Chapter 25 Section 2

Ceramics Ceramics are materials that are made from dried clay or clay like mixtures. Ceramics can be made from easy to obtain materials like clay, sand and feldspar. It can also be made of metallic elements, carbon, nitrogen, or sulfur. After the raw materials are processed the they are molded into a desired shape and then heated to temperatures between 1000°C and 1700°C.

The heating process is called firing. When a ceramic is heated it shrinks the spaces between the particles of the ceramic. The entire object shrinks as the spaces become smaller. This makes the ceramic strong in some aspects like heat resistance. However ceramics are still fragile and can break if dropped or if the temperature changes too quickly.

Traditional Ceramics Ceramics are known for their chemical resistance to oxygen, water, acids, bases, salts, and strong solvents. Because of this they are more commonly used when interacting with any of those substances. An example would be tableware. Ceramics are also used as insulators as it does not conduct heat or electricity.

Modern Ceramics Today ceramics can be manufactured with properties that non traditional. Chromium dioxide is a special ceramic that can be conductive. Some copper based ceramics even have superconductive properties. One use of these special ceramics would be in airplane windshields. Because they conduct heat they can transfer heat from inside the cabin to prevent it from freezing.

Modern ceramics also have medical uses. Many joint replacements such as a hip replacement are made from ceramics since they are durable and resistant to body fluids. Dentists also use ceramics to repair teeth. If you have a filling or cap that is white then it would be a ceramic not the silver mercury alloy.

Semiconductors A semiconductor is a poorer at conducting than metals, but better than nonmetals. These are known as metalloids on the periodic table. Their electrical conductivity can be controlled by adding other elements to the metalloids.

An example of controlling conductivity would be silicon An example of controlling conductivity would be silicon. Pure silicon is stable and allows no room for electrons to move. However if you add impurities such as arsenic or gallium then the electron balance is destabilized. Since both elements have less electrons than silicon there is a gap where an electron can now move to, thus allowing for an electrical flow.

The process of adding the impurities to a semiconductor is called doping. Depending on the elements added the overall number of electrons will increase or decrease. N-type is when the number of electrons is increased. P-type is when the number of electrons is decreased.

By placing n-types and p-types together then you can make things like transistors and diodes. While this was being done the integrated circuit was also developed. An integrated circuit is a tiny chip that contains millions of semiconducting devices like transistors. They are also know as microchips. These chips were a beak through for technology and enable a lot of what we enjoy today to work.

Section Check What are some uses of ceramics? Describe the electrical conductivity of ceramics. What is a semiconductor? What is the difference from a n-type and p-type semiconductor?