Nanopowder Compounds

Strontium titanate nanoparticles (SrTiO3, ST) with a perovskite-type structure is an important ceramic material having wide uses in the catalysis, sensors, actuators, electro-optical devices, random access memory devices, and multilayer capacitor. Because it has a lot of physical and chemical properties, such as, high thermal and chemical stability, low coefficient of thermal expansion, large dielectric constant, low dielectric loss, high nonlinear optical coefficient, it is widely accepted that the practical performances of product are strongly influenced by its phase, morphology, particle size, crystal defects, surface properties, etc., which ultimately depend on its preparation method and condition.

Strontium titanate nanoparticles (STO) are well known for its capability as a resistive high-temperature oxygen sensor. STO is stable without recrystallization over a wide temperature range between 104 K and about 2300 K. Furthermore, STO accepts very high donor dopant concentrations up to 30% without any phase transition thus allowing to vary the sensor capacity over a wide range. Especially very porous donor doped STO was found to be of interest because it provides quick response times in contrast to STO crystals.

Perovskite-type alkaline earth titanates (MTiO3: M = Sr, Ba and Ca) are well known as functional materials with piezoelectric, ferroelectric, and dielectric properties and widely used as gas sensors, non-volatile memories, capacitors, microwave devices, and photocatalysts.SrTiO3 is one of the most plausible candidates as high-performance photocatalysts for water splitting reaction. To improve the photocatalytic activity, size and shape control of the SrTiO3 particles might be a promising tool because a drastic increase in the activity is observed for size- and shape-controlled TiO2-based photocatalysts with specific crystal planes.

Strontium titanate nanoparticles are known to be an incipient ferroelectric material in which the onset of ferroelectricity is suppressed at low temperatures by quantum fluctuations and the existing soft modes of the system never become unstable. Strontium titanate nanoparticles possess a transition to a non-ferroelectric state near 105 K, corresponding to the rotation of the TiO6 polyhedra, which preserves the inversion center. The close proximity of the high purity SrTiO3  to the ferroelectric state was emphasized by its conversion to this state by 16O to 18O isotopic substitution.

Similarly, barium-strontium titanate (BST) is a useful electronic material due to its high electric permittivity and the Curie temperature depending upon the composition. BST is applied in piezoelectric sensors, dynamic random access memories, microwave phase shifters and uncooled infrared detectors because of its good dielectric, ferroelectric, and pyroelectric properties