Synthesis, structures and photocatalytic activities of microcrystalline ABi2Nb2O9 (A=Sr, Ba) powders

Effects of Samarium Doping on the Dielectric Properties of BaBi2Nb2O9 Aurivillius Ceramics

This study investigates the influence of samarium (Sm3+) doping on the structural, microstructural, mechanical, and dielectric properties of BaBi2Nb2O9 (BBN) ceramics. Using the solid-state reaction method, samples of BaBi2-xSmxNb2O9 with varying concentrations of Sm (x = 0.01; 0.02; 0.04; 0.06; 0.08; 0.1) were prepared. Thermal analysis, microstructure characterization via SEM and EDS, X-ray diffraction, mechanical testing, and dielectric measurements were conducted. The results revealed that increasing Sm3+ concentration led to the formation of single-phase materials with a tetragonal structure at room temperature. Mechanical properties, such as Young's modulus and stiffness, improved with Sm doping, indicating stronger atomic bonding. Dielectric properties showed that low concentrations of Sm3+ slightly increased electrical permittivity, while higher concentrations reduced it. The presence of Sm3⁺ also affected the relaxor properties, evidenced by changes in the freezing temperature and activation energy. Overall, the study concludes that samarium doping enhances the structural and functional properties of BBN ceramics, making them promising candidates for high-temperature piezoelectric and dielectric applications. The findings provide valuable insights into tailoring ceramic materials for advanced technological applications.

Impedance Spectroscopy of Sm-Doped of BaBi2Nb2O9 Aurivillius Ceramics

This investigation focuses on the impact of Sm3+ dopants on BaBi2Nb2O9 (BBN) ceramics. These ceramics were obtained using the traditional solid state reaction approach. Techniques like scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) were employed to explore the structure and morphology of the ceramics. The results showed that the chemical composition of the ceramic samples matched well with the initial ceramic powder stoichiometry. Increasing the amount of samarium resulted in a slight reduction in the average ceramic grain size. The ceramics exhibited a tetragonal structure categorized under the space group I4/mmm. The electrical properties were analyzed using complex impedance spectroscopy (SI) across various temperatures and frequencies, revealing that both grains and intergranular boundaries are significant in the material's conductivity.

Emerging aspects of metal ions-doped zinc oxide photocatalysts in degradation of organic dyes and pharmaceutical pollutants - A review

In recent periods, a broad assortment of continual organic contaminants has been released into our natural water resources. Indeed, it is exceedingly poisonous and perilous to living things; thus, the elimination of these organic pollutants before release into the water bodies is vital. A variety of techniques have been utilized to remove these organic pollutants with advanced oxidation photocatalytic methods with zinc oxide (ZnO) nanoparticles being commonly used as a capable catalyst for contaminated water treatment. Nevertheless, its broad energy gap, which can be only stimulated under an ultraviolet (UV) light source, and high recombination pairs of electrons and holes limit their photocatalytic behaviors. However, numerous methods have been suggested to decrease its energy gap for visible regions. Including, the doping ZnO with metal ions (dopant) can be considered as an effectual route not only the reason for a movement of the absorption edges toward the higher (visible light) region but also to lower the electron-hole pair (e--h+) recombination. This review concentrated on the impact of dissimilar types of metal ions (dopants) on the advancement in the degradation performance of ZnO. So, this work demonstrates a vital review of contemporary attainments in the alteration of ZnO nanoparticles for organic pollutants eliminations. Besides, the effect of doping ions including transition metals, rare earth metals, and metal ions (substitutional and interstitial) concerning numerous types of altered ZnO are summarized. The photodegradation mechanisms for pristine and metal-modified ZnO nanoparticles are also conferred.

Reactive species specific RhB assisted collective photocatalytic degradation of tetracycline antibiotics with triple-layer Aurivillius perovskites

Triple-layer Aurivillius perovskites degrade tetracycline antibiotic and rhodamine B together in acidic aqueous solution. Primarily the superoxide radical generated via a semiconductor assisted dye sensitization process degrades the tetracycline.

Utilization of layered double hydroxides (LDHs) and their derivatives as photocatalysts for degradation of organic pollutants

Direct or indirect discharge of wastes containing organic pollutants have contributed to the environmental pollution globally. Decontamination of highly polluted natural resources such as water using an effective treatment is a great challenge for public health and environmental protection. Photodegradation of organic pollutants using efficient photocatalyst has attracted extensive interest due to their stability, effectiveness towards degradation efficiency, energy, and cost efficiency. Among various photocatalysts, layered double hydroxides (LDHs) and their derivatives have shown great potential towards photodegradation of organic pollutants. Herein, we review the mechanism, key factors, and performance of LDHs and their derivatives for the photodegradation of organic pollutants. LDH-based photocatalysts are classified into three different categories namely unmodified LDHs, modified LDHs, and calcined LDHs. Each LDH category is reviewed separately in terms of their photodegradation efficiency and kinetics of degradation. In addition, the effect of photocatalyst dose, pH, and initial concentration of pollutant as well as photocatalytic mechanisms are also summarized. Lastly, the stability and reusability of different photocatalysts are discussed. Challenges related to modeling the LDHs and its derivatives are addressed in order to improve their functional capacity.

Coupled-substituted double-layer Aurivillius niobates: structures, magnetism and solar photocatalysis

Heterovalent coupled-substituted double-layer Aurivillius niobates, LaBi₂Nb_1.5M_0.5O₉ (M = Cr, Mn, Fe, Co), show interesting structural and magnetic characteristics in addition to sunlight-driven photocatalytic activity.

Active Site-Directed Tandem Catalysis on Single Platinum Nanoparticles for Efficient and Stable Oxidation of Formaldehyde at Room Temperature

The application of tandem catalysis is rarely investigated in degrading organic pollutants in the environment. Herein, a tandem catalyst on single platinum (Pt) nanoparticles (Pt⁰ NPs) is prepared for the sequential degradation of formaldehyde (HCHO) to carbon dioxide gas [CO₂(g)] at room temperature. The synthesis approach includes coating of uniform Pt NPs on SrBi₂Ta₂O₉ platelets using a photoreduction process, followed by calcination of the sample in the atmosphere to tune partial transformation of Pt⁰ atoms to Pt²⁺ ions in the tandem catalyst. The conversion of HCHO to CO₂(g) is monitored by in situ Fourier transform infrared spectroscopy, which shows first conversion of HCHO to CO₃^2- ions onto Pt⁰ active sites and subsequently the conversion of CO₃^2- ions to CO₂(g) by neighboring Pt²⁺ species of the catalyst. The later process with Pt²⁺ species does not allow CO₃^2- poisoning of the catalyst. The enhanced activity of the prepared tandem catalyst to oxidize HCHO is maintained continuously for 680 min. Comparatively, the catalyst without Pt²⁺ shows activity for only 40 min. Additionally, the tandem catalyst presented herein performs better than the Pt/titanium dioxide (TiO₂) catalyst to degrade HCHO. Overall, the tandem catalyst may be applied to degrade organic pollutants efficiently.

Ferroelectric fatigue in layered perovskites from self-energy corrected density functional theory

We employed GGA-1/2 to investigate the band alignment between platinum and various layered perovskite Aurivillius ferroelectrics. A model is proposed for ferroelectric fatigue in bismuth titanate based on our calculation.

Inorganic perovskite photocatalysts for solar energy utilization

This review specifically summarizes the recent development of perovskite photocatalysts and their applications in water splitting and environmental remediation.