:Complex oxide
{{Short description|Oxide compound with cations of multiple elements or different oxidation states}}
{{See also|Mixed oxide}}
File:Bi2212 Unit Cell.png and complex oxide.]]
A complex oxide is a chemical compound that contains oxygen and at least two other elements (or oxygen and just one other element that's in at least two oxidation states).{{cite book |last1=Ishihara |first1=Tatsumi |title=Perovskite Oxide for Solid Oxide Fuel Cells |date=2009 |publisher=Springer US |isbn=978-0-387-77708-5 |page=1 |edition=1 |doi=10.1007/978-0-387-77708-5 |series=Fuel Cells and Hydrogen Energy}} Complex oxide materials are notable for their wide range of magnetic and electronic properties, such as ferromagnetism, ferroelectricity, and high-temperature superconductivity. These properties often come from their strongly correlated electrons in d or f orbitals.
Natural occurrence
Many minerals found in the ground are complex oxides. Commonly studied mineral crystal families include spinels and perovskites.
Applications
Complex oxide materials are used in a variety of commercial applications.
=Magnets=
File:Cable end.JPG near the end of a Mini USB cable helps suppress high-frequency noise.]]
Magnets made of the complex oxide ferrite are commonly used in transformer cores and in inductors.{{cite book |last1=Goldman |first1=Alex |title=Modern Ferrite Technology |date=2006 |publisher=Springer US |isbn=978-0-387-28151-3 |pages=217–226 |edition=2nd |doi=10.1007/978-0-387-29413-1_8 |chapter=Applications and Functions of Ferrites}} Ferrites are ideal for these applications because they are magnetic, electrically insulating, and inexpensive.
=Transducers and actuators=
Piezoelectric transducers and actuators are often made of the complex oxide PZT (lead zirconate titanate).{{cite web |title=What is "PZT"? |url=https://www.americanpiezo.com/piezo-theory/pzt.html |website=American Piezo |publisher=APC International, Ltd. |access-date=19 June 2015}} These transducers are used in applications such ultrasound imaging and some microphones. PZT is also sometimes used for piezo ignition in lighters and gas grills.
=Capacitors=
Complex oxide materials are the dominant dielectric material in ceramic capacitors.{{cite journal | last1=Ho |first1=J. |last2=Jow |first2=T. R. |last3=Boggs |first3=S. |title=Historical introduction to capacitor technology |doi=10.1109/MEI.2010.5383924 |journal=IEEE Electrical Insulation Magazine |volume=26 |pages=20–25 |year=2010 |s2cid=23077215 |url=https://zenodo.org/record/1232215}}[http://www.ifre.re.kr/board/filedown.php?seq=179] {{Webarchive|url=https://web.archive.org/web/20161205144753/http://www.ifre.re.kr/board/filedown.php?seq=179 |date=2016-12-05}} About one trillion ceramic capacitors are produced each year to be used in electronic equipment.
=Fuel cells=
Solid oxide fuel cells often use complex oxide materials as their electrolytes, anodes, and cathodes.{{cite web |title=Lanthanum strontium cobalt oxide cathode powder |url=https://www.fuelcellmaterials.com/site/powders-and-pastes/cathodes?page=shop.product_details&category_id=11&flypage=vmj_naru.tpl&product_id=199 |website=Fuel Cell Materials |access-date=19 June 2015}}
=Gemstone jewelry=
File:Spanish jewellery-Gold and emerald pendant at VAM-01.jpg.{{cite web |url=https://collections.vam.ac.uk/item/O73034/pendant-unknown/ |title=Pendant | V&A Search the Collections |website=Victoria and Albert Museum |access-date=30 Jan 2014 |others=Given by Dame Joan Evans}} Museum item number M.138-1975 ]]
Many precious gemstones, such as emerald and topaz, are complex oxide crystals. Historically, some complex oxide materials (such as strontium titanate, yttrium aluminium garnet, and gadolinium gallium garnet) were also synthesized as inexpensive diamond simulants, though after 1976 they were mostly eclipsed by cubic zirconia.
=New electronic devices=
As of 2015, there is research underway to commercialize complex oxides in new kinds of electronic devices, such as ReRAM, FeRAM, and memristors. Complex oxide materials are also being researched for their use in spintronics.
Another potential application of complex oxide materials is superconducting power lines.{{cite web |title=Superconductor cable systems |url=http://www.amsc.com/gridtec/superconductor_cable_systems.html |publisher=AMSC}} A few companies have invested in pilot projects, but the technology is not widespread.
Commonly studied complex oxides
- Barium titanate (a multiferroic material)
- Bismuth ferrite (a multiferroic material)
- Bismuth strontium calcium copper oxide (a high-temperature superconductor)
- Lanthanum aluminate (a high-dielectric insulator)
- Lanthanum strontium manganite (a material exhibiting colossal magnetoresistance)
- Lead zirconate titanate (a piezoelectric material)
- Strontium titanate (a high-dielectric semiconductor)
- Yttrium barium copper oxide (a high-temperature superconductor)
See also
References
{{Reflist}}
External links
- [https://www.nature.com/articles/459028a Materials science: Enter the oxides], Nature. (subscription required)
- [https://www.nature.com/articles/nmat2264 Condensed-matter physics: Complex oxides on fire]
- [https://www.nature.com/articles/nmat2414 Complex oxides: A tale of two enemies]
- [https://www.nature.com/collections/ylkptpstlg Oxide interfaces]