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The microstructures and dielectric properties of Y/Zn codoped BaTiO3 ceramics sintered in a reducing atmosphere were investigated. XRD analysis indicated the crystal structure of samples change from tetragonal to pseudocubic with increasing Y2O3 and ZnO content. SEM micrographs showed Y2O3 can suppress grain growth more effectively compared with ZnO, which is ascribed to the presence of second phase Y2Ti2O7. Proper amount of Y2O3 and ZnO can significantly improve the dielectric temperature characteristics due to the formation of grain core-shell structure. The high performance dielectrics meeting the X7R code were achieved by codoping 1.5 mol% Y2O3 and 3.0 mol% ZnO. [ABSTRACT FROM AUTHOR]

BaTiO3-based ultrafine nonreducible dielectrics for multilayer ceramic capacitors were prepared by a newly developed nanocomposite doping process. According to TG-DTA, XRD and TEM analysis, the nanocomposite dopants via sol–gel method were uniform and well dispersive. The micromechanism was investigated based on comparing conventional process with nano-doping process. It indicated that due to the special nano-effect, doping effect of additives became more effective and the microstructure and dielectric properties of ceramics were improved. The results showed that high performance dielectrics satisfying X8R specification were achieved, with high dielectric constant of 2,900, low dielectric loss of 0.6% and large insulation resistivity of 1012 Ω cm. [ABSTRACT FROM AUTHOR]

The effect of sintering atmosphere on the microstructure and capacity-temperature characteristics (TCC) of Yb-Mg and Yb-Mn substituted BaTiO3 was investigated. The XRD and SEM results indicated the suppression of the solubilities of the acceptor ions when firing under reducing conditions. Mn was confirmed to promote the grain growth of Yb2Ti2O7 while Mg could suppress the grain growth of this second phase. The X8R specification (−55 to 150°C, ΔC/C=±15% or less) could be satisfied by firing under proper conditions for the two compositions. It is suggested that the change of the solubilities of the acceptor ions, as well as the valence states of the Mn ions would affect the TCC behavior of the core-shell-structured BaTiO3 materials. [ABSTRACT FROM AUTHOR]