Mixed oxide
Encyclopedia
In chemistry
, a mixed oxide is a somewhat informal name for an oxide
that contains more than one chemical element
in its cation, or of a single element cation that has atoms in several states of oxidation.
The term is usually applied to solid ionic compounds that contain the oxide anion O2− and two or more element cations. A typical example is the mineral ilmenite
(FeTiO3), a mixed oxide of iron
(Fe2+) and titanium
(Ti4+) cations. The cations may be the same element in different ionization states: a notable example is magnetite
Fe3O4, which contains the cations Fe2+ ("ferrous" iron) and Fe3+ ("ferric" iron) in 1:1 ratio. Other notable examples include the ferrite
s, strontium titanate
SrTiO3 (which, despite its name, contains Ti4+ cations and not the TiO32- anion), yttrium aluminum garnet Y3Al5O12, and many more.
Mixed oxides are intermediate between a metal oxide and a metal salt. Sometimes mixed oxides are the salts of weak metallic acids. Most other times they are just two different oxides that bond together strongly.
However, the term is sometimes also applied to compounds of oxygen and two or more other elements, where some or all of the oxygen atoms are covalently bound into oxoanions.; or to fine mixtures of two or more oxides. An example would be the zincate
s. Zinc hydroxide can react with concentrated sodium hydroxide to become sodium zincate. This contains zincate ions.
Mixed oxide minerals are plentiful in nature. Synthetic mixed oxides are components of many ceramics with remarkable properties and important advanced technological applications, such as strong magnet
s, fine optics
, laser
s, semiconductor
s, piezoelectrics, superconductors, catalysts, refractories
, gas mantle
s, nuclear fuel
s, and more. Piezoelectric mixed oxides, in particular, are extensively used in pressure
and strain
gauges, microphone
s, ultrasound
transducer
s, micromanipulator
s, delay line
s, etc..
Chemistry
Chemistry is the science of matter, especially its chemical reactions, but also its composition, structure and properties. Chemistry is concerned with atoms and their interactions with other atoms, and particularly with the properties of chemical bonds....
, a mixed oxide is a somewhat informal name for an oxide
Oxide
An oxide is a chemical compound that contains at least one oxygen atom in its chemical formula. Metal oxides typically contain an anion of oxygen in the oxidation state of −2....
that contains more than one chemical element
Chemical element
A chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. Familiar examples of elements include carbon, oxygen, aluminum, iron, copper, gold, mercury, and lead.As of November 2011, 118 elements...
in its cation, or of a single element cation that has atoms in several states of oxidation.
The term is usually applied to solid ionic compounds that contain the oxide anion O2− and two or more element cations. A typical example is the mineral ilmenite
Ilmenite
Ilmenite is a weakly magnetic titanium-iron oxide mineral which is iron-black or steel-gray. It is a crystalline iron titanium oxide . It crystallizes in the trigonal system, and it has the same crystal structure as corundum and hematite....
(FeTiO3), a mixed oxide of iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
(Fe2+) and titanium
Titanium
Titanium is a chemical element with the symbol Ti and atomic number 22. It has a low density and is a strong, lustrous, corrosion-resistant transition metal with a silver color....
(Ti4+) cations. The cations may be the same element in different ionization states: a notable example is magnetite
Magnetite
Magnetite is a ferrimagnetic mineral with chemical formula Fe3O4, one of several iron oxides and a member of the spinel group. The chemical IUPAC name is iron oxide and the common chemical name is ferrous-ferric oxide. The formula for magnetite may also be written as FeO·Fe2O3, which is one part...
Fe3O4, which contains the cations Fe2+ ("ferrous" iron) and Fe3+ ("ferric" iron) in 1:1 ratio. Other notable examples include the ferrite
Ferrite (magnet)
Ferrites are chemical compounds consisting of ceramic materials with iron oxide as their principal component. Many of them are magnetic materials and they are used to make permanent magnets, ferrite cores for transformers, and in various other applications.Many ferrites are spinels with the...
s, strontium titanate
Strontium titanate
Strontium titanate is an oxide of strontium and titanium with the chemical formula SrTiO3. At room temperature, it is a centrosymmetric paraelectric material with a perovskite structure...
SrTiO3 (which, despite its name, contains Ti4+ cations and not the TiO32- anion), yttrium aluminum garnet Y3Al5O12, and many more.
Mixed oxides are intermediate between a metal oxide and a metal salt. Sometimes mixed oxides are the salts of weak metallic acids. Most other times they are just two different oxides that bond together strongly.
However, the term is sometimes also applied to compounds of oxygen and two or more other elements, where some or all of the oxygen atoms are covalently bound into oxoanions.; or to fine mixtures of two or more oxides. An example would be the zincate
Zincate
In chemistry the term zincate may refer to* a salt containing Zn42−,also called the tetrahydroxozincate ion. It is an ore of Zinc. Examples include calcium zincate CaZn4.2H2O or Na2Zn4 or the polymeric anion [Zn3−] in for example NaZn3· H2O * an alkali solution prepared from dissolving zinc...
s. Zinc hydroxide can react with concentrated sodium hydroxide to become sodium zincate. This contains zincate ions.
Mixed oxide minerals are plentiful in nature. Synthetic mixed oxides are components of many ceramics with remarkable properties and important advanced technological applications, such as strong magnet
Magnet
A magnet is a material or object that produces a magnetic field. This magnetic field is invisible but is responsible for the most notable property of a magnet: a force that pulls on other ferromagnetic materials, such as iron, and attracts or repels other magnets.A permanent magnet is an object...
s, fine optics
Optics
Optics is the branch of physics which involves the behavior and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behavior of visible, ultraviolet, and infrared light...
, laser
Laser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of photons. The term "laser" originated as an acronym for Light Amplification by Stimulated Emission of Radiation...
s, semiconductor
Semiconductor
A semiconductor is a material with electrical conductivity due to electron flow intermediate in magnitude between that of a conductor and an insulator. This means a conductivity roughly in the range of 103 to 10−8 siemens per centimeter...
s, piezoelectrics, superconductors, catalysts, refractories
Refractory
A refractory material is one that retains its strength at high temperatures. ASTM C71 defines refractories as "non-metallic materials having those chemical and physical properties that make them applicable for structures, or as components of systems, that are exposed to environments above...
, gas mantle
Gas mantle
An incandescent gas mantle, gas mantle, or Welsbach mantle is a device for generating bright white light when heated by a flame. The name refers to its original heat source, existing gas lights, which filled the streets of Europe and North America in the late 19th century, mantle referring to the...
s, nuclear fuel
MOX fuel
Mixed oxide fuel, commonly referred to as MOX fuel, is nuclear fuel that contains more than one oxide of fissile material. MOX fuel contains plutonium blended with natural uranium, reprocessed uranium, or depleted uranium. MOX fuel is an alternative to the low-enriched uranium fuel used in the...
s, and more. Piezoelectric mixed oxides, in particular, are extensively used in pressure
Pressure
Pressure is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure.- Definition :...
and strain
Strain
Strain can refer to:* Strain , variants of plants, viruses or bacteria; or an inbred animal used for experimental purposes* Strain , a chemical stress of a molecule...
gauges, microphone
Microphone
A microphone is an acoustic-to-electric transducer or sensor that converts sound into an electrical signal. In 1877, Emile Berliner invented the first microphone used as a telephone voice transmitter...
s, ultrasound
Ultrasound
Ultrasound is cyclic sound pressure with a frequency greater than the upper limit of human hearing. Ultrasound is thus not separated from "normal" sound based on differences in physical properties, only the fact that humans cannot hear it. Although this limit varies from person to person, it is...
transducer
Transducer
A transducer is a device that converts one type of energy to another. Energy types include electrical, mechanical, electromagnetic , chemical, acoustic or thermal energy. While the term transducer commonly implies the use of a sensor/detector, any device which converts energy can be considered a...
s, micromanipulator
Micromanipulator
A micromanipulator is a device which is used to physically interact with a sample under a microscope, where a level of precision of movement is necessary that cannot be achieved by the unaided human hand...
s, delay line
Delay line
Delay line may refer to:* Propagation delay, the length of time taken for something to reach its destination* Analog delay line, used to delay a signal...
s, etc..