Kentaro Sawamura

Core-shell domain structure in lead complex perovskite material

Core-shell structures in Pb(Mg1/3Nb2/3)O3-PbTiO3-Pb(Mg1/2W1/2)O3 (PMN-PT-PMW) with 2 wt% excess WO3 were discussed. With microstructural measurements, core-shell structures were observed in almost all grains. The cores, which show ferroelectric fringe patterns, were Nb-and-Ti-rich, while the shells were W-rich, accompanied by clear superlattice diffraction spots. In electrical measurements, the material showed ferroelectric D-E hysteresis loops and frequency dependence of the dielectric constant. These results can be explained by the structure wherein the cores consist of PMN-PT-rich solid solution which has a higher phase transition temperature, and the shells consist of PMW-rich solid solution which has a lower phase transition temperature.

JIS YB Lead Complex Perovskite Ferroelectric Material

Excess WO3 and higher sintering temperature were used for decreasing the temperature dependence of the dielectric constant in Pb(Mg1/3Nb2/3)O3-PbTiO3-Pb(Mg1/2W1/2)O3 ternary systems. Under some conditions, materials with both JIS YB specifications (dielectric constant change less than 10% over the temperature range from -25 to 85°C) and high dielectric constant, 5000-7400, were obtained. In the materials, core-shell-like distributions of B-site components were observed. These core-shell structures consist of W-rich regions and Ti, Nb-rich regions. In the compositions containing 2% WO3, sintered at 1150°C, core-shell-like domain structures are observed. The fringe pattern corresponded to the Ti, Nb-rich region, and superlattice electron diffraction spots indicating B-site ordering were observed in the W-rich region. In addition, the amounts of WO3 varied the appearance of the core-shell structure.

DiCI5a: Multilayer capacitors with copper inner electrodes

Abstract A new Multilayer Capacitor(MLC), made from relaxor material and copper inner electrodes was fabricated by using atmosphere controlled heat treatments. Pb(Mg1/3Nb2/3)O3-PbTiO3 modified material was used as a dielectric material. MgO and CaO additives were used to keep its IR in a low PO2 sintering state. The organic binder burnout section needs accurate atmosphere control. The carbon residue causes lead oxide to be reduced to metal, and other serious influences. On the other hand, treatment in higher PO2 induces copper oxidation. In this study, as a new technique, an H2-H2O-N2 gas mixture was used for the binder burnout section. The obtained MLC has a high capacitance, low DC bias dependence.

Control of valence structures in lead-magnesium niobate

Abstract The possibility of the valence control of lead-magnesium niobate has been examined by measurements of equilibrium electrical conductivity. The results indicate that the control of the magnesium/niobium ratio is significantly effective for the control of valence structures.