Yttrium
Yttrium is a chemical element with the symbol Y and atomic number 39, classified as a transition metal in group 3 and period 5 of the periodic table. It appears as a silvery-white, lustrous, and relatively soft metal at room temperature, with a density of 4.47 g/cm³, a melting point of 1526°C, and a boiling point of 2930°C. Chemically, yttrium exhibits properties akin to the lanthanide series, forming a stable oxide layer that protects it from rapid oxidation at room temperature, though it reacts with water and acids.[1] Discovered in 1794 by Finnish chemist Johan Gadolin, yttrium was isolated from the mineral yttria (yttrium oxide) found in a quarry near the Swedish village of Ytterby, from which the element derives its name.[1] The pure metal was not isolated until 1828 by German chemist Friedrich Wöhler through reduction of yttrium chloride with potassium.[2] Yttrium occurs naturally in the Earth's crust at an abundance of approximately 33 ppm, making it about as common as copper, primarily in association with rare earth elements in minerals such as monazite, bastnäsite, and xenotime.[3] It is not considered a true rare-earth element but is often grouped with them due to similar geochemical behavior and co-occurrence in deposits.[3] Yttrium has diverse industrial applications, serving as a key component in high-strength alloys for magnesium and aluminum, enhancing their resistance to corrosion and high temperatures.[4] It is essential in ceramics, such as yttria-stabilized zirconia for high-temperature applications, and in electronics for phosphors in LED lighting, television screens, and superconductors.[4] In optics and medicine, yttrium forms the basis of yttrium aluminum garnet (YAG) lasers used in manufacturing, surgery, and military targeting, while the radioactive isotope yttrium-90 is employed in radioembolization therapy for treating liver cancer via microsphere delivery.[5] Global production, largely as a byproduct of rare-earth mining dominated by China, was estimated at 15,000 to 20,000 tons of yttrium oxide (Y₂O₃) equivalent in 2024, with major uses in catalysts, metallurgy, and phosphors; as of November 2025, supplies are facing shortages due to rising demand.[4][6]Characteristics
Physical properties
Yttrium (atomic number 39) has a standard atomic weight of 88.90585 u and an electron configuration of [Kr] 4d¹ 5s².[7][8] The element appears as a soft, silvery-white, lustrous metal that is malleable and ductile.[7]| Property | Value | Conditions/Source |
|---|---|---|
| Density | 4.47 g/cm³ | 20 °C[7] |
| Melting point | 1522 °C | Standard pressure[7] |
| Boiling point | 3345 °C | Standard pressure[7] |
| Specific heat capacity | 0.30 J/g·K | 25 °C[9] |
| Thermal conductivity | 17.2 W/m·K | 25 °C[10] |
| Electrical resistivity | 570 nΩ·m | 20 °C[11] |
| Young's modulus | 63.5 GPa | Ambient conditions[7] |
| Ultimate tensile strength | 115 MPa | Annealed state[10] |
Chemical properties and reactivity
Yttrium primarily exhibits the +3 oxidation state in its compounds, with rare examples of +1 and +2 states observed in specialized organometallic or cluster species. The Y³⁺ cation has an ionic radius of 0.90 Å in six-coordinate environments, which contributes to its ionic bonding tendencies and lanthanide-like reactivity.[13][14][15] This ionic radius renders yttrium chemically analogous to heavier rare earth elements, such as dysprosium (ionic radius 0.91 Å for Dy³⁺), due to the lanthanide contraction—a progressive decrease in atomic and ionic sizes across the 4f series from poor shielding by f-electrons, allowing yttrium to mimic the bonding and reactivity patterns of these elements despite its position in group 3.[16] As a highly electropositive metal, yttrium readily reacts with water, especially in finely divided form or when heated, liberating hydrogen gas and forming yttrium(III) hydroxide:$2\mathrm{Y} + 6\mathrm{H_2O} \to 2\mathrm{Y(OH)_3} + 3\mathrm{H_2}
It also oxidizes in air, particularly at elevated temperatures, to yield yttrium(III) oxide via the reaction:
$4\mathrm{Y} + 3\mathrm{O_2} \to 2\mathrm{Y_2O_3}
Yttrium forms trihalides like YF₃ and YCl₃ through direct combination with halogens, and it reacts with hydrogen to produce hydrides such as YH₂ (fluorite structure) and YH₃. In coordination compounds, the large size of Y³⁺ enables high coordination numbers from 6 to 12, often with oxygen or nitrogen donors, facilitating stable polyhedral geometries.[17][18][19][20] In contrast to typical d-block transition metals like iron, which display variable oxidation states and d-d electronic transitions responsible for color and magnetic properties, yttrium's +3 state dominates without such variability, and its d⁰ electronic configuration in Y³⁺ precludes d-d transitions, leading to generally colorless and diamagnetic compounds./22%3A_d-Block_Metal_Chemistry_-The_Heavier_Metals/22.04%3A_Group_3-_Yttrium/22.4B%3A_Yttrium(III)_Ion)
Isotopic composition
Yttrium possesses a single stable isotope, ^{89}Y, which accounts for 100% of its natural abundance. This isotope has a relative atomic mass of 88.905848 and a nuclear spin of 1/2. All other known isotopes of yttrium, numbering 25 with mass numbers ranging from 79 to 103, are radioactive, exhibiting half-lives that span from fractions of a second to several years.[21][22] Among the radioactive isotopes, several stand out due to their relatively longer half-lives and applications. Yttrium-88 (^{88}Y) has a half-life of 106.6 days and decays primarily by beta emission to stable ^{88}Sr. Yttrium-90 (^{90}Y), a pure beta emitter with a half-life of 64.1 hours and a maximum beta energy of 2.28 MeV, is widely used in targeted radionuclide therapy for cancer treatment. Yttrium-91 (^{91}Y) possesses a half-life of 58.5 days and beta decays to ^{91}Zr, appearing as an intermediate in certain fission product decay chains.[23] The nucleosynthesis of yttrium isotopes, particularly ^{89}Y, occurs predominantly through the slow neutron capture process (s-process) in the envelopes of asymptotic giant branch (AGB) stars, where neutrons from ^{13}C(\alpha,n)^{16}O reactions enable sequential captures and beta decays to build heavier nuclei. A minor contribution arises from the rapid neutron capture process (r-process) in extreme astrophysical events such as neutron star mergers. The cosmic abundance of yttrium reflects this origin, with an estimated solar system value of approximately 1.0 \times 10^{-6} by number relative to silicon (log \epsilon(Y) \approx 2.24), underscoring its production in stellar environments beyond iron-peak elements.[24][25] Due to the exclusivity of ^{89}Y as the sole stable isotope in natural yttrium, isotopic separation techniques—such as ion exchange chromatography or solvent extraction—are not pursued for commercial enrichment purposes, unlike in elements with multiple stable isotopes. Instead, such methods are reserved for isolating radioactive isotopes produced artificially, for example, in nuclear reactors or cyclotrons.[21] A key nuclear property of ^{89}Y is its thermal neutron capture cross-section of 1.28 barns, which is relatively low owing to its magic neutron number (N=50), making it significant for modeling neutron fluxes in stellar s-process environments and nuclear reactors. This value influences the branching in neutron capture pathways during nucleosynthesis.[26][27]History and Discovery
Early identification
In 1787, Swedish army lieutenant Carl Axel Arrhenius discovered a peculiar black mineral in a quarry near the village of Ytterby, Sweden, during a geological survey for potential fortification sites. Initially mistaken for a tungsten-bearing ore, the mineral—later named gadolinite or ytterbite—was notable for its heavy weight and unusual properties, prompting Arrhenius to collect samples and send them to his colleague, chemist Johan Gadolin, for analysis.[28][29] Gadolin, a professor at the University of Åbo in Finland, conducted detailed examinations of the mineral starting in 1792 and published his findings in 1794, successfully isolating a white, infusible earth that he named yttria after the Ytterby locality. Through precipitation and calcination techniques, Gadolin demonstrated that yttria was distinct from known alkaline earths like lime or magnesia, exhibiting unique solubility behaviors—insoluble in water but soluble in acids—and a high specific gravity, marking it as a novel substance in the emerging field of rare earth chemistry. This isolation represented the first identification of what would become yttrium oxide (Y_2O_3), though Gadolin did not obtain the pure metal.[30][31] In the early 19th century, chemists including Jöns Jacob Berzelius grappled with yttria's characterization amid growing confusion over rare earths, as initial analyses often conflated it with similar oxides from other minerals like cerite. Berzelius, in his systematic studies of inorganic compounds around 1803–1828, helped attribute specific chemical behaviors to yttria, such as its resistance to reduction and formation of stable salts, while distinguishing it from the newly identified ceria; however, the lack of effective separation methods led to ongoing debates about whether yttria represented a single element or a mixture. This period of attribution solidified yttria's place in chemical nomenclature, though its complexity foreshadowed further subdivisions.[32][31] A pivotal advancement came in 1843 when Swedish chemist Carl Gustaf Mosander, building on fractional precipitation techniques, separated yttria from gadolinite-derived samples into three distinct oxides: pure colorless yttria, rose-colored erbia (later identified as erbium oxide), and yellow terbia (terbium oxide). Mosander's work confirmed yttria's composite nature and provided early quantitative insights, such as its solubility in ammonium oxalate solutions under controlled heating, which aided in purity assessments and highlighted the challenges of rare earth isolation. These separations clarified yttria's fundamental properties, setting the stage for more precise elemental analysis.[28][33]Isolation and naming
The name yttrium derives from the Swedish village of Ytterby, near Stockholm, where the rare earth mineral gadolinite was first found in a local quarry in 1787. The village's name itself comes from the Swedish words ytter, meaning "outer," and by, meaning "village" or "farm," reflecting its position on the outskirts of the parish and adjacent to the quarry site.[7][34] The element's isolation as a metal occurred in 1828, when German chemist Friedrich Wöhler produced an impure form by heating anhydrous yttrium(III) chloride (YCl₃) with potassium metal, yielding a gray powder that was the first metallic yttrium.[7] This method relied on the strong reducing power of potassium to displace yttrium from its chloride, though the product contained significant impurities due to the challenges of handling reactive rare earth compounds at the time. Pure metallic yttrium was not obtained until 1953, when American chemists A. H. Daane and F. H. Spedding developed a high-purity process involving the reduction of yttrium chloride with lanthanum metal in a vacuum, producing ductile, massive yttrium with over 99% purity.[35] Yttrium's formal recognition as element 39 emerged in the 1860s amid the formulation of the periodic table, where Dmitri Mendeleev positioned it based on its atomic weight of approximately 88 and chemical similarities to other transition metals. The element's chemical symbol, Y, came into common use in the early 1920s.[28] Early work on yttrium was complicated by nomenclature confusion with other rare earths separated from the same Ytterby minerals, particularly terbium and erbium. In 1843, Swedish chemist Carl Gustaf Mosander fractionated yttria (yttrium oxide) into components he named terbia and erbia, but subsequent analyses in the 1860s by chemists like Marc Delafontaine and Francis Carey revealed misattributions, leading to reversed names and clarified distinctions by the late 19th century—terbium for the yellow oxide and erbium for the rose-colored salt.[36]Occurrence and Extraction
Natural abundance
Yttrium is present in the Earth's crust at an average concentration of 33 parts per million (ppm) by weight, ranking it as the 28th most abundant element overall.[22] This abundance is notably higher in certain geological settings, particularly alkaline igneous rocks, where yttrium enrichment can exceed crustal averages due to its geochemical affinity for such environments.[37] In oceanic settings, dissolved yttrium concentrations are extremely low, approximately $10^{-9} g/L in seawater, reflecting its limited solubility and rapid scavenging by particles.[38] Atmospheric levels of yttrium are negligible, with no significant gaseous or particulate presence under natural conditions.[22] On a cosmic scale, yttrium exhibits an abundance of about 1.5 ppm in the solar system, originating primarily from the s-process nucleosynthesis in asymptotic giant branch stars and explosive events in supernovae.[39] This low overall concentration underscores yttrium's rarity among stellar and interstellar materials, though it aligns with patterns observed in chondritic meteorites that represent primitive solar system compositions. Yttrium's primary mineral hosts include xenotime (YPO₄), a phosphate mineral that can contain up to several percent yttrium as a dominant component.[37] It also occurs as a minor constituent (1-3% by weight) in monazite ((Ce,La)PO₄), a common accessory mineral in granitic and heavy mineral sands, and as trace impurities in bastnäsite ((Ce,La)CO₃F), a carbonate-fluoride mineral found in carbonatite deposits.[40] These associations highlight yttrium's tendency to substitute for larger rare earth ions in phosphate and carbonate structures. Geochemically, yttrium behaves as a highly incompatible element during magmatic differentiation, partitioning strongly into the melt rather than crystallizing early minerals, which leads to its enrichment in fractionated late-stage products like pegmatites and carbonatites.[37] This incompatible nature results in yttrium concentrations that can reach thousands of ppm in such settings, far surpassing average crustal levels and facilitating its economic recovery from specialized deposits.[41]Commercial production methods
Yttrium is primarily extracted from monazite and bastnäsite ores, which are processed through hydrometallurgical methods to recover rare earth elements including yttrium.[42] These ores are first beneficiated using flotation, gravity, or magnetic separation to concentrate the rare earth minerals.[42] The concentrated ore is then digested with concentrated sulfuric acid at temperatures between 150 and 200 °C, dissolving the rare earth phosphates or fluorocarbonates into a sulfate solution.[43] Following digestion, the solution undergoes precipitation to form rare earth hydroxides or oxalates, which are subsequently redissolved in acid for further separation. Solvent extraction is employed to isolate yttrium from lanthanides, typically using di-(2-ethylhexyl)phosphoric acid (DEHPA) in kerosene as the extractant in sulfuric acid media, where yttrium preferentially partitions into the organic phase at optimized pH levels.[44][45] Global production of yttrium contained in rare earth mineral concentrates was estimated at 15,000 to 20,000 metric tons in 2024.[4] To produce metallic yttrium, the purified yttrium compounds are reduced via electrolysis or thermal methods. In the electrolytic process, anhydrous yttrium chloride (YCl₃) is electrolyzed in a molten NaCl-KCl eutectic salt at temperatures around 700–800 °C, depositing yttrium at the cathode while chlorine gas evolves at the anode.[46] Alternatively, thermal reduction involves reacting yttrium oxide or fluoride with lanthanum metal at high temperatures under vacuum, leveraging the stronger reducing power of lanthanum to yield yttrium metal.[47] These methods typically produce yttrium metal with initial purities of 95–99.5%.[48] Further purification to high-purity levels, such as 99.999% (5N), is achieved through zone refining, where a molten zone is passed along a yttrium ingot to segregate impurities via differences in solubility.[49] Additional techniques like vacuum distillation or plasma arc melting can remove volatile and refractory impurities, enhancing overall purity.[50] Yttrium is also recycled from end-of-life phosphors in fluorescent lamps and catalysts in petroleum refining, involving acid leaching followed by solvent extraction and precipitation to recover up to 75–90% of the yttrium content.[51][52] China dominates yttrium production, accounting for approximately 95% of global supply, with significant operations in Australia (e.g., Lynas at Mount Weld) and the United States (e.g., Mountain Pass mine) contributing the remainder.[53] This concentration creates supply chain vulnerabilities, as evidenced by China's export restrictions on rare earths, which have disrupted global access to yttrium for electronics and defense applications.[54][55] In April 2025, China imposed additional export controls on yttrium and six other rare earth elements in response to U.S. tariffs, leading to reduced exports, supply shortages, and a significant price surge (over 1,000% rally in yttrium prices by November 2025).[6]Chemical Compounds
Inorganic compounds
Yttrium forms a variety of inorganic compounds, predominantly in the +3 oxidation state, due to its stable Y³⁺ ion configuration. These compounds exhibit largely ionic bonding, though some covalency is observed in lighter halides.[56] The principal oxide is yttrium(III) oxide, Y₂O₃, which adopts a cubic bixbyite structure in the Ia-3 space group, featuring two inequivalent yttrium sites coordinated to six and seven oxygen atoms, respectively.[57] This refractory oxide has a high melting point of approximately 2425°C and is typically prepared by calcination of yttrium(III) hydroxide, Y(OH)₃, at temperatures above 800°C, following the decomposition reaction:\ce{2 Y(OH)3 -> Y2O3 + 3 H2O}
Y(OH)₃ itself is obtained by precipitation from yttrium salts with alkali hydroxides.[58] Yttrium halides are well-characterized, with yttrium(III) fluoride, YF₃, crystallizing in the rhombohedral tysonite structure (a distorted fluorite-type), space group R-3c, where yttrium is nine-coordinated to fluoride ions, reflecting partial covalent character in the Y-F bonds.[59] It is synthesized by direct reaction of yttrium metal with hydrogen fluoride gas:
\ce{Y + 3 HF -> YF3 + 3/2 H2}
or by treating yttrium oxide with hydrofluoric acid followed by dehydration. Yttrium(III) chloride, YCl₃, forms a hexahydrate, YCl₃·6H₂O, which is highly soluble in water (approximately 217 g/100 mL at 20°C) and deliquescent, consisting of [Y(H₂O)₆]³⁺ octahedra linked by chloride ions.[60] The hexahydrate is prepared by dissolving Y₂O₃ in hydrochloric acid and crystallizing from solution:
\ce{Y2O3 + 6 HCl -> 2 YCl3 + 3 H2O}
Anhydrous YCl₃ adopts a layered AlCl₃-type structure. Similar methods apply to the bromide, YBr₃, and iodide, YI₃, which are also hygroscopic but less stable to hydrolysis.[61] Yttrium nitride, YN, crystallizes in the cubic rock-salt structure (NaCl-type, space group Fm-3m) with a lattice parameter of about 4.87 Å, where yttrium is octahedrally coordinated to nitrogen.[62] It is synthesized at high temperatures (around 1200°C) by direct combination of yttrium metal with nitrogen gas under controlled pressure. Yttrium phosphide, YP, similarly adopts a rock-salt structure and is prepared by heating yttrium and phosphorus elements in a sealed ampoule at 800–1000°C. Both compounds are refractory and exhibit semiconductor properties with band gaps near 2–3 eV.[63] Among chalcogenides, yttrium sesquisulfide, Y₂S₃, exists in multiple polymorphs, including a cubic γ-phase (Th₃P₄-type) and hexagonal forms, with yttrium coordinated to seven or eight sulfur atoms; it displays semiconducting behavior with a band gap of about 2.5 eV.[64] Synthesis involves high-temperature reaction of yttrium with sulfur vapor (above 1000°C). Other chalcogenides, such as YS and Y₂Se₃, follow analogous preparative routes and structures, showing increasing covalency down the group. In aqueous solution, the Y³⁺ ion forms the hydrated complex [Y(H₂O)₈]³⁺ or [Y(H₂O)₉]³⁺ (coordination number 8–9), with log K values for stepwise ligand substitutions indicating strong hydration (e.g., for chloride, log K₁ ≈ 0.1).[56]