Dielectric composition and multilayer ceramic capacitor containing the same

Abstract

A multilayer ceramic capacitor includes: a ceramic body including dielectric layers and first and second internal electrodes disposed to face each other with respective dielectric layers interposed therebetween; and first and second external electrodes disposed on an external surface of the ceramic body, wherein the dielectric layer contains a barium titanate-based powder particle having a core-shell structure including a core and a shell around the core, the shell having a structure in which titanium is partially substituted with an element having the same oxidation number as that of the titanium in the barium titanate-based powder particle and having an ionic radius different from that of the titanium in the barium titanate-based powder particle, and the shell covers at least 30% of a surface of the core.

What is claimed is: 
     
       1. A multilayer ceramic capacitor comprising:
 a ceramic body including dielectric layers and first and second internal electrodes disposed to face each other with respective dielectric layers interposed therebetween; and 
 first and second external electrodes disposed on an external surface of the ceramic body, 
 wherein each at least one of the dielectric layer layers contains a barium titanate-based powder particle material comprising dielectric grains having a core-shell structure including a core and a shell around the core, the shell including Ba(Ti 1-x M x )O 3  in which titanium is partially substituted with an element M including at least one of Sn and Hf, and the shell covering at least 30% of a surface of the core, and 
 a content of M in the shell is higher than a content of M in the core, 
 wherein the core includes M, and a content ratio of M in the core to that in the shell is 1/10 or more. 
 
     
     
       2. The multilayer ceramic capacitor of  claim 1 , wherein M is Sn. 
     
     
       3. The multilayer ceramic capacitor of  claim 1 , wherein the core includes M, and a content ratio of M in the core to that in the shell is 1/10 or more. 
     
     
       4. The multilayer ceramic capacitor of  claim 1 , wherein a molar ratio (Ba/Ti) of Ba to Ti is 1.0150 or more. 
     
     
       5. The multilayer ceramic capacitor of  claim 1 , wherein in each dielectric layer, the shell covers at least 50% of the surface of the core before sintering. 
     
     
       6. The multilayer ceramic capacitor of claim  5  1, wherein in each dielectric layer the barium titanate-based material, the a number of dielectric grains of which the shell covers at least 50% of the surface of the core before sintering and covers at least 30% of the surface of the core after sintering is within in a range of from 35 to 85% of the an overall number of dielectric grains. 
     
     
       7. The multilayer ceramic capacitor of  claim 1 , wherein the shell has a thickness within in a range of from 2 nm to 50 nm. 
     
     
       8. The multilayer ceramic capacitor of  claim 1 , wherein the core includes M, and a content ratio of M in the core to that in the shell is 1/5 or more before sintering and 1/10 or more after sintering. 
     
     
       9. A dielectric composition comprising:
 a barium titanate-based powder particle material comprising dielectric grains having a core-shell structure including a core and a shell around the core, 
 wherein the shell has a structure in which titanium is partially substituted with an element M having the same oxidation number as that of titanium and having an ionic radius different from that of titanium, and the element M is at least one of Sn and Hf, and 
 a content of M in the shell is higher than a content of M in the core, 
 wherein the core includes the at least one Sn and Hf, and a content ratio of the at least one Sn and Hf in the core to that in the shell is 1/5 or more. 
 
     
     
       10. The dielectric composition of  claim 9 , wherein the at least one of Sn and Hf is coated or doped on the core. 
     
     
       11. The dielectric composition of  claim 9 , wherein the shell has a radius within thickness in a range of from 2% to 30% of a radius of the barium titanate-based powder particle dielectric grains. 
     
     
       12. The dielectric composition of  claim 9 , wherein the shell covers at least 50% of a surface of the core. 
     
     
       13. The dielectric composition of  claim 9 , wherein the core includes the at least one of Sn and Hf, and a content ratio of the at least one of Sn and Hf in the core to that in the shell is 1/5 or more. 
     
     
       14. The dielectric composition of  claim 9 , further comprising:
 an oxide or carbonate containing at least one of Mn, V, Cr, Fe, Ni, Co, Cu, and Zn in a content within in a range of from 0.2 to 2.0 at % based on 100 at % of the barium titanate-based powder particle material; 
 an oxide or carbonate containing at least one of Ba and Ca, in a content of in a range from 0.0 to 3.0 at % based on 100 at % of the barium titanate-based powder particle material; 
 an oxide or carbonate containing Si or the glass compound containing Si, in a content of in a range from 0.2 to 5.0 at % based on 100 at % of the barium titanate-based powder particle material; 
 an oxide or carbonate containing at least one of Y, Dy, Ho, Er, Gd, Ce, Nd, Sm, La, Tb, Yb, and Pr, in a content of in a range from 0.0 to 4.0 at % based on 100 at % of the barium titanate-based powder particle material; and 
 an oxide or carbonate containing Mg or Al in a content of in a range from 0.0 to 2.0 at % based on 100 at % of the barium titanate-based powder particle material. 
 
     
     
       15. The multilayer ceramic capacitor of  claim 1 , wherein M has the same oxidation number as that of the titanium in the barium titanate-based powder particle material and has an ionic radius different from that of the titanium in the barium titanate-based powder particle material. 
     
     
       16. The multilayer ceramic capacitor of  claim 1 , wherein M is Hf. 
     
     
       17. The dielectric composition of  claim 9 , wherein the shell contains Sn. 
     
     
       18. The dielectric composition of  claim 9 , wherein the shell contains Hf. 
     
     
       19. A multilayer ceramic capacitor comprising:
 a ceramic body including dielectric layers and first and second internal electrodes disposed to face each other with respective dielectric layers interposed therebetween; and 
 first and second external electrodes disposed on an external surface of the ceramic body, 
 wherein each at least one of the dielectric layer layers contains a barium titanate-based powder particle material comprising dielectric grains having a core-shell structure including a core and a shell around the core, the shell having a structure in which titanium is partially substituted with an element having the same oxidation number as that of the titanium in the barium titanate-based powder particle material and having an ionic radius different from that of the titanium in the barium titanate-based powder particle material, and 
 a number of dielectric grains of which the shell covers at least 50% 30% of the surface of the core before sintering is within in a range of 35 35% to 85% of the overall number of dielectric grains. 
 
     
     
       20. The multilayer ceramic capacitor of claim 1, wherein the dielectric layers have a thickness of 0.2 μm or more, and the first and second internal electrodes have a thickness in a range from 0.1 μm to 5 μm. 
     
     
       21. The multilayer ceramic capacitor of claim 1, wherein in the at least one dielectric layer, a number of dielectric grains of which the shell covers at least 30% of the surface of the core is in a range of 35 to 85% of an overall number of dielectric grains. 
     
     
       22. The multilayer ceramic capacitor of claim 1, wherein each of the dielectric layers contains a barium titanate-based material comprising dielectric grains having the core-shell structure. 
     
     
       23. The multilayer ceramic capacitor of claim 19, wherein the element having the same oxidation number as that of titanium is selected from the group consisting of Hf, and Sn. 
     
     
       24. The multilayer ceramic capacitor of claim 19, wherein a molar ratio (Ba/Ti) of Ba to Ti is 1.0150 or more. 
     
     
       25. A multilayer ceramic capacitor comprising:
 a ceramic body including dielectric layers and first and second internal electrodes disposed to face each other with respective dielectric layers interposed therebetween; and   first and second external electrodes disposed on an external surface of the ceramic body,   wherein at least one of the dielectric layers contains a barium titanate-based material having core-shell structures, each of the core-shell structures including a core and a shell around the core, the shell having a structure in which titanium is partially substituted with an element having an ionic radius different from that of titanium in the barium titanate-based material, and   a number of core-shell structures of which the shell covers at least 30% of the surface of the core is in a range of 35% to 85% of an overall number of core-shell structures.