A melilite Ba2CuGe2O7 ceramic was characterized by low sintering temperature and moderate microwave dielectric properties.Sintered at 960℃,the Ba2CuGe2O7 ceramic had a high relative density 97%,a low relative permitt...A melilite Ba2CuGe2O7 ceramic was characterized by low sintering temperature and moderate microwave dielectric properties.Sintered at 960℃,the Ba2CuGe2O7 ceramic had a high relative density 97%,a low relative permittivity(εr)9.43,a quality factor(Q×f)of 20,000 GHz,and a temperature coefficient of resonance frequency(τf)-76 ppm/℃.To get a deep understanding of the relationship between composition,structure,and dielectric performances,magnesium substitution for copper in Ba2CuGe2O7 was conducted.Influences of magnesium doping on the sintering behavior,crystal structure,and microwave dielectric properties were studied.Mg doping in Ba2CuGe2O7 caused negligible changes in the macroscopic crystal structure,grain morphology,and size distribution,while induced visible variation in the local structure as revealed by Raman analysis.Microwave dielectric properties exhibit a remarkable dependence on composition.On increasing the magnesium content,the relative permittivity featured a continuous decrease,while both the quality factor and the temperature coefficient of resonance frequency increased monotonously.Such variations in dielectric performances were clarified in terms of the polarizability,packing fraction,and band valence theory.展开更多
XRD,TEM,ED,and NMR analyzed four types of blast furnace slags (BFS) with different structures in this paper. The composition requirement for phase separation in BFS glass phase was then put forward,that is the composi...XRD,TEM,ED,and NMR analyzed four types of blast furnace slags (BFS) with different structures in this paper. The composition requirement for phase separation in BFS glass phase was then put forward,that is the composition of slag locates in the coexisting phase region of melilite and any silicate mineral with Q0 units. The special structure of melilite units,a 5-membered ring with high degree of polymerization (DOP),plays a key role in the formation of phase separation. In BFS system,one with chemical composition of larger ratio of (CaO + MgO/(SiO2 + Al2O3) would be more promising to meet the requirement for phase separation.展开更多
基金National Natural Science Foundation of China(No.62061011)National Key R&D Program of China(No.2017YFB0406300)+1 种基金Natural Science Foundation of Guangxi Zhuang Autonomous Region(No.2018GXNSFAA281253)high-level innovation team and outstanding scholar program of Guangxi institutes.
文摘A melilite Ba2CuGe2O7 ceramic was characterized by low sintering temperature and moderate microwave dielectric properties.Sintered at 960℃,the Ba2CuGe2O7 ceramic had a high relative density 97%,a low relative permittivity(εr)9.43,a quality factor(Q×f)of 20,000 GHz,and a temperature coefficient of resonance frequency(τf)-76 ppm/℃.To get a deep understanding of the relationship between composition,structure,and dielectric performances,magnesium substitution for copper in Ba2CuGe2O7 was conducted.Influences of magnesium doping on the sintering behavior,crystal structure,and microwave dielectric properties were studied.Mg doping in Ba2CuGe2O7 caused negligible changes in the macroscopic crystal structure,grain morphology,and size distribution,while induced visible variation in the local structure as revealed by Raman analysis.Microwave dielectric properties exhibit a remarkable dependence on composition.On increasing the magnesium content,the relative permittivity featured a continuous decrease,while both the quality factor and the temperature coefficient of resonance frequency increased monotonously.Such variations in dielectric performances were clarified in terms of the polarizability,packing fraction,and band valence theory.
基金supported by the National Natural Science Foundation of China (Grant No.50954004)the National Science & Technology Pillar Program of China (Grant No.2007AA03Z529)
文摘XRD,TEM,ED,and NMR analyzed four types of blast furnace slags (BFS) with different structures in this paper. The composition requirement for phase separation in BFS glass phase was then put forward,that is the composition of slag locates in the coexisting phase region of melilite and any silicate mineral with Q0 units. The special structure of melilite units,a 5-membered ring with high degree of polymerization (DOP),plays a key role in the formation of phase separation. In BFS system,one with chemical composition of larger ratio of (CaO + MgO/(SiO2 + Al2O3) would be more promising to meet the requirement for phase separation.
