Fine-grain silver oxide powder
View Patent ↗A silver oxide powder that replaces silver powder as a silver conductive paste filler has a specific surface area measured by the BET method is 1.0–25.0 m 2 /g, average primary particle diameter is 1–50 nm, and average secondary particle diameter is 1–1000 nm. The silver oxide powder is made by preparing a neutralization medium that is an aqueous solution containing one or both of sodium hydroxide and potassium hydroxide in a total amount of 0.5 mole/L or less, simultaneously adding an aqueous solution containing silver salt in an amount of 6.0 mole/L or less and an aqueous solution of at least one of sodium hydroxide and potassium hydroxide to the liquid medium to conduct a neutralization reaction, thereby obtaining a neutralized precipitate, maintaining the liquid at a pH in the range of 12±1.5 during the reaction, and subjecting the precipitate to filtration, washing, and drying.
1. A fine-grain silver oxide dry powder comprising secondary particles which are a cluster of primary particles produced by a neutralization process, whose specific surface area measured by the BET method is 1.0–25.0 m 2 /g, average primary particle diameter is 1–50 nm, and average secondary particle diameter is 1–1000 nm.
2. A fine-grain silver oxide dry powder according to claim 1 , whose particle size distribution measured by the laser beam method using a 0.2 wt % aqueous solution of sodium hexametaphosphate is in the range of 1–1000 nm and exhibits a single distribution peak.
3. A fine-grain silver oxide dry powder according to claim 1 whose half-value width of diffraction peak on the (111) plane measured by X-ray diffraction was 0.25° or greater.
4. A method of producing a fine-grain silver oxide dry powder comprising secondary particles which are a cluster of primary particles produced by a neutralization process, whose specific surface area measured by the BET method is 1.0–25.0 m 2 /g, average primary particle diameter is 1–50 nm, and average secondary particle diameter is 1–1000 nm, the method comprising:
preparing a liquid neutralization medium that is an aqueous solution containing one or both of sodium hydroxide and potassium hydroxide in a total amount of 0.5 mole/L or less;
simultaneously adding an aqueous solution containing silver salt in an amount of 6.0 mole/L or less and an aqueous solution of at least one of sodium hydroxide and potassium hydroxide to the liquid medium to conduct a neutralization reaction, thereby obtaining a neutralized precipitate;
maintaining the liquid at a pH in the range of 12±1.5 during the neutralization reaction; and
subjecting the neutralized precipitate to filtration and washing followed by drying to form the fine grain silver oxide dry powder.
5. A method of producing a fine-grain silver oxide dry powder, comprising:
preparing a liquid neutralization medium that is an aqueous solution containing one or both of sodium hydroxide and potassium hydroxide in a total amount of 0.5 mole/L or less;
simultaneously adding an aqueous solution containing silver salt in an amount of 6.0 mole/L or less and an aqueous solution of at least one of sodium hydroxide and potassium hydroxide to the liquid medium to conduct a neutralization reaction, thereby obtaining a neutralized precipitate;
maintaining the liquid at a pH in the range of 12±1.5 during the neutralization reaction;
filtering off the obtained neutralized precipitate; and
redispersing the neutralized precipitate in a dispersant or organic solvent and subjecting it to wet pulverization;
subjecting the obtained dispersion to filtration and washing followed by drying the precipitate.
6. A method of producing a fine-grain silver oxide dry powder, comprising:
preparing a liquid neutralization medium that is an aqueous solution containing one or both of sodium hydroxide and potassium hydroxide in a total amount of 0.5 mole/L or less;
simultaneously adding an aqueous solution containing silver salt in an amount of 6.0 mole/L or less and an aqueous solution of at least one of sodium hydroxide and potassium hydroxide to the liquid medium to conduct a neutralization reaction, thereby obtaining a neutralized precipitate;
maintaining the liquid at a pH in the range of 12±1.5 during the neutralization reaction;
conducting the neutralization reaction in the presence of a protective colloid and/or a dispersant;
conducting the neutralization reaction at a temperature equal to or higher than the congealing point of the protective colloid and/or dispersant used and equal or lower than 110° C.; and
subjecting the neutralized precipitate to filtration and washing followed by drying.
7. A method of producing a fine-grain silver oxide dry powder, comprising:
preparing a liquid neutralization medium that is an aqueous solution containing one or both of sodium hydroxide and potassium hydroxide in a total amount of 0.5 mole/L or less;
simultaneously adding an aqueous solution containing silver salt in an amount of 6.0 mole/L or less and an aqueous solution of at least one of sodium hydroxide and potassium hydroxide to the liquid medium to conduct a neutralization reaction, thereby obtaining a neutralized precipitate;
maintaining the liquid at a pH in the range of 12±1.5 during the neutralization reaction;
conducting the neutralization reaction in the presence of a protective colloid and/or a dispersant;
conducting the neutralization reaction at a temperature equal to or higher than the congealing point of the protective colloid and/or dispersant used and equal or lower than 110° C.;
filtering off the obtained neutralized precipitate; and
redispersing the neutralized precipitate in a dispersant or organic solvent and subjecting it to wet pulverization;
subjecting the obtained dispersion to filtration and washing followed by drying the precipitate.
8. A method according to claim 6 , wherein the protective colloid is at least one of gelatin, gum arabic, dextrin and polyvinyl alcohol.
9. A method according to claim 6 , wherein the dispersant is at least one of sodium hexametaphosphate and ethylene glycol.
10. A method according to claim 5 , wherein the organic solvent is at least one among alcohols, esters, ketones and aldehydes.
11. A fine-grain silver oxide powder dispersion comprising the silver oxide dry powder set out in claim 1 dispersed in an organic solvent or sodium hexametaphosphate.
12. A dispersion set out in claim 11 , wherein the organic solvent is at least one among alcohols, esters, ketones and aldehydes.
13. A fine-grain silver oxide dry powder according to claim 2 whose half-value width of diffraction peak on the (111) plane measured by X-ray diffraction was 0.25° or greater.
14. A method according to claim 7 , wherein the protective colloid is at least one of gelatin, gum arabic, dextrin and polyvinyl alcohol.
15. A method according to claim 7 , wherein the dispersant is at least one of sodium hexametaphosphate and ethylene glycol.
16. A method according to claim 7 , wherein the organic solvent is at least one among alcohols, esters, ketones and aldehydes.
17. A fine-grain silver oxide powder dispersion comprising the silver oxide dry powder set out in claim 2 dispersed in an organic solvent or sodium hexametaphosphate.
18. A fine-grain silver oxide powder dispersion comprising the silver oxide dry powder set out in claim 3 dispersed in an organic solvent or sodium hexametaphosphate.