Intro

It is hard to imagine the modern world without metal products. Automobiles, bridges, household appliances, jewelry, tableware – almost everything around us contains metals. 

In a school course of history we were taught that on a historic scale the “Iron Age”, which replaced the “Bronze Age” about 3-4 thousand years ago, became revolutionary for humanity. 

But our days can be called “the century of rare and rare-earth metals”. They became a basis for all electronics around us, which, in fact, our civilization is built on. Without these metals neither modern aviation nor space exploration, and breakthrough medical technologies would be possible.

Definition, properties and fields of application.

Definition of “rare and rare-earth elements“

“Rare elements” is a conventional name for a group of chemical elements of the Periodic Table of D. Mendeleev. Rare elements are conventionally divided into categories: 

  • Light: lithium Li, rubidium Rb, caesium Cs, berillium Be; 
  • High melting: titanium Ti, zirconium Zr, hafnium Hf,  vanadium V, niobium Nb, tantalum Ta, molybdenum Mo, wolframium W; 
  • Trace elements: gallium Ga, indium In, thallium Tl, germanium Ge, cadmium Cd, selenium Se, tellurium Te, rhenium Re; 
  • Rare-earth: scandium Sc, yttrium Y, lantanium La and lantanides; 
  • Radioactive: Po, Tc, Fr, Ra, Ac, Th, Pa, U, Pu, Np, Cm, Cf, Am and others).

However, many of these elements can be classified into different groups at the same time. 

The appearance of the term “rare elements” is explained by relatively late development and use of these elements, their low abundance (or scattering in the earth crust), as well as difficulties of extraction from raw materials in their pure form. 

The names “rare metals”, “rare elements”, “rare-earth elements” are not quite correct, because these chemical elements are not that rare at all. Their average content in the earth crust is comparable or even higher than that of most metals, widely used in our everyday life. For example, such rare metals as scandium, cerium, lanthanum, lithium, yttrium, niobium, gallium are contained in the earth crust approximately as much as chromium, zinc, nickel, copper, lead, and strontium, zirconium, rubidium – even by an order more. 

 History and use of rare and rare-earth metals.

The first rare and rare-earth elements were discovered at the end of the 18th – beginning of the 19th centuries. However, they began to find practical application only in the 20th century. The situation has drastically changed in the second half of the 20th century, when the appearance of new industrial technologies provided rationale for wide use of such metals and their compounds in various fields. But their consumption is still negligible, if compared to the consumption of metals traditional for humanity. 

Half a century ago they believed that rare elements were not able to form large deposits and high concentrations in ore. Now it is known that this is not the case: the measured world reserves, for example, of niobium, lithium and cerium earths are not less than the reserves of titanium, nickel and exceed the reserves of lead and tin. The largest deposits of cerium earth, niobium, lithium, strontium, zirconium, and vanadium store millions of tons of these most valuable rare metals. In terms of their ability to concentrate in ores of workable deposits rare elements are not less and often even more than nonferrous and minor metals. 

Perhaps, it would be more correct to call these metals not rare, but “new”, as suggested by academician V.Smirnov. Indeed, all rare elementshave been discovered over the past 60-220 years, and their use in industry really began only 40-50 years ago. 

Properties of rare and rare-earth elements.

In their free state rare and rare-earth elements have a typical metallic structure and are present in almost every rock of the earth crust, but their highest content is in alkali rocks. 

Rare and rare-earth metals are very active, easily interact with oxygen (at normal temperatures), when heated – with halogens, hydrogen (> 200 ° C), nitrogen (> 800 ° C), sulfur, bromine, phosphorus, and other non-metals, easily alloyed with metals. Their alloys have pyrophoric properties, due to which they are used in tracer shells and rounds, lighters, etc. Simple fluorides, oxalates, phosphates and carbonates are poorly soluble in water, while complex carbonates, sulfates and fluorides are highly soluble. 

The most characteristic oxidation level is +3. Due to the fact the most characteristic oxides are R2O3 – solid, strong and high-melting compounds. At the beginning of the 19th century and earlier such oxides were called “earths”, that is why some sources use the name

Definition of “rare and rare-earth elements“

Rare-earth elements usually occur in nature in combination with  uranium and thorium, as, for example, in monazite and euxenite. For lanthanides compounds of triads are more typical. The exception is cerium, which easily transforms into a tetravalent state. In addition to cerium, tetravalent compounds form praseodymium and terbium. Divalent compounds are known by samarium, europium and ytterbium. In terms of physicochemical properties, lanthanides are very close to each other. This is explained by the peculiarity of the structure of their electronic shells. 

Rare and rare-earth metals have unusual fluorescent, conductive and magnetic properties, making them very useful when alloyed or mixed. Such metals are used in metallurgy to increase plasticity and strength of alloys. They are used in small quantities for deoxidation with more common metals such as iron. 

Each metal is valuable in its own way, but there are some that are very rare or their cost is too high due to the difficulty of mining. The list of the most expensive metals includes, of course, rare and rare-earth metals, such as (price per 1 gram $): 

  • palladium – 21,2.
  • californium-252 – 10 mio.;
  • osmium -187 – 200,0 ths.;
  • rhodium – 113,1;
  • osmium – 41,6;
  • iridium – 35;
  • ruthenium – 28;

Application fields of rare and rare-earth elements.

Rare metals have proven themselves in the last century throughout the world as effective catalysts for scientific and technological progress. Academician A.E. Fersman called them “vitamins of industry”. 

Many rare metals which found little use for a long time, are now widely applied in the world. They brought to life such new fields of industry, science and technology as solar power engineering, high-speed magnetic levitation transport, infrared optics, optoelectronics, lasers and the latest generations of computers. 

Rare and rare-earth elements are used in:

  • radio electronics; 
  • instrumentation; 
  • atomic power engineering; 
  • machine-building; 
  • chemical industry;
  •  metallurgy

and other important industries.

Rare and rare-earth elements in glass production.

Such elements as La, Ce, Nd, Pr are widely used in the industry in the form of oxides and other compounds. They increase light translucency of the glass. Rare-earth elements are included as a compound in special-purpose glass that pass infra-red and absorb ultraviolet rays, acid- and in heat-resistant glass. 

Chemical industry.

Rare and rare-earth elements and their compounds have gained great importance in chemical industry, for example, in production of pigments, varnishes and paints and as catalysts in oil industry. They are used for production of some explosives, special steels and alloys as gas absorbers.

Application in optoelectronics

Single-crystal compounds of rare-earth elements are used for creating lasers and other optically active and nonlinear components in optoelectronics. Based on them alloys with outstanding magnetic properties (high magnetizing and coercive forces) are obtained to create permanent magnets of enormous power, compared to simple ferroalloys.

Industrial and civil construction

When using low-alloy steels, containing only 0.03-0.07% niobium and 0.01-0.1% vanadium, it is possible to reduce the weight of structures by 30-40% in construction of bridges, multi-story buildings, gas and oil pipelines, drilling equipment for geological serveys etc. The service life of structures increases by 2-3 times in this case.

Magnetic levitated vehicles

Magnets using niobium-based superconducting materials made it possible to build hovertrains in Japan, moving at a speed of up to 570 km/h. 

Car industry

An ordinary American car uses 100 kg of HSLA steel with niobium, vanadium, rare earths, 25 parts made of copper-beryllium alloys, zirconium, yttrium. At the same time the weight of a car in the USA (from 1980 to 1990) decreased by 1.4 times. Since 1986, cars began to be equipped with neodymium-containing magnets (37 g of neodymium per car). 

Electric vehicles with lithium batteries have been created and are being intensively used, vehicles, operating on hydrogen fuel with lanthanum nitride and others are being developed.

Application in energy-efficient lighting devices.

Lamps with luminophor, containing yttrium, europium, terbium, and cerium, have been created. 27 W lamps successfully replace 60-75 W incandescent filament lamps. Electricity consumption for lighting is reduced by 2-3 times. 

Implications for the modern world

To realize technological breakthroughs fundamentally new materials will be required. Forbes studied the reports of foreign researchers and also contacted a number of metallurgical experts with a question: “What raw materials will be the most in-demand in the world in the coming years?”. 

It turned out that rare and rare-earth metals will take first place. 

The global industry, which is rapidly moving towards modern electronics, electric vehicles and “green” technologies, needs titanium, molybdenum, zinc, lithium, cobalt and other metals in all areas where possible. 

Currently, rare and rare-earth metals are two of the main types of materials, the presence of which determines the level of development of high technologies. In modern conditions, the demand for these metals is constantly growing. 

The high efficiency of using rare and rare-earth metals in knowledge-based industries and technologies (electronics, laser technology, superalloys, high-quality steels, electromagnetic and optical materials, new ceramics and composites, medicine, etc.) determines dynamic expansion of their use in economically developed countries of the world. Rare and rare-earth metals are necessary for leading industrial sectors, such as rocket-, aircraft-, machine- and instrument building, for production of high-quality steels and alloys, for oil and gas industry. These industries fast growing in the global economy. 

In recent years global production of rare and rare-earth metals has been grown at a high rate, driven by an increased demand from new fields of consumption. In the global rare-earth industry a number of projects are currently being implemented and prepared for construction of new enterprises both for raw materials mining and processing. The rare-earth industry is characterized by a fairly rapid expansion of consumer markets, associated with high technologies, such as production of nickel-hydride batteries, lithium ion batteries, permanent rare-earth magnets and catalytic exhaust gas filters for automobiles. 

Since the second half of the twentieth century levels of production and consumption of rare and rare-earth elements began to be considered as indicators of economic and national security of industrialized and developing countries. Over the past 10 years global consumption of lithium, niobium, vanadium, tantalum, rare-earths and some other rare metals has increased by 2-3 times, and the most scarce and strategically important elements (for example, rhenium and indium) – by 7-10 times. 

According to the International Energy Agency, production of critical minerals, containing rare and rare-earth metals, needs to be significantly expanded in order to meet the projected demand by 2030. To meet global net carbon emissions targets by 2030 additional 50 lithium, 60 nickel and 17 cobalt mines should be developed. 

Mankind will always strive for flying higher, driving faster, penetrating deeper into the earth crust interior and at the same time reducing the cost of the resources, needed for that. It means that materials of a new generation must be superior to previous ones and have new, unique properties. Such properties can be provided by rare and rare-earth metals.



CONCLUSION

The 21st century can be called the “century of rare and rare-earth metals”. They became the basis for all electronics around us, which, in fact, our civilization is built on.

The unique physical and chemical properties of both individual rare and rare-earth metals and their compounds open up a fundamentally new level of their use in modern technologies. 

The demand for copper and rare earth elements is expected to increase by more than 40% over the next two decades, nickel and cobalt – by 60-70%, and lithium – by almost 90%. 

Taking into consideration the importance of rare and rare-earth metals for modern industry, their production has actually become a powerful tool of geopolitics.