Capacitance aging under de field has been studied on BaTiO3-based diel
ectrics with X7R characteristics for multilayer ceramic capacitors wit
h Ni internal electrodes. Capacitance change strongly depends on addit
ives and firing conditions as well as microstructure. Aging behavior u
nder no dc field is well explained by Richter's relaxation curve. On t
he other hand, aging under de field cannot be fitted by Richter's curv
e. Therefore, a new model which assumes two factors that affect relaxa
tion is proposed. According to the new model, capacitance changes in t
wo stages, short-term and long-term relaxations. Capacitance change in
short-term relaxation strongly depends on applied de field. On the co
ntrary, that of long-term relaxation does not depend on de field.