Ceria-zirconia solid solution crystal fine particles and their production process
View Patent ↗To provide a process for producing ceria-zirconia solid solution crystal fine particles having high crystallinity, being excellent in uniformity of composition and particle size, having a small particle size and a high specific surface area and being excellent in heat resistance, and such solid solution crystal fine particles. A process comprises a step of obtaining a melt containing, as represented by mol % based on oxides, from 5 to 50% of (ZrO 2 +CeO 2 ), from 10 to 60% of RO (wherein R is at least one member selected from the group consisting of Mg, Ca, Sr and Ba) and from 25 to 70% of B 2 O 3 , a step of quenching the melt to obtain an amorphous material, a step of heating the amorphous material at a temperature of from 550 to 1000° C. to precipitate a ceria-zirconia solid solution crystal in the amorphous material, and a step of separating components other than the ceria-zirconia solid solution crystal from the obtained precipitates to obtain the ceria-zirconia solid solution crystal fine particles, in this order.
1. A process for producing ceria-zirconia solid solution crystal fine particles, comprising (1) obtaining a melt containing, as represented by mol % based on oxides, from 5 to 50% of (ZrO 2 +CeO 2 ), from 10 to 60% of RO (wherein R is at least one member selected from the group consisting of Mg, Ca, Sr and Ba) and from 25 to 70% of B 2 O 3 by heating at a temperature of from 1200 to 1600° C., (2) quenching the melt to obtain an amorphous material, (3) heating the amorphous material at a temperature of from 550 to 1000° C. to precipitate ceria-zirconia solid solution crystals in the amorphous material, and (4) separating components other than the ceria-zirconia solid solution crystals from the obtained precipitates to obtain the ceria-zirconia solid solution crystal fine particles, in this order.
2. The process for producing ceria-zirconia solid solution crystal fine particles according to claim 1 , wherein in the chemical composition of the melt, ZrO 2 /(ZrO 2 +CeO 2 )=3 to 97%, as represented by mol % based on oxides.
3. The process for producing ceria-zirconia solid solution crystal fine particles according to claim 1 , wherein in the chemical composition of the melt, RO/(RO+B 2 O 3 )=10 to 70%, as represented by mol % based on oxides.
4. The process for producing ceria-zirconia solid solution crystal fine particles according to claim 1 , wherein in the chemical composition of the melt, Ca is contained as R.
5. The process for producing ceria-zirconia solid solution crystal fine particles according to claim 1 , wherein in the chemical composition of the melt, R is Ca.
6. The process for producing ceria-zirconia solid solution crystal fine particles according to claim 1 , wherein the amorphous material is of a flake form or a fiber form.
7. The process for producing ceria-zirconia solid solution crystal fine particles according to claim 1 , wherein (4) is carried out by using an acid.
8. The process for producing ceria-zirconia solid solution crystal fine particles according to claim 1 , wherein the ceria-zirconia solid solution crystals have a cubic crystal structure.
9. The process for producing ceria-zirconia solid solution crystal fine particles according to claim 1 , wherein in the chemical composition of the ceria-zirconia solid solution crystal fine particles, ZrO 2 /(ZrO 2 +CeO 2 )=1 to 99%, as represented by mol % based on oxides.
10. The process for producing ceria-zirconia solid solution crystal fine particles according to claim 1 , wherein in the chemical composition of the ceria-zirconia solid solution crystal fine particles, RO/(CeO 2 +ZrO 2 +RO+B 2 O 3 )=0.01 to 20%, as represented by mol % based on oxides.
11. The process for producing ceria-zirconia solid solution crystal fine particles according to claim 1 , wherein the ceria-zirconia solid solution crystal fine particles have an average primary particle size of from 5 to 200 nm.
12. The process for producing ceria-zirconia solid solution crystal fine particles according to claim 1 , wherein the ceria-zirconia solid solution crystal fine particles have a specific surface area of at least 20 m 2 /g.