Method for manufacturing dielectric ceramic powder, and multilayer ceramic capacitor obtained by using the ceramic powder

Abstract

The invention relates to a method for manufacturing dielectric ceramic powder and a multilayer ceramic capacitor using the ceramic powder. According to the invention, BaCO 3 powder is dispersed into a solution of solvent and dispersant to prepare BaCO 3 slurry and then the resultant BaCO 3 slurry is wet-milled. Also, TiO 2 powder slurry is mixed into the wet-milled BaCO 3 slurry to form mixed slurry and then the mixed slurry is dried into mixed powder. Finally, the dried mixed powder is calcined to produce BaTiO 3 powder.

1 . A method for manufacturing dielectric ceramic powder comprising steps of: 
 dispersing BaCO 3  powder into a solution of solvent and dispersant to prepare a slurry and then wet-milling the slurry;    mixing TiO 2  powder slurry into the wet-milled BaCO 3  slurry to form mixed slurry and then drying the mixed slurry into mixed powder; and    calcining the dried mixed powder to produce BaTiO 3  powder.    
     
     
         2 . The method according to  claim 1 , wherein the solvent comprises distilled water or alcohol.  
     
     
         3 . The method according to  claim 1 , wherein the dispersant is polyacrylic, and added to 1˜5 weight parts with respect to the BaCO 3  powder.  
     
     
         4 . The method according to  claim 1 , wherein the BaCO 3  powder has a specific surface area ranging from 5 to 30 m 2 /g by BET measurement.  
     
     
         5 . The method according to  claim 1 , wherein BaCO 3  powder is dispersed into the solution to such an extent that the BaCO 3  slurry contains 10 to 60 wt % BaCO 3 .  
     
     
         6 . The method according to  claim 1 , wherein the BaCO 3  slurry is wet-milled to such an extent that BET specific surface area of BaCO 3  powder is at least 30 m 2 /g.  
     
     
         7 . The method according to  claim 1 , wherein in the wet-milling step, ammonia is added to reduce viscosity of the slurry.  
     
     
         8 . The method according to  claim 7 , wherein the ammonia is added to at least 0.1 weight parts with respect to the solvent.  
     
     
         9 . The method according to  claim 1 , wherein the TiO 2  powder has a specific surface area of at least 20 m 2 /g.  
     
     
         10 . The method according to  claim 1 , wherein the calcination temperature ranges from 900 to 1100° C.  
     
     
         11 . The method according to  claim 1 , further comprising pulverizing the produced BaTiO 3  powder.  
     
     
         12 . The method according to  claim 11 , wherein the pulverized BaTiO 3  powder has uniform particle size distribution, with mean particle size of 150 nm to 250 nm, D10/D50 of at least 0.6 and D90/D50 of up to 1.4 based on FE-SEM picture.  
     
     
         13 . The method according to  claim 11 , wherein the pulverized BaTiO 3  powder has at least 5.0 m 2 /g of BET specific surface area, and based on FE-SEM picture, a c/a ratio of C-axis to a-axis of the powder crystal lattice is at least 1.009.  
     
     
         14 . A method for manufacturing dielectric ceramic powder comprising steps of: 
 dispersing BaCO 3  powder into a solution of solvent and dispersant to prepare a slurry and then wet-milling the slurry;    mixing CaCO 3  powder slurry and TiO 2  powder slurry into the wet-milled BaCO 3  slurry to form mixed slurry, and then drying the mixed slurry; and    calcining the dried mixed powder to produce BaCaTiO 3  powder.    
     
     
         15 . The method according to  claim 14 , wherein the solvent comprises distilled water or alcohol.  
     
     
         16 . The method according to  claim 14 , wherein the dispersant is polyacrylic, and added to 1-5 weight parts with respect to the BaCO 3  powder.  
     
     
         17 . The method according to  claim 14 , wherein the BaCO 3  powder has a specific surface area of 5 to 30 m 2 /g by BET measurement.  
     
     
         18 . The method according to  claim 14 , wherein BaCO 3  powder is dispersed into the solution so that the BaCO 3  slurry contains 10 to 60 wt % BaCO 3 .  
     
     
         19 . The method according to  claim 14 , wherein the BaCO 3  slurry is wet-milled to such an extent that the BaCO 3  powder has a specific surface area of at least 30 m 2 /g.  
     
     
         20 . The method according to  claim 14 , wherein in the wet-milling step, ammonia is added to reduce viscosity of the slurry.  
     
     
         21 . The method according to  claim 20 , wherein the ammonia is added to at least 0.1 weight parts with respect to the solvent.  
     
     
         22 . The method according to  claim 14 , wherein the TiO 2  powder has a specific surface area of at least 20 m 2 /g.  
     
     
         23 . The method according to  claim 14 , wherein the calcination temperature ranges from 900 to 1100° C.  
     
     
         24 . The method according to  claim 14 , further comprising pulverizing the produced BaCaTiO 3  powder.  
     
     
         25 . The method according to  claim 24 , wherein the pulverized BaCaTiO 3  powder has uniform particle size distribution, with mean particle size of 150 nm to 250 nm, D10/D50 of at least 0.6 and D90/D50 of up to 1.4 based on FE-SEM picture.  
     
     
         26 . The method according to  claim 24 , wherein the pulverized BaCaTiO 3  powder has at least 5.0 m 2 /g of BET specific surface area, and based on FE-SEM picture, a c/a ratio of C-axis to a-axis of the powder crystal lattice is at least 1.009.  
     
     
         27 . A multilayer ceramic capacitor comprising: 
 a multilayer ceramic structure having a plurality of dielectric layers and a plurality of internal electrodes alternating with the dielectric layers; and    external electrodes provided at both ends of the multilayer ceramic, electrically connected to at least one of the internal electrodes,    wherein the dielectric layers comprise the dielectric ceramic powder manufactured according to  claim 1 .    
     
     
         28 . The multilayer ceramic capacitor according to  claim 27 , wherein the ceramic power has uniform particle size distribution, with mean particle size of 150 nm to 250 nm, D10/D50 of at least 0.6 and D90/D50 of up to 1.4 based on FE-SEM picture.  
     
     
         29 . The multilayer capacitor according to  claim 27 , wherein the ceramic powder has at least 5.0 m 2 /g of BET specific surface area, and based on FE-SEM picture, a c/a ratio of c-axis to a-axis of the powder crystal lattice is at least 1.009.