Design and Synthesis of Dielectric Hybrid Nano Particles

近年来，通信系统的迅速发展要求高介电常数的介电材料具有平坦的温度特性和低损耗。Ba5Nb4O15、Sr2Nb2O7和LiNbO_3等Nb酸盐材料因其优异的介电性能和在微波通信中具有潜在的无铅应用前景而备受关注。为了设计和形成优良的介电基片，我们以化学成分可控的新型双金属醇盐为原料合成了Nb酸盐杂化纳米粒子。合成了Ba5Nb4O15、Sr2Nb2O7、LiNbO_3、NaNbO_3纳米粒子及其杂化材料。考察了醇盐前驱体的烷氧基对产物的影响。用透射电子显微镜、能谱仪和X射线衍射仪对样品的结构进行了表征，以阐明样品的形成过程、晶化过程、离子的取代极限、元素的分布和固结。以双金属醇盐为前驱体，采用受控放电等离子烧结工艺，获得了具有良好显微结构的纳米Nb_2O_3陶瓷。与传统的合成和烧结陶瓷相比，测量的介电常数显示出更高的数值和平坦的温度依赖关系，这可能是由于其设计的组成、精细的微结构和更高的密度所致。

The recent rapid expansion of telecommunication systems demand dielectric substances with high dielectric constant whose temperature dependence is flat and low loss. Some kinds of niobates such as Ba_5Nb_4O_<15>, Sr_2Nb_2O_7 and LiNbO_3 have recently attracted much attention because of excellent dielectric properties and lead-free materials potentially applicable in microwave communication.In this work, to design and form excellent dielectric substamces, we synthesized niobate hybrid nano-particles from the novel double-metal alkoxides with controlled chemical composition including Nb, Ba, Sr, Li and/or Na. Thus, nano-particles of Ba_5Nb_4O_<15>, Sr_2Nb_2O_7 , LiNbO_3 , NaNbO_3 and their hybrids were synthesized. The effects of alkoxyl group of the alkoxide precursors on the products were also examined. Structural characterization of the specimens were carried out with TEM, EDS and XRD to clarify formation process, crystallization, substitution limit of ions, elemental distribution and consolidation. The optimum consolidation conditions by spark-plasma-sintering, i.e., heating rate, temperature and time, were elucidated for niobate nano-particlesDense these niobate ceramics consisting of fine microstructures were obtained by the combination of using double metal alkoxides as the precursor for synthesis of the niobates and applying the controlled spark-plasma-sintering process. The measured permittivity showed higher values and flat dependence on temperature compared with those of the conventionally synthesized and sintered ceramics, due probably to its designed composition, fine microstructures and higher density