Process for producing niobium suboxide
View Patent ↗A method is described for preparing a niobium suboxide represented by the formula, NbO x , in which 0.7<x<1.3. The method involves reacting NbOy (in which y<1.8<2.1) with a stoichiometric amount of niobium metal, in the presence of hydrogen. The niobium suboxide produced by such method may be used to fabricate anodes for solid electrolyte capacitors.
1. A method of producing NbO x consisting essentially of the sequential steps of
A) producing NbO y , wherein 1.8<y<2.1, by reducing niobium pentoxide under flowing hydrogen at a hydrogen partial pressure of 50 to 1100 mbar, the temperature during the reduction of the pentoxide to form the dioxide is to be gradually increased from a starting temperature in the range from 1,000° C. to 1,100° C. to a temperature in the range from 1300° C. to 1600° C. the temperature in the range of 1300° C. to 1600° C. being a maximum temperature, and the NbO y is held at a temperature of from 900° C. to 1600° C. in order to stabilize and densify the NbO y lattice and then
B) reacting said NbO y with a stoichiometric quantity of niobium metal, in the presence of hydrogen, wherein for NbO x , 0.7<x<1.3, said.
2. The method of claim 1 , wherein the reaction is conducted at a temperature and for a reaction time, said temperature and said reaction time each being independently selected such that the reaction takes place substantially completely.
3. The method of claim 2 wherein the reaction temperature is from 900° C. to 1600° C., and the reaction time is 0.5 to 4 hours.
4. The method of claim 1 , wherein the reduction of niobium pentoxide is carried out at a temperature of from 1000 to 1600° C.
5. The method of claim 4 wherein the product NbO y has a crystal lattice, and after the reduction of niobium pentoxide in flowing hydrogen is completed product NbO y is held at a temperature of from 900 to 1600° C. in order to stabilize and densify the crystal lattice of the product NbO y .
6. The method of claim 5 wherein the niobium pentoxide is in the form of a powder comprising agglomerates of niobium pentoxide, the agglomerates comprising primary particles of niobium pentoxide having a mean minimum particle size of 0.4 to 2 μm.
7. The method of claim 1 , wherein the niobium metal is a niobium metal powder which has been formed by reduction of NbO y with magnesium vapour, the NbO y , that is reduced with magnesium vapour, is formed by reducing niobium pentoxide in flowing hydrogen.
8. The method of claim 7 wherein the reduction of the NbO y in magnesium vapour is conducted at a temperature of from 750 to 1150° C.
9. The method as claimed in claim 1 , wherein x is between 0.9 and 1.15.
10. The method as claimed in claim 1 , wherein x is between 1 and 1.05.
11. The method as claimed in claim 1 , wherein y is between 1.9 and 2.