Characterization And Preparation Of High-performance Barium Titanatebased Dielectric Materials Sintered In Different Sintering Atmospheres

The rapid development of the electronic information industry is increasingly demanding low-cost,high-capacity,high-performance multilayer ceramic capacitors(MLCC).A substantial cost saving can be achieved by utilizing base matel electrode as internal metallization over the more expensive precious metals such as Pd or Ag/Pd.Meanwhile,dielectric materials with higherpermittivity,excellent temperature stability,and being able to co-fire with base metal electrode are urgently needed.Barium titanate with a high permittivity(?_r>10³)can be co-fired with the base metal electrode by doping modification.However,it's not easy to regulate the polarization mechanism while sintered in reducing atmospheres,and it becomes difficult to achieve synergistic optimization of permittivity and temperature stability.In this work,the dielectric properties of barium titanate-based dielectric materials under reducing atmosphere were studied.The internal polarization mechanism was revealed and the influence factors of dielectric properties were investigated.And then,the barium titanate-based dielectric materials with ultra-high permittivity(?_r>10⁴)and excellent temperature stability were successfully prepared.This work has important theoretical significance and application value.The main work of this paper is as follows:(1)In order to adjust the dielectric propertie of BaTiO₃-0.5 wt%Na_0.5Ba_0.5Ti O₃-0.2 wt%Mn Nb₂O₆-0.9 wt%Ni Nb₂O₆-1.0 wt%CaZrO₃ system,the sintering atmosphere was effectively changed.(a)By analyzing the dielectric spectrum,the polarization relaxation processes were established.Combining with impedance spectrum and defect chemistry test,the polarization mechanisms were revealed and clarified.When sintered in 0.1%H₂/N₂,the sample possesses a most prominent comprehensive performance.(2)Based on the above research,in order to simplify the preparation process and to investigate the effect of donor ion doping on the dielectric properties of barium titanate under reducing atmosphere,ions of Nb⁵⁺were used to substitute B-site for barium titanate.(a)And then,the mechanism of Nb⁵⁺doping modification was explored by the analysis of dielectric responses,defect compensation and internal polarization mechanism.(b)When the doping content was 1.0 mol%,the sample with ultra-high permittivity and excellent insulation resistivity was prepared:?_r=66886,tan?=0.0347,?_v=4.21×10¹¹?·cm.However,with the change of temperature,the permittivity of this system changes sharply,the temperature stability needs to be improved.(3)In order to improve the temperature stability,ions of Mg²⁺were doped.(a)The establishment and change process of internal self-compensation mechanism was studied by the characterization of crystal structuremicrostructure and dielectric properties.Combining with the analysis of dielectric temperature curves and impedance spectrum,the influence of different polarization mechanisms on the temperature stability was investigated.(b)When the doping content was 1.0 mol%,the sample with ultra-high permittivity,excellent insulation resistivity and temperature stability was prepared:?_r=45844,tan?=0.0185,?_v=5.20×10¹¹?·cm,meeting the EIA X8R criteria:-55??150?,|?C/C25?(%)|?15%.(c)In order to further improve the temperature stability of this system,CaZrO₃ was introduced to control the“shell-core”structure,causes a large internal stress to shift the high-temperature permittivity peak.When the doping content was 2.0 wt%,the temperature change rate of the system material at 150?is increased from-14.8%to-11.5%,and the sample with excellent properties was prepared:?_r=45714,tan?=0.0216,?_v=6.52×10¹¹?·cm,meeting the EIA X8R criteria.