Comparative study on organic effluent degradation capabilities and electrical transport properties of polygonal ZnCo2O4 spinels fabricated using different green fuels

A Comprehensive Bibliometric Study in the Context of Chemical Hazards in Coffee

The research aimed to carefully review the chemical hazards linked to the coffee production chain to analyse the risks and opportunities for consumers and the environment, as well as identify potential knowledge gaps. The Scopus database was consulted from 1949 to April 2024 to conduct a bibliometric analysis. As a result, 680 articles were analysed. Results indicated a significant increase in research activity since 2015. China, Brazil, and the USA were the leading countries in scientific production and collaborations. The most prolific journals in this field were Chemosphere, Science of the Total Environment, Food Chemistry, Journal of Agricultural and Food Chemistry, and Journal of Environmental Management, all of which are in the first quartile. The word analysis revealed two main themes: the first focuses on the chemical hazards of coffee and their impact on health, while the second explores the waste generated during coffee production and its potential for reuse. The topics covered in the research include the composition of coffee, associated chemical hazards, possible health risks, and ways to reuse waste for environmental protection. Future research should concentrate on optimising techniques and processes to ensure quality, safety, and sustainability.

Effect of sodium substitution by yttrium on the structural, dielectric and electrical properties of Ba2Na(1-3x)YxNb5O15 ceramics

The effects of Na+ substitution by Y3+ on the structural, microstructural, dielectric and electrical properties of Ba2Na(1-3x)YxNb5O15 compositions with (x = 0, 0.02 and 0.04) have been studied in detail. The solid solutions of different compositions were prepared by the solid state reaction route method and characterized by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and Complex Impedance Spectroscopy (CIS) techniques. The XRD study confirmed that all prepared compositions have a single-phase orthorhombic tungsten bronze structure with space group Cmm2 at room temperature. The microstructural studies revealed a grain shape and size change in response to increasing Y3+ concentration. The dielectric properties of the obtained compositions are evaluated over a temperature range of 40-600 °C. The dielectric properties were improved for the Y2O3-substituted Ba2NaNb5O15 compound compared to the undoped Ba2NaNb5O15 compound. The non-Debye type relaxation mechanism is confirmed by the -Z″ versus Z' traces. The grain contribution was studied using an equivalent electrical circuit with a Resistor R, a Capacitor C, and a Constant-Phase Element CPE in parallel, in the absence of the grain boundary response and the electrode effect in the frequency range 10 Hz-1MHz. The experimental AC conductivity data were evaluated by using Jonscher's power law. The activation energies obtained from the relaxation and conduction processes, present two different regions as a function of temperature related to the two electrical processes for the prepared ceramics.

Structural, electrical, and dielectric study of the influence of 3.4% lanthanide (Ln3+ = Sm3+ and La3+) insertion in the A-site of perovskite Ba0.95Ln0.034Ti0.99Zr0.01O3

This paper presents a systematic study of the substitution effect by lanthanides (Ln3+ = Sm3+ and La3+) in the A-site of perovskite Ba(1-x)Ln2x/3(Ti0.99Zr0.01)O3 with a substitution rate equal to 3.4%. All samples were synthesized by the classical solid-state reaction route and characterized by X-ray diffraction and a complex impedance spectroscopy technique. The synthesized compounds exhibit single-phase perovskite structures without detectable secondary phases. The P4mm space group was verified by the Rietveld method from the X-ray diffraction data, with the tetragonal distortion decreasing with the increasing ionic radius of the lanthanides. SEM micrographs of all ceramics revealed high densification, low porosity and homogeneous distribution of grains of different sizes over the entire surface. The dielectric properties of non-doped and Sm3+ and La3+ doped Ba(1-x)Ln2x/3(Ti0.99Zr0.01)O3 compound are studied in the temperature range of 40-250 °C. The dielectric permittivity ε' increases and the ferroelectric-paraelectric phase transition temperature decreases when the lanthanides are inserted into the A-site of Ba(1-x)Ln2x/3(Ti0.99Zr0.01)O3 perovskite. The Nyquist plots indicate a non-Debye type relaxation process. Conductivity and electrical modulus plots as a function of frequency (10 to 106 Hz) include two electrical responses corresponding to grain and grain boundary effects for all ceramics studied.

Using ZnCo2O4 nanoparticles as the hole transport layer to improve long term stability of perovskite solar cells

Inorganic metal oxides with the merits of high carrier transport capability, low cost and superior chemical stability have largely served as the hole transport layer (HTL) in perovskite solar cells (PSCs) in recent years. Among them, ternary metal oxides have gradually attracted attention because of the wide tenability of the two inequivalent cations in the lattice sites that offer interesting physicochemical properties. In this work, ZnCo2O4 nanoparticles (NPs) were prepared by a chemical precipitation method and served as the HTL in inverted PSCs. The device based on the ZnCo2O4 NPs HTL showed better efficiency of 12.31% and negligible hysteresis compared with the one using PEDOT:PSS film as the HTL. Moreover, the device sustained 85% of its initial efficiency after 240 h storage under a halogen lamps matrix exposure with an illumination intensity of 1000 W/m2, providing a powerful strategy to design long term stable PSCs for future production.