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{{short description|Inorganic, nonmetallic solid prepared by the action of heat}}
{{about|the material properties of ceramics}}
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A '''ceramic''' is any of the various hard, [[Brittleness|brittle]], [[Heat resistance|heat-resistant]], and [[corrosion-resistant]] [[Material|materials]] made by shaping and then firing an inorganic, nonmetallic material, such as [[clay]], at a high temperature.<ref>{{cite book|last1=Heimann|first1=Robert B.|url=https://books.google.com/books?id=JiJsfP_DiL4C&q=ceramics+are&pg=PR15|title=Classic and Advanced Ceramics: From Fundamentals to Applications, Preface|date=16 April 2010|publisher=John Wiley & Sons |isbn=9783527630189|access-date=30 October 2020|archive-date=10 December 2020|archive-url=https://web.archive.org/web/20201210175959/https://books.google.com/books?id=JiJsfP_DiL4C&q=ceramics+are&pg=PR15|url-status=live}}</ref><ref>{{cite web |website=The Free Dictionary |title=ceramic |url=https://www.thefreedictionary.com/ceramic#:~:text=(s%C9%99%2Dr%C4%83m%E2%80%B2%C4%ADk),2. |access-date=2020-08-03 |archive-date=2020-08-03 |archive-url=https://web.archive.org/web/20200803020110/https://www.thefreedictionary.com/ceramic#:~:text=(s%C9%99%2Dr%C4%83m%E2%80%B2%C4%ADk),2. |url-status=live }}</ref> Common examples are [[earthenware]], [[porcelain]], and [[brick]].

The earliest ceramics made by humans were [[pottery]] objects (pots, vessels, or vases) or [[figurine]]s made from [[clay]], either by itself or mixed with other materials like [[silicon dioxide|silica]], hardened and [[sintering|sintered]] in fire. Later, ceramics were [[glazing (ceramics)|glazed]] and fired to create smooth, colored surfaces, decreasing [[porosity]] through the use of glassy, amorphous ceramic coatings on top of the crystalline ceramic substrates.<ref>{{cite book |last1=Carter|first1=C. B. |last2=Norton|first2=M. G. |title=Ceramic materials: Science and engineering |publisher=[[Springer (publisher)|Springer]] |year=2007 |isbn=978-0-387-46271-4 |url=https://books.google.com/books?id=aE_VQ8I24OoC&pg=PA20 |pages=20, 21}}</ref> Ceramics now include domestic, industrial, and building products, as well as a wide range of materials developed for use in advanced ceramic engineering, such as [[semiconductor]]s.

The word ''[[wikt:ceramic|ceramic]]'' comes from the [[Ancient Greek]] word {{wikt-lang|grc|κεραμικός}} ({{grc-transl|κεραμικός}}), meaning "of or for pottery"<ref>{{LSJ|keramiko/s|ref}}</ref> ({{etymology||''{{wikt-lang|grc|κέραμος}}'' ({{grc-transl|κέραμος}})|potter's clay, tile, pottery}}).<ref>{{LSJ|ke/ramos|ref}}</ref> The earliest known mention of the root ''ceram-'' is the [[Mycenaean Greek]] {{nowrap|{{transl|gmy|ke-ra-me-we}}}}, workers of ceramic, written in [[Linear B]] syllabic script.<ref>{{cite web |title=keramewe |website=Palaeolexicon |url=http://www.palaeolexicon.com/default.aspx?static=12&wid=383 |url-status=live |archive-url=https://web.archive.org/web/20110501113622/http://www.palaeolexicon.com/default.aspx?static=12&wid=383 |archive-date=2011-05-01}}</ref> The word ''ceramic'' can be used as an adjective to describe a material, product, or process, or it may be used as a noun, either singular or, more commonly, as the [[plurale tantum|plural]] noun ''ceramics''.<ref>{{OED|ceramic}}</ref>

==Materials==
[[File:Si3N4thruster.jpg|thumb|upright=1.35|right|Silicon nitride rocket thruster. Left: Mounted in test stand. Right: Being tested with H<sub>2</sub>/O<sub>2</sub> propellants.]]
Ceramic material is an inorganic, metallic oxide, nitride, or carbide material. Some elements, such as [[carbon]] or [[silicon]], may be considered ceramics. Ceramic materials are brittle, hard, strong in compression, and weak in [[shear stress|shearing]] and tension. They withstand the chemical erosion that occurs in other materials subjected to acidic or caustic environments. Ceramics generally can withstand very high temperatures, ranging from 1,000&nbsp;°C to 1,600&nbsp;°C (1,800&nbsp;°F to 3,000&nbsp;°F).

[[Image:Ceramic fractured SEM.TIF|thumb|upright=1.2|A low magnification [[Scanning electron microscope|SEM micrograph]] of an advanced ceramic material. The properties of ceramics make fracturing an important inspection method.]]
The [[crystallinity]] of ceramic materials varies widely. Most often, fired ceramics are either [[Vitrification|vitrified]] or semi-vitrified, as is the case with earthenware, [[stoneware]], and porcelain. Varying crystallinity and [[electron]] composition in the ionic and covalent bonds cause most ceramic materials to be good thermal and [[Insulator (electricity)|electrical insulators]] (researched in [[ceramic engineering]]). With such a large range of possible options for the composition/structure of a ceramic (nearly all of the elements, nearly all types of bonding, and all levels of crystallinity), the breadth of the subject is vast, and identifiable attributes ([[hardness]], [[toughness]], [[electrical resistivity and conductivity|electrical conductivity]]) are difficult to specify for the group as a whole. General properties such as high melting temperature, high hardness, poor conductivity, high [[elastic modulus|moduli of elasticity]], chemical resistance, and low ductility are the norm,<ref>{{cite book |author1=Black, J. T. |author2=Kohser, R. A. |title=DeGarmo's materials and processes in manufacturing |publisher=Wiley |year=2012 |isbn=978-0-470-92467-9 |pages=226}}</ref> with known exceptions to each of these rules ([[piezoelectricity|piezoelectric ceramics]], [[glass transition]] temperature, [[superconductivity|superconductive ceramics]]).

Composites such as [[fiberglass]] and [[carbon-fiber-reinforced polymer|carbon fiber]], while containing ceramic materials, are not considered to be part of the ceramic family.<ref>{{cite book |author1=Carter, C. B. |author2=Norton, M. G. |title=Ceramic materials: Science and engineering |publisher=Springer |year=2007 |isbn=978-0-387-46271-4 |url=https://books.google.com/books?id=aE_VQ8I24OoC&pg=PA3 |pages=3 & 4}}</ref>

Highly oriented crystalline ceramic materials are not amenable to a great range of processing. Methods for dealing with them tend to fall into one of two categories: either making the ceramic in the desired shape by reaction ''in situ'' or "forming" powders into the desired shape and then [[sintering]] to form a solid body. [[Ceramic forming techniques]] include shaping by hand (sometimes including a rotation process called "throwing"), [[slip casting]], [[tape casting]] (used for making very thin ceramic capacitors), [[injection molding]], dry pressing, and other variations. 

Many ceramics experts do not consider materials with an [[amorphous]] (noncrystalline) character (i.e., glass) to be ceramics, even though glassmaking involves several steps of the ceramic process and its mechanical properties are similar to those of ceramic materials. However, heat treatments can convert glass into a semi-crystalline material known as [[glass-ceramic]].<ref>{{Cite web |url=https://www.twi-global.com/technical-knowledge/faqs/faq-how-are-glass-ceramics-and-glass-ceramics-defined.aspx|title=How are Glass, Ceramics and Glass-Ceramics Defined?|website=TWI Global |access-date=2021-10-01|archive-date=2021-10-01|archive-url=https://web.archive.org/web/20211001044001/https://www.twi-global.com/technical-knowledge/faqs/faq-how-are-glass-ceramics-and-glass-ceramics-defined|url-status=live}}</ref><ref>{{Cite web|url=https://www.sciencedirect.com/topics/engineering/ceramics-and-glass|title=Ceramics and Glass - an overview |website=ScienceDirect Topics |access-date=2021-08-09 |archive-date=2021-08-09|archive-url=https://web.archive.org/web/20210809121212/https://www.sciencedirect.com/topics/engineering/ceramics-and-glass |url-status=live}}{{nonspecific|date=October 2021}}<!-- Which article/chapter is being cited --></ref> 

Traditional ceramic raw materials include clay minerals such as [[kaolinite]], whereas more recent materials include aluminium oxide, more commonly known as [[alumina]]. Modern ceramic materials, which are classified as advanced ceramics, include [[silicon carbide]] and [[tungsten carbide]]. Both are valued for their abrasion resistance and are therefore used in applications such as the wear plates of crushing equipment in mining operations. Advanced ceramics are also used in the medical, electrical, electronics, and armor industries.

==History==
[[File:Vestonicka venuse edit.jpg|thumb|upright=0.55 |Earliest known ceramics are the [[Gravettian]] figurines that date to 29,000–25,000 BC.]]
Human beings appear to have been making their own ceramics for at least 26,000 years, subjecting clay and silica to intense heat to fuse and form ceramic materials. The earliest found so far were in southern central Europe and were sculpted figures, not dishes.<ref>{{Cite web |url=https://depts.washington.edu/matseed/mse_resources/Webpage/Ceramics/ceramichistory.htm|title=Ceramic history |website=Materials Science and Engineering Education |publisher=University of Washington Departments |access-date=2020-03-02 |url-status=live |archive-date=2020-11-06|archive-url= https://web.archive.org/web/20201106232849/http://depts.washington.edu/matseed/mse_resources/Webpage/Ceramics/ceramichistory.htm}}</ref> The earliest known pottery was made by mixing animal products with clay and firing it at up to {{cvt|800|°C|-2}}. While pottery fragments have been found up to 19,000 years old, it was not until about 10,000 years later that regular pottery became common. An early people that spread across much of Europe is named after its use of pottery: the [[Corded Ware culture]]. These early [[Indo-European languages|Indo-European]] peoples decorated their pottery by wrapping it with rope while it was still wet. When the ceramics were fired, the rope burned off but left a decorative pattern of complex grooves on the surface.

[[File:Museum_für_Vor-_und_Frühgeschichte_Berlin_031.jpg | right|thumb|Corded-Ware culture pottery from 2500&nbsp;BC]]
The invention of the wheel eventually led to the production of smoother, more even pottery using the wheel-forming (throwing) technique, like the [[pottery wheel]]. Early ceramics were porous, absorbing water easily. It became useful for more items with the discovery of [[Ceramic glaze|glazing]] techniques, which involved coating pottery with silicon, bone ash, or other materials that could melt and reform into a glassy surface, making a vessel less pervious to water. 

===Archaeology===
Ceramic artifacts have an important role in archaeology for understanding the culture, technology, and behavior of peoples of the past. They are among the most common artifacts to be found at an archaeological site, generally in the form of small fragments of broken pottery called [[sherd]]s. The processing of collected sherds can be consistent with two main types of analysis: technical and traditional.

The traditional analysis involves sorting ceramic artifacts, sherds, and larger fragments into specific types based on style, composition, manufacturing, and morphology. By creating these typologies, it is possible to distinguish between different cultural styles, the purpose of the ceramic, and the technological state of the people, among other conclusions. Besides, by looking at stylistic changes in ceramics over time, it is possible to separate (seriate) the ceramics into distinct diagnostic groups (assemblages). A comparison of ceramic artifacts with known dated assemblages allows for a chronological assignment of these pieces.<ref>{{cite web |publisher=Mississippi Valley Archaeological Center |website=The Process of Archaeology |url=http://www.uwlax.edu/mvac/processarch/processarch/lab_ceramic.html |access-date=2004-11-12 |title=Ceramic Analysis |url-status=dead |archive-date=June 3, 2012 |archive-url= https://web.archive.org/web/20120603053406/http://www.uwlax.edu/mvac/processarch/processarch/lab_ceramic.html}}</ref>

The technical approach to ceramic analysis involves a finer examination of the composition of ceramic artifacts and sherds to determine the source of the material and, through this, the possible manufacturing site. Key criteria are the composition of the clay and the [[Temper (pottery)|temper]] used in the manufacture of the article under study: the temper is a material added to the clay during the initial production stage and is used to aid the subsequent drying process. Types of temper include [[seashell|shell]] pieces, [[granite]] fragments, and ground sherd pieces called '[[Grog (clay)|grog]]'. Temper is usually identified by microscopic examination of the tempered material. Clay identification is determined by a process of refiring the ceramic and assigning a color to it using [[Munsell color system|Munsell Soil Color]] notation. By estimating both the clay and temper compositions and locating a region where both are known to occur, an assignment of the material source can be made. Based on the source assignment of the artifact, further investigations can be made into the site of manufacture.

==Properties==
The physical properties of any ceramic substance are a direct result of its crystalline structure and chemical composition. [[Solid-state chemistry]] reveals the fundamental connection between microstructure and properties, such as localized density variations, grain size distribution, type of porosity, and second-phase content, which can all be correlated with ceramic properties such as mechanical strength σ by the Hall-Petch equation, [[hardness]], [[toughness]], [[dielectric constant]], and the [[optical]] properties exhibited by [[transparent materials]].

[[Ceramography]] is the art and science of preparation, examination, and evaluation of ceramic microstructures. Evaluation and characterization of ceramic microstructures are often implemented on similar spatial scales to that used commonly in the emerging field of nanotechnology: from [[nanometer]]s to tens of micrometers (µm). This is typically somewhere between the minimum wavelength of visible light and the resolution limit of the naked eye.

The microstructure includes most grains, secondary phases, grain boundaries, pores, micro-cracks, structural defects, and hardness micro indentions. Most bulk mechanical, optical, thermal, electrical, and magnetic properties are significantly affected by the observed microstructure. The fabrication method and process conditions are generally indicated by the microstructure. The root cause of many ceramic failures is evident in the cleaved and polished microstructure. Physical properties which constitute the field of [[materials science]] and [[engineering]] include the following:

===Mechanical properties===
[[File:Ultra-thin separated (Carborundum) disk.jpg|thumb|Cutting disks made of [[silicon carbide]] ]]
Mechanical properties are important in structural and building materials as well as textile fabrics. In modern [[materials science]], fracture mechanics is an important tool in improving the mechanical performance of materials and components. It applies the [[physics]] of [[stress (mechanics)|stress]] and [[Deformation (mechanics)|strain]], in particular the theories of [[Elasticity (physics)|elasticity]] and [[Plasticity (physics)|plasticity]], to the microscopic [[crystallographic defects]] found in real materials in order to predict the macroscopic mechanical failure of bodies. [[Fractography]] is widely used with fracture mechanics to understand the causes of failures and also verify the theoretical [[failure]] predictions with real-life failures.

Ceramic materials are usually [[ionic bond|ionic]] or [[covalent]] bonded materials. A material held together by either type of bond will tend to [[Fracture#Brittle|fracture]] before any [[plastic deformation]] takes place, which results in poor [[toughness]] in these materials. Additionally, because these materials tend to be porous, the [[porosity|pore]]s and other microscopic imperfections act as [[Stress concentration|stress concentrators]], decreasing the toughness further, and reducing the [[tensile strength]]. These combine to give [[catastrophic failure]]s, as opposed to the more ductile [[failure mode]]s of metals.

These materials do show [[plasticity (physics)|plastic deformation]]. However, because of the rigid structure of crystalline material, there are very few available slip systems for [[dislocation]]s to move, and so they deform very slowly.

To overcome the brittle behavior, ceramic material development has introduced the class of [[ceramic matrix composite]] materials, in which ceramic fibers are embedded and with specific coatings are forming fiber bridges across any crack. This mechanism substantially increases the fracture toughness of such ceramics. Ceramic [[Disc brake|disc brakes]] are an example of using a ceramic matrix composite material manufactured with a specific process.

Scientists are working on developing ceramic materials that can withstand significant deformation without breaking. A first such material that can deform in room temperature was found in 2024.<ref>{{Cite journal |date=2024-02-23 |title=The first bulk ceramic that deforms like a metal at room temperature |url=https://www.nature.com/articles/d41586-024-00443-8 |journal=Nature |language=en |doi=10.1038/d41586-024-00443-8}}</ref>

====Ice-templating for enhanced mechanical properties====
If a ceramic is subjected to substantial mechanical loading, it can undergo a process called [[Freeze-casting|ice-templating]], which allows some control of the [[microstructure]] of the ceramic product and therefore some control of the mechanical properties. Ceramic engineers use this technique to tune the mechanical properties to their desired application. Specifically, the [[Strength of materials|strength]] is increased when this technique is employed. Ice templating allows the creation of macroscopic pores in a unidirectional arrangement. The applications of this oxide strengthening technique are important for [[solid oxide fuel cell]]s and [[Water purification|water filtration]] devices.<ref>{{cite journal |url=https://www.researchgate.net/publication/329036928 |via=[[ResearchGate]]|doi=10.21278/brod69405 |title=Application and Analysis of Solid Oxide Fuel Cells in Ship Energy Systems |year=2018 |last1=Martinić |first1=Frane |last2=Radica |first2=Gojmir |last3=Barbir |first3=Frano |journal=Brodogradnja |volume=69 |issue=4 |pages=53–68 |s2cid=115752128 |doi-access=free }}</ref>

To process a sample through ice templating, an aqueous [[Colloid|colloidal suspension]] is prepared to contain the dissolved ceramic powder evenly dispersed throughout the colloid,{{clarify|reason=is the powder in suspension or actually dissolved?|date=December 2019}} for example [[Yttria-stabilized zirconia]] (YSZ). The solution is then cooled from the bottom to the top on a platform that allows for unidirectional cooling. This forces ice crystals to grow in compliance with the unidirectional cooling, and these ice crystals force the dissolved YSZ particles to the solidification front{{clarify|date=June 2023}} of the solid-liquid interphase boundary, resulting in pure ice crystals lined up unidirectionally alongside concentrated pockets of colloidal particles. The sample is then heated and at the same the pressure is reduced enough to force the ice crystals to [[Sublimation (phase transition)|sublime]] and the YSZ pockets begin to [[Annealing (metallurgy)|anneal]] together to form macroscopically aligned ceramic microstructures. The sample is then further [[Sintering|sintered]] to complete the [[evaporation]] of the residual water and the final consolidation of the ceramic microstructure.{{cn|date=December 2019}}

During ice-templating, a few variables can be controlled to influence the pore size and morphology of the microstructure. These important variables are the initial solids loading of the colloid, the cooling rate, the sintering temperature and duration, and the use of certain additives which can influence the microstructural morphology during the process. A good understanding of these parameters is essential to understanding the relationships between processing, microstructure, and mechanical properties of anisotropically porous materials.<ref>{{cite journal |last1=Seuba |first1=Jordi |last2=Deville |first2=Sylvain |last3=Guizard |first3=Christian |last4=Stevenson |first4=Adam J. |title=Mechanical properties and failure behavior of unidirectional porous ceramics |journal=Scientific Reports |date=14 April 2016 |volume=6 |issue=1 |pages=24326 |doi=10.1038/srep24326 |pmid=27075397 |pmc=4830974 |bibcode=2016NatSR...624326S }}</ref>

===Electrical properties===

====Semiconductors====
Some ceramics are [[semiconductor]]s. Most of these are [[transition metal oxides]] that are II-VI semiconductors, such as [[zinc oxide]]. While there are prospects of mass-producing blue [[LED]]s from zinc oxide, ceramicists are most interested in the electrical properties that show [[grain boundary]] effects. One of the most widely used of these is the varistor. These are devices that exhibit the property that resistance drops sharply at a certain [[threshold voltage]]. Once the voltage across the device reaches the threshold, there is a [[Electrical breakdown|breakdown]] of the electrical structure{{clarification needed|date=November 2021}} in the vicinity of the grain boundaries, which results in its [[electrical resistance]] dropping from several megohms down to a few hundred [[Ohm (unit)|ohm]]s. The major advantage of these is that they can dissipate a lot of energy, and they self-reset; after the voltage across the device drops below the threshold, its resistance returns to being high. This makes them ideal for [[Surge protector|surge-protection]] applications; as there is control over the threshold voltage and energy tolerance, they find use in all sorts of applications. The best demonstration of their ability can be found in [[electrical substation]]s, where they are employed to protect the infrastructure from [[lightning]] strikes. They have rapid response, are low maintenance, and do not appreciably degrade from use, making them virtually ideal devices for this application. Semiconducting ceramics are also employed as [[gas sensor]]s. When various gases are passed over a polycrystalline ceramic, its electrical resistance changes. With tuning to the possible gas mixtures, very inexpensive devices can be produced.

====Superconductivity====
[[File:Magnet 4.jpg|thumb|The [[Meissner effect]] demonstrated by levitating a magnet above a cuprate superconductor, which is cooled by [[liquid nitrogen]]]]
Under some conditions, such as extremely low temperatures, some ceramics exhibit [[high-temperature superconductivity]]. {{clarify|reason=contradictory: why is it high-temperature superconductivity if extremely low temperatures are required? In superconductivity high temperature means above 30 K|date=December 2019}} The reason for this is not understood, but there are two major families of superconducting ceramics.

====Ferroelectricity and supersets====
[[Piezoelectricity]], a link between electrical and mechanical response, is exhibited by a large number of ceramic materials, including the quartz used to [[crystal oscillator|measure time]] in watches and other electronics. Such devices use both properties of piezoelectrics, using electricity to produce a mechanical motion (powering the device) and then using this mechanical motion to produce electricity (generating a signal). The unit of time measured is the natural interval required for electricity to be converted into mechanical energy and back again.

The piezoelectric effect is generally stronger in materials that also exhibit [[pyroelectricity]], and all pyroelectric materials are also piezoelectric. These materials can be used to inter-convert between thermal, mechanical, or electrical energy; for instance, after synthesis in a furnace, a pyroelectric crystal allowed to cool under no applied stress generally builds up a static charge of thousands of volts. Such materials are used in [[motion sensor]]s, where the tiny rise in temperature from a warm body entering the room is enough to produce a measurable voltage in the crystal.

In turn, pyroelectricity is seen most strongly in materials that also display the [[ferroelectric effect]], in which a stable electric dipole can be oriented or reversed by applying an electrostatic field. Pyroelectricity is also a necessary consequence of ferroelectricity. This can be used to store information in [[ferroelectric capacitor]]s, elements of [[ferroelectric RAM]].

The most common such materials are [[lead zirconate titanate]] and [[barium titanate]]. Aside from the uses mentioned above, their strong piezoelectric response is exploited in the design of high-frequency [[loudspeaker]]s, transducers for [[sonar]], and actuators for [[atomic force microscope|atomic force]] and [[scanning tunneling microscope]]s.

====Positive thermal coefficient====
Temperature increases can cause grain boundaries to suddenly become insulating in some semiconducting ceramic materials, mostly mixtures of [[heavy metals|heavy metal]] [[titanate]]s. The critical transition temperature can be adjusted over a wide range by variations in chemistry. In such materials, current will pass through the material until [[joule heating]] brings it to the transition temperature, at which point the circuit will be broken and current flow will cease. Such ceramics are used as self-controlled heating elements in, for example, the rear-window defrost circuits of automobiles.

At the transition temperature, the material's [[dielectric]] response becomes theoretically infinite. While a lack of temperature control would rule out any practical use of the material near its critical temperature, the dielectric effect remains exceptionally strong even at much higher temperatures. Titanates with critical temperatures far below room temperature have become synonymous with "ceramic" in the context of ceramic capacitors for just this reason.

===Optical properties===
[[File:cermax.jpg|thumb|upright|Cermax [[xenon arc lamp]] with [[synthetic sapphire]] output window]]
[[Optics|Optically transparent materials]] focus on the response of a material to incoming light waves of a range of wavelengths. [[Optical filter|Frequency selective optical filters]] can be utilized to alter or enhance the brightness and contrast of a digital image. Guided lightwave transmission via frequency selective [[waveguides]] involves the emerging field of fiber [[optics]] and the ability of certain glassy compositions as a [[transmission medium]] for a range of frequencies simultaneously ([[multi-mode optical fiber]]) with little or no [[adjacent-channel interference|interference]] between competing [[wavelengths]] or frequencies. This [[resonant]] [[normal mode|mode]] of [[energy]] and [[data transmission]] via electromagnetic (light) [[wave propagation]], though low powered, is virtually lossless. Optical waveguides are used as components in [[Integrated optical circuit]]s (e.g. [[light-emitting diodes]], LEDs) or as the transmission medium in local and long haul [[optical communication]] systems. Also of value to the emerging materials scientist is the sensitivity of materials to radiation in the thermal [[infrared]] (IR) portion of the [[electromagnetic spectrum]]. This heat-seeking ability is responsible for such diverse optical phenomena as [[night-vision]] and IR [[luminescence]].

Thus, there is an increasing need in the [[military]] sector for high-strength, robust materials which have the capability to [[transmit]] [[light]] ([[electromagnetic waves]]) in the [[visible spectrum|visible]] (0.4 – 0.7 micrometers) and mid-[[infrared]] (1 – 5 micrometers) regions of the spectrum. These materials are needed for applications requiring [[transparency and translucency]] [[transparent]] armor, including next-generation high-speed [[missile]]s and pods, as well as protection against improvised explosive devices (IED).

In the 1960s, scientists at [[General Electric]] (GE) discovered that under the right manufacturing conditions, some ceramics, especially [[aluminium oxide]] (alumina), could be made [[translucent]]. These translucent materials were transparent enough to be used for containing the electrical [[plasma (physics)|plasma]] generated in high-[[pressure]] [[sodium]] street lamps. During the past two decades, additional types of transparent ceramics have been developed for applications such as nose cones for [[heat-seeking]] [[missiles]], [[window]]s for fighter [[aircraft]], and [[scintillation counter]]s for computed [[tomography]] scanners.
Other ceramic materials, generally requiring greater purity in their make-up than those above, include forms of several chemical compounds, including:

#[[Barium titanate]]: (often mixed with [[strontium titanate]]) displays [[ferroelectricity]], meaning that its mechanical, electrical, and thermal responses are c
#[[Sialon]] (silicon aluminium oxynitride) has high strength; resistance to thermal shock, chemical and wear resistance, and low density. These ceramics are used in non-ferrous molten metal handling, weld pins, and the chemical industry.
#[[Silicon carbide]] (SiC) is used as a [[susceptor]] in microwave furnaces, a commonly used abrasive, and as a [[refractory|refractory material]].
#[[Silicon nitride]] (Si<sub>3</sub>[[nitrogen|N]]<sub>4</sub>) is used as an [[abrasive]] powder.
#[[Magnesium silicide|Steatite (magnesium silicates)]] is used as an [[electrical insulator]].
#[[Titanium carbide]] Used in space shuttle re-entry shields and scratchproof watches.
#[[Uranium oxide]] ([[uranium|U]]O<sub>2</sub>), used as [[nuclear fuel|fuel]] in [[nuclear reactor]]s.
#[[Yttrium barium copper oxide]] (Y[[barium|Ba]]<sub>2</sub>[[copper|Cu]]<sub>3</sub>[[oxygen|O]]<sub>7−x</sub>), a [[high-temperature superconductor]].
#[[Zinc oxide]] ([[zinc|Zn]]O), which is a [[semiconductor]], and used in the construction of [[varistor]]s.
#[[Zirconium dioxide]] (zirconia), which in pure form undergoes many [[phase transition|phase changes]] between room temperature and practical [[sintering]] temperatures, can be chemically "stabilized" in several different forms. Its high oxygen [[ion conductivity]] recommends it for use in [[fuel cell]]s and automotive [[oxygen sensor]]s. In another variant, [[metastable]] structures can impart [[fracture toughness|transformation toughening]] for mechanical applications; most [[ceramic knife]] blades are made of this material. Partially stabilised zirconia (PSZ) is much less brittle than other ceramics and is used for metal forming tools, valves and liners, abrasive slurries, kitchen knives and bearings subject to severe abrasion.<ref>{{cite journal |doi=10.1038/258703a0 |volume=258 |issue=5537 |title=Ceramic steel? |year=1975 |last1=Garvie |first1=R. C. |last2=Hannink |first2=R. H. |last3=Pascoe |first3=R. T. |journal=Nature |pages=703–704 |bibcode=1975Natur.258..703G |s2cid=4189416}}</ref>

==Products==

===By usage===
For convenience, ceramic products are usually divided into four main types; these are shown below with some examples:<ref>'Whitewares: Production, Testing And Quality Control.' W. Ryan, C. Radford. Pergamon Press, 1987.</ref>
#Structural, including [[brick]]s, [[pipe (material)|pipe]]s, [[Flooring|floor]] and [[roof tile]]s
#[[refractory|Refractories]], such as [[kiln]] linings, gas fire radiants, [[steel]] and glass making crucibles
#Whitewares, <!--DO NOT WIKILINK TO WHITEWARE, OR PORCELAIN--> including [[tableware]], cookware, wall tiles, pottery products and sanitary ware<ref name="whiteware">{{cite web|title=Whiteware Pottery |url=https://www.britannica.com/art/whiteware|website=Encyclopædia Britannica|access-date=30 June 2015|archive-date=9 July 2015 |archive-url=https://web.archive.org/web/20150709085045/https://www.britannica.com/art/whiteware|url-status=live}}</ref><!-- REF DOES NOT SUPPORT DEFINITION GIVEN! -->
#Technical, also known as engineering, advanced, special, and fine ceramics. Such items include: 
#*gas burner [[nozzle]]s 
#*[[Ballistic vest|ballistic protection]], [[vehicle armor]]
#*[[nuclear fuel]] uranium oxide pellets
#*[[Implant (medicine)|biomedical implants]] 
#*coatings of [[jet engine]] [[turbine]] blades
#*[[ceramic matrix composite]] gas turbine parts
#*[[reinforced carbon–carbon]] ceramic [[disc brake]]s
#*[[missile]] nose cones
#*[[bearing (mechanical)|bearings]]
#*tiles used in the [[Space Shuttle program]]

===Ceramics made with clay===
{{main|Pottery}}
Frequently, the raw materials of modern ceramics do not include clays.<ref>Geiger, Greg. [https://web.archive.org/web/20060815173829/http://www.newi.ac.uk/buckleyc/ceramics.htm Introduction To Ceramics], American Ceramic Society</ref>
Those that do have been classified as:
#[[Earthenware]], fired at lower temperatures than other types
#[[Stoneware]], [[Vitrification#Ceramics|vitreous]] or semi-vitreous
#[[Porcelain]], which contains a high content of [[kaolin]]
#[[Bone china]]

===Classification===
Ceramics can also be classified into three distinct material categories: 
# '''[[Oxide]]s:''' [[alumina]], [[beryllia]], [[ceria]], [[zirconia]]
# '''Non-oxides:''' [[carbide]], [[boride]], [[nitride]], [[silicide]]
# '''[[Composite material]]s:''' particulate reinforced, [[Ceramic matrix composite|fiber reinforced]], combinations of [[oxide]]s and nonoxides.

Each one of these classes can be developed into unique material properties.

==Applications==
[[File:CeramicKnife1.jpg|thumb|right|Kitchen knife with a ceramic blade]]
[[File:Qimei watch on Zulu strap.jpg|thumb|Technical ceramic used as a durable top material on a [[Diving_watch#Bezel_markings|diving watch bezel insert]]]]

# '''Knife blades:''' the blade of a [[ceramic knife]] will stay sharp for much longer than that of a steel knife, although it is more brittle and susceptible to breakage.
# [[Disk brake|'''Carbon-ceramic brake disks''']] for vehicles: highly resistant to [[brake fade]] at high temperatures.
# Advanced '''[[Composite armor |composite ceramic and metal matrices]]''' have been designed for most modern [[Armoured fighting vehicles]] because they offer superior penetrating resistance against [[shaped charge]] ([[High-explosive anti-tank|HEAT]] rounds) and [[kinetic energy penetrator]]s.
# Ceramics such as '''[[alumina]]''' and '''[[boron carbide]]''' have been used as plates in [[bulletproof vest|ballistic armored vests]] to repel high-velocity [[rifle]] fire. Such plates are known commonly as [[Small Arms Protective Insert|small arms protective insert]]s, or SAPIs. Similar low-weight material is used to protect the [[Cockpit (aviation)|cockpits]] of some military aircraft.
#Ceramic [[ball bearing|'''ball bearings''']] can be used in place of steel. Their greater hardness results in lower susceptibility to wear. Ceramic bearings typically last triple the lifetime of steel bearings. They deform less than steel under load, resulting in less contact with the bearing retainer walls and lower friction. In very high-speed applications, heat from [[friction]] causes more problems for metal bearings than ceramic bearings. Ceramics are chemically resistant to corrosion and are preferred for environments where steel bearings would rust. In some applications their electricity-insulating properties are advantageous. Drawbacks to ceramic bearings include significantly higher cost, susceptibility to damage under shock loads, and the potential to wear steel parts due to ceramics' greater hardness.
# In the early 1980s [[Toyota]] researched production of an '''[[adiabatic]] [[internal combustion engine|engine]]''' using ceramic components in the hot gas area. The use of ceramics would have allowed temperatures exceeding 1650°C. Advantages would include lighter materials and a smaller cooling system (or no cooling system at all), leading to major weight reduction. The expected increase of [[fuel efficiency]] (due to higher operating temperatures, demonstrated in [[Carnot heat engine|Carnot's]] theorem) could not be verified experimentally. It was found that heat transfer on the hot ceramic cylinder wall was greater than the heat transfer to a cooler metal wall. This is because the cooler gas film on a metal surface acts as a [[thermal insulator]]. Thus, despite the desirable properties of ceramics, prohibitive production costs and limited advantages have prevented widespread ceramic engine component adoption. In addition, small imperfections in ceramic material along with low [[fracture toughness]] can lead to cracking and potentially dangerous equipment failure. Such engines are possible experimentally, but mass production is not feasible with current technology. {{Citation needed|date=July 2009|reason=Where are any other references to Toyota's work?}}
# Experiments with ceramic parts for [[gas turbine]] [[heat engine|engines]] are being conducted. Currently, even blades made of [[superalloy|advanced metal alloys]] used in the engines' hot section require cooling and careful monitoring of operating temperatures. Turbine engines made with ceramics could operate more efficiently, providing for greater range and payload.
# Recent advances have been made in ceramics which include [[bioceramic]]s such as dental implants and synthetic bones. [[Hydroxyapatite]], the major mineral component of bone, has been made synthetically from several biological and chemical components and can be formed into ceramic materials. Orthopedic implants coated with these materials bond readily to bone and other tissues in the body without rejection or inflammatory reaction. They are of great interest for gene delivery and [[tissue engineering]] scaffolding. Most hydroxyapatite ceramics are quite porous and lack mechanical strength and are therefore used solely to coat metal orthopedic devices to aid in forming a bond to bone or as bone fillers. They are also used as fillers for orthopedic plastic screws to aid in reducing inflammation and increase the absorption of these plastic materials. Work is being done to make strong, fully dense nanocrystalline hydroxyapatite ceramic materials for orthopedic weight bearing devices, replacing foreign metal and plastic orthopedic materials with a synthetic but naturally occurring bone mineral. Ultimately, these ceramic materials may be used as bone replacement, or with the incorporation of protein [[collagen]]s, the manufacture of synthetic bones.
# Applications for actinide-containing ceramic materials include nuclear fuels for burning excess plutonium (Pu), or a chemically-inert source of alpha radiation in power supplies for uncrewed space vehicles or microelectronic devices. Use and disposal of radioactive actinides require immobilization in a durable host material. Long half-life radionuclides such as actinide are immobilized using chemically-durable crystalline materials based on polycrystalline ceramics and large single crystals.<ref>{{Cite book |author1=B.E. Burakov |author2=M.I Ojovan |author3=W.E. Lee |title=Crystalline Materials for Actinide Immobilisation |series=Materials for Engineering |url=http://www.worldscientific.com/worldscibooks/10.1142/p652 |publisher=Imperial College Press |date=July 2010 |volume=1 |doi=10.1142/p652 |isbn=978-1-84816-418-5 |access-date=2017-08-31 |archive-date=2021-10-01 |archive-url=https://web.archive.org/web/20211001044004/https://www.worldscientific.com/worldscibooks/10.1142/p652 |url-status=live}}{{pn|date=October 2021}}</ref>
# High-tech ceramics are used for producing watch cases. The material is valued by watchmakers for its light weight, scratch resistance, durability, and smooth touch. [[International Watch Company|IWC]] is one of the brands that pioneered the use of ceramic in watchmaking.<ref>{{cite web|title=Watch Case Materials Explained: Ceramic|url=http://www.ablogtowatch.com/watch-case-materials-explained-ceramic/|website=aBlogtoWatch|date=18 April 2012|access-date=8 March 2017|archive-date=8 March 2017|archive-url=https://web.archive.org/web/20170308141620/http://www.ablogtowatch.com/watch-case-materials-explained-ceramic/|url-status=live}}</ref>

==See also==
* {{annotated link|Ceramic chemistry}}
* {{annotated link|Ceramic engineering}}
* {{annotated link|Ceramic nanoparticle}}
* {{annotated link|Ceramic matrix composite}}
* {{annotated link|Ceramic art}}
* {{annotated link|Pottery fracture}}

==References==

{{reflist|30em}}

==Further reading==
*{{cite book|title=Oriental trade ceramics in South-East Asia, ninth to sixteenth centuries: with a catalogue of Chinese, Vietnamese and Thai wares in Australian collections|first=John|last=Guy|editor-first=John|editor-last=Guy|edition=illustrated, revised|year=1986|publisher=Oxford University Press|url=https://books.google.com/books?id=GxrrAAAAMAAJ|isbn=9780195825930|access-date=24 April 2014}}

==External links==
{{Sister project links| wikt=no | commons=Category:Ceramics | b=no | n=no | q=Ceramic | s=no | v=no | voy=no | species=no | d=no}}

* [https://onlinelibrary.wiley.com/doi/book/10.1002/9783527631940 Ceramics Science and Technology]

{{Fundamental aspects of materials science}}
{{Authority control}}

[[Category:Ceramics| ]]