•Alluaudite-like glasses of various compositions have been synthesized.•Kinetics of glass transition and crystallization were investigated.•Crystallization led to nanomaterial with crystallites of ...alluaudite phase.•Electric conductivity increased from 10−16 - 10−9 to 10−12 - 10−7 S/cm.
In this decade, an interest in alluaudites as potential cathode materials for sodium batteries revived. However, only crystalline compounds have been studied so far. In this work, alluaudite-like glasses of nominal composition Na2M3(PO4)3 (where M3 = Fe3, VFe2, VFeMn) were successfully synthesized using standard melt-quenching technique. Temperatures of glass transition and crystallization were determined at various heating rates in DTA experiments and the activation energies of these processes were calculated using Kissinger’s model. XRD studies confirmed that heat-treatment of the glasses led to nanocrystalline materials with alluaudite structure. Glasses exhibited modest, predominant electronic conductivity. After their thermal nanocrystallization, the conductivity increased approximately 2–4 orders of magnitude and the activation energy decreased noticeably. The ionic counterpart of the conductivity became much more pronounced. These preliminary electrical results show that there is a room for further optimization, which may result in highly-conducting nanocrystalline alluaudite-like cathode materials for sodium-ion batteries.
In this work, two series of glasses, i.e. (68-x) CuO – xV2O5 – 32TeO2 (x = 0–68 mol%, Te32 series) and (35-x) CuO – xV2O5 – 65TeO2 (x = 0–35 mol%, Te65 series), were synthesized by the melt-quenching ...method and subjected to physical, thermal and electrical characterization. Their vitreous nature was confirmed by X-Ray diffraction and differential scanning calorimetry, while their structural units were determined by Raman spectroscopy. CuO substitution by V2O5 led to a decrease in density and glass-transition temperature, together with a conductivity increase. Conduction mechanism was interpreted as mainly due to small polaron hopping from the lower (V4+) to the higher (V5+) vanadium valence states.
Te32 glasses, possessing the highest electronic conductivities (ranging from 2 E−4 to 5 E−7 Ω−1 cm−1), were investigated by the Electron Paramagnetic Resonance technique, in order to more deeply analyze their structure-conductivity correlation. Particularly, the observed signals were determined to consist in a superposition of a first line due to paramagnetic Cu2+ ions and a second line due to exchange-coupled CuO clusters. Differences in the spectra were determined between samples with higher (i.e. 20-30 mol%) Cu2+ concentrations and samples with lower Cu2+ concentrations, suggesting they are located in different local environments. Finally, it was found that the Cu2+ ions are not involved in the process of electron transfer.
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•Electronic conductive glass systems containing two TMOs were investigated.•Two series of CuO–V2O5–TeO2 glasses with 32 and 65 mol% of TeO2 were compared.•Conduction mechanism mainly due to small polaron hopping between vanadium ions.•Cu2+ ions are not involved in the conduction mechanism.•The 32 mol% TeO2 series was deepened by EPR since possessing higher conductivity.
Six NASICON‐type phosphate glasses with a wide variety of compositions (Na3M2(PO4)2F3, where M2 = V2, Ti2, Fe2, TiV, FeV, and FeTi) were synthesized using melt‐quenching and double‐crucible ...techniques. Their glass transition and crystallization temperatures were determined from differential thermal analysis experiments. The electrical properties were studied with impedance spectroscopy. We found that depending on temperature and composition the studied materials exhibit predominant electronic, ionic, or mixed conduction. This observation is interesting from both fundamental and application point of view (eg, in all‐solid‐state batteries). In general, the conductivity of glasses ranged from 3·10−13 to 10−10 S/cm at room temperature, with activation energies varying from 0.65 to 0.73 eV. After crystallization at 600°C, the values of conductivity noticeably increased. For nanocrystalline materials, they were between 10−11 and 10−7 S/cm (at room temperature). The values of the activation energy spread from 0.53 to 0.70 eV. Most of the glasses exhibited predominant electronic conductivity. After nanocrystallization, the ionic transference number considerably increased in almost all samples. This study proves that thermal nanocrystallization can be used to synthesize nanocrystalline NASICON‐like cathode materials for Na‐ion batteries from their glassy analogs. We believe that this method can be adopted also to other interesting sodium compounds in the future.
A new nanocomposite material was prepared by high pressure processing of starting glass of nominal composition NaFePO4. Thermal, structural, electrical and dielectric properties of the prepared ...samples were studied by differential thermal analysis (DTA), X-ray diffraction (XRD) and broadband dielectric spectroscopy (BDS). It was demonstrated that high-pressure-high-temperature treatment (HPHT) led to an increase in the electrical conductivity of the initial glasses by two orders of magnitude. It was also shown that the observed effect was stronger than for the lithium analogue of this material studied by us earlier. The observed enhancement of conductivity was explained by Mott's theory of electron hopping, which is more frequent in samples after pressure treatment. The final composite consisted of nanocrystalline NASICON (sodium (Na) Super Ionic CONductor) and alluaudite phases, which are electrochemically active in potential cathode materials for Na batteries. Average dimensions of crystallites estimated from XRD studies were between 40 and 90 nm, depending on the phase. Some new aspects of local dielectric relaxations in studied materials were also discussed. It was shown that a combination of high pressures and BDS method is a powerful method to study relaxation processes and molecular movements in solids. It was also pointed out that high-pressure cathode materials may exhibit higher volumetric capacities compared with commercially used cathodes with carbon additions.
A novel, sandwich‐layered Ti/TiO2/Ti/fluorine‐doped tin oxide (FTO) architecture is reported. The Ti layers play a critical role in the formation of long pear‐necklace chains made of interconnected ...TiO2 nanoparticles. The chains interpenetrate a network structure on FTO glass substrates under alkaline hydrothermal‐processing conditions. A significant enhancement in the photocurrent density of dye‐sensitized solar cells employing non‐volatile polymer‐based electrolytes is obtained.
Electrodeposition of a material onto a conducting substrate with strong adhesion and exceptional uniformity through the use of platinum nanoparticles as the seed layer is reported. The use of ...platinum nanoparticles also creates an optimum voltage range to selectively electroplate various metals on substrate into areas seeded with the nanoparticles.
Solar cells are getting familiar to science teachers as teaching materials in a new course of study which started in 2011. Among many types of solar cells, researchers are paying attention to the ...dye-sensitized solar cells experiment because students can produce by themselves. After the Great East Japan Earthquake, we cannot teach the experiment classes to produce the dye-sensitized solar cells because we cannot obtain the electrically conductive glasses. Therefore, we developed a production method of the electrically conductive glasses which high school students can perform, and practiced the dye-sensitized solar cells experiment with them. We report on the results.
•The first comprehensive study of conductive glass as transparent microwave absorber.•Tailoring impedance matching and electromagnetic attenuation through Ag+ conduction.•Both high optical ...transmission and outstanding microwave absorption were achieved.
The rapid development of the electronics industry has sparked widespread interest in transparent microwave-absorbing materials. Herein, iodide-based transparent conductive glass was used as a candidate material for transparent microwave absorption. AgI-AgPO3-WO3 glasses with varying AgI content were synthesized employing a quench-melting method. Their structures, optical and electrical properties, microwave absorption performance, and radar cross section (RCS) reduction were thoroughly investigated. The 45AgI-45AgPO3-10WO3 sample exhibited satisfactory microwave absorption, achieving a minimum reflection loss (RLmin) of − 47.18 dB, effective absorption bandwidth (EAB) of 1.97 GHz, and RCS reduction of 31.46 dB m2 in the X band. This was attributed to the synergistic effects of dielectric and magnetic losses, and impedance matching and electromagnetic attenuation. It also manifested acceptable performance in the Ku band (RLmin = − 14.58 dB, EAB = 1.38 GHz, and RCS reduction = 13.37 dB m2), which was primarily attributed to dielectric loss and electromagnetic attenuation. The conductive glass exhibited an optical transmittance of ∼80 % in the range of 500–2000 nm. In summary, this study highlights the potential use of transparent conductive glasses as transparent microwave-absorbing media for electromagnetic interference shielding applications in optical windows and domes, and stealth applications in high-performance optical cameras and optical detection device systems.
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