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Microstructures, phase structures, and dielectric properties of Li and Sc co-doped NiO ceramics were systematically investigated. A high ε′ (~10) is observed in a wide temperature (200-420 K) and frequency (100-10 kHz) range. The increase of ε′ with Li concentration is related to the increase of grain size. With increasing temperature, ε′ enhances and the ε″ peak shifts to higher frequency, indicating a thermally activated relaxation process. The activation energy for relaxation is nearly comparable to that for grain conduction, implying the polarization process depends on the conducting of the charge in the grain interior. Complex impedance spectroscopy analysis shows the dielectric behavior is attributed to the boundary-layer capacitor mechanism and existing huge polarization. [ABSTRACT FROM AUTHOR]

The microstructure and corresponding tensile properties of both plain and Nb-microalloyed grades of ultrathin cast strip (UCS) low alloy steel produced using the CASTRIP process were studied. Both as-cast and hot-rolled strip cast steels with various levels of Nb microalloying were manufactured and investigated in this study. Hot rolling had little effect on the yield strength of Nb microalloyed UCS specimens for a given chemical composition, but resulted in a slightly finer microstructure. The effect of Nb microalloying was significant, and this is attributable to the promotion of finer, tougher austenite transformation products such as bainite and acicular ferrite at the expense of large polygonal ferrite grains. A fine dispersion of Nb solute clusters was observed in all Nb-containing steels following hot rolling, and it is suggested that this also contributes to the observed strengthening. [ABSTRACT FROM AUTHOR]

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]