Multilayer ceramic capacitor and its production method
The invention aims to provide a multilayer ceramic capacitor with high dielectric constant, a high capacitance, and an excellent reliability by eliminating oxygen vacancy in dielectric layers and suppressing oxidation of Ni inner electrodes. The multilayer ceramic capacitor comprises a multilayered dielectric body composed by alternately piling up dielectric layers containing mainly barium titanate and inner electrode layers containing mainly Ni and a first hetero-phase containing Mg—Si—O as constituent elements exists in the capacitor.
1. A multilayer ceramic capacitor comprising a multilayered dielectric body composed by alternately piling up a dielectric layer comprising a dielectric containing mainly barium titanate and an inner electrode layer containing mainly Ni, wherein a first hetero-phase containing Mg—Si—O as constituent elements exists.
2. The multilayer ceramic capacitor according to claim 1 , wherein the first hetero-phase exists in interfaces between the dielectric layers and the inner electrode layers or in the inner electrode layers.
3. The multilayer ceramic capacitor according to claim 2 , wherein the first hetero-phase further contains at least one element selected from Mn and Cr.
4. The multilayer ceramic capacitor according to claim 3 , wherein the second hetero-phase further contains Ca as a constituent element.
5. The multilayer ceramic capacitor according to claim 1 , wherein the first hetero-phase further contains at least one element selected from Mn and Cr.
6. The multilayer ceramic capacitor according to claim 1 , wherein a second hetero-phase containing Re—Si—O (wherein Re denotes one or more elements selected from Y, Dy, and Ho) does not exist in the dielectric layers or exists in a ratio smaller than that of the first hetero-phase if existing.
7. The multilayer ceramic capacitor according to claim 6 , wherein the dielectrics contain SiO 2 and MgO as first sub-components and the composition ratio of Si and Mg is (Si/Mg)<6.
8. The multilayer ceramic capacitor according to claim 6 , wherein the thickness of each dielectric layer between neighboring inner electrode layers is 5 μm or thinner and the average grain diameter of the ceramic grains composing the dielectric layers is 0.05 μm or larger.
9. The multilayer ceramic capacitor according to claim 6 , wherein the number of the dielectric layers layered between the inner electrode layers is 100 or more.
10. The multilayer ceramic capacitor according to claim 1 , wherein the dielectrics contain SiO 2 and MgO as first sub-components and the composition ratio of Si and Mg is (Si/Mg)<6.
11. The multilayer ceramic capacitor according to claim 10 , wherein the dielectrics contain a rare earth oxide Re 2 O 3 as a second sub-component at the composition ratio of Re and Mg (Re/Mg)≦6.
12. The multilayer ceramic capacitor according to claim 10 , wherein the content of MgO in the dielectrics is 2.5 mol or less to 100 mol of barium titanate.
13. The multilayer ceramic capacitor according to claim 12 , wherein the dielectrics contain at least one selected from MnO and Cr 2 O 3 as a third sub-component.
14. The multilayer ceramic capacitor according to claim 13 , wherein the dielectrics contain at least one selected from V 2 O 5 , MoO 3 , and WO 3 as a fourth sub-component.
15. The multilayer ceramic capacitor according to claim 1 , wherein the content of MgO in the dielectrics is 2.5 mol or less to 100 mol of barium titanate.
16. The multilayer ceramic capacitor according to claim 1 , wherein the thickness of each dielectric layer between neighboring inner electrode layers is 5 μm or thinner and the average grain diameter of the ceramic grains composing the dielectric layers is 0.05 μm or larger.
17. A production method of a multilayer ceramic capacitor comprising:
a green laminated body formation step of obtaining a green laminated body to be the multilayered dielectric body by alternately piling up the dielectric layers of dielectrics containing mainly barium titanate and inner electrode layers containing mainly Ni,
a firing step of forming the fired laminated body by firing the green laminated body in reducing atmosphere and precipitating the first hetero-phase containing Mg—Si—O as constituent elements in the dielectric layers, and
an annealing step of annealing the fired laminated body at a temperature lower than that in the firing step and in an oxygen partial pressure higher than that in the firing step.
18. The production method of a multilayer ceramic capacitor according to claim 17 , wherein in the annealing step, the first hetero-phase is shifted to the interfaces between the dielectric layers and the inner electrode layers or to the inner electrode layers.