There are many varieties of ceramic products in China, and their chemical composition, mineral composition, physical properties, and manufacturing methods are often close to each other without clear boundaries, but there are significant differences in their applications. Therefore, it is difficult to rigidly generalize into several systems, and there are different opinions on the detailed classification method. There is still no unified classification method internationally. There are two commonly used classification methods from different perspectives:
（1） Classified by different purposes
1. Daily ceramics: such as tableware, tea sets, jars, pots, jars, plates, dishes, bowls, etc.
2. Artistic (craft) ceramics: such as vases, sculptures, garden ceramics, vessels, furnishings, etc.
3. Industrial ceramics: refers to ceramic products used in various industries. It can be divided into the following six aspects:
① Building 1: Sanitary ceramics: such as bricks, tiles, drainage pipes, face bricks, exterior wall tiles, sanitary cleaning, etc;
② Chemical (chemical) ceramics: acid resistant bricks, ash, etc. used for acid resistant containers, pipelines, towers, pumps, valves, and enamel reaction pots in various chemical industries;
③ Electric porcelain: used as insulators on high and low voltage transmission lines in the power industry. Motor bushings, pillar insulators, low-voltage electrical and lighting insulators, as well as telecommunications insulators, radio insulators, etc;
④ Special ceramics: Special ceramic products used in various modern industries and scientific technologies, including high alumina ceramics, magnesia ceramics, titanium magnesia ceramics, zircon ceramics, lithium ceramics, as well as magnetic ceramics, metal ceramics, etc.
（2） According to the density of the raw materials used and the body, it can be divided into
Brick ware or Terra cotta, fine pottery, stone ware, semi porcelain, and even porcelain (130relin) are made from raw materials ranging from coarse to fine, with the body gradually becoming dense from coarse to porous, and then sintered. The firing temperature also gradually increases from low to high.
Coarse pottery is a primitive and low-grade ceramic ware, usually made from a type of fusible clay. In some cases, clay can also be mixed with clinker or sand to reduce shrinkage. The firing temperature of these products varies greatly, depending on the nature and amount of impurities contained in the chemical composition of the clay. To manufacture bricks and tiles, if the porosity is too high, the frost resistance of the body will be poor, and if the porosity is too low, it will not easily hang on the mortar. Therefore, the water absorption rate should generally be maintained between 5-15%. The color of the green body after firing depends on the content of colored oxides in the clay and the firing atmosphere. When fired in an oxidizing flame, it is mostly yellow or red, while when fired in a reducing flame, it is mostly blue or black.
The green bricks in China's building materials are made from yellow or red clay containing Fe2O3 as raw materials, which are calcined with a reducing flame near the end of the fire to reduce Fe203 to FeO and turn green. Pottery can be divided into two types: ordinary pottery and fine pottery. Ordinary pottery refers to products with porous colored bodies such as earthenware pots, jars, jars, jars, and refractory bricks. The water absorption rate of fine pottery body is still 4-12%, so it has permeability and no translucency. It is generally white, but also colored. Glazes often use melting glazes containing lead and boron. Compared with stoneware, due to the lower amount of flux and firing temperature not exceeding 1300 ℃, the green body has not been fully sintered; Compared with porcelain, the requirements for raw materials are lower, the plasticity of the blank is greater, and the firing temperature is lower. Not easily deformed, thus simplifying the forming, potting, and other processes of the product. But the mechanical strength and impact strength of fine pottery are smaller than porcelain and stoneware, and its glaze is softer than the glaze of the above-mentioned products. When its glaze layer is damaged, the porous body is easily contaminated, which affects hygiene.
Fine pottery can be divided into four types based on the composition of the body: clay, calcareous, feldspar, and clinker. Clay clay fine pottery is close to ordinary pottery. Limestone fine pottery uses limestone as a flux, and its manufacturing process is similar to that of feldspar fine pottery, but its quality is inferior to that of feldspar fine pottery. Therefore, it has been rarely produced in recent years and has been replaced by feldspar fine pottery. Long stone fine pottery, also known as hard fine pottery, uses feldspar as a flux. It is a widely used type of pottery. In modern times, many countries used large-scale production of daily tableware (cups, plates, etc.) and sanitary ware to replace expensive porcelain. Hot material fine pottery is a process of adding a certain amount of clinker to the fine pottery billet, with the aim of reducing shrinkage and avoiding waste. This type of billet is commonly used for large and thick tire products (such as bathtubs, washbasins, etc.).
Stoneware is called "stone body porcelain" in ancient Chinese literature, with a dense body that has been completely sintered, which is very close to porcelain. But it has not yet vitrified, still has a water absorption rate of less than 2%, the body is opaque, some are white, and most allow color to appear after firing, so the requirement for raw material purity is not as high as that of porcelain, and the raw material is easy to obtain. Stoneware has high strength and good thermal stability, making it suitable for modern mechanized washing and able to smoothly handle temperature fluctuations from refrigerators to ovens. In the international market, due to the development of the tourism industry and the socialization of food, stoneware has a larger sales volume than enamel.
The raw material of semi porcelain is similar to that of porcelain, but still has a water absorption rate of 3-5% after firing (true porcelain has a water absorption rate of less than 0.5%, so its performance is not as good as porcelain, but better than fine pottery).
Porcelain is a higher stage in the development of ceramics. Its characteristic is that the body has been completely sintered and vitrified, making it very dense and impermeable to liquids and gases. The tire is thin and translucent, with a shell like cross-section that feels smooth and not stuck when licked with the tongue. Hard porcelain has excellent performance among ceramics. Used to manufacture high-end daily utensils, such as electric porcelain, chemical porcelain, etc.
Soft porcelain contains more flux and has a lower firing temperature, resulting in lower mechanical strength and lower thermal stability compared to hard porcelain. However, it has high transparency and is rich in decorative properties, making it commonly used in the production of artistic display porcelain. As for Fritted porcelain and bone china, their firing temperature is similar to that of soft porcelain, and their advantages and disadvantages are also similar to those of soft porcelain, so they should belong to the scope of soft porcelain. These two types of porcelain are not widely produced due to their high difficulty in production (poor plasticity and drying strength of the body, severe deformation during firing), high cost. The UK is the origin of bone ash porcelain, and Tangshan in China also produces bone ash porcelain.
Special ceramics have developed with the rapid development of modern industries such as electrical appliances, radio, aviation, atomic energy, metallurgy, machinery, chemistry, as well as science and technology such as electronic computers, space technology, and new energy development. The main raw materials used for these ceramics are no longer clay, feldspar, quartz. Some ceramics also use some clay or feldspar, but more pure oxides and materials with special properties are used, and the manufacturing process and performance requirements are also different.
