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Published in Gianni Montagna, Cristina Carvalho, Textiles, Identity and Innovation: In Touch, 2020
M.J. Nunes, A. Lopes, M.J. Pacheco, L. Ciríaco, P.T. Fiadeiro
Strontium titanate (STO) is a well-known cubic perovskite (space group Pm3m) with a lattice parameter of 0.390 nm (Grabowska 2016). This oxide dis- plays high chemical and photochemical stabilities and exhibits photocatalytic activity for the degradation of organic pollutants under UV light (Ahuja & Kutty 1996, Chen et al. 2009). However, due to its wide band gap energy (Eg) of ~3.2 eV, the photocatalytic process cannot be initiated by the absorption of visible light radiation (Wang et al. 2015, Tonda et al. 2014). This hinders the application of low-cost solar radiation in the photocatalytic degradation processes using strontium titanate as the catalyst, considering that less than 5% of solar radiation belongs to the UV region (< 400 nm). To expand the photoabsorption range of SrTiO3 to visible radiation, the band gap width must be reduced. The most commonly applied method to decrease the energy gap of wide band gap semiconductors, like strontium titanate, is element doping, due to its simplicity and low cost (Wang et al. 2015, Grabowska 2016). This partial ionic substitution can originate the rise of the valence-band maximum or cause distortions in the perovskite structure, leading to the reduction of the Eg (Wang et al. 2015). Liu et al. (2006) and Tonda et al. (2014) reported that by doping SrTiO3 with Cr or co-doping with Cr and La, Eg of 2.11 eV and 1.89 eV can be achieved, respectively. Similar lowering of band gap energy was obtained when doping SrTiO3 with Ni (Eg decreased to 1.8 eV) or co-doping with Ni and La (Eg down to 1.9 eV) (Jia et al. 2010, Li et al. 2010).
Tunable Metamaterials
Published in Pankaj K. Choudhury, Metamaterials, 2021
In 2008, Zhao et al. [23] proposed a thermally tunable dielectric metamaterial based on the temperature sensitivity of dielectric ceramic material barium strontium titanate (Ba1–xSrxTiO3) doped with MgO. As the temperature increases from 258 K to 308 K, the frequency of Mie resonance shifts from 13.65 GHz to 19.28 GHz. Similar to barium strontium titanate, strontium titanate (SrTiO3, STO) obtains typical perovskite structure with high permittivity and low loss. It is a kind of electronic functional ceramic material with wide applications, and its temperature sensitivity can be improved by employing a reasonable doping process.
Ceramic Capacitor Technology
Published in Lionel M. Levinson, Electronic Ceramics, 2020
Manfred Kahn, Darnall P. Burks, Ian Burn, Walter A. Schulze
Strontium titanate-based dielectrics. Strontium titanate also has a perovskite structure, but it is cubic and paraelectric at room temperature. Its dielectric constant at room temperature is about 320, increasing gradually with decreasing temperature to about 20,000 near 0 K, with no evidence of a ferroelectric transition.
Construction of SrTiO3-BiOCl composite catalyst via facial microwave hydrothermal for highly efficient photocatalytic activity towards organic compounds degradation
Published in Environmental Technology, 2023
Jinfen Niu, Jiahui Shi, Ziqi Zhang, Yue Zhang, Yuhang Zhang, Binghua Yao, Xiaojiao Yu, Hong Wei
Strontium titanate (SrTiO3), as a typical metal oxide with a perovskite structure, has the advantages of high dielectric constant, low dielectric loss, and good thermal stability. SrTiO3 is a type of semiconductor photocatalytic material with great potential application besides TiO2. As a typical perovskite-type compound, it is insulating, metallic, and superconducting under special conditions, and it is also a typical n-type semiconductor. Due to its physical and chemical stability, non-toxicity, and excellent photocatalytic activity, SrTiO3 is considered as a promising photocatalyst. Olim Ruzimuradov et al. fabricated the lanthanum and N-co-doped on SrTiO3-TiO2, which was heterostructure macroporous monolithic material, and it has high photocatalytic degradation of organic dyes under visible light [29]. Yu et al. prepared Z-scheme SrTiO3/Ag/Ag3PO4 photocatalyst with oxygen vacancies [30]. However, due to the wide bandgap (about 3.2 eV) of SrTiO3 limits it to apply in the visible light photocatalytic degradation of pollutants or water decomposition [31].
Effect of Nb doping on the structural, optical, and photocatalytic properties of SrTiO3 nanopowder synthesized by sol-gel auto combustion technique
Published in Journal of Asian Ceramic Societies, 2022
Pornnipa Nunocha, Malinee Kaewpanha, Theerachai Bongkarn, Apiluck Eiad-Ua, Tawat Suriwong
Strontium titanate (SrTiO3, STO) is an oxide ceramic which has an oxide crystal with a cubic perovskite structure. STO is also a semiconductor material with a wide band gap (Eg) with intriguing electronic, optical, magnetic, and photocatalytic properties. The electrical properties of STO are indicated by the sizable dielectric permittivity and ferroelectric phase. Furthermore, the band structure of STO is in two band gaps: direct 3.75 eV and indirect 3.2 eV [12]. Therefore, the photocatalyst properties of STO, with these outstanding features, were fascinating to study. Nanostructure, doping, and heterojunction are modification techniques of the STO based on the photocatalyst. Nanostructures are attractive because of their high specific surface area and the migration of e− – h+ on the surface in chemical reactions that occur before recombination [13]. These properties of nanostructures improve photocatalysis efficiency. Several processes for synthesizing materials result in nanoscale structures. Using doping to tune the luminescent, electronic, optical, and other physical properties leads to improved semiconductors with a wide band gap.
Computational energy gap estimation for strontium titanate photocatalyst using extreme learning machine method
Published in Cogent Engineering, 2023
Strontium titanate photocatalyst is a metal oxide with known highest electron mobility. Contraction in strontium titanate semiconductor crystallography occurs when strontium cations are replaced and substituted with ions of reduced ionic radii. Similarly, substitution of Ti4+ with cations of reduced ionic radii further leads to lattice contraction (Yang et al., 2009). Oxygen vacancy creation in strontium titanate semiconductor completely modifies physical and chemical features of the semiconductor for many technological applications such as photocatalysis and nuclear power (Kumar et al., 2021). Presence of oxygen vacancies has potentials to alter photo-absorption capacity of the semiconductor for photocatalytic activity enhancement (Owolabi et al., 2022). The number of electron spins that are unpaired at defect levels controls the intrinsic magnetic intensity of un-doped oxide as well as the absorption photon energies. Hence, the impurity band associated with oxygen vacancy creation extends the applicability of strontium titanate semiconductor opto-magnetic devices to visible light region range. Strontium titanate crystallizes in cubic perovskite structure with pm3m space group. The crystal structure contains Ti4+ ions with six-fold O2− ions coordination, while TiO6 octahedra surround every strontium Sr2+ ions. This means that there are 12 O2− ions co-coordinating each of strontium Sr2+ ions. Covalent bonding exists due to hybridization of Ti-3d states with O-2p states within octahedra TiO6, while O2− and Sr2+ ions show the characteristics of ionic bonding. Therefore, strontium titanate has a mixed covalent and ionic bonding feature (Ur et al., 2021). This unique chemical bonding feature translates to interesting properties exhibited by strontium titanate for various industrial and technological applications. This work establishes a relationship between the crystallite size, lattice distortions and energy gap of strontium titanate using ELM.