Interaction between rare earth metals and other elements

Rare earth metals have typical metal properties. They have strong chemical activity and can form a variety of compounds, including hydrides, chlorides, silicides, carbides, organic / inorganic salts and complexes. This is the basis for the rare earth metal in the metallurgical industry as a purification, impurity removal and refinement modifier.

Rare earth metals are unstable in air, and their stability increases with increasing atomic number; in other words, the rare earth metals with larger atomic radius have weaker oxidation resistance; light rare earth metals can be easier oxidized than heavy rare earth metals, and lanthanum is the most active. Lutetium and Scandium are the most resistant to air oxidation.

Rare earth metals are widely used as reducing agents, which can reduce oxides of iron, cobalt, nickel, chromium, vanadium, niobium, tantalum, zirconium, titanium, silicon and other elements into metals. Due to the difference in the reducing ability of rare earth metals, and the vapor pressure of the lanthanum is much smaller than that of Samarium, Europium, Ytterbium and Thulium, Lanthanum (cerium) can be used to reduce europium, europium, europium, europium metal from its oxides. However, the activity of rare earth metals is lower than that of alkali metals and alkaline earth metals, so lithium and calcium are commonly used as reducing agents to reduce rare earth metals from their halides.

Interactions between rare earth metals occur. If the two rare earth metals have the same crystal structure at the corresponding temperature, they can form a continuous solid solution; if the two rare earth metals have different crystal structures, they can only form a finite solid solution; Only two rare earth metals belonging to different subgroups (cerium and yttrium) can form intermetallic compounds.

The behavior of Yttrium and scandium in alloys is similar to that of heavy rare earth metals; the behavior of Ytterbium in magnesium alloys is similar to that of light rare earths. The melting point and elastic modulus of Europium and Ytterbium are similar to those of light rare earth lanthanum and cerium.

Rare earth metals and transition metals (iron, manganese, nickel, gold, silver, copper, zinc) and magnesium, aluminum, gallium, indium, thallium can form many alloys. Moreover, many intermetallic compounds are formed in their binary and multicomponent alloys.

Some of these compounds have high melting points, high hardness, high thermal stability, and are dispersed in the non-ferrous alloy matrix or grain boundaries. They play an important role in resisting high temperature, creep resistance, and improving the strength of the alloy. Many of these rare earth intermetallic compounds have been widely used in high and new technology with special functions. It is expected that more new intermetallic compounds will be developed in succession.

Only tantalum / niobium and tungsten / molybdenum and their alloys have little interaction with rare earth metals. Tantalum and molybdenum have almost no interaction with rare earth metals and their halides. Under vacuum or inert gas, tantalum can be used at 1700 °C, molybdenum can be used at 1400 °C, and it is used as the electrode for molten salt electrolysis and the carrying crucible for rare earth metals and rare earth alloys.