Study On Microwave Dielectric Ceramics Based On CaTiO₃

As one kind of key information function materials, microwave dielectric ceramics are widely applied in microwave communication technologies. The compounds were prepared by means of solid state reaction in this paper. XRD analysis, SEM observation and the measurements of dielectric properties at microwave frequency were employed in the present study. The sintering condition, the phase constitution, microstructure and microwave dielectric properties of microwave dielectric materials based on CaTiO₃ were investigated as well as the relationship between the microstructure and the property.CaTiO₃(ε=170,Q?f=3600GHz,Ï„f=+800ppm/℃)has large positiveÏ„f. This study based on CaTiO₃ or CaTiO₃ doped with Nd. The Ca(Mg1/3Nb2/3)O₃ with negativeÏ„f and high Q combined with CaTiO₃ to conduct B-site substitution. The (Li_1/2Sm_1/2)TiO₃ with negativeÏ„f and highεcombined with CaTiO₃ doped with Nd to conduct A-site substitution. The NdAlO₃ with negativeÏ„f and high Q combined with CaTiO₃ to conduct substitution between different microstructure materials. The modification of microwave dielectric properties of CaTiO₃ with the high Q and negativeÏ„f materials, which were chosen to compensate the temperature coefficient, was trying to search near-zeroÏ„f with highε, high Q?f.(1-x)CaTiO₃-xCa(Mg1/3Nb2/3)O₃ system formed a complete solid solution with a single orthorhombic perovskite structure within the entire composition range of the investigation(x=0.4⁰.7). The permittivity decreased from 73 to 31.5, Q?f value increased from 12233GHz to 32446GHz, andÏ„f moved to negative form 56.1ppm/℃to -13.3ppm/℃. Good microwave dielectric properties were obtained for (1-x)CaTiO₃-xCa(Mg_1/3Nb_2/3)O₃ ceramics with x=0.65:ε=39.89, Q?f=30721GHz,Ï„f=-7.2ppm/℃.(1-x)(Ca0.61Nd0.26)TiO₃-x(Li_1/2Sm_1/2)TiO₃(x=0.2⁰.7) system sintered to densification at 1250℃×3h. A complete solid solution with orthorhombic perovskite structure formed in the entire composition range of the investigation. The permittivityand Q?f value decreased gradually as (Li1/2Sm1/2)TiO3 content(0.2≤x≤0.7) increased.ε: 117.67⁹0.30, Q?f:5991GHz³181GHz. When x=0.5,ε=98, Q?f=4259GHz,Ï„f≈0ppm/℃.(1-x)CaTiO3-xNdAlO3(x=0.2, 0.25, 0.3, 0.35) system formed a complete solid solution with a single orthorhombic perovskite structure within the entire composition range of the investigation. The permittivity and coefficient of resonant frequency decreased linely with the increasing x. Sintered at 1450℃×4h,ε: 60.42³4.80;Ï„f: 90ppm/℃^-23ppm/℃. The Q?f value increased from 23000GHz to 29300Ghz, and it depended on the cooling rate severely. When x=0.3ε=40.4, Q?f=34100GHz,Ï„f≈0ppm/℃.