Dielectric ceramic and laminated ceramic capacitor using the same
A dielectric ceramic that includes a sintered body of BaTiO 3 based ceramic grains, in which the ceramic grains each include a shell part as a surface layer part and a core part inside the shell part. The ceramic grains contain, as accessory constituents, R (R, which is a rare-earth element, is at least one selected from the group consisting of Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, and Y) and M (M is at least one selected from the group consisting of Mg, Mn, Ni, Co, Fe, Cr, Cu, Al, Mo, W, and V). R and M are present in the shell part of the ceramic grain, and concentrations of R and M contained in the shell part are increased from a grain boundary toward the core part.
1. A dielectric ceramic comprising a sintered body including BaTiO 3 based ceramic grains as main phase grains,
wherein the ceramic grains each include a shell part as a surface layer part and a core part inside the shell part,
the ceramic grains contain, as accessory constituents, R and M,
R is at least one rare-earth element selected from the group consisting of Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, and Y,
M is at least one element selected from the group consisting of Mg, Mn, Ni, Co, Fe, Cr, Cu, Al, Mo, W, and V,
the R and the M are present in the shell part of the ceramic grain,
concentrations of the R and the M contained in the shell part increase from a grain boundary toward the core part,
a concentration of the R at the grain boundary<a concentration of the R at a core-shell boundary, and
a concentration of the M at the grain boundary<a concentration of the M at the core-shell boundary.
2. The dielectric ceramic according to claim 1 , wherein some of Ba in the BaTiO 3 based ceramic grains is substituted with Ca or Sr.
3. The dielectric ceramic according to claim 2 , wherein some of the Ti in the BaTiO 3 based ceramic grains is substituted with Zr.
4. The dielectric ceramic according to claim 1 , wherein some of the Ti in the BaTiO 3 based ceramic grains is substituted with Zr.
5. The dielectric ceramic according to claim 1 , wherein the BaTiO 3 based ceramic grains are formed from a ceramic raw material that comprises a first BaTiO 3 powder having an average grain size of 200 nm and a second BaTiO 3 powder having an average grain size of 50 nm.
6. The dielectric ceramic according to claim 5 , wherein a ratio of the first BaTiO 3 powder to the second BaTiO 3 powder is 8 to 2.
7. A laminated ceramic capacitor comprising:
a structure in which a plurality of dielectric layers and a plurality of internal electrodes are stacked,
wherein the dielectric layers comprise the dielectric ceramic according to claim 1 .