The doping effect of rare-earths on the temperature-capacitance characteristics of MLCCs with Ni electrodes has been investigated for a BaTiO_3-MgO-Rare-earth system. The temperature dependence of capacitance is improved by the doping of smaller ionic radii rare-earth such as Er, Tm, Yb, and Lu. The Curie temperature shifts higher temperature by the doping of smaller ionic radii rare-earth elements. The tetragonality is increased by the doping of smaller ionic radii rare-earth elements, however the their grain sizes do not change. Many interference fringes aere observed in the sample which showed the increase of Curie temperature. A XRD analysis shows that the unit-cell volume of the shell phase replica, which has BaTiO_3-MgO-Re_2O_3 composition, is smaller than that of pure BaTiO_3. The tensile stress induced inside the core is calculated as 70MPa derived from the FEM analysis. The degree of Curie temperature shift that is expected from the calculated tensile stress shows the good agreement with Temperature Capacitance Characteristics (TCC) measurement result.
展开▼
