Highly crystalline silver powder and method for producing the same

Abstract

An object of the present invention is to provide highly crystalline silver powder which is characterized in fine particles, showing high dispersibility, it's particle size distribution is not excessively sharp but relatively broad and crystallites are large; and a method for producing the same. In order to achieve the object, a method for producing highly crystalline silver powder is characterized in that mixing a first aqueous solution and a second aqueous solution, wherein the first aqueous solution contains silver nitrate, a dispersing agent and nitric acid, and the second solution contains ascorbic acid. For dispersing agent, polyvinylpyrrolidone or gelatin is preferred. Highly crystalline silver powder produced by the above-described method is preferred to be a crystallite diameter of 300 Å or more, an average particle diameter D 50 in the range from 0.5 μm to 10 μm, and a thermal shrinkage rate for the length direction after heating at 700° C. in the range from −3% to 3%. For ratio D 90 /D 10 of the silver powder is preferred to be in the range from 2.1 to 5.0.

1 . A method for producing highly crystalline silver powder which is characterized in that mixing a first aqueous solution and a second aqueous solution, wherein the first aqueous solution contains silver nitrate, a dispersing agent and nitric acid, and the second solution contains ascorbic acid. 
   
   
       2 . The method for producing highly crystalline silver powder according to  claim 1 , wherein the dispersing agent is polyvinylpyrrolidone. 
   
   
       3 . The method for producing highly crystalline silver powder according to  claim 1 , wherein the dispersing agent is a gelatin. 
   
   
       4 . The method for producing highly crystalline silver powder according to  claim 2 , the first aqueous solution when it contains 100 parts by weight of silver nitrate, it further contains 5 parts by weight to 60 parts by weight of polyvinylpyrrolidone and 35 parts by weight to 70 parts by weight of nitric acid. 
   
   
       5 . The method for producing highly crystalline silver powder according to  claim 3 , the first aqueous solution when it contains 100 parts by weight of silver nitrate, it further contains 0.5 parts by weight to 10 parts by weight of gelatin and 35 parts by weight to 70 parts by weight of nitric acid. 
   
   
       6 . The method for producing highly crystalline silver powder according to  claim 1 , when the first aqueous solution contains 100 parts by weight of silver nitrate, ascorbic acid contained in the second aqueous solution to be mixed with the first aqueous solution is 30 parts by weight to 90 parts by weight. 
   
   
       7 . The method for producing highly crystalline silver powder according to  claim 1 , when the second aqueous solution contains 100 parts by weight of ascorbic acid, nitric acid contained in the first aqueous solution to be mixed with the second aqueous solution is 40 parts by weight to 150 parts by weight. 
   
   
       8 . Highly crystalline silver powder which is characterized in that the powder is produced by the method according to  claim 1 . 
   
   
       9 . The highly crystalline silver powder according to  claim 8 , wherein crystallite diameter of the powder is 300 Å or more. 
   
   
       10 . The highly crystalline silver powder according to  claim 8 , wherein an average particle diameter D 50  of the powder is in the range from 0.5 μm to 10 μm. (where D 50  is a median diameter (μm) calculated as 50% of volume cumulative distributions examined by a laser diffraction scattering particle size distribution measuring method). 
   
   
       11 . The highly crystalline silver powder according to  claim 8 , wherein a thermal shrinkage rate of the powder after heating at 700° C. is in the range from −3% to 3%. 
   
   
       12 . The highly crystalline silver powder according to  claim 8 , wherein a ratio D 90 /D 10  of the powder is in the range from 2.1 to 5.0 (where D 10  is diameter (μm) at 10% of volume cumulative distributions and D 90  is diameter (μm) at 90% of volume cumulative distributions examined by a laser diffraction scattering particle size distribution measuring method, respectively). 
   
   
       13 . Highly crystalline silver powder which is characterized in that a crystallite diameter is 300 Å or more, an average particle diameter D 50  is in the range from 0.5 μm to 10 μm, and a thermal shrinkage ratio after heating at 700° C. in the length direction is in the range from −3% to 3%. 
   
   
       14 . The highly crystalline silver powder according to  claim 13 , wherein a ratio D 90 /D 10  of the powder is in the range from 2.1 to 5.0 (where D 10  is diameter (μm) at 10% of volume cumulative distributions and D 90  is diameter (μm) at 90% by volume of cumulative distributions examined by a laser diffraction scattering particle size distribution measuring method, respectively).