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[en] Highlights: • Spongy network of La2S3 film is prepared by simple, inexpensive, chemical bath deposition method. • The supercapacitive performance of air-annealed La2S3 is higher than that of as-deposited electrode. • The flexible lightweight supercapacitor exhibits good electrochemical performance. - Abstract: In this work, the electrochemical properties of rare earth lanthanum sulfide (La2S3) films obtained by chemical bath deposition method are investigated as an electrode material for supercapacitor application. The effect of air annealing on structural, surface morphological and wettability properties of La2S3 films is studied. The X-ray diffraction and FT-Raman analysis confirm the formation La2S3 film. A porous spongy network of La2S3 film reveals the hydrophilic nature. The supercapacitive properties of La2S3 electrode are evaluated using cyclic voltammetry and galvanostatic charge–discharge mode. The maximum specific capacitance of 294 F g−1 is achieved for air-annealed La2S3 electrode at a scan rate of 5 mV s−1 with 89 % electrochemical cyclic stability over 1000 cycles. The spongy network of air-annealed La2S3 film enhances the supercapacitive performance. The auspicious properties of La2S3 electrode are effective for the fabrication of flexible La2S3/LiClO4-PVA/La2S3 solid-state supercapacitor device. The specific capacitance of supercapacitor device with diverse bending angles and cyclic stability is examined.
[en] The development of high-performance miniaturized electrochemical energy storage systems is one of the important technological challenges for innovative electronic gadgets. Flexible microelectromechanical systems-based supercapacitors are considered one of the most aggressive on-chip power sources for advanced integrated electronics. Achieving high power efficiency with excellent flexibility and transparency for the micro-supercapacitors is a major challenge nowadays. Generally, these characteristics of micro-supercapacitors are dependent on the fabrication methods, electrical, mechanical and electrochemical properties of the microelectrode materials, current collectors and electrolytes. In the present review, we have summarized the various strategies used in materials engineering to develop flexible micro-supercapacitors and their electrochemical performance characteristics. Meanwhile, this review presents the latest developments in the design, fabrication and application of flexible micro-supercapacitors. (topical review)
[en] Research highlights: → Preparation of nanocrystalline Cr3+ substituted lithium ferrite by sol-gel method. → We examine the structural and magnetic properties of the prepared samples. → Prepared samples have high potential for cathode materials in rechargeable lithium batteries. - Abstract: Li0.5CrxFe2.5-xO4 powders with fine sized particles were successfully synthesized by sol-gel auto combustion, using lithium nitrate, ferric nitrate, chromium nitrate, and citric acid as the starting materials. The process takes only a few minutes to obtain as-prepared Cr-substituted lithium ferrite powders. The resultant powders were annealed at 600 deg. C for 4 h and investigated by thermogravimeter/differential thermal analyzer (TG/DTA), X-ray diffractometer (XRD) and vibrating sample magnetometer (VSM). Lattice parameter, bulk density and particle size are found to decrease with increasing Cr concentration, whereas X-ray density and porosity showed an increasing trend with the Cr content. Cation distribution indicates that the chromium ion occupy octahedral B-site. The magnetic moments calculated from Neel's molecular field model are in agreement in the experiment result, which indicates that the saturation magnetization decreases linearly from 37.36 to 4.27 emu/g with increasing Cr3+ content. However, coercivity, it increases with the Cr3+ substitution.
[en] Highlights: ► Al3+ ion substituted Mn–Zn ferrite nanoparticles. ► Single phase cubic spinel structure changes with Al3+ substitution. ► Magnetization and coercivity decreased with increasing Al3+. ► Resistivity increased with Al3+ substitution. - Abstract: In this work the nano-structural, magnetic and resistivity properties of Al3+ substituted Mn–Zn ferrites powders were investigated. Mn0.5Zn0.5AlxFe2−xO4 powders, where x = 0.0, 0.1, 0.2, 0.3, 0.4 and 0.5 were obtained by the sol–gel auto-combustion method. X-ray diffraction data indicate that, after substitution, all the samples consisted of the main spinel phase in combination with a small amount of a foreign Al2O3 phase. The addition of Al3+ resulted in a reduction of particle size and density of the prepared samples. Cation distribution in the present study was estimated by using X-ray diffraction data. The tetrahedral site radii initially increased with Al3+ content while the octahedral site radii decreased with the Al3+ substitution. FTIR spectra show two strong absorption bands at 529–548 cm−1 and 445–452 cm−1 which are the typical bands for the cubic spinel crystal structure. The magnetic properties were measured by employing a vibrating sample magnetometer. It was observed that the saturation magnetization, coercivity and anisotropy field decreased with the increase of Al3+ substitution. Introduction of Al3+ ions into the Mn–Zn ferrite increased the values of the resistivity, especially in the lower temperature range
[en] The effect of Cr3+ substitution in Mg-Zn ferrite, with a chemical formula Mg0.5Zn0.5CrxFe2-xO4 (x=0.0-1.0), synthesized by a sol-gel auto-combustion reaction is presented in this paper. The resultant powders were investigated by various techniques, including X-ray diffractometry (XRD), transmission electron microscopy (TEM), infrared spectroscopy (IR), vibrating sample magnetometry (VSM), and DC resistivity. The XRD pattern revealed that the cubic spinel structure is maintained for the all the compositions. The particle sizes measured from XRD and TEM are in good agreement with each other. The cation distribution suggests that Mg2+, Cr3+ and Fe3+ have strong preference towards octahedral B-site. The theoretical lattice constant and experimental lattice constant match each other very well. The IR analysis supports the presently accepted cation distribution. The saturation magnetization decreases linearly with increasing Cr3+ content. Curie temperatures are obtained by the Laoria and AC susceptibility techniques. The dc resistivity has been investigated as a function of temperature and composition.