Guide to Ceramics: Types, Materials, & How
Traditional types of ceramic pottery
Common examples are earthenware, stoneware, porcelain, and bone china. Clay is one of the widely available raw materials for creating ceramic objects. Different types of clay and combinations of clay with different variations of silica and other minerals result in different types of ceramic pottery.
Earthenware
Earthenware is pottery that has not been fired to vitrification, which is the process of crystalline silicate compounds bonding into noncrystalline glass compounds. This makes the pottery more porous and coarser to the touch. Earthenware pottery was the most common type of ceramics until the 18th century. Terracotta, a clay-based and unglazed ceramic, is a common type of earthenware. Today, we commonly see planters made from terracotta, along with bricks, water pipes, and more.
Stoneware
Stoneware is a vitreous or semi-vitreous ceramic, meaning it is coated in enamel to make it appear glassy and to make it nonporous. Stoneware is fired at high temperatures compared to other ceramics. It is typically an earth tone color because of impurities in the clay and is normally glazed.
Porcelain
Porcelain ceramics are made by heating materials, generally kaolin clay, in a kiln to temperatures between 2,200 and 2,600 degrees Fahrenheit. Porcelain is a very heat-resistant and strong material compared to other types of ceramics. This is because of the vitrification process and formation of the silicate mineral mullite when fired. Common types of porcelain ceramics are bathroom and kitchen tiles, vessels, decorative sculptures, and more.
Bone china
Bone china, also known as fine china, is a type of porcelain that is known for its translucency, high strength, and chip resistance. It is made from a combination of bone ash, feldspathic material, and kaolin, and was developed by English ceramicist Josiah Spode around 1800. Because it is such a strong material, bone china ceramics can be shaped into thinner forms than porcelain. It is vitrified but is translucent due to differing mineral properties.
Ceramics throughout history
The oldest known ceramics
The oldest ceramics that have been found date back to at least 25,000 BC. Uncovered in Czechoslovakia by archaeologists, these ceramics were in the form of animal and human figurines. They were made from a mixture of animal fat, bone, bone ash, and clay and were fired in ground kilns at low temperatures around 1000 degrees Fahrenheit, or simply dried in the sun to harden.
First functional ceramic vessels
The first examples of functional ceramics vessels are believed to be from about 9,000 BC and were likely used to store food, grains, and water. This was also around the time that small farming communities became more common in Asia, the Middle East, and Europe.
Decorative glazes and surface design
Early ceramics were generally simple in design and texture and were fired without glazes. In the 6th and 5th centuries BC, Greek Attic vases showed the first known use of oxidizing and reducing atmosphere during firing to achieve surface patterns and varying colors.
The invention of the wheel
One of the first breakthroughs in the fabrication of ceramics was the invention of the wheel in 3,500 BC. It allowed potters to go beyond the restrictions of hand building, and to dive into creating pieces with radial symmetry.
The introduction of porcelain
Around 600 CE, Chinese potters introduced high-temperature kilns and developed porcelain from kaolin clay, which is also known as China clay. This opened up possibilities for less porous and much stronger ceramic vessels. Throughout the 16th century, low fire earthenware remained the most common type of ceramic in Europe and the Middle East. It was not until the Middle Ages that trade through the Silk Road allowed for the introduction of porcelain and high-temperature kilns throughout Islamic countries and Europe.
Modern-day ceramics
Over the course of thousands of years, the ceramic industry has undergone a huge transformation. After World War II, ceramics contributed to the expansion of technology, electronics, medical equipment, transportation, and more. Today, you can learn ceramics for artistic or practical purposes.
How to learn ceramics
The Crucible offers a unique place to learn the different ceramic and pottery building techniques of pinching, coiling, and using slabs, in addition to press molds and slip casting with plaster molds. Students have the opportunity to explore different glazing techniques in low fire, high fire, and other firing alternatives, such as raku firing. Functional tableware, vessels, sculpture, installations, and mixed media—the possibilities in ceramics are endless for youth and adults of all levels.
Types of ceramic materials
Ceramics are omnipresent from our kitchen pantries to tool closets. They go far beyond the simple use of a ceramic vessel or sculpture and are applied in everything from science to mechanical engineering.
Ceramics FAQs
What is the cone system used to measure kiln firing temperatures?
The cone system measures how hot the kiln is and how long the clay body is fired in the kiln. Cones are essential when firing so that you know when your kiln has reached the necessary temperature and if the kiln was evenly heated. Each cone has a number assigned to it that corresponds to a specific temperature range. For example, cone 03 indicates a temperature range of about 1960 to 1987 degrees Fahrenheit.
Cones are placed in the kiln when firing to absorb heat, and as they reach the desired temperature, the tip begins to bend. You can watch the cones through the window in your kiln to make sure the kiln is heated evenly and the temperature is being reached.
What does it mean if clay or glaze is low, mid, or high fire?
Low fire clay fires in the kiln between 1940-2109 degrees Fahrenheit. The pro of low fire clay is that it is easy and economical to fire, however, it is porous and not the best option for liquid-bearing vessels. Mid-fire clay fires between 2157-2232 degrees Fahrenheit, making it easily fired in an electric kiln. It is a versatile clay, strong once fired, and not porous. High fire clay fires at about 2381 degrees Fahrenheit. It is durable and waterproof, making it a long-lasting and strong option. The downside of high fire is that it is best to fire it in a gas kiln, making it less accessible to most potters.
What are reduction and oxidation and what do they do?
Oxidation and reduction refer to how much oxygen is present in the kiln when the clay is fired. An oxidized atmosphere has lots of oxygen, while a reduced atmosphere has very little. This can change the texture of your clay and interact with specialty glazes.
What is the difference between using a gas kiln and an electric kiln?
Electric kilns are more common in both home and professional studios because of ease of convenience and setup. Electric kilns work well for low and mid-fire clay, while gas kilns work for high-fire clay. Compared to gas kilns, electric kilns do not require special permits. Gas firings generally result in earthier colors and can be used in reduction firing to achieve interesting surface textures.
What are the safety concerns for using clay? Can I use it safely at home?
When you are working with clay, one of the most important precautions is to protect yourself from inhaling the powder that results from dried clay. This contains silica, which can hang in the air for hours and can damage your lungs. In order to protect yourself, wear a mask, understand what ingredients are in the clay you are using, and use premixed, wet clay bodies.
Types and Applications of All Kinds of Ceramic Materials
Ceramics greatly differ in their basic composition, and their properties also vary greatly due to differences in bonding. Classification of ceramics based on their specific applications and composition are the two most important ways among many ceramic classification methods.
Classification of Ceramics by Composition
Based on their composition, ceramics are classified as silicates, oxides, carbides, nitrides, sulfides, fluorides, etc.
i) Silicate Ceramics
Silicates are materials generally having a composition of silicon and oxygen. The main types of silicate ceramics are based either on alumosilicates or magnesium silicates. Silicate ceramics are traditionally categorized into coarse or fine and, according to water absorption, into dense (< 2 % for fine and < 6 % for coarse) or porous ceramics (> 2% and > 6 %, respectively).
Further Reading: What are Silicate Ceramics
(ii) Oxide Ceramics
Oxide ceramics include alumina, zirconia, silica, magnesia, and other metal oxide-based materials. These are non-metallic and inorganic compounds by nature that include oxygen, carbon, or nitrogen.
Oxide ceramics possess the following properties:
- (a) High melting points
- (b) Low wear resistance
- (c) An extensive collection of electrical properties
These types of ceramics are available with a variety of special features. For example, glazes and protective coatings seal porosity, improve water or chemical resistance and enhance joining to metals or other materials. Oxide ceramics are used in a wide range of applications, which include materials and chemical processing, radiofrequency and microwave applications, electrical and high voltage power applications, and foundry and metal processing. Aluminum oxide (Al2O3) is the most important technical oxide ceramic material. This synthetically manufactured material consists of aluminum oxide ranging from 80 % to more than 99 %.
(iii) Non-Oxide Ceramics
Non-oxide ceramics include materials such as carbides, nitrides, and borides. The use of non-oxide ceramics has enabled extreme wear and corrosion problems to be overcome, even at high temperatures and severe thermal shock conditions. These types of ceramics find their application in different spheres such as pharmaceuticals, the oil and gas industry, valves, seals, rotating parts, wear plates, location pins for projection welding, cutting tooltips, abrasive powder blast nozzles, metal forming tooling, etc.
(iv) Glass-ceramics
These are basically polycrystalline materials manufactured through the controlled crystallization of base glass. Glass-ceramic materials share many common characteristics with both glass and ceramics. Glass ceramics possess an amorphous phase and more than one crystalline phase. These are produced by a controlled crystallization procedure. Glass ceramics hold the processing advantage of glass and have special characteristics of ceramics.
Classification of Ceramics by Application
The other important classification of ceramics is based on their application, such as glasses, clay products, refractories, abrasives, cement, and advanced ceramics.
In general, ceramic materials used for engineering applications can be divided into two groups: traditional ceramics, and advanced ceramics. Typically, traditional ceramics are made from three basic components: clay, silica (flint), and feldspar. For example, bricks, tiles, and porcelain articles. However, advanced ceramic materials consist of highly pure compounds of aluminum oxide (Al2O3), silicon carbide (SiC), and silicon nitride (Si3N4).
Glasses
Glasses are a familiar group of ceramics – containers, windows, mirrors, lenses, etc. They are non-crystalline silicates containing other oxides, usually CaO, Na2O, K2O, and Al2O3 which influence the glass properties and its color. A typical property of glasses that is important in engineering applications is their response to heating. There is no definite temperature at which the liquid transforms into a solid as with crystalline materials. A specific temperature, known as glass transition temperature or fictive temperature is defined based on viscosity above which material is named as supercooled liquid or liquid, and below it is termed as glass.
Clay Products
Clay is one of the most widely used ceramic raw materials. It is found in great abundance and popular because of the ease with which products are made. Clay products are mainly two kinds – structural products (bricks, tiles, sewer pipes) and whitewares (porcelain, chinaware, pottery, etc.).
Refractories
These are described by their capacity to withstand high temperatures without melting or decomposing, and their inertness in severe environments. Thermal insulation is also an important function of refractories.
Abrasive Ceramics
Abrasive ceramics are used to grind, wear, or cut away other materials. Thus the prime requisite for this group of materials is hardness or wear resistance in addition to high toughness. As they may also be exposed to high temperatures, they need to exhibit some refractoriness. Diamond, silicon carbide, tungsten carbide, silica sand, and aluminum oxide/corundum are some typical examples of abrasive ceramic materials.
Cement
Cement, plaster of paris and lime come under this group of ceramics. The characteristic property of these materials is that when they are mixed with water, they form a slurry that sets subsequently and hardens finally. Thus it is possible to form virtually any shape. They are also used as bonding phases, for example between construction bricks.
Advanced Ceramics
Advanced ceramic materials are newly developed and manufactured in a limited range for specific applications. Usually, their electrical, magnetic, and optical properties and a combination of properties are exploited. Typical applications: heat engines, ceramic armors, electronic packaging, etc.
Further Reading: An Overview of Advanced Ceramic Materials
Examples of Specific Ceramics and Respective Applications
Aluminum oxide / Alumina (Al2O3)
Alumina is one of the most commonly used ceramic materials. is used in many applications such as to contain molten metal, where the material is operated at very high temperatures under heavy loads, as insulators in spark plugs, and in some unique applications such as dental and medical use. Chromium-doped alumina is used for making lasers.
Aluminum nitride (AlN)
Because of its typical properties such as good electrical insulation but high thermal conductivity, aluminum nitride is used in many electronic applications such as in electrical circuits operating at a high frequency. It is also suitable for integrated circuits. Other electronic ceramics include – barium titanate (BaTiO3) and Cordierite (2MgO-2Al2O3-5SiO2).
Diamond (C)
It is the hardest material known to be available in nature. It has many applications such as industrial abrasives, cutting tools, abrasion-resistant coatings, etc. It is, of course, also used in jewelry.
Lead Zirconium Titanate (PZT)
PZT is the most widely used piezoelectric material and is used as gas igniters, ultrasound imaging, in underwater detectors.
Further Reading: Piezoelectric Materials and Their Diverse Applications
Silica (SiO2)
Silica is an essential ingredient in many engineering ceramics and thus is the most widely used ceramic material. Silica-based materials are used in thermal insulation, abrasives, laboratory glassware, etc. It also found application in communications media as an integral part of optical fibers. Fine particles of silica are used in tires, paints, etc.
Silicon Carbide (SiC)
Silicon carbide is known as one of the best ceramic materials for very high-temperature applications. It is used as coatings on other materials for protection from extreme temperatures. It is also used as an abrasive material. It is used as a reinforcement in many metallic and ceramic-based composites. It is a semiconductor and is often used in high-temperature electronics. Silicon nitride (Si3N4) has properties similar to those of SiC but is somewhat lower, and found applications in such automotive and gas turbine engines.
Titanium Oxide (TiO2)
It is mostly found as a pigment in paints. It also forms part of certain glass ceramics. It is used to make other ceramics like BaTiO3.
Titanium Boride (TiB2)
It exhibits great toughness properties and hence found applications in armor production. It is also a good conductor of both electricity and heat.
Uranium Oxide (UO2)
It is mainly used as nuclear reactor fuel. It has exceptional dimensional stability because its crystal structure can accommodate the products of the fission process.
Yttrium Aluminum Garnet (YAG, Y3Al5O12)
Yttrium Aluminum Garnet has a main application in lasers (Nd-YAG lasers).
Zirconia (ZrO2)
It is also used in producing many other ceramic materials. Zirconia is also used in making oxygen gas sensors, as an additive in many electronic ceramics. Its single crystals are part of the jewelry.
