Yttrium is achemical element; it hassymbolY andatomic number 39. It is a silvery-metallictransition metal chemically similar to thelanthanides and has often been classified as a "rare-earth element".^[8] Yttrium is almost always found in combination with lanthanide elements inrare-earth minerals and is never found in nature as a free element.⁸⁹Y is the only stableisotope and the only isotope found in theEarth's crust.

Yttrium, ₃₉Y

Yttrium
Pronunciation	/ˈɪtriəm/​(IT-ree-əm)
Appearance	silvery white
Standard atomic weightAr°(Y)
	88.905838±0.000002[1] 88.906±0.001 (abridged)[2]
Yttrium in theperiodic table
Hydrogen Helium Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson Sc ↑ Y ↓ Lu strontium ←yttrium →zirconium
Atomic number(Z)	39
Group	group 3
Period	period 5
Block	d-block
Electron configuration	[Kr] 4d1 5s2
Electrons per shell	2, 8, 18, 9, 2
Physical properties
Phaseat STP	solid
Melting point	1799 K ​(1526 °C, ​2779 °F)
Boiling point	3203 K ​(2930 °C, ​5306 °F)
Density (at 20° C)	4.469 g/cm3[3]
when liquid (at m.p.)	4.24 g/cm3
Heat of fusion	11.42 kJ/mol
Heat of vaporization	363 kJ/mol
Molar heat capacity	26.53 J/(mol·K)
Vapor pressure P (Pa) 1 10 100 1 k 10 k 100 k at T (K) 1883 2075 (2320) (2627) (3036) (3607)
Atomic properties
Oxidation states	common:+3 0,[4] +1,? +2[5]
Electronegativity	Pauling scale: 1.22
Ionization energies	1st: 600 kJ/mol 2nd: 1180 kJ/mol 3rd: 1980 kJ/mol
Atomic radius	empirical: 180 pm
Covalent radius	190±7 pm
Spectral lines of yttrium
Other properties
Natural occurrence	primordial
Crystal structure	​hexagonal close-packed (hcp) (hP2)
Lattice constants	a = 364.83 pm c = 573.17 pm (at 20 °C)[3]
Thermal expansion	11.21×10−6/K (at 20 °C)[3][a]
Thermal conductivity	17.2 W/(m⋅K)
Electrical resistivity	α, poly: 596 nΩ⋅m (atr.t.)
Magnetic ordering	paramagnetic[6]
Molar magnetic susceptibility	+2.15×10−6 cm3/mol (2928 K)[7]
Young's modulus	63.5 GPa
Shear modulus	25.6 GPa
Bulk modulus	41.2 GPa
Speed of soundthin rod	3300 m/s (at 20 °C)
Poisson ratio	0.243
Brinell hardness	200–589 MPa
CAS Number	7440-65-5
History
Naming	afterYtterby (Sweden) and its mineralytterbite (gadolinite)
Discovery	Johan Gadolin (1794)
First isolation	Friedrich Wöhler (1838)
Isotopes of yttrium v e
Main isotopes Decay abun­dance half-life(t1/2) mode pro­duct 87Y synth 3.4 d ε 87Sr γ – 88Y synth 106.6 d ε 88Sr γ – 89Y 100% stable 90Y synth 2.7 d β− 90Zr γ – 91Y synth 58.5 d β− 91Zr γ –
Category: Yttrium view talk edit |references

The most important present-day use of yttrium is as a component ofphosphors, especially those used inLEDs. Historically, it was once widely used in the red phosphors in television setcathode ray tube displays.^[9] Yttrium is also used in the production ofelectrodes,electrolytes,electronic filters,lasers,superconductors, various medical applications, andtracing various materials to enhance their properties.

Yttrium has no knownbiological role. Exposure to yttrium compounds can causelung disease in humans.^[10]

The element is named afterytterbite, a mineral first identified in 1787 by the chemistCarl Axel Arrhenius. He named the mineral after the village ofYtterby, inSweden, where it had been discovered. When one of the chemicals in ytterbite was later found to be a previously unidentified element, the element was then named yttrium after the mineral.

Yttrium is a soft, silver-metallic, lustrous and highly crystallinetransition metal ingroup 3. As expected byperiodic trends, it is lesselectronegative than its predecessor in the group,scandium, and less electronegative than the next member ofperiod 5,zirconium. However, due to thelanthanide contraction, it is also less electronegative than its successor in the group,lutetium.^[11][12][13] Yttrium is the firstd-block element in the fifth period.

The pure element is relatively stable in air in bulk form, due topassivation of a protective oxide (Y
₂O
₃) film that forms on the surface. This film can reach a thickness of 10 μm when yttrium is heated to 750 °C inwater vapor.^[14] When finely divided, however, yttrium is very unstable in air; shavings orturnings of the metal can ignite in air at temperatures exceeding 400 °C.^[15]Yttrium nitride (YN) is formed when the metal is heated to 1000 °C innitrogen.^[14]

The similarities of yttrium to thelanthanides are so strong that the element has been grouped with them as arare-earth element,^[8] and is always found in nature together with them inrare-earth minerals.^[16] Chemically, yttrium resembles those elements more closely than its neighbor in the periodic table,scandium,^[17] and if physical properties were plotted againstatomic number, it would have an apparent number of 64.5 to 67.5, placing it between the lanthanidesgadolinium anderbium.^[18]

It often also falls in the same range for reaction order,^[14] resemblingterbium anddysprosium in its chemical reactivity.^[9] Yttrium is so close in size to the so-called 'yttrium group' of heavy lanthanide ions that in solution, it behaves as if it were one of them.^[14][19] Even though the lanthanides are one row farther down the periodic table than yttrium, the similarity in atomic radius may be attributed to thelanthanide contraction.^[20]

One of the few notable differences between the chemistry of yttrium and that of the lanthanides is that yttrium is almost exclusivelytrivalent, whereas about half the lanthanides can have valences other than three; nevertheless, only for four of the fifteen lanthanides are these other valences important in aqueous solution (Ce^IV,Sm^II,Eu^II, andYb^II).^[14]

As a trivalent transition metal, yttrium forms variousinorganic compounds, generally in the +3 oxidation state, by giving up all three of itsvalence electrons.^[21] A good example isyttrium(III) oxide (Y
₂O
₃), also known as yttria, a six-coordinate white solid.^[22]

Yttrium forms a water-insolublefluoride,hydroxide, andoxalate, but itsbromide,chloride,iodide,nitrate andsulfate are allsoluble in water.^[14] The Y³⁺ion is colorless in solution due to the absence of electrons in the d and felectron shells.^[14]

Water readily reacts with yttrium and its compounds to formY
₂O
₃.^[16] Concentratednitric andhydrofluoric acids do not rapidly attack yttrium, but other strong acids do.^[14]

Withhalogens, yttrium formstrihalides such asyttrium(III) fluoride (YF
₃),yttrium(III) chloride (YCl
₃), andyttrium(III) bromide (YBr
₃) at temperatures above roughly 200 °C.^[10] Similarly,carbon,phosphorus,selenium,silicon andsulfur all formbinary compounds with yttrium at elevated temperatures.^[14]

Organoyttrium chemistry is the study of compounds containing carbon–yttrium bonds. A few of these are known to have yttrium in the oxidation state 0.^[4][23] (The +2 state has been observed in chloride melts,^[24] and +1 in oxide clusters in the gas phase.^[25]) Sometrimerization reactions were generated with organoyttrium compounds as catalysts.^[23] These syntheses useYCl
₃ as a starting material, obtained fromY
₂O
₃ and concentratedhydrochloric acid andammonium chloride.^[26][27]

Hapticity is a term to describe the coordination of a group of contiguous atoms of aligand bound to the central atom; it is indicated by the Greek letter eta, η. Yttrium complexes were the first examples of complexes wherecarboranyl ligands were bound to a d⁰-metal center through a η⁷-hapticity.^[23] Vaporization of thegraphite intercalation compounds graphite–Y or graphite–Y
₂O
₃ leads to the formation ofendohedral fullerenes such as Y@C₈₂.^[9]Electron spin resonance studies indicated the formation of Y³⁺ and (C₈₂)³⁻ ion pairs.^[9] Thecarbides Y₃C, Y₂C, and YC₂ can be hydrolyzed to formhydrocarbons.^[14]

Yttrium in theSolar System was created bystellar nucleosynthesis, mostly by thes-process (≈72%), but also ther-process (≈28%).^[28] The r-process consists of rapidneutron capture by lighter elements duringsupernova explosions. The s-process is a slowneutron capture of lighter elements inside pulsatingred giant stars.^[29]

Yttrium isotopes are among the most common products of thenuclear fission of uranium in nuclear explosions and nuclear reactors. In the context ofnuclear waste management, the most important isotopes of yttrium are⁹¹Y and⁹⁰Y, with half-lives of 58.51 days and 64 hours, respectively.^[30] Though⁹⁰Y has a short half-life, it exists insecular equilibrium with its long-lived parent isotope,strontium-90 (⁹⁰Sr) (half-life 29 years).^[15]

All group 3 elements have an oddatomic number, and therefore few stableisotopes.^[11]Scandium has onestable isotope, and yttrium itself has only one stable isotope,⁸⁹Y, which is also the only isotope that occurs naturally. However, the lanthaniderare earths contain elements of even atomic number and many stable isotopes. Yttrium-89 is thought to be more abundant than it otherwise would be, due in part to the s-process, which allows enough time for isotopes created by other processes to decay byelectron emission (neutron → proton).^[29][b] Such a slow process tends to favor isotopes withatomic mass numbers (A = protons + neutrons) around 90, 138 and 208, which have unusually stableatomic nuclei with 50, 82, and 126 neutrons, respectively.^[29][c] This stability is thought to result from their very lowneutron-capture cross-section.^[29] Electron emission of isotopes with those mass numbers is simply less prevalent due to this stability, resulting in them having a higher abundance.^[15]89Y has a mass number close to 90 and has 50 neutrons in its nucleus.

At least 32 synthetic isotopes of yttrium have been observed, and these range inatomic mass number from 76 to 108.^[30] The least stable of these is¹⁰⁹Y with ahalf-life of 25 ms and the most stable is⁸⁸Y with half-life 106.629 days.^[31] Apart from⁹¹Y,⁸⁷Y, and⁹⁰Y, with half-lives of 58.51 days, 79.8 hours, and 64 hours, respectively; all other isotopes have half-lives of less than a day and most of less than an hour.^[30]

Yttrium isotopes with mass numbers at or below 88 decay mainly bypositron emission (proton → neutron) to formstrontium (Z = 38) isotopes.^[30] Yttrium isotopes with mass numbers at or above 90 decay mainly by electron emission (neutron → proton) to formzirconium (Z = 40) isotopes.^[30] Isotopes with mass numbers at or above 97 are also known to have minor decay paths of β⁻ delayedneutron emission.^[32]

Yttrium has at least 20metastable ("excited") isomers ranging in mass number from 78 to 102.^[30][d] Multiple excitation states have been observed for⁸⁰Y and⁹⁷Y.^[30] While most yttrium isomers are expected to be less stable than theirground state;^{78m, 84m, 85m, 96m, 98m1, 100m, 102m}Y have longer half-lives than their ground states, as these isomers decay by beta decay rather thanisomeric transition.^[32]

In 1787, part-time chemistCarl Axel Arrhenius found a heavy black rock in an old quarry near the Swedish village ofYtterby (now part of theStockholm Archipelago).^[33] Thinking it was an unknown mineral containing the newly discovered elementtungsten,^[34] he named itytterbite^[e] and sent samples to various chemists for analysis.^[33]

Johan Gadolin at theRoyal Academy of Åbo (Turku) identified a new oxide (or "earth") in Arrhenius' sample in 1789, and published his completed analysis in 1794.^[35][f]Anders Gustaf Ekeberg confirmed the identification in 1797 and named the new oxideyttria.^[36] In the decades afterAntoine Lavoisier developed the first modern definition ofchemical elements, it was believed that earths could be reduced to their elements, meaning that the discovery of a new earth was equivalent to the discovery of the element within, which in this case would have beenyttrium.^{[g][37][38][39]}

Friedrich Wöhler is credited with first isolating the metal in 1828 by reacting a volatile chloride that he believed to beyttrium chloride with potassium.^[40][41][42]

In 1843,Carl Gustaf Mosander found that samples of yttria contained three oxides: whiteyttrium oxide (yttria), yellowterbium oxide (confusingly, this was called 'erbia' at the time) and rose-colorederbium oxide (called 'terbia' at the time).^[43][44] A fourth oxide,ytterbium oxide, was isolated in 1878 byJean Charles Galissard de Marignac.^[45] New elements were later isolated from each of those oxides, and each element was named, in some fashion, after Ytterby, the village near the quarry where they were found (seeytterbium,terbium, anderbium).^[46] In the following decades, seven other new metals were discovered in "Gadolin's yttria".^[33] Since yttria was found to be a mineral and not an oxide,Martin Heinrich Klaproth renamed itgadolinite in honor of Gadolin.^[33]

Until the early 1920s, the chemical symbolYt was used for the element, after whichY came into common use.^[47][48]

In 1987,yttrium barium copper oxide was found to achievehigh-temperature superconductivity.^[49] It was only the second material known to exhibit this property,^[49] and it was the first-known material to achievesuperconductivity above the (economically important) boiling point of nitrogen.^[h]

Yttrium is found in mostrare-earth minerals,^[12] and someuranium ores, but never in the Earth's crust as a free element.^[50] About 31 ppm of the Earth's crust is yttrium,^[9] making it the 43rd most abundant element.^[51]: 615 Yttrium is found in soil in concentrations between 10 and 150 ppm (dry weight average of 23 ppm) and in sea water at 9 ppt.^[51] Lunar rock samples collected during theAmericanApollo Project have a relatively high content of yttrium.^[46]

Yttrium is not considered a "bone-seeker" likestrontium andlead.^[52] Normally, as little as 0.5 milligrams (0.0077 gr) is found in the entire human body; humanbreast milk contains 4 ppm.^[53] Yttrium can be found in edible plants in concentrations between 20 ppm and 100 ppm (fresh weight), withcabbage having the largest amount.^[53] With as much as 700 ppm, the seeds of woody plants have the highest known concentrations.^[53]

As of April 2018^[update] there are reports of the discovery of very large reserves of rare-earth elements in the deep seabed several hundred kilometers from the tiny Japanese island ofMinami-Torishima Island, also known as Marcus Island. This location is described as having "tremendous potential" for rare-earth elements and yttrium (REY), according to a study published inScientific Reports.^[54] "This REY-rich mud has great potential as a rare-earth metal resource because of the enormous amount available and its advantageous mineralogical features," the study reads. The study shows that more than 16 millionshort tons (15 billion kilograms) of rare-earth elements could be "exploited in the near future." As well as yttrium (Y), which is used in products like camera lenses and mobile phone screens, the rare-earth elements found are europium (Eu), terbium (Tb), and dysprosium (Dy).^[55]

As yttrium is chemically similar to lanthanides, it occurs in the same ores (rare-earth minerals) and is extracted by the same refinement processes. A slight distinction is recognized between the light (LREE) and the heavy rare-earth elements (HREE), but the distinction is not perfect. Yttrium is concentrated in the HREE group due to its ion size, though it has a loweratomic mass.^[56][57]

Rare-earth elements (REEs) come mainly from four sources:^[58]

• Carbonate and fluoride containing ores such as the LREEbastnäsite ((Ce, La, etc.)(CO₃)F) contain on average 0.1%^[15][56] yttrium compared to the 99.9% for the 16 other REEs.^[56] The main source of bastnäsite from the 1960s to the 1990s was theMountain Pass rare earth mine in California, making the United States the largest producer of REEs during that period.^[56][58] The name "bastnäsite" is actually a group name, and the Levinson suffix is used in the correct mineral names, e.g., bästnasite-(Y) has Y as a prevailing element.^[59][60][61]
• Monazite ((Ce,La, etc.)PO₄), which is mostly phosphate, is aplacer deposit of sand created by the transportation and gravitational separation of eroded granite. Monazite as a LREE ore contains 2%^[56] (or 3%)^[62] yttrium. The largest deposits were found in India and Brazil in the early 20th century, making those two countries the largest producers of yttrium in the first half of that century.^[56][58] Of the monazite group, the Ce-dominant member, monazite-(Ce), is the most common one.^[63]
• Xenotime, a REE phosphate, is the main HREE ore containing as much as 60% yttrium asyttrium phosphate (YPO₄).^[56] This applies to xenotime-(Y).^[61][64][60] The largest mine is theBayan Obo deposit in China, making China the largest exporter for HREE since the closure of the Mountain Pass mine in the 1990s.^[56][58]
• Ion absorption clays or Longnan clays are the weathering products of granite and contain only 1% of REEs.^[56] The final ore concentrate can contain as much as 8% yttrium. Ion absorption clays are mostly in southern China.^[56][58][65] Yttrium is also found insamarskite andfergusonite (which also stand for group names).^[51]

One method for obtaining pure yttrium from the mixed oxide ores is to dissolve the oxide insulfuric acid and fractionate it byion exchangechromatography. With the addition ofoxalic acid, the yttrium oxalate precipitates. The oxalate is converted into the oxide by heating under oxygen. By reacting the resulting yttrium oxide withhydrogen fluoride,yttrium fluoride is obtained.^[66] When quaternary ammonium salts are used as extractants, most yttrium will remain in the aqueous phase. When thecounter-ion is nitrate, the light lanthanides are removed, and when the counter-ion is thiocyanate, the heavy lanthanides are removed. In this way, yttrium salts of 99.999% purity are obtained. In the usual situation, where yttrium is in a mixture that is two-thirds heavy-lanthanide, yttrium should be removed as soon as possible to facilitate the separation of the remaining elements.

Annual world production of yttrium oxide had reached 600tonnes (660short tons) by 2001; by 2014 it had increased to 6,400 tonnes (7,000 short tons).^[51][67] Global reserves of yttrium oxide were estimated in 2014 to be more than 450,000 tonnes (500,000 short tons). The leading countries for these reserves included Australia, Brazil, China, India, and the United States.^[67] Only a few tonnes of yttrium metal are produced each year by reducingyttrium fluoride to ametal sponge withcalciummagnesium alloy. The temperature of anarc furnace, in excess of 1,600 °C, is sufficient to melt the yttrium.^[51][66]

The red component ofcolor televisioncathode ray tubes is typically emitted from anyttria (Y
₂O
₃) or yttrium oxide sulfide (Y
₂O
₂S) host latticedoped witheuropium (III) cation (Eu³⁺)phosphors.^[15][9][i] The red color itself is emitted from the europium while the yttrium collects energy from theelectron gun and passes it to the phosphor.^[68] Yttrium compounds can serve as host lattices for doping with differentlanthanide cations.Tb³⁺ can be used as a doping agent to produce greenluminescence. As such yttrium compounds such as yttrium aluminium garnet (YAG) are useful for phosphors and are an important component of whiteLEDs.

Yttria is used as asintering additive in the production of poroussilicon nitride.^[69]

Yttrium compounds are used as acatalyst forethylenepolymerization.^[15] As a metal, yttrium is used on the electrodes of some high-performancespark plugs.^[70] Yttrium is used ingas mantles forpropanelanterns as a replacement forthorium, which isradioactive.^[71]

Yttrium is used in the production of a large variety ofsynthetic garnets,^[72] and yttria is used to makeyttrium iron garnets (Y
₃Fe
₅O
₁₂, "YIG"), which are very effectivemicrowavefilters^[15] which were recently shown to have magnetic interactions more complex and longer-ranged than understood over the previous four decades.^[73] Yttrium,iron,aluminium, andgadolinium garnets (e.g.Y₃(Fe,Al)₅O₁₂ andY₃(Fe,Gd)₅O₁₂) have importantmagnetic properties.^[15] YIG is also very efficient as an acoustic energy transmitter and transducer.^[74]Yttrium aluminium garnet (Y
₃Al
₅O
₁₂ or YAG) has ahardness of 8.5 and is also used as agemstone in jewelry (simulateddiamond).^[15]Cerium-doped yttrium aluminium garnet (YAG:Ce) crystals are used as phosphors to make whiteLEDs.^[75][76][77]

YAG, yttria,yttrium lithium fluoride (LiYF₄), andyttrium orthovanadate (YVO₄) are used in combination withdopants such asneodymium,erbium,ytterbium in near-infraredlasers.^[78][79] YAG lasers can operate at high power and are used for drilling and cutting metal.^[62] The single crystals of doped YAG are normally produced by theCzochralski process.^[80]

Small amounts of yttrium (0.1 to 0.2%) have been used to reduce the grain sizes ofchromium,molybdenum,titanium, andzirconium.^[81] Yttrium is used to increase thestrength of aluminium andmagnesium alloys.^[15] The addition of yttrium to alloys generally improves workability, adds resistance to high-temperature recrystallization, and significantly enhances resistance to high-temperatureoxidation (see graphite nodule discussion below).^[68]

Yttrium can be used todeoxidizevanadium and othernon-ferrous metals.^[15]Yttria stabilizes thecubic form of zirconia in jewelry.^[82]

Yttrium has been studied as a nodulizer inductile cast iron, forming thegraphite into compact nodules instead of flakes to increaseductility and fatigue resistance.^[15] Having a highmelting point, yttrium oxide is used in someceramic andglass to impartshock resistance and lowthermal expansion properties.^[15] Those same properties make such glass useful incamera lenses.^[51]

The radioisotopeyttrium-90 (⁹⁰Y) is used to label drugs such asedotreotide andibritumomab tiuxetan for the treatment of variouscancers, includinglymphoma,leukemia, liver, ovarian, colorectal, pancreatic and bone cancers.^[53] It works by adhering tomonoclonal antibodies, which in turn bind to cancer cells and kill them via intenseβ-radiation from the⁹⁰Y (seemonoclonal antibody therapy).^[83]

A technique calledradioembolization is used to treathepatocellular carcinoma andliver metastasis. Radioembolization is a low toxicity, targeted liver cancer therapy that uses millions of tiny beads made of glass or resin containing⁹⁰Y. The radioactive microspheres are delivered directly to the blood vessels feeding specific liver tumors/segments or lobes. It is minimally invasive and patients can usually be discharged after a few hours. This procedure may not eliminate all tumors throughout the entire liver, but works on one segment or one lobe at a time and may require multiple procedures.^[84]

Also see radioembolization in the case of combined cirrhosis and hepatocellular carcinoma.

Needles made of⁹⁰Y, which can cut more precisely than scalpels, have been used to sever pain-transmittingnerves in thespinal cord,^[34] and⁹⁰Y is also used to carry out radionuclidesynovectomy in the treatment of inflamed joints, especially knees, in people with conditions such asrheumatoid arthritis.^[85]

A neodymium-doped yttrium–aluminium–garnet laser has been used in an experimental, robot-assisted radicalprostatectomy in canines in an attempt to reduce collateral nerve and tissue damage,^[86] and erbium-doped lasers are coming into use for cosmetic skin resurfacing.^[9]

Yttrium is a key ingredient in theyttrium barium copper oxide (YBa₂Cu₃O₇, aka 'YBCO' or '1-2-3')superconductor developed at theUniversity of Alabama in Huntsville and theUniversity of Houston in 1987.^[49] This superconductor is notable because the operating superconductivity temperature is aboveliquid nitrogen's boiling point (77.1 K).^[49] Since liquid nitrogen is less expensive than theliquid helium required for metallic superconductors, the operating costs for applications would be less.

The actual superconducting material is often written as YBa₂Cu₃O_7–d, whered must be less than 0.7 for superconductivity. The reason for this is still not clear, but it is known that the vacancies occur only in certain places in the crystal, the copper oxide planes, and chains, giving rise to a peculiar oxidation state of the copper atoms, which somehow leads to the superconducting behavior.

The theory of low temperature superconductivity has been well understood since theBCS theory of 1957. It is based on a peculiarity of the interaction between two electrons in a crystal lattice. However, the BCS theory does not explain high temperature superconductivity, and its precise mechanism is still a mystery. What is known is that the composition of the copper-oxide materials must be precisely controlled for superconductivity to occur.^[87]

This superconductor is a black and green, multi-crystal, multi-phase mineral. Researchers are studying a class of materials known asperovskites that are alternative combinations of these elements, hoping to develop a practicalhigh-temperature superconductor.^[62]

Yttrium is used in small quantities in the cathodes of someLithium iron phosphate battery (LFP), which are then commonly called LiFeYPO₄ chemistry, orLYP. Similar toLFP, LYP batteries offer highenergy density, good safety and long life. But LYP offers highercathode stability, and prolongs the life of the battery, by protecting the physical structure of thecathode, especially at higher temperatures and higher charging / discharge current. LYP batteries find use in stationary applications (off-grid solar systems),electric vehicles (some cars), as well other applications (submarines, ships), similar to LFP batteries, but often at improved safety and cycle life time. LYP cells have essentially the samenominal voltage as LFP, 3.25 V, but the maximum charging voltage is 4.0 V,^[88] and the charging and discharge characteristics are very similar.^[89]

In 2009, ProfessorMas Subramanian and associates atOregon State University discovered that yttrium can be combined withindium andmanganese to form an intenselyblue, non-toxic, inert, fade-resistantpigment,YInMn blue, the first new blue pigment discovered in 200 years.

Yttrium can be highlytoxic to humans, animals and plants.^[10]Water-soluble compounds of yttrium are considered mildly toxic, while its insoluble compounds are non-toxic.^[53] In experiments on animals, yttrium and its compounds caused lung and liver damage, though toxicity varies with different yttrium compounds. In rats, inhalation of yttrium citrate causedpulmonary edema anddyspnea, while inhalation ofyttrium chloride caused liver edema,pleural effusions, and pulmonary hyperemia.^[10]

Exposure to yttrium compounds in humans may cause lung disease.^[10] Workers exposed to airborne yttrium europium vanadate dust experienced mild eye, skin, and upper respiratory tract irritation—though this may be caused by thevanadium content rather than the yttrium.^[10] Acute exposure to yttrium compounds can cause shortness of breath, coughing, chest pain, andcyanosis.^[10] TheOccupational Safety and Health Administration (OSHA)limits exposure to yttrium in the workplace to 1 mg/m³ (5.8×10⁻¹⁰ oz/cu in) over an 8-hour workday. TheNational Institute for Occupational Safety and Health (NIOSH)recommended exposure limit (REL) is 1 mg/m³ (5.8×10⁻¹⁰ oz/cu in) over an 8-hour workday. At levels of 500 mg/m³ (2.9×10⁻⁷ oz/cu in), yttrium isimmediately dangerous to life and health.^[90] Yttrium dust is highly flammable.^[10]

•  Chemistry portal

• Yttrium by Paul C.W. Chu at acs.org
• Yttrium atThe Periodic Table of Videos (University of Nottingham)
• "Yttrium" .Encyclopædia Britannica (11th ed.). 1911.
• Encyclopedia of Geochemistry - Yttrium