Abstract
BaTiO3 is the dielectric ceramic which is usually used in multilayer ceramic capacitors. In order to decrease the manufacturing cost of multilayer ceramic capacitors, developing the BaTiO3-based X7R ceramic which can cofire with Cu electrodes becomes one of the important developing target. In this research, an as-received non-reducible BaTiO3-based X7R ceramic powder was used with the addition of Li2O-ZnO-B2O3 glass sintering aids (LZB-G) and Li2O-ZnO-B2O3 mixture sintering aids (LZB-M). Samples were sintered at 950 oC for 2 hours in the reducing atmosphere. The densification of X7R+LZB-M samples is better than that of X7R+LZB-G samples and the densification of samples increases as Li2O content increases. The results are attributed to the reaction between sintering aids and BaTiO3 which creates oxygen vacancies. The oxygen vacancies lead to higher diffusion rate and promote the densification. The dielectric constant of X7R+LZB-M samples is higher than that of X7R+LZB-G samples under the condition of the same Li2O content. Furthermore, the dielectric constant of samples increases as the amount of Li2O increases. By analysis, it is concluded that the densification of samples, residual glassy state, and c/a cause the difference between dielectric constants. X7R+LZB-G samples show higher temperature stability of the dielectric constants. Moreover, the temperature stability of the dielectric constants of samples enhances as the Li2O decreases. By TEM observation, semi-coherent interfaces between core and shell are found in the X7R+LZB-M sample with 30 mol% Li2O. The lower temperature stability in X7R+LZB-M sample with 30 mol% Li2O is caused by the lower strain present in the core-shell structure. XRD fitting is performed and the results show that c/a and the fraction of cubic phase both increase as the amount of Li2O increases, which consists with the conclusion from the previous sections.