Branches of ceramics

Ceramics and glass are typically classified according to two main categories based on end-use application: traditional products versus advanced/technical products. Traditional ceramics and glass, which are summarized in Table 1, consist of products that have been used since ancient times for construction, decoration, furnishing, food and beverages, transportation, and industrial applications. Ceramics include refractories, structural clay products, whiteware, earthenware (i.e., pottery), abrasives, and cements, whereas glass includes primarily flat, container, and pressed and blown glass.

From a market standpoint, cements are the largest category, at approximately $340 billion globally in 2018, followed by structural clay products at $135 billion. Both of these groups of products find their main application in the construction sector. Cement products include mainly Portland cement in addition to concrete and mortars. New cement products focus on CO₂ reduction and ultrahigh performance. Structural clay products include many type of tiles (e.g., floor, wall, decorative, and roof), construction bricks (i.e., nonrefractory bricks), and other unconventional shapes, such as drainage, sewer, and chimney pipes and linings.

Refractories constitute another relevant class of traditional ceramics, with estimated sales of $36 billion in 2018. Refractories are defined as materials for high temperatures applications (1,000°F or above). In addition to being heat-resistant, they must also be able to withstand harsh conditions such as corrosion, abrasion, thermal shock, and mechanical impact. Refractories are used as bricks and liners for kiln and furnaces as well as molds, crucibles, ladles and other high-temperature items. They find application primarily in the metallurgical sector (for both ferrous and nonferrous metals), and also in other industrial sectors such as glass, ceramics, and cement manufacturing and power generation.

Traditional glass is also a large market at approximately $105 billion in 2018. Traditional glass includes products such as flat glass for construction and transportation (e.g., windows, facades, doors, windshields, security glass, control glass, and smart glass); container glass (e.g., bottles for beverages and perfumes); pressed and blown glass (i.e., tableware glass); glass fibers (used primarily as reinforcing agents); and other glass for household use and consumer products (e.g., mirrors and glass for furniture, glass for lighting fixtures, decorative and art glass, and eyewear).

By comparison, advanced ceramic and glass materials comprise products used in nontraditional industries. Many of these products were introduced after World War II to meet the requirements of fast-growing industry sectors such as electronics, optoelectronics, energy, and healthcare.

In recent years, the terms technical or engineered are increasingly being used instead of the term advanced to designate these products. In fact, the word advanced most often indicates recently developed and innovative manufactured products. For example, solar-control glass is a type of flat glass and therefore falls within the traditional ceramic/glass category, but it is also considered an advanced product because it is obtained by applying very thin films to the glass to modify its refractive index and reflect infrared radiation. Another example of a traditional but advanced ceramic is represented by tiles that incorporate photovoltaic cells.

From a market standpoint, the three largest categories of technical ceramics are electroceramics, structural ceramics and ceramics for extreme environments, and medical ceramics.

Electroceramics are products in which the ceramic is utilized for its electrical properties, typically for its insulating properties and its capacity to store electrical energy (dielectric properties). Although ceramics are traditionally considered to be insulators, their composition can be tailored to exhibit semiconducting, conducting, piezoelectric, or magnetic properties as well.

As such, ceramics find numerous applications in electronic and electrical applications, either as components of circuits (e.g., capacitors, inductors, and resistors) or as circuit devices (e.g., low-temperature co-fired ceramics [LTCCs]). Circuit boards and modules containing these components are ubiquitous. These components and devices also are used to manufacture intelligent systems for defense and security and many types of sensors.

Structural ceramics and ceramics for extreme environments include a variety of items such as friction products (e.g., ceramic brakes), cutting inserts, and other wear and corrosion resistant products. The most popular, however, are filtration media (i.e., filters and membranes), catalysts, and catalyst carriers (i.e., substrates and media that support the catalyst). Catalysts are used in  petroleum refining, chemical processing, and automotive emissions control, whereas filtration media find applications in separation processes (e.g., water and wastewater filtration).

Medical ceramics are becoming quite popular as well. Dental ceramics have been available for some time, while ceramic parts and coatings for hip, knee, joint, cranio-maxillofacial, and spinal implants have recently found increasing use driven by a rising number of orthopedic procedures, primarily due to a rapidly expanding elderly population worldwide and by the growing availability of these procedures in developing countries.

Table 1. Classification of traditional ceramics and glass by product type

Product Type	Main products	End-use	Examples
CERAMICS
Refractories	Refractory bricks, tiles, blocks, linings, crucibles, spouts, ladles and fibers	Industrial applications	1
Structural clay products	Tiles, bricks, drainage and sewer pipes, chimney pipes and linings	Construction, furnishing and decoration	2
Whitewares	Fine tableware and cookware, china, sanitary ware, decorative articles, porcelain coatings	Food and beverage, construction, furnishing and decoration	3
Earthenware	Tableware, cookware, vases, pots, figurines, decorative objects	Food and beverage, furnishing and decoration	4
Abrasives	Abrasive powders, grains, beads, and wheels	Industrial applications	5
Cements	Portland cement, mortars, concrete bricks and blocks	Construction	6
GLASS
Traditional glass	Flat glass, container glass, pressed and blown glass, lighting fixture glass, mirrors, decorative glass, glass fibers, eyewear	Construction, transportation, furnishing and decoration, food and beverages	7

Image credits: 1. iStock; 2. Our United Villages/The ReBuilding Center, Flickr; 3. amandadevries, Flickr; 4. Pixabay; 5. WurthAus, YouTube; 6. Petter Duvander, Flickr; 7. Pixabay

Table 2. Classification of advanced/technical ceramics and glass by product type

Product Type	Main products	End-use	Examples
CERAMICS
Medical ceramics	Medical implants, dental implants and prostheses, orthodontic products, biomedical coatings, part for implantable electronic devices, surgical instruments, drug delivery devices, tissue engineering scaffolds, pumps	Life sciences	1
Electroceramics	Capacitors, inductors, fixed and variable resistors, circuit protection devices, piezoelectric devices, antennas, substrates and films for circuit devices, ceramic packages, low- and high-temperature co-fired ceramics, sensing elements, permanent magnets, spark plugs, electrical insulators, ceramic arc tubes, hermetic insulating packaging	Electronics and electrical applications, defense and security, sensors and instrumentation, energy	2
Optoceramics	Transparent conductive coatings, substrates and films for photonic integrated circuits, optical filters, parts for solid-state lasers, components for solid-state lighting devices, optical coatings, optical switches, scintillators, non-linear optical components, components for military systems	Optical applications, optoelectronics, defense and security, sensors and instrumentation (Image courtesy Kyocera, semiconductor components division)	3
Structural ceramics and ceramics for extreme environments	Cutting tools, bearings, pump seals, valves, nozzles, friction products, wear-resistant coatings, catalysts, catalyst carriers, filtration media, high- and ultra-high temperature components, armors, parts for nuclear reactors	Mechanical applications, chemical applications, environmental applications, defense and security, aerospace and space exploration, sensors and instrumentation	4
Ceramics for energy transfer, storage and conversion	Components for solar energy storage, thermoelectric generators, superconducting devices, batteries, and fuel cells	Energy	5
Other ceramics	Cosmetic products, antibacterial agents, food packaging, additives for lubricants, paint and ink additives, food additives	Consumer products, chemical applications	6
GLASS
Glass for technical use	Flat panel display glass, glass for solar and thermal panels, optical waveguides, optical filters, precision lenses and mirrors, glass sealants for fuel cells, optical components for microscopes and other instruments, night vision systems, passivation glass for electronic devices, medical implants, dental restoration, tissue engineering scaffolds, microfluidic chips, drug carriers, periodontic products, glass microsphere for cancer therapy, anti-inflammatory agents, containers for pharmaceutical packaging	Electronics, optoelectronics, life sciences, energy, defense and security, aerospace and space exploration, sensors and instrumentation, consumer products	7

Image credits: 1. Imperial College London, YouTube; 2. Pixabay; 3. Kyocera; 4. doubleboost, YouTube; 5. stopvibrationcomau, YouTube; 6. Pixabay; 7. ACerS (picture of Bioglass)

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