Today, let’s take a look at interesting facts about Ytterbium and answer the following questions: “Why Is Ytterbium Considered A Rare Earth Element?”, and “Why Is Ytterbium Considered A Critical Raw Material?”

For more information, check out the light rare earth elements (LREEs) as a group, the heavy rare earth elements (HREEs) as a group, and all rare earth elements (REEs). Be sure to check out all other critical raw materials (CRMs), as well.

Why Is Ytterbium Considered A Rare Earth Element?

Ytterbium is considered a rare earth element because it is one of the 15 lanthanide elements that constitute the core group of rare earth elements. With atomic number 70, ytterbium sits near the end of the lanthanide series between thulium (69) and lutetium (71), within the sequence that spans from lanthanum (atomic number 57) through lutetium (atomic number 71). As a lanthanide, ytterbium exhibits all the characteristic chemical properties that define this group, including the typical trivalent oxidation state (Yb3+) and an ionic radius that follows the systematic “lanthanide contraction” pattern. Like europium, ytterbium can also exist in a divalent state (Yb2+), but its trivalent state dominates in most geological and industrial contexts, aligning it firmly with the other rare earth elements.

Ytterbium’s classification as a heavy rare earth element (HREE) reflects both its position in the periodic table and its geochemical behavior. With a crustal abundance of 3.2 parts per million, ytterbium is less abundant than the light rare earth elements but still more common than silver, gold, or platinum. The heavy rare earth elements, which comprise “terbium through lutetium (atomic numbers 65 through 71),” have smaller ionic radii due to lanthanide contraction and tend to be less abundant in rare earth deposits. This pattern is evident in ore compositions: at Mountain Pass, the combined content of europium through lutetium plus yttrium totals only 0.4% of the rare earth oxides, while at Bayan Obo, ytterbium is present but in concentrations too low to be specifically reported in many analyses.

Ytterbium’s geochemical behavior perfectly aligns with the defining characteristics of rare earth elements. Like all REEs, ytterbium has a high charge (+3) and ionic radius that prevents its incorporation into common rock-forming minerals, causing it to concentrate with other rare earth elements during magmatic processes. Ytterbium invariably occurs with other REEs in nature, particularly in minerals that can accommodate heavy rare earth elements such as xenotime (Y,HREE,Th,U)PO4, where it substitutes for yttrium and other heavy lanthanides. The ability of rare earth minerals to accommodate ytterbium stems from the fact that “REEs can substitute for one another in crystal structures, and multiple REEs typically occur within a single mineral.” In ion-adsorption clay deposits of southern China, which are the world’s primary source of heavy rare earth elements, ytterbium occurs alongside other HREEs in economically recoverable concentrations.

From both scientific and industrial perspectives, ytterbium exemplifies the rare earth element group. Its name derives from Ytterby, the Swedish village that also gave its name to yttrium, terbium, and erbium, highlighting the historical tendency for rare earth elements to occur together and the difficulty in separating them. Industrially, ytterbium’s applications leverage its rare earth properties: it is used in specialized stainless steel alloys and lasers, where its unique electronic configuration provides specific optical properties. One reference notes that “for many years the main use of lutetium was the study of the behavior of lutetium,” a statement that could equally apply to ytterbium and other heavy rare earth elements, reflecting how their scarcity and high cost limited applications until recent technological developments. 

The combination of ytterbium’s position in the lanthanide series, its characteristic REE chemistry including the Yb3+ oxidation state, its consistent co-occurrence with other REEs in minerals like xenotime and ion-adsorption clays, and its specialized applications that depend on its rare earth electronic structure unequivocally establishes ytterbium as a rare earth element.

Why Is Ytterbium Considered A Critical Raw Material?

Ytterbium is considered a critical raw material due to its specialized applications in high-technology sectors combined with severe supply constraints and concentration. As one of the heavy rare earth elements (HREEs), ytterbium has unique properties essential for specific industrial applications, particularly in specialized stainless steel alloys and laser technologies. With a crustal abundance of only 3.2 parts per million, ytterbium is among the less common rare earth elements, and its concentration in economically viable deposits is extremely limited. At Mountain Pass, California, the combined content of all heavy rare earth elements from europium through lutetium plus yttrium totals only 0.4% of the rare earth oxides, making ytterbium availability heavily dependent on processing large quantities of light rare earth ores or accessing specialized deposits enriched in heavy rare earth elements.

The criticality of ytterbium is fundamentally driven by the extreme concentration of global supply, particularly for heavy rare earth elements. Between 2011 and 2017, China produced approximately 84% of the world’s rare earth elements, but more critically, China’s ion-adsorption clay deposits in the southern provinces are “the world’s primary source of the heavy REEs.” These clay deposits, despite having modest REE concentrations of 0.03 to 0.2 percent, are the only economically viable source of ytterbium and other HREEs because “the REEs can be easily extracted from the clays with weak acids” and “the deposits are often enriched in the high-value HREEs.” When China announced export restrictions in 2010 through quotas, licenses, and taxes, it created particular vulnerability for heavy rare earth elements like ytterbium, as no alternative sources existed at comparable scales.

The strategic importance of ytterbium extends to critical industrial and potential future applications that have no adequate substitutes. While current applications in stainless steel and lasers may seem limited, the text reveals that “for many years the main use of lutetium was the study of the behavior of lutetium,” a situation that historically applied to ytterbium and other HREEs. This suggests that ytterbium’s applications have been constrained by its scarcity and high cost rather than lack of utility. As prices potentially decrease or new technologies emerge, ytterbium could see expanded use in applications where its unique properties – particularly its electronic configuration and optical characteristics – provide advantages. The inclusion of rare earth elements in expert panel assessments by the National Research Council, U.S. Department of Energy, and European Commission as materials with high “criticality” ratings encompasses ytterbium as part of the critical HREE group.

The processing complexity and infrastructure limitations compound ytterbium’s critical status. Separating individual heavy rare earth elements requires sophisticated solvent extraction facilities, with “nearly all REE separation and refining” occurring within China. Even when rare earth ores are mined elsewhere, they often must be sent to China for processing into individual elements. The statement that “deposits containing relatively high grades of the scarcer and more valuable heavy REE (HREE: Gd to Lu, Y) and Eu are particularly desirable” underscores ytterbium’s value, yet such deposits remain extremely rare globally. With only 6 of 500 known carbonatites being mined for REEs, and most being LREE-dominated, the supply of ytterbium remains precarious. 

The combination of ytterbium’s specialized applications with no substitutes, its scarcity even within rare earth deposits, the concentration of both mining and processing capabilities for HREEs in China, and the lack of alternative supply sources establishes ytterbium as a critical raw material whose availability could constrain technological development in specialized sectors.

Interesting Facts About Ytterbium

1. Ytterbium is the only lanthanide that can exist in three different oxidation states (+2, +3, and +4) in aqueous solution, making it uniquely versatile among rare earth elements for chemical applications.
2. It has the smallest atomic radius of all the lanthanides due to the “lanthanide contraction,” making it the densest of the rare earth elements at 6.90 g/cm³.
3. Ytterbium-171 has a nuclear spin of 1/2, making it ideal for quantum computing applications and atomic clocks – it’s used in some of the world’s most precise optical lattice clocks.
4. Unlike most lanthanides, ytterbium has a completely filled 4f electron shell (4f¹⁴), giving it unique magnetic and electronic properties compared to its neighbors.
5. Ytterbium has seven stable isotopes – more than most lanthanides – ranging from Yb-168 to Yb-176, providing diverse options for various applications.
6. The element exhibits unusual pressure-induced phase transitions, transforming from a semiconductor to a metal at about 16,000 atmospheres, one of the lowest pressures for such transitions.
7. Ytterbium-doped fiber amplifiers can achieve higher power efficiency than erbium-doped amplifiers, making them preferred for high-power laser applications and industrial cutting.
8. It has the second-lowest melting point (819°C) among the lanthanides, only higher than europium, due to its closed-shell electron configuration.
9. Ytterbium exhibits a phenomenon called “mixed valency” where Yb²⁺ and Yb³⁺ can coexist in certain compounds, creating unique electronic and magnetic behaviors.
10. The element’s vapor pressure is unusually high for a lanthanide, making it one of the few rare earths that can be easily purified by sublimation.
11. Ytterbium-169 emits gamma rays with specific energies ideal for portable radiographic devices, particularly useful in remote medical diagnostics.
12. It forms unusual Zintl phases – compounds where it behaves more like an alkaline earth metal than a typical lanthanide, expanding its chemical versatility.
13. Ytterbium has one of the largest electronic heat capacities among metals at low temperatures, making it valuable for studying quantum phenomena.
14. The element can form quantum gases at ultracold temperatures more easily than most atoms, making it a favorite for Bose-Einstein condensate research.
15. Ytterbium’s ground state has zero orbital angular momentum and zero spin, making it immune to certain types of magnetic field fluctuations – crucial for precision measurements.
16. It exhibits the Kondo effect more strongly than other lanthanides, where magnetic impurities affect electrical resistance in unique ways useful for quantum materials research.
17. Ytterbium compounds can display heavy fermion behavior, where electrons behave as if they have masses hundreds of times greater than normal, important for superconductivity research.
18. The element has an unusually large change in atomic volume between its +2 and +3 oxidation states (about 20%), useful for pressure-sensitive applications.
19. Ytterbium-based atomic clocks have achieved fractional frequency stability better than 10⁻¹⁸, making them among the most precise timekeeping devices ever created.
20. It’s the only lanthanide that forms a stable dihydride (YbH₂) under normal conditions, while others typically form trihydrides, demonstrating its unique bonding characteristics.

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