The word ceramic can be traced back to the Greek term keramos,
meaning "a potter" or "pottery." Keramos in
turn is related to an older Sanskrit root meaning "to burn."
Thus the early Greeks used the term to mean "burned stuff" or
"burned earth" when referring to products obtained through the
action of fire upon earthy materials1. Ceramics can be
defined as inorganic, nonmetallic materials. They are typically
crystalline in nature and are compounds formed between metallic and
nonmetallic elements such as aluminum and oxygen (alumina-Al2O3),
calcium and oxygen (calcia - CaO), and silicon and nitrogen (silicon
The broad categories or segments that make up the ceramic industry can
be classified as follows:
Industry of Ceramic Segments
Most of the above segments can be further broken down into more specific
product classifications as seen on the table below. In 1974, the U.S.
market for the ceramic industry was estimated at $20 million. Today, the
U.S. market is estimated to be over $35 billion.
- structural clay products
- advanced ceramics
Overview of Ceramic and Glass Manufacturing
|Structural clay products
||Brick, sewer pipe, roofing tile, clay floor and
wall tile (i.e., quarry tile), flue linings
||Dinnerware, floor and wall tile, sanitaryware,
electrical porcelain, decorative ceramics
||Brick and monolithic products are used in iron
and steel, non-ferrous metals, glass, cements, ceramics, energy
conversion, petroleum, and chemicals industries
||Flat glass (windows), container glass (bottles),
pressed and blown glass (dinnerware), glass fibers (home
insulation), and advanced/specialty glass (optical fibers)
||Natural (garnet, diamond, etc.) and synthetic (silicon
carbide, diamond, fused alumina, etc.) abrasives are used for
grinding, cutting, polishing, lapping, or pressure blasting of
||Used to produce concrete roads, bridges,
buildings, dams, and the like
Wear parts, bioceramics, cutting tools, and engine components
Capacitors, insulators, substrates, integrated circuit
packages, piezoelectrics, magnets and superconductors
Engine components, cutting tools, and industrial wear parts
Chemical and environmental
Filters, membranes, catalysts, and catalyst supports
Ceramics are typically produced by the application of heat upon
processed clays and other natural raw materials to form a rigid product.
Ceramic products that use naturally occurring rocks and minerals as a
starting material must undergo special processing in order to control
purity, particle size, particle size distribution, and heterogeneity.
These attributes play a big role in the final properties of the finished
ceramic. Chemically prepared powders also are used as starting materials
for some ceramic products. These synthetic materials can be controlled
to produce powders with precise chemical compositions and particle size.
Structure and Properties
The next step is to form the ceramic particles into a desired shape.
This is accomplished by the addition of water and/or additives such as
binders, followed by a shape forming process. Some of the most common
forming methods for ceramics include extrusion, slip casting, pressing,
tape casting and injection molding. After the particles are formed,
these "green" ceramics undergo a heat-treatment (called firing
or sintering) to produce a rigid, finished product. Some ceramic
products such as electrical insulators, dinnerware and tile may then
undergo a glazing process. Some ceramics for advanced applications may
undergo a machining and/or polishing step in order meet specific
engineering design criteria.
The processing of glass products is different than for ceramics. In
glass production, raw materials such as silica, lime, and soda ash are
melted in a furnace, then formed into the desired shape (i.e.; pressed
plate, fibers, molded bottle, plate glass, etc.) while still molten.
After the molten glass is formed, it is quickly cooled, "freezing"
the glass into place to form the finished product. The glass typically
undergoes additional processing steps such as cutting, etching, coating,
grinding, decorating, or heat treating (tempering).
Some of the challenges that face ceramic and glass manufacturers, and
suppliers include availability and cost of raw materials, quality and
cost of labor, changing markets, quality control, capital for expansion,
import pressure, and environmental, health and safety standards.
The properties of ceramic materials, like all materials, are dictated by
the types of atoms present, the types of bonding between the atoms, and
the way the atoms are packed together. This is known as the atomic scale
structure. Most ceramics are made up of two or more elements. This is
called a compound. For example, alumina (Al2O3),
is a compound made up of aluminum atoms and oxygen atoms.
The atoms in ceramic materials are held together by a chemical bond. The
two most common chemical bonds for ceramic materials are covalent and
ionic. For metals, the chemical bond is called the metallic bond. The
bonding of atoms together is much stronger in covalent and ionic bonding
than in metallic. That is why, generally speaking, metals are ductile
and ceramics are brittle.
Another structure that plays an important factor in the final property
of a material is called microstructure. The microstructure of a material
is the structure that can be seen using a microscope, but seldom with
the naked eye. For ceramics, the microstructure can be entirely glassy (glasses
only); entirely crystalline; or a combination of crystalline and glassy.
In the last case, the glassy phase usually surrounds small crystals,
bonding them together.
The atomic structure primarily effects the chemical, physical, thermal,
electrical, magnetic, and optical properties. The microstructure also
can effect these properties but has its major effect on mechanical
properties and on the rate of chemical reaction. Due to ceramic
materials wide range of properties, they are used for a multitude of
applications. In general, most ceramics are:
Of course there are many exceptions to these generalizations. For
example, borosilicate glasses (glasses that contain silica and boron as
major ingredients) and certain glass ceramics (glasses that contain a
crystalline phase) and NZP ceramics are very resistant to thermal shock
and are used in applications such as ovenware, stove tops and kiln
furniture respectively. Also, some ceramics are excellent electrical
conductors and an entire commercial market is based on the fact that
certain ceramics (ferrites) are magnetic.
- thermal insulators,
- electrical insulators,
- oxidation resistant,
- prone to thermal shock, and
- chemically stable.
Archeologists have uncovered human-made ceramics that date back to at
least 24,000 BC. These ceramics were found in Czechoslovakia and were in
the form of animal and human figurines, slabs, and balls. These ceramics
were made of animal fat and bone mixed with bone ash and a fine claylike
material. After forming, the ceramics were fired at temperatures between
500-800°C in domed and horseshoe shaped kilns partially dug into the
ground with loess walls. While it is not clear what these ceramics were
used for, it is not thought to have been a utilitarian one. The first
use of functional pottery vessels is thought to be in 9,000 BC. These
vessels were most likely used to hold and store grain and other foods.
Impact on Society
It is thought that ancient glass manufacture is closely related to
pottery making, which flourished in Upper Egypt about 8,000 BC. While
firing pottery, the presence of calcium oxide (CaO) containing sand
combined with soda and the overheating of the pottery kiln may have
resulted in a colored glaze on the ceramic pot. Experts believe that it
was not until 1,500 BC that glass was produced independently of ceramics
and fashioned into separate items.
Since these ancient times, the technology and applications of ceramics (including
glass) has steadily increased. We often take for granted the major role
that ceramics have played in the progress of humankind. Below are just a
few examples of how important ceramics are to society.
We all know that metals and their alloys are used to make automobiles,
machinery, planes, buildings, and a myriad of other useful things
possible. But metal production would not be possible without the use of
a ceramic material called refractories. Refractories can withstand
volatile and high-temperature conditions encountered in the processing
of metals. Refractory ceramics are enabling materials for other
industries as well. The chemical, petroleum, energy conversion, glass
and other ceramic industries all rely upon refractory materials.
Uses in the Construction Industry
The multi-billion dollar construction industry encompasses areas such as
commercial buildings, residential homes, highways, bridges, and water
and sewer systems. These areas, which we often take for granted, would
not be possible without ceramic materials. Products such as floor, wall
and roofing tile, cement, brick, gypsum, sewer pipe, and glass are the
building blocks in the world of construction.
What would our homes and businesses be if we did not have windows? The
applications of glass in the construction industry include various types
of windows to let in natural light. Approximately three billion square
feet of glass is produced each year to make various types of windows. To
put things in perspective, imagine a 200-foot wide glass highway
stretching from New York to Los Angeles. The different types of glass
for windows include safety, stained, tinted, laminated and
non-reflective. Additionally, glass fibers are used for insulation,
ceiling panels and roofing shingles, helping us stay warm and dry.
Clay brick is used to build homes and commercial buildings because of
its strength, durability, and beauty. Brick is the only building product
that will not burn, melt, dent, peel, warp, rot, rust or be eaten by
termites. Brick comes in approximately 10,000 different colors, textures,
sizes, and shapes. Ceramic tile is used in applications such as flooring,
walls, countertops, and fireplaces. Tile also is a very durable and
hygienic construction product that adds beauty to any application.
An important invention that changed the lives of millions of people was
the incandescent light bulb. This important invention by Thomas Edison
in 1879 would not be possible without the use of glass. Glass properties
of hardness, transparency, and its ability to withstand high
temperatures and hold a vacuum at the same time made the light bulb a
The evolution of lighting technology since this time has been
characterized by the invention of increasingly brighter and more
efficient light sources. By the middle of twentieth century, methods of
lighting seemed well established - with filament and fluorescent lamps
for interiors, neon lamps for exterior advertising and signs, and sodium
discharge lamps for streets. Since this time, light-emitting diode (LED)
technology has been developed with applications in watches, instrument
panel indicators, telecommunications (optical fiber networks), data
storage (CD technology), and document production (laser printers).
The vast electronic industry would not exist without ceramics. Ceramics
have a wide range of electrical properties including insulating,
semi-conducting, superconducting, piezoelectric and magnetic. Ceramics
are critical to products such as cell phones, computers, television, and
other consumer electronic products.
Magnetic storage of data has developed in parallel with semiconductor
computer chips and has been equally vital to computing and information
handling. Without magnetic storage there would be no Internet, no
personal computers, no large databases and no gigabytes, terabytes and
exabytes of data which computers now manipulate. Today more than 150
million hard disc drives and 50 million videocassette recorders are made
Ceramics are even being used to enhance our sporting activities.
Piezoelectric ceramics (piezoceramics) are being used to make
"smart" sporting goods equipment. That is, sporting goods that
can respond to its surrounding environment in order to increase its
effectiveness. Uses include snow skis, baseball/softball bats, and shock
absorbers in mountain bicycles.
For example, K2 Corporation uses a control module produced by Active
Control eXperts inside a line of its skis. The control module contains a
piezoceramic material that dampens vibrations from the ice and snow,
helping keep the skis on the snow and thus enhancing stability, control,
and ultimately speed. Worth, Inc. now has a line of bats that
incorporates a similar module. The piezoceramic control module helps to
increase the bats sweet spot and reduces unwanted sting on off-center
Ceramic spark plugs, which are electrical insulators, have had a large
impact on society. They were first invented in 1860 to ignite fuel for
internal combustion engines and are still being used for this purpose
today. Applications include automobiles, boat engines, lawnmowers, and
the like. High voltage insulators make it possible to safely carry
electricity to houses and businesses.
Glass optic fibers have provided a technological breakthrough in the
area of telecommunications. Information that was once carried
electrically through hundreds of copper wires can now be carried through
one high-quality, transparent, silica (glass) fiber. Using this
technology has increased the speed and volume of information that can be
carried by orders of magnitude over that which is possible using copper
Optical fibers are a reliable conduit for delivering an array of
interactive services, using combinations of voice, data and video.
Whether it's multimedia and video applications, high-speed data
transmissions and Internet access, telecommuting or sophisticated,
on-demand services, optical fibers make it easier to communicate.
Ceramics are becoming increasingly useful to the medical world. Surgeons
are using bioceramic materials for repair and replacement of human hips,
knees, and other body parts. Ceramics also are being used to replace
diseased heart valves. When used in the human body as implants or even
as coatings to metal replacements, ceramic materials can stimulate bone
growth, promote tissue formation and provide protection from the immune
Dentists are using ceramics for tooth replacement implants and braces.
Glass microspheres smaller than a human hair are being used to deliver
large, localized amounts of radiation to diseased organs in the body.
Ceramics are one of the few materials that are durable and stable enough
to withstand the corrosive effect of bodily fluids.
Imaging systems are critical for medical diagnostics. Modern ceramic
materials play an important role in both ultrasonic and X-ray computed
tomography (CT) systems. Transducers utilizing lead zirconate titanate (PZT)
based piezoelectric ceramics are the heart of ultrasonic systems.
Transducers generate the ultrasonic acoustic waves and detect the
reflected signals to form the image.
Ultrasound can be used to examine many parts of the body including the
abdomen, breasts, female pelvis, prostate, thyroid and parathyroid, and
the vascular system. Most commonly, ultrasound is used during the first,
second, or third trimester of pregnancy. New developments in ultrasound
now enable doctors to see reliable images of ulcerated plaque or
irregularities in the blood vessels - something doctors have never been
able to see before. This may allow doctors to better identify those at
risk for stroke because of its ability to more clearly illustrate the
flow of blood, the walls of the carotid artery, and the movement of
X-ray CT scans are now a common diagnostic procedure in hospitals and
clinical sites to image selected regions inside the human body for
detection of cancer and other diseases. For CT scans, an x-ray detector
is a crucial component that must have high efficiency to obtain high
quality images. In 1988 GE Medical Systems unveiled an
ultrahigh-performance detector with a breakthrough ceramic scintillator
which gives better images using lower x-ray doses to the patient.
Environmental and Space Applications
Ceramics play an important role in addressing various environmental
needs. Ceramics help decrease pollution, capture toxic materials and
encapsulate nuclear waste. Today's catalytic converters in trucks and
cars are made of cellular ceramics and help convert noxious hydrocarbons
and carbon monoxide gases into harmless carbon dioxide and water.
Advanced ceramic components are starting to be used in diesel and
automotive engines. Ceramics light-weight, high-temperature and wear
resistant properties results in more efficient combustion and
significant fuel savings. Ceramics also are used in oil spill
containment booms that corral oil so it can be towed away from ships,
harbors, or offshore oil drilling rigs before being burned off safely.
Reusable, lightweight, ceramic tile make NASA's space shuttle program
possible. The 34,000 thermal barrier tiles protect the astronauts and
the shuttles aluminum frame from the extreme temperatures (up to
approximately 1600°C) encountered upon re-entry into the earth's
While the list could go on, one can begin to grasp the critical impact
that ceramics have played in our past and present and will continue to
play in the future.
source: American Ceramic Society
1 "Report of the Committee on Definition of the Term
Ceramics;" Journal of the American Ceramic Society, Vol. 3,
No. 7, July 1920, pp. 526-542.