Multi-layer ceramic capacitor and method of manufacturing the same

Abstract

A multi-layer ceramic capacitor has a structure where the dispersion, nd, of average grain size of the dielectric grains constituting the dielectric layer (a value (D90/D10) obtained by dividing D90 which is a grain size including 90% cumulative abundance of grains by D10 which is a grain size including 10% cumulative abundance of grains) is smaller than 4.

The invention claimed is: 
     
       1. A multi-layer ceramic capacitor constituted by sintered dielectric layers and internal electrode layers alternately layered with one another, wherein dielectric grains constitute a sintered grain body which forms the sintered dielectric layers, and a dispersion, nd, of average grain size of the dielectric grains (a value (D90/D10) obtained by dividing D90 which is a grain size including 90% cumulative abundance of grains by D10 which is a grain size including 10% cumulative abundance of grains) is smaller than 4, said dielectric grains being sintered and grown to wherein an average size of sintered grains in the sintered grain body is greater than 300 nm but smaller than 1000 nm. 
     
     
       2. A multi-layer ceramic capacitor according to  claim 1 , wherein the dielectric layer does not contain Mg. 
     
     
       3. A multi-layer ceramic capacitor according to  claim 2 , wherein an average of the dielectric grains is greater than 300 nm but smaller than 100 nm. 
     
     
       4. A multi-layer ceramic capacitor according to  claim 1 , wherein the dielectric layer contains 0.03 mol or less of Mg per 100 mol of BaTiO 3 . 
     
     
       5. A multi-layer ceramic capacitor according to  claim 4 , wherein the dielectric layer contains 0.01 mol or more but 0.03 mol or less of Mg per 100 mol of BaTiO 3 . 
     
     
       6. A multi-layer ceramic capacitor according to  claim 5 , wherein an average size of the dielectric grains is greater than 300 nm but smaller than 1000 nm. 
     
     
       7. A multi-layer ceramic capacitor according to  claim 4 , wherein an average size of the dielectric grains is greater than 300 nm but smaller than 1000 nm. 
     
     
       8. A multi-layer ceramic capacitor according to  claim 1 , wherein the multi-layer ceramic capacitor has an accelerated life of 25 hours or longer as measured by an accelerated life test conducted under conditions of 150° C. and 8.5 V/μm. 
     
     
       9. A multi-layer ceramic capacitor according to  claim 1 , wherein the multi-layer ceramic capacitor has a specific dielectric constant of 5000 or greater. 
     
     
       10. A method of manufacturing a multi-layer ceramic capacitor comprising:
 a step to prepare a dielectric material powder whose average grain size is 200 nm or less, and 
 a step to sinter the dielectric material powder in such a way that a dispersion of average grain size nd (grain size D90 equivalent to 90% cumulative abundance divided by grain size D10 equivalent to 10% cumulative abundance (D90/D10)) of dielectric grains constituting a dielectric layer becomes smaller than 4, and an average size of the dielectric grains becomes greater than 300 nm but smaller than 1000 nm. 
 
     
     
       11. A method of manufacturing multi-layer ceramic capacitor according to  claim 10 , wherein an average grain size of the dielectric material powder is 80 nm or greater but 200 nm or smaller.