结构分别对毫米波和厘米波实现较好的吸收，然后以厘米波吸收层作为内层，以毫米波吸收层作为外层，并进一步改善内外层之间的阻抗匹配，利用两层结构可以对毫米波和厘米波实现较好的兼容吸收。
The result of research into electromagnetic beheaviours of polymeric magnets as follows : all of the two agents ( acrylic acid and polycarbonate ) can reduce effectively magnetic loss and dielectric loss , moreover , acrylic acid can increase the dielectric constant of the polymeric magnet at high frequency and microwave band . on the whole , the polymeric magnet modified by acrylic acid is preferable . the research of ir spectrum and xps of the polymeric magnets have showed that modifying polymeric magnet with acrylic acid is a chemical method in the part of composing polymer , we have chosen ferrocene as raw stuff 对改性前后高分子磁体的电磁性能研究结果表明：用丙烯酸或聚碳酸酯对高分子磁体进行表面改性，两种试剂均不影响高分子的磁导率，并且它们均有效地降低了高分子磁体的磁损耗和介电损耗，更有研究意义的足：丙烯酸使高分子磁体在高频微波下的介电常数得到明显提高：从总的方面来说，丙烯酸改性高分子磁体优于用聚碳酸酯改性的高分子磁体。
The dielectric constants of silica - rich , alumina - rich , and stoichiometric mullite ceramics are 5 . 5 , 6 . 0 and 6 . 3 respectively . the dielectric constant of mullite - si / c / n composites is related with the sintering parameters . with the increase of the sintering temperature and dwelling time , the " " and tg of mullite - si / c / n composites are decreased , this phenomenon is related with the change of the microstructure and phase composition of nano si / c / n powders 莫来石- si c n复合材料的介电常数与热压烧结工艺有很大的关系，随热压烧结温度( 1450 1600之间)的升高，烧结时间(烧结温度为1550 )的增长，莫来石- si c n复合材料的介电常数实部、虚部及介电损耗角正切均明显下降，这与吸收剂的性质随温度和时间的变化有关。
And it also found that the relative densities of the samples annealed under loompa were 10 percent above those of the samples annealed without pressure . based on this fabrication process , the pan was introduced to enhance the uniformity of the composite , thus the piezoelectricity was greatly improved and the poling voltage can be lowered 在此基础上，发现在pvdf pzt体系中引入少量导电聚合物pan并使其均匀分布于材料内部时提高了陶瓷相的极化率和压电复合材料的压电性能，并且根据介电常数介电损耗及与温度关系的分析可知，添加少量pan的pzt pvdf压电复合材料具有更宽的温度使用范围，温度依赖性小。
Compared with cmo and cpm , scm had many advantages not only simpling preparation process , lowing calcining and sintering temperatures , shorting reacting time , but also preparing ceramics with excellent dielectric properties . with identical calcining conditions , the content of perovskite phase in calcined powders prepared by scm was much higher than that by cmo , what ' s more , by scm , the sintered ceramics had clear crystal boundaries , large - sized crystal grains and high density 、 pbo bi仙混合助烧剂（摩尔比为1 ： 1 ： 1 ）都达到了理想的助烧效果，可将烧结温度降低到900oc ，且介电性能优良，样品介电常数分别不小于is000和22000 ，介电损耗分别不大于0
Furthermore , the absorbent ' s electroconductibility as the function of its permittivity and permeability was also uncovered . the reflectance of the absorbents was calculated , and the effects of the preparation and the thickness on the absorbing ability were discussed . in a word , the prepared ilmenite absorbents are non - magnetic materials , at given thickness used in applications , the single - layered absorbents have the minimal reflectivity of - 50db and maximal bandwidth of 5ghz 初步研究表明：钛酸亚铁类化合物属于电损耗材料；在实际应用允许的设定厚度范围内( 2 . 0mm ) ，单层吸收剂的最小反射率( rmin )可达- 50db左右，最大带宽( ? db )接近5个ghz ，吸波性能很好。
But there is a main question that pvdf does not be in p phase with higher piezoelectric property , but be in other phases with lower or without piezoelectric property , thus , which can not improve distinctly piezoelectric constant d33 , reduce notably dielectric spoilage ( tg5 ) and raise remarkably mechanical coupling factor ( kp ) of 0 - 3 pzt / pvdf piezoelectric composite , so these will restrict its development and application . in this paper , 0 - 3 pzt / pvdf piezoelectric composite will be prepared by room pressing - solidity , high - temperature - pressing and room - pressing techniques respectively 由于这个压电复合材料体系存在一个主要问题? pvdf在0 ? 3型pzt / pvdf压电复合材料中通常不是以具有较强压电性的相晶态形式呈现，多是以其它的相态存在，不能有效地提高0 ? 3型pzt / pvdf压电复合材料的压电常数d _ ( 33 ) 、降低介电损耗tg和增大机电耦合系数kp等压电和介电性能，从而严重地制约它的发展和应用。
