Properties of Strontium Titanate
Strontium titanate is an oxide that consists of two chemical elements, strontium and titanium. This compound is used as a diamond simulant because of its cubic structure and high dispersion. Its chemical formula is SrTiO3. The natural counterpart of strontium titanate is tausonite, which is a rare mineral in nature. It was discovered in Siberia in 1982, and the International Mineralogical Association (IMA) recognized it. Strontium titanate can synthesize at a low temperature. The method used to cause this reaction is the sol-gel method. Gels transform into strontium titanate powders by drying and calcination. These powders have a low impurity level.
Other People Are Reading
-
Physical Properties
-
Strontium titanate is a material much denser and softer than diamond, but it has a cubic crystal system, which is why it is used as a diamond simulant. Synthetic strontium titanate, although usually transparent, can turn red, blue, yellow or brown if doped with certain earth and transition metals. The compound of strontium and titanium is brittle and has a conchoidal fracture. In addition, strontium titanate is insoluble in water.
Electrical Properties
-
Electrical properties of strontium titanate depend on its oxygen content. In the phase of reduced oxygen, the compound becomes metallic. On the other hand, when stoichiometry recovers, it has dielectric characteristics. Stoichiometry refers to the relative proportion of components and it must balance. During this ferroelectric phase, strontium titanate has a high dielectric constant of 104. As the dielectric constant increases, the electric flux density also grows if all the other factors stay the same. This property allows strontium titanate to hold its electric charge for long time or to hold large quantities of charge. It also has a low electric field.
-
Optical Properties
-
Strontium titanate belongs to the group of ceramic oxides. Its optical properties are isotropic, which results from the fact that it crystallizes in the cubic perovskite structure. Perovskite structure is a type of structure that includes at least 150 synthetic compounds. Its crystal structure is cubic and occurs as rounded cubes modified by the octahedral and dodecahedral forms. Absorption edge is the wavelength corresponding to a discontinuity in the variation of the absorption coefficient of a substance with the wavelength of the radiation. The strontium titanate-based crystals are transparent and grown by flame fusion. Their refractive index varies between 2.37 at 0.7 micron and 2.67 at 0.4 micron. On this level, the absorption edge corresponds to the activation energy of 3.1 electron volts. This reflective index is close to the reflexive index of diamond, although dispersion of strontium titanate is four times higher. Its high reflecting index and optical dispersion make it suitable for different optic applications.
Thermal Properties
-
The melting point of strontium titanate is 2080 °C. It has a cubic form at room temperature, but turns into a tetragonal structure at temperatures lower than 105K. If temperature is very low, the compound of strontium and titanium shows piezoelectric and superconducting characteristics. Piezoelectric materials generate electric charges when mechanically deformed. It is a substrate for epitaxial growth of high-temperature superconductors and oxide-based thin films. Epitaxy refers to the growth of one crystal on the surface of another one, which is its substrate.
-
References
- Optics Info Base: Some Optical Properties of Strontium Titanate Crystal
- EurekAlert: Strontium Titanate - A Deformable Ceramic
- Reade: Strontium Titanate
- Lamia: Transparent Oxides
- Global Oneness: Strontium Titanate -- Properties
- AZo Materials: Strontium Titanate (SrTiO3) -- Properties and Applications
