Zirconium dioxide

Some white stones look like shiny diamonds.

People use them for pretty jewelry. Scientists can make these stones in many colors. This helps them look like real gems.

This material is also very strong. It can be used to make sharp knives. It is used to make fake teeth for smiles.

Some parts of engines use it too. It helps them stay safe when they are hot. This special stone is very useful in our world.

Zirconium dioxide is a white material. It is often called zirconia.

In nature, it is found as a mineral called baddeleyite. People also make a version called cubic zirconia. This looks like a diamond. It is used in jewelry to look like real gems.

Zirconia is a very strong ceramic. It can change its shape when it gets hot. This can make it crack. To stop this, scientists add tiny amounts of other things. They might add yttria, which is a type of oxide. This helps the material stay stable. This process is called stabilization.

Stabilized zirconia is very useful. It is used to make dental crowns for teeth. It can also make very sharp ceramic knives. Some engines use it as a coating. This helps them handle high heat. Zirconia can even move oxygen ions. This makes it great for fuel cells. Scientists even think it could help make fuel on Mars.

Zirconium dioxide is a white, crystalline material. It is often called zirconia.

In nature, it can be found as a mineral named baddeleyite. People also make a special version called cubic zirconia. This version is used as a gemstone to look like a diamond. It has a cubic structure and a high index of refraction. This makes it look very bright and shiny. Scientists study it because it is a very special ceramic material.

This material works in different ways depending on its heat. It has three main phases or shapes. Below 1170 °C, it has a monoclinic structure. Between 1170 °C and 2370 °C, it becomes tetragonal. Above 2370 °C, it becomes cubic. When it cools down, the change in shape can cause stress. This stress can make the material crack. To fix this, scientists add small amounts of other oxides.

Adding yttria, or yttrium oxide, helps stabilize the material. This keeps the shape steady and makes it much stronger.

Researchers have studied how to make zirconia better for a long time. One way is called transformation toughening. This happens when the material is under stress. A tiny amount of the tetragonal phase turns into the monoclinic phase. This change makes the material expand in volume. This expansion puts pressure on any cracks to stop them from growing. This makes the products much more reliable. Using 3 mol% of yttrium oxide helps this happen at room temperature. Using 5 mol% makes it more clear but less strong.

There are many specific facts about how zirconia behaves. It is chemically unreactive, but strong acids can slowly attack it. When heated with carbon, it turns into zirconium carbide. It can also be turned into zirconium(IV) chloride using carbon and chlorine. This is a way to purify zirconium metal. In 2015, a watch company called Omega released a watch named "The Dark Side of The Moon." This watch used a ceramic case that was four times harder than steel. It was designed to resist scratches during everyday use.

Zirconia connects to many things you might see every day. Dentists use it to make strong crowns and bridges for teeth. You might also find it in very sharp ceramic knives. Some jet engines use it as a thermal barrier coating. This helps the engine run at higher temperatures to be more efficient. Scientists even think it could help people on Mars. They suggest using it to make fuel from the atmosphere there. It is a material that helps us build things for Earth and beyond.

Zirconium dioxide, often called zirconia, is a white crystalline oxide of zirconium. It is a highly significant ceramic material used in many different industries. In nature, the most common form of this material is a mineral known as baddeleyite. Because of its unique properties, scientists and engineers study it extensively. It is used for everything from medical tools to space exploration technology.

The physical structure of zirconia changes depending on the temperature. This is known as a phase change. Below 1170 °C, the material has a monoclinic crystalline structure. Between 1170 °C and 2370 °C, it enters a tetragonal phase. Above 2370 °C, it becomes a cubic phase. As temperatures rise, the symmetry of the crystal structure typically increases. This shifting structure can cause the material to crack during cooling. This happens because the changes in volume create large internal stresses.

To prevent cracking, scientists use a process called stabilization. They add small amounts of other oxides, known as dopants, to the material. Common dopants include magnesium oxide, yttria, calcium oxide, and cerium(III) oxide. Adding yttria, or yttrium oxide, is a very common method. This prevents the disruptive phase changes from occurring. Stabilized zirconia possesses much better thermal, mechanical, and electrical properties. It is often more useful to engineers in this stabilized state.

One fascinating process is called transformation toughening. This occurs when zirconia contains a metastable tetragonal phase. A metastable phase is one that stays in a state that is not its most stable form. When a crack begins to form, the stress at the crack tip causes the tetragonal phase to convert to the monoclinic phase. This conversion causes a volume expansion. This expansion puts the crack into compression, which stops the crack from growing. This mechanism significantly increases the fracture toughness and lifetime of the product.

Different amounts of dopants create different results. For example, adding 3 mol% of yttrium oxide creates 3Y-ZrO2. At high temperatures of about 1500 °C, this improves hardness and flexural strength. This is because it retains the metastable tetragonal phase at room temperature. In contrast, adding 5 mol% of yttrium oxide creates 5Y-ZrO2. This version is mostly in the cubic phase. While 5Y-ZrO2 has better optical translucency, it does not benefit from transformation toughening.

Zirconia has many important uses in modern life. In dentistry, it is used to make durable crowns, bridges, and dental prostheses. Because it is very hard, it is also used to make ceramic knives that stay sharp longer than steel. In engineering, it serves as a thermal barrier coating in jet and diesel engines. These coatings allow engines to operate at higher temperatures, which increases efficiency. It is also used in oxygen sensors because oxygen ions can move freely through its crystal structure at high temperatures.

Beyond Earth, zirconia might help humans explore Mars. Scientists have proposed using zirconia electrolysis to produce fuel. This process could extract carbon monoxide and oxygen from the Martian atmosphere. This would provide both fuel and oxidizer for surface transportation. On Earth, the material is even used in luxury items. In 2015, the company Omega released a watch called "The Dark Side of The Moon." It featured a ceramic case that was four times harder than stainless steel.