Materials design and development of microwave dielectrics based on the crystal structure

基于晶体结构，研究了支持先进信息化社会微波通信的陶瓷谐振器在原子水平上的涌现机制。本研究是为了设计和开发新型陶瓷谐振器而进行的。1：成功地将烧结温度降低到1350℃，合成了改性Ba_<6-3x>R_<8+2x>Ti_<18>O_<54> (R=Sm, Nd)固溶体，其微波介电性能与1450℃烧结固溶体基本相当。这是通过将混合组分稍微筛向TiO_2一侧，使其成为共晶组分来实现的。2：明确了Bi阳离子在Ba_<6-3x>R_<8+2x>Ti_<18>O_<54> (R=Sm, Nd)固溶体中的溶解条件与微波介电性能的关系。之所以选择铋作为研究对象，是因为铋是一种阳离子，即使在相对较低的温度下也能促进烧结。在Ba_<6-3x>R_<8+2x>Ti_<18>O_<54> (R=Sm, Nd)固溶体中加入Bi，使材料在1350℃的工业适用温度下烧结成为可能，该温度比纯Ba_<6-3x>R_<8+2x>Ti_<18>O_<54> (R=Sm, Nd)固溶体所需温度低100℃。研究了BaWO_4对钨青铜类nd系固溶体的加性作用。虽然形成共晶混合物，但未观察到固溶体，烧结温度高达1460℃。添加BaWO_4后，质量系数（Q值为2500以上）得到改善。另一方面，随着BaWO_4.4的加入，介电常数降低，频率对温度的依赖性增加。从晶体结构的内部应变考察了Ba_<6-3x>R_<8+2x>Ti_<18>O_<54> (R=Sm, Nd, La)固溶体的质量因子。利用高能加速器研究组织（KEK）的光子工厂获得的精确的FWHM数据表明，在固溶体中观察到的质量因子显著依赖于晶体结构的内部应变。结果表明，在所有体系中表现出最佳微波介电性能的sm系固溶体，其晶体结构的内部应变最小。5：进一步研究了Eu添加剂对Ba_<6-3x>R_<8+2x>Ti_<18>O_<54> (R=Sm, Nd)固溶体微波介电性能的影响。显然，Sm-Nd和Eu系统形成了坚实的解决方案。加入Eu后，质量因子Q f提高到11000GHz，谐振频率处的温度系数τ_f减小。在Sm-Eu系统中，得到了τ_f为0，qf为9500GHz的固溶体。少

We investigated emergence mechanisms in the properties of ceramic resonators, which support microwave communication for advanced information-oriented society, in the atom level based on the crystal structure. This research was performed for the purpose of the design and development of new ceramic resonators.1 : It was succeeded in making sintering temperature decrease to 1350℃ for synthesis of modified Ba_<6-3x>R_<8+2x>Ti_<18>O_<54> (R=Sm, Nd) solid solutions with almost equivalent microwave dielectric properties to the solid solutions sintered at 1450℃. This was attained by that the starting mixing composition was sifted slightly to the TiO_2 side for making it the eutectic composition.2 : The correlation with the soluble condition of Bi cation into Ba_<6-3x>R_<8+2x>Ti_<18>O_<54> (R=Sm, Nd) solid solutions and their micowave dielectric properties was made clear. The reason why Bi was chosen for the investigation was that Bi is known as a cation which made it promote sintering even at … More relative low temperature. Addition of Bi into Ba_<6-3x>R_<8+2x>Ti_<18>O_<54> (R=Sm, Nd) solid solutions was made it possible that the material was sintered at industrial applicable temperature of 1350℃ which was 100℃ lower than that needed for pure Ba_<6-3x>R_<8+2x>Ti_<18>O_<54> (R=Sm, Nd) solid solutions.3 : Additive effects of BaWO_4 to the tungstenbronze type like Nd-system solid solutions were studied. Although an eutectic mixture was formed, no solid solutions were observed and its sintering temperature was as high as 1460℃. However, the improvement of the quality coefficient (Q fvalue : 2500 up) was seen by the addition of BaWO_4. On the other hand, the dielectric constant decrease and the temperature dependence of the frequency increased with addition of BaWO_4.4 : The quality factor of the tungstenbronze type like Ba_<6-3x>R_<8+2x>Ti_<18>O_<54> (R=Sm, Nd, La) solid solutions was examined from the internal strain in the crystal structure. Accurate FWHM data obtained by using photon factory in the High Energy Accelerator Research Organization (KEK) made it clear that the quality factor observed in the solid solutions significantly depended on the internal strain of the crystal structure. It was cleared that Sm-system solid solutions, which exhibited the best microwave dielectric properties of all the systems, demonstrated the smallest internal strain of the crystal structure of the specimens examined.5 : Further, effects of Eu additive on the microwave dielectric properties of Ba_<6-3x>R_<8+2x>Ti_<18>O_<54> (R=Sm, Nd) solid solutions were studied. It was cleared that Sm-Nd and Eu systems forms solid solutions. The quality factor Q f was improved to 11000GHz and the temperature coefficient (τ_f) at the resonant frequency was decreased by the addition of Eu. In the Sm-Eu system, a solid solution with τ_f of 0 and Q f of 9500GHz was obtained. Less