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The four major crystal structures of barium titanate: how do they affect the material's amazing properties?
Barium Titanate (BTO for short) is an inorganic compound with the chemical formula BaTiO3. The material, a carbonate of sodium and titanium, appears as a white powder but is transparent when it is made into large crystals. Barium titanate has piezoelectric, pyroelectric and photorefractive properties and is widely used in capacitors, electromechanical converters and nonlinear optics.
Structure and phase transition
The solid form of barium titanate will appear in four different polymorphic structures depending on the temperature. From high to low temperature, they are cubic, tetragonal, orthorhombic and rhombohedral phases. All these phases exhibit ferroelectric effects except the cubic phase.
The structure of the cubic phase is the easiest to describe. This phase is composed of regular corner-sharing octahedral TiO6 units and forms a cube with oxygen vertices and Ti-O-Ti edges.
Manufacturing and handling characteristics
The synthesis method of barium titanate is relatively simple. Common solutions include the solution-hydrothermal method or the reaction of heating barium carbonate and titanium dioxide for liquid phase sintering. Single crystals can be grown from molten potassium fluoride at high temperatures of approximately 1100°C.
The relationship between the particle morphology and properties of barium titanate has always been a hot topic of research. This material is one of the few ceramic compounds that exhibits abnormal grain growth.
Application status
Barium titanate is a dielectric ceramic used in capacitors with a dielectric constant as high as 7000. In a narrow temperature range, the dielectric constant can reach 15,000, which is unmatched by most common ceramic and polymer materials.
As a piezoelectric material, barium titanate has been widely used in microphones and other transducers, and is critical for thermal imaging resident sensor applications.
Future trends
With the continuous advancement of materials science, barium titanate is increasingly used in various fields, and its key position in the capacitor energy storage system of electric vehicles cannot be underestimated. In addition, barium titanate nanoparticles (BTNPs) have recently been used as nanocarriers for drug delivery due to their high biocompatibility.
Barium titanate not only flexes its muscles in electronic products, but how will its future potential be unleashed in fields such as medical care and environmentally responsible energy solutions?
