Dielectric Properties and Reliability of Zn_(0.95)Mg_(0.05)TiO_3+0.25TiO_2 MLCCs with Different Pd/Ag Ratios of Electrodes

摘要

In order to study the micromechanism of silver migration that influences the dielectric properties and reliability of Zn_(0.95)Mg_(0.05)TiO_3 + 0.25TiO_2 (ZMT") with 1 wt% 3ZnO-B_2O_3 multilayer ceramic capacitors (MLCCs), various silver (Ag)-palladium (Pd) ratios of conductors were used as inner electrodes. It was found that the electrical resistance of a MLCC sample with pure Ag as inner electrodes was degraded drastically to compared with the Ag/Pd inner electrodes at measuring temperatures ranging from 25℃ to 175℃. It may be explained that the pure Ag migrates easily into the dielectric layer along the grain boundary during co-firing. The ZMT" MLCCs exhibited increasing dielectric constant and insulation resistance considerably with increasing sintering temperature. Moreover, the results also indicate that Ag diffusion changes the dielectric properties and decreases the breakdown voltage. A ZMT" MLCC with a high Ag content in the inner electrode exhibits poor reliability, and the effect of Ag~+ migration is markedly enhanced when the activation energy of the ZMT" dielectric is considerably lowered due to the excessive formation of oxygen vacancies and the semiconducting Zn_2TiO_4 phase when Ag~+ substitutes for Zn~(2+) during co-firing.