Design and Synthesis of Dielectric Hybrid Nano Particles

近年来，通信系统的快速发展对介电常数高、温度依赖性平、损耗低的介电物质提出了更高的要求。近年来，Ba_5Nb_4O_<15>、Sr_2Nb_2O_7和LiNbO_3等铌酸盐因其优异的介电性能和无铅材料在微波通信中的潜在应用而备受关注。在这项工作中，为了设计和形成优异的介电物质，我们从新型双金属醇氧化物中合成了铌酸盐杂化纳米颗粒，其化学成分包括Nb， Ba, Sr， Li和/或Na。合成了Ba_5Nb_4O_<15>、Sr_2Nb_2O_7、LiNbO_3、NaNbO_3及其杂化物的纳米颗粒。还考察了醇酮前体中烷氧基对产物的影响。利用TEM、EDS和XRD对试样进行了结构表征，以弄清试样的形成过程、结晶、离子取代极限、元素分布和固结情况。研究了铌酸盐纳米颗粒在火花等离子烧结过程中的最佳固结条件，即加热速率、温度和时间。采用双金属醇氧化物作为铌酸盐的前驱体，采用可控的火花等离子烧结工艺制备铌酸盐纳米陶瓷，得到了具有良好微观结构的致密铌酸盐陶瓷。与常规合成和烧结陶瓷相比，所测得的介电常数值更高，对温度的依赖程度更低，这可能是由于其设计的成分、精细的微观结构和更高的密度

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