Barium Titanate
Introduction
Barium titanate (BaTiO3) is a ferroelectric ceramic material, with a perovskite structure. It has a wide range of applications due to its excellent dielectric, ferroelectric, and piezoelectric properties. Barium titanate is a member of a large family of compounds with the general formula ABO3 called perovskite.
Structure and Properties
Barium titanate crystallizes in the cubic perovskite structure until its Curie temperature of 120 °C, where it transforms to a tetragonal phase. This phase transition is associated with a large change in volume, which can induce significant mechanical strain. The tetragonal phase exists until the temperature is reduced to -90 °C, where the material transforms into an orthorhombic phase, and then at -183 °C, into a rhombohedral phase. Each of these phase transitions is accompanied by a significant change in the material's electrical properties.
Applications
Due to its high dielectric constant and piezoelectric properties, barium titanate is used in a wide variety of applications. These include capacitors, sensors, actuators, and transducers. It is also used in electro-optic devices, and in nonlinear optics.
Capacitors
Barium titanate is used in ceramic capacitors, due to its high dielectric constant. The high dielectric constant allows for a large amount of charge to be stored, making barium titanate capacitors useful in a wide range of electronic devices.
Sensors and Actuators
The piezoelectric properties of barium titanate make it useful in the production of sensors and actuators. The change in shape that barium titanate undergoes when an electric field is applied makes it an ideal material for these devices.
Electro-Optic Devices
Barium titanate's refractive index changes with the application of an electric field, making it useful in electro-optic devices. These devices are used in a variety of applications, including optical communication systems and laser systems.
Synthesis
Barium titanate can be produced by the relatively simple and cost-effective sol-gel method. This involves the reaction of barium carbonate and titanium dioxide at high temperatures. Other methods of synthesis include the hydrothermal method, solid state reaction method, and the solvothermal method.