Learn details of niobium (Nb) in niobium oxide capacitor

Nb is placed 41 in the periodic table and belongs to the third subgroup with V.  It is said that structure determines properties, and properties determine uses. So let's first introduce the structure of Nb atom. Its outermost electronic structure, 4d45S1, is different from the outermost electron of V, 3d34S2.  In addition, Nb has one more shell than V, so its atomic radius is larger than V, and V and Fe have roughly the same radius.  Just like V, it loses five electrons to form the most stable 5-valent compound.  

So where does niobium come from?  In nature,Nb is basically symbiotic with Ta, niobite, (Fe,Mn)(Nb,Ta)2O6, coltan ((Fe,Mn)(Ta,Nb)2O6). Currently, the world's largest Nb concentrate is located in Minas Gerais state of Brazil, and another mine is located in Goas. These two mines account for 75% of the global Nb ore supply market share.

Niobium applied in the various industries

1. Steel industry  

Niobium oxide - Niobium oxide 80%~90% is consumed in the iron and steel industry, niobium oxide as an additive with iron ore melting, deoxidation, decarbonization, denitrification and other impurities.  Nb steel doping is one of the most cost-effective trace elements. The yield strength of ordinary steel is about 250Mpa, while the strength of 0.05% Nb can reach 350-800mpa. Other elements have no such obvious effect.  Nb can combine with impurity elements C, N and S in steel to form stable compounds, which make the steel microcrystals more dispersed and uniform, thus improving the overall toughness of the material.  At the same time, the brittle transition temperature of the material is reduced, and the welding performance of steel is improved obviously.  As can be seen from the figure below, in fe-C-Mn steel containing Nb, the final ferrite crystal phase becomes finer after Nb is added.

The cost savings brought by NB-doped steel are very obvious. Under the condition of the same target strength, the application of iron ore can be greatly reduced, and the structure can also be made lighter, further reducing the overall use cost.  

2. Electronics  

At present, tantalum capacitors are almost all the high-end capacitors in the world. Its high dielectric constant 27 is almost four times that of aluminum. Because of its excellent stability, tantalum capacitors are the first choice for harsh environment capacitors.  However, the emergence of niobium oxide capacitor has broken the monopoly position of tantalum capacitor in high-end capacitors, and niobium oxide has more obvious advantages as a capacitor: it has higher dielectric coefficient, more heat resistant and flame retardant.  Niobium oxide capacitors also have a self-healing property, which greatly improves their reliability life.  At present, it is difficult to mass produce niobium oxide capacitor because of the availability of high purity niobium powder. As mentioned above, 80% of niobium is used in the iron and steel industry, and the problem that niobium capacitor is facing is how to share a supply system with the iron and steel industry.

With the development of electronic industry, niobium oxide capacitor may become another high value-added application industry.  

3. Superconducting industry  

In 1973, the superconducting temperature of niobium and germanium alloy was mentioned to 23.3K. This record has been maintained for 13 years, until 1986, when an oxide increased the superconducting temperature by 35K, and then the superconducting oxide presented a pulse explosion.  Subsequently, in 1987, more than 260 research groups around the world were put into research, and the superconductivity temperature was rapidly pushed up to 40K, 53K, 100K, and some teams even promoted at 240K(-30℃). Soon, Kagoshima University in Japan developed 287K(room temperature 14℃), which can be called a miracle in the history of technology. Now looking back,  Although oxide can increase superconductivity temperature, but its ratio, stability is not as stable as niobium and germanium alloy.  

4. Biomedical  

Niobium is a very good biophilic metal, so niobium lines can be used to suture nerves and tendons, niobium can be used to make artificial joints, and it can even be used to replace bone.  Mainly because it has excellent corrosion resistance, will not react with the human body.