- Zirconium dioxide
:"Zirconia redirects here. For the
Sailor Mooncharacter, see Dead Moon Circus."Chembox new
Name = Zirconium dioxide
ImageFile = CZ brilliant.jpg
IUPACName = Zirconium dioxide; Zirconium(IV) oxide
OtherNames = Zirconia;
Name = Thermodynamic data
Section1 = Chembox Identifiers
CASNo = 1314-23-4
Section2 = Chembox Properties
Formula = ZrO2
MolarMass = 123.22 g/mol
Appearance = white solid
Density = 5.89 g/cm³, solid
Solubility = Insoluble
MeltingPt = 2715 °C
BoilingPt = °C
Section4 = Chembox Thermochemistry
DeltaHf = −1080 kJ/mol
Entropy = 50.3 J.K−1.mol−1
Section7 = Chembox Hazards
EUClass = not listed
Section8 = Chembox Related
Titanium dioxide; Hafnium dioxide
Zirconium dioxide (ZrO2), sometimes known as zirconia, is a white crystalline
oxideof zirconium. Its most naturally occurring form, with a monocliniccrystalline structure, is the rare mineral, baddeleyite. The high temperature cubic crystalline form, called ' cubic zirconia', is rarely found in nature as mineral tazheranite (Zr,Ti,Ca)O2 (and a doubtful mineral arkelite), but is synthesized in various colours for use as a gemstone. The cubic crystal structured variety cubic zirconiais the best-known diamond simulant.
Ceramic and engineering properties
Zirconium dioxide is one of the most studied
ceramicmaterials. Pure ZrO2 has a monoclinic crystal structureat room temperature and transitions to tetragonaland cubic at increasing temperatures. The volume expansion caused by the cubic to tetragonal to monoclinic transformation induces very large stresses, and will cause pure ZrO2 to crack upon cooling from high temperatures. Several different oxides are added to zirconia to stabilize the tetragonal and/or cubic phases: magnesium oxide(MgO), yttrium oxide, (Y2O3), calcium oxide(CaO), and cerium(III) oxide(Ce2O3), amongst others.
Zirconia is very useful in its 'stabilized' state. In some cases, the tetragonal phase can be
metastable. If sufficient quantities of the metastable tetragonal phase is present, then an applied stress, magnified by the stress concentrationat a crack tip, can cause the tetragonal phase to convert to monoclinic, with the associated volume expansion. This phase transformation can then put the crack into compression, retarding its growth, and enhancing the fracture toughness. This mechanism is known as "transformation toughening", and significantly extends the reliability and lifetime of products made with stabilized zirconia. A special case of zirconia is that of tetragonal zirconia polycrystalineor TZP, which is indicative of polycrystalline zirconia composed of only the metastable tetragonal phase.
The cubic phase of zirconia also has a very low thermal conductivity, which has led to its use as a
thermal barrier coatingor TBC in jet turbineand diesel engines to allow operation at higher temperatures. Thermodynamically the higher the operation temperature of an engine, the greater the possible efficiency (see Carnot heat engine). As of 2004, a great deal of research is ongoing to improve the quality and durability of these coatings.It is used as a refractorymaterial, in insulation, abrasives, enamels and ceramic glazes. Stabilized zirconia is used in oxygen sensors and fuel cellmembranes because it has the ability to allow oxygen ions to move freely through the crystal structure at high temperatures. This high ionic conductivity (and a low electronic conductivity) makes it one of the most useful electroceramics.
The ZrO2 bandgap is dependent on the phase (cubic, tetragonal, monoclinic, or amorphous) and preparation methods, with typical estimates from 5-7 eV. [J.P. Chang, Y-S. Lin, and K. Chu, "Rapid thermal chemical vapor deposition of zirconium oxide for metal-oxide-semiconductor field effect transistor application," J. Vac. Sci. Technol. B 195 , pp. 1782-1787, (2001)]
This material is also used in the manufacture of subframes for the construction of dental restorations such as crowns and bridges which are then veneered with a conventional feldspathic porcelain.
Zirconium dioxide can occur as a white powder which possesses both
acidic and basic properties. On account of its infusibility and brilliant luminosity when incandescent, it was used as an ingredient of sticks for limelight.
Zirconia is also an important
high-k dielectricmaterial that is being investigated for potential applications as an insulator in transistors in future nanoelectronicdevices.
Single crystals of the cubic phase of zirconia are commonly used as a substitute for
diamond( diamond simulant) in jewellery. Like diamond, cubic zirconiahas a cubic crystal structure and a high index of refraction. Discerning a good quality cubic zirconia gem from a diamond is difficult, and most jewellers will have a thermal conductivity tester to identify cubic zircona by its low thermal conductivity(diamond is a very good thermal conductor). This state of zirconia is commonly called "cubic zirconia," "CZ," or "zircon" by jewellers, but the last name is not chemically accurate. Zirconis actually the mineral name for naturally occurring zirconium silicate(ZrSiO4). Its transparent form is also used as a gemstone, and its opaque form as a refractory.
August 7, 2006, Apple Computerfiled a patent for using zirconia as casing for mobile devices. Future iPodslikely will contain radios for Bluetooth and wide area wireless. Using zirconia rather than steel or aluminum for its radio transparency characteristics enables antennas to be hidden internally in the device. Additionally, some iPods with plastic fronts have been known to scratch easily.]
* [http://www.cdc.gov/niosh/npg/npgd0677.html NIOSH Pocket Guide to Chemical Hazards]
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Look at other dictionaries:
zirconium dioxide — cirkonio(IV) oksidas statusas T sritis chemija formulė ZrO₂ atitikmenys: angl. zircon alba; zirconia; zirconium anhidride; zirconium dioxide; zirconium(IV) oxide rus. циркония диоксид; циркония(IV) оксид ryšiai: sinonimas – cirkonio dioksidas … Chemijos terminų aiškinamasis žodynas
zirconium dioxide — noun a white crystalline oxide; used in refractories and in insulation and abrasives and enamels and glazes • Syn: ↑zirconium oxide, ↑zirconia • Hypernyms: ↑oxide * * * noun see zirconium oxide … Useful english dictionary
zirconium dioxide — /zɜkoʊniəm daɪˈɒksaɪd/ (say zerkohneeuhm duy oksuyd) noun a white crystalline oxide of zirconium, ZrO2, occurring naturally as a rare mineral. See cubic zirconia … Australian English dictionary
Zirconium — (pronEng|zɚˈkoʊniəm, IPA|/ˌzɝˈkoʊniəm/) is a chemical element with the symbol Zr and atomic number 40. It is a lustrous, gray white, strong transition metal that resembles titanium. Zirconium is used as an alloying agent due to its high… … Wikipedia
zirconium oxide — n. zirconium dioxide, ZrO2, a white, infusible powder used in making crucibles, furnace linings, pigments, etc. and, because of its luminosity, in incandescent burners … English World dictionary
zirconium — zirconic /zerr kon ik/, adj. /zerr koh nee euhm/, n. Chem. a metallic element found combined in zircon, baddeleyite, etc., resembling titanium chemically: used in steel metallurgy, as a scavenger, as a refractory, and as an opacifier in vitreous… … Universalium
zirconium oxide — noun a white crystalline oxide; used in refractories and in insulation and abrasives and enamels and glazes • Syn: ↑zirconia, ↑zirconium dioxide • Hypernyms: ↑oxide * * * noun or zirconium dioxide … Useful english dictionary
zirconium anhidride — cirkonio(IV) oksidas statusas T sritis chemija formulė ZrO₂ atitikmenys: angl. zircon alba; zirconia; zirconium anhidride; zirconium dioxide; zirconium(IV) oxide rus. циркония диоксид; циркония(IV) оксид ryšiai: sinonimas – cirkonio dioksidas … Chemijos terminų aiškinamasis žodynas
zirconium(IV) oxide — cirkonio(IV) oksidas statusas T sritis chemija formulė ZrO₂ atitikmenys: angl. zircon alba; zirconia; zirconium anhidride; zirconium dioxide; zirconium(IV) oxide rus. циркония диоксид; циркония(IV) оксид ryšiai: sinonimas – cirkonio dioksidas … Chemijos terminų aiškinamasis žodynas
zirconium oxide — Chem. a white, heavy, amorphous, odorless and tasteless, infusible, water insoluble powder, ZrO2, used chiefly as a pigment for paints, an abrasive, and in the manufacture of refractory crucibles. Also called zirconia /zerr koh nee euh/,… … Universalium