Perovskite (structure)

Some things are built like tiny blocks.

These blocks have a special shape. They use three different parts. The parts fit together in a pattern.

One part is very large. One part is much smaller. The third part connects them. This pattern makes a cube shape.

Sometimes the blocks are not perfect. They can be missing a part. These are called defect blocks.

Some blocks are made in layers. They can be very thin. Some are only a few atoms thick.

These special shapes are very useful. They can even help carry electricity. It is a very cool pattern.

A perovskite is a special kind of crystal.

A crystal is a solid with a repeating pattern. This pattern follows a rule called ABX3. This rule tells us how three parts fit together.

The first part, A, is a large ion. An ion is a tiny piece of matter with a charge. The second part, B, is a much smaller ion. The third part, X, connects the other two.

In a perfect shape, these parts make a cube. The B ion sits in the middle. The A ions sit at the corners. The X ions sit on the flat faces.

Not all crystals are perfect cubes. Sometimes the parts shift or tilt. This can change how the crystal works. Some crystals are missing parts. We call these defect perovskites.

One example is rhenium trioxide. It is missing the A parts.

Other perovskites are built in layers. These layers can be very thin. Some are only one unit cell thick. Scientists use these layers to study how atoms move.

Perovskites can even help carry electricity.

A perovskite is a special kind of crystal structure. This structure is named after the mineral perovskite, which is calcium titanium oxide.

This mineral is part of a huge family of many different materials. Perovskites are very important because they have many different uses. They can help carry electricity or even act as superconductors.

Scientists study them to understand how tiny parts work together. These materials are found all over the physical world.

Most perovskites follow a specific rule called the ABX3 formula. This rule describes how three different parts fit together. The 'A' part is a large, positively charged ion. The 'B' part is a smaller, positively charged ion. The 'X' part is a negatively charged ion, often oxygen.

In a perfect cubic shape, the B ion sits in the very center. The A ions sit at the eight corners of the cube. The X ions sit in the middle of each flat face. This creates a repeating pattern that makes up the whole crystal.

Humans first found the mineral perovskite in 1839. It was discovered in the Ural mountains of Russia.

A man named Gustav Rose found it there. The mineral was named to honor a Russian mineralogist named L. A. Perovski. Perovski lived from 1792 to 1856. Knowing this history helps us see how people have studied these crystals for a long time.

Not every perovskite looks like a perfect cube. Sometimes the parts shift or tilt to stay stable. This can create different shapes like orthorhombic or tetragonal structures. Some crystals are even missing parts, which are called defect perovskites.

Rhenium trioxide is a simple example because it is missing its A atoms. Another example is YBCO, which is a famous superconductor. This material is missing some oxygen atoms, making it a defect perovskite.

Perovskites can also be built in very special ways. Some are made of thin layers that are only a few nanometres thick.

You can even have "double perovskites" where two different B ions take turns in a pattern. There are also "antiperovskites" where the positions of the ions are swapped. These different versions allow scientists to tune how the material works. This makes perovskites a very useful tool for modern science.

A perovskite is a specific type of crystalline material. It is named after the mineral perovskite, which is calcium titanium oxide (CaTiO3).

This mineral structure is very important in science. It represents one of the most abundant structural families in chemistry. Perovskites are useful because they possess a wide range of physical properties. They can be used in technology to carry electricity or act as superconductors.

Most perovskites follow the chemical formula ABX3. This formula describes how three different parts fit together in a repeating pattern. The 'A' and 'B' parts are cations, which are positively charged ions. The 'A' cation is generally much larger than the 'B' cation. The 'X' part is an anion, which is a negatively charged ion. In many cases, the X ion is oxygen.

In an ideal cubic structure, these ions arrange themselves very precisely. The B cation sits in the center of the unit cell. It is surrounded by six anions in a shape called an octahedron. This is known as 6-fold coordination. The A cation sits at the corners of the cube. It is surrounded by twelve anions in a cuboctahedral coordination. This is known as 12-fold coordination. The X atoms sit at the center of each flat face of the cube.

While the cubic form is the ideal model, it is rarely found in nature. The structure can change based on the size of the ions. If the ions do not fit perfectly, the structure may tilt or buckle. This can change the shape into orthorhombic, tetragonal, or trigonal forms. For example, barium titanate can change between these shapes depending on the temperature.

Such distortions can create an electric dipole. This specific property is known as ferroelectricity.

Some perovskites are known as defect perovskites because they are missing parts. In a perfect crystal, every position is filled. However, defect perovskites may lack some A, B, or X atoms. Rhenium trioxide is a simple example because it is missing the A atoms.

Another important example is yttrium barium copper oxide, or YBCO. YBCO is a high-temperature superconductor with the formula YBa2Cu3O7. It is a defect perovskite because it is missing two oxygen atoms.

Scientists can also create complex versions of these crystals. Double perovskites have the formula A2BO6. In these structures, two different types of B cations occupy the B sites in an ordered pattern. This often creates a rock-salt ordering. This means the different B cations alternate like a chessboard.

There are also antiperovskites. In an antiperovskite, the positions of the anions and cations are swapped. The stability of these structures depends on the Goldschmidt tolerance factor. This factor is calculated using the radii of the A, B, and X ions.

Perovskites were first discovered in 1839. A scientist named Gustav Rose found the mineral in the Ural mountains of Russia. He named the mineral after the Russian mineralogist L. A. Perovski. Perovski lived from 1792 to 1856. Since that discovery, the study of these structures has grown immensely. Today, researchers use them to explore magnetism and electronic properties. They can even grow perovskites as thin films only a few nanometres thick.