The cold sintering process (CSP) is an innovative technique to densify ceramic powders at ultralow temperatures by applying uniaxial pressure and using a transient solvent. However, obtaining dense Li1.5Al0.5Ge1.5(PO4)3 (LAGP) ceramics, which have high ionic conductivity, by CSP has been a challenging subject, because incongruent dissolution from the powder to a solvent can happen during CSP, and that deteriorates the grain boundary. In this study, LiNO3-LiOH salt is used as the transient solvent to suppress the incongruent dissolution. LAGP ceramics densified by the CSP at 220 °C and 400 MPa for 5 h have no damage at the grain boundary. As the result, the total ionic conductivity reaches 1.9 × 10−5 S cm−1, which is the highest value ever reported among LAGP ceramics prepared by CSP only using inorganic materials.

One of the methods to improve the lifetime of a multilayer ceramic capacitor with Ni electrode (Ni-MLCC) is vanadium addition. With the addition of vanadium, insulation resistance deteriorates and reliability improves. The resistance elements of the three resistor-capacitor electrical equivalent circuit: dielectric-electrode interface, grain boundary, and grain, all deteriorated. In particular, the interface resistance significantly deteriorated with the increase in vanadium. The experimental results suggest that the high interface resistance is not always necessary to improve reliability of Ni-MLCCs. It is deduced that oxygen vacancy formation is suppressed with vanadium addition from the first principles calculation and the thermally stimulated depolarization current analysis. Therefore, the decrease in oxygen concentration is the main factor for improving reliability with vanadium addition.

The effect of slight molybdenum doping of perovskite-type BaTiO3-based ceramics on the reliability of a multilayer ceramic capacitor (MLCC) and on the valence state of molybdenum in the BaTiO3-based ceramics has been investigated by highly accelerated lifetime tests and X-ray absorption fine structure analysis. The molybdenum added to the BaTiO3-based ceramics is located at Ti sites and improves the highly accelerated lifetime and lowers the initial dielectric resistivity in MLCCs. Through sintering in a reducing atmosphere, which is an important process in the fabrication of BaTiO3-based MLCCs, the oxidation state of the molybdenum added could be adjusted from +6 to a value close to +4.

In order to obtain material design guidelines for next-generation multilayer ceramic capacitors (MLCCs) from the viewpoint of polarization behavior, we investigated the changes in polarization behavior with AC-and Unipoling treatment using (Ba,Ca)(Ti,Zr)O 3 -based MLCC samples in which a part of the BaTiO 3 in the core was modified with Ca and Zr. Comparisons with DC-aging measurements confirmed that the AC-and Uni-poling treated samples clearly showed a unique phenomenon in which the domain wall of the (Ba,Ca)(Ti,Zr)O 3 -based core phase moves faster than that of the BaTiO 3 -based core phase. AC-and Uni-poling treatments are expected to be useful tools for evaluating the relationship between more detailed microstructure and polarization behavior of dielectric materials.

The Schottky barrier (SB) height at insulator/metal interfaces is important for a wide variety of electronic devices. We performed first-principles analysis of the SB formed between BaTiO3 (BTO) and metals with a cubic crystal structure. We found that the barrier height strongly depends on the contact metal and the BTO termination surface. These results were quantitatively understood by analyzing the contributions of the atomic and charge rearrangement at the interfaces. It was also found that when a different metal is substituted for one of the monoatomic Ni layers at the BTO/Ni interface, the SB is significantly influenced by the nature of the substituting metal.