Control of Shrinkage Behavior and Thermal Expansion Coefficient in BaTiO_3-added Ni Electrodes

摘要

In this study, shrinkage behavior and coefficient of thermal expansion (CTE) of novel nickel (Ni) powder with an addition of dielectric material, BaTiO_3, have been investigated to reduce the large shrinkage mismatch between Ni electrode and dielectric material and to control the thermal and/or residual stresses created by CTE mismatch in MLCCs (multilayer ceramic capacitors). For which two kinds of Ni powders were used. The component of Ni powders is analyzed by XRF, and the thermal behavior is measured by TG/DTA. The Ni and BaTiO_3 powders were mixed with 9:1, 8:2, and 7:3 volume ratios. The BaTiO_3-added Ni green bodies were fabricated through cold isostatic pressing, and then sintered to 1300℃ in a reduction atmosphere. The shrinkage behavior with volume ratio was checked during sintering from 700 to 1300℃ with 300℃ interval. The CTE was measured in inert (argon) atmosphere with sintered samples. It is found that the shrinkage behavior and the CTE of Ni electrode are dependent on the volume of BaTiO_3 added. The particle size of Ni powder also affects the microstructure and its sintering density, with less effect of its component.