Solid-state impedance spectroscopy (SS-IS) was used to investigate the influence of structural modifications resulting from the addition of Nb
2
O
5
on the dielectric properties and relaxation ...processes in the quaternary mixed glass former (MGF) system 35Na
2
O-10V
2
O
5
-(55−
x
)P
2
O
5
−
x
Nb
2
O
5
(
x
= 0–40, mol%). The dielectric parameters, including the dielectric strength and dielectric loss, are determined from the frequency and temperature-dependent complex permittivity data, revealing a significant dependence on the Nb
2
O
5
content. The transition from a predominantly phosphate glass network (
x
< 10, region I) to a mixed niobate-phosphate glass network (10 ≤
x
≤ 20, region II) leads to an increase in the dielectric parameters, which correlates with the observed trend in the direct-current (DC) conductivity. In the predominantly niobate network (
x
≥ 25, region III), the highly polarizable nature of Nb
5+
ions leads to a further increase in the dielectric permittivity and dielectric strength. This is particularly evident in Nb-40 glass-ceramic, which contains Na
13
Nb
35
O
94
crystalline phase with a tungsten bronze structure and exhibits the highest dielectric permittivity of 61.81 and the lowest loss factor of 0.032 at 303 K and 10 kHz. The relaxation studies, analyzed through modulus formalism and complex impedance data, show that DC conductivity and relaxation processes are governed by the same mechanism, attributed to ionic conductivity. In contrast to glasses with a single peak in frequency dependence of imaginary part of electrical modulus,
M
″(
ω
), Nb-40 glass-ceramic exhibits two distinct contributions with similar relaxation times. The high-frequency peak indicates bulk ionic conductivity, while the additional low-frequency peak is associated with the grain boundary effect, confirmed by the electrical equivalent circuit (EEC) modelling. The scaling characteristics of permittivity and conductivity spectra, along with the electrical modulus, validate time-temperature superposition and demonstrate a strong correlation with composition and modification of the glass structure upon Nb
2
O
5
incorporation.
Five charge transfer complexes of electron donor N,N,N′,N′-tetramethyl-p-phenylenediamine (TMPD or Wurster’s blue) with quinoid electron acceptors tetrafluoro- (F4Q), tetrachloro- (Cl4Q), ...tetrabromoquinone (Br4Q), 7,7,8,8-tetracyanoquinodimethane (TCNQ), and 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ) were prepared and studied by X-ray crystallography, impedance spectroscopy, and DFT computations. Mixed donor–acceptor π-stacks were observed in all compounds; in TMPD·F4TCNQ, the moieties formed 2D stacked arrays. All moieties had a partial radical character due to charge transfer. The presence of two-electron multicenter bonding (pancake bonding) was confirmed by quantum chemical computation. In TMPD·F4Q, alternating longer and shorter interplanar distances were consistent with formation of pancake-bonded dimers; in complexes of TMPD with Cl4Q, Br4Q, and TCNQ, the stacks were equidistant implying existence of pancake-bonded polymers.
The aim of this study is to investigate the influence of different glass fibers made of commercial silicate, borosilicate, and laboratory-made iron–phosphate compositions, on the preparation of ...polylactic acid (PLA) composites and their structural and physical properties. The thermal, structural, and electrical properties of prepared PLA–glass fiber composites were studied using differential scanning calorimetry, X-ray diffraction, microscopy, and impedance spectroscopy. The structural as well as morphological, thermal, and electrical properties of all PLA–glass composites were found to be very similar and independent of the composition and aspect ratio of glass fibers. All types of glass fibers improve mechanical properties, increase thermal stability, and decrease the electrical conductivity of PLA, thereby producing mechanical strong electrically insulating composite material with potential in various applications.
The present study investigates the relationship between the local structure, photocatalytic ability, and cathode performances in sodium-ion batteries (SIBs) and lithium-ion batteries (LIBs) using ...Ni-substituted goethite nanoparticles (NixFe1−xOOH NPs) with a range of ‘x’ values from 0 to 0.5. The structural characterization was performed applying various techniques, including X-ray diffractometry (XRD); thermogravimetry differential thermal analysis (TG-DTA); Fourier transform infrared spectroscopy (FT-IR); X-ray absorption spectroscopy (XANES/EXAFS), both measured at room temperature (RT); 57Fe Mössbauer spectroscopy recorded at RT and low temperatures (LT) from 20 K to 300 K; Brunauer–Emmett–Teller surface area measurement (BET), and diffuse reflectance spectroscopy (DRS). In addition, the electrical properties of NixFe1−xOOH NPs were evaluated by solid-state impedance spectroscopy (SS-IS). XRD showed the presence of goethite as the only crystalline phase in prepared samples with x ≤ 0.20, and goethite and α-Ni(OH)2 in the samples with x > 0.20. The sample with x = 0.10 (Ni10) showed the highest photo-Fenton ability with a first-order rate constant value (k) of 15.8 × 10−3 min−1. The 57Fe Mössbauer spectrum of Ni0, measured at RT, displayed a sextet corresponding to goethite, with an isomer shift (δ) of 0.36 mm s−1 and a hyperfine magnetic distribution (Bhf) of 32.95 T. Moreover, the DC conductivity decreased from 5.52 × 10−10 to 5.30 × 10−12 (Ω cm)–1 with ‘x’ increasing from 0.10 to 0.50. Ni20 showed the highest initial discharge capacity of 223 mAh g−1, attributed to its largest specific surface area of 174.0 m2 g−1. In conclusion, NixFe1−xOOH NPs can be effectively utilized as visible-light-activated catalysts and active cathode materials in secondary batteries.
This study aimed to synthesize molybdenum complexes coordinated with an aroyl hydrazone-type ligand (H
L), which was generated through the condensation of 2-hydroxy-5-nitrobenzaldehyde with ...benzhydrazide. The synthesis yielded two types of mononuclear complexes, specifically MoO
(L)(MeOH) and MoO
(L)(H
O), as well as a bipyridine-bridged dinuclear complex, (MoO
(L))
(4,4'-bpy). Those entities were thoroughly characterized using a suite of analytical techniques, including attenuated total reflectance infrared spectroscopy (IR-ATR), elemental analysis (EA), thermogravimetric analysis (TGA), and single-crystal X-ray diffraction (SCXRD). Additionally, solid-state impedance spectroscopy (SS-IS) was employed to investigate the electrical properties of these complexes. The mononuclear complexes were tested as catalysts in the epoxidation of cyclooctene and the oxidation of linalool. Among these, the water-coordinated mononuclear complex, MoO
(L)(H
O), demonstrated superior electrical and catalytic properties. A novel contribution of this research lies in establishing a correlation between the electrical properties, structural features, and the catalytic efficiency of the complexes, marking this work as one of the pioneering studies in this area for molybdenum coordination complexes, to the best of our knowledge.
Na-V-P-Nb-based materials have gained substantial recognition as cathode materials in high-rate sodium-ion batteries due to their unique properties and compositions, comprising both alkali and ...transition metal ions, which allow them to exhibit a mixed ionic–polaronic conduction mechanism. In this study, the impact of introducing two transition metal oxides, V2O5 and Nb2O5, on the thermal, (micro)structural, and electrical properties of the 35Na2O-25V2O5-(40 − x)P2O5 − xNb2O5 system is examined. The starting glass shows the highest values of DC conductivity, σDC, reaching 1.45 × 10−8 Ω−1 cm−1 at 303 K, along with a glass transition temperature, Tg, of 371 °C. The incorporation of Nb2O5 influences both σDC and Tg, resulting in non-linear trends, with the lowest values observed for the glass with x = 20 mol%. Electron paramagnetic resonance measurements and vibrational spectroscopy results suggest that the observed non-monotonic trend in σDC arises from a diminishing contribution of polaronic conductivity due to the decrease in the relative number of V4+ ions and the introduction of Nb2O5, which disrupts the predominantly mixed vanadate–phosphate network within the starting glasses, consequently impeding polaronic transport. The mechanism of electrical transport is investigated using the model-free Summerfield scaling procedure, revealing the presence of mixed ionic–polaronic conductivity in glasses where x < 10 mol%, whereas for x ≥ 10 mol%, the ionic conductivity mechanism becomes prominent. To assess the impact of the V2O5 content on the electrical transport mechanism, a comparative analysis of two analogue series with varying V2O5 content (10 and 25 mol%) is conducted to evaluate the extent of its polaronic contribution.
The influence of A-site cation doping, crystal structure and structural defects (oxygen nonstoichiometry) on the electrical conductivity of Sr-doped CaMnO3 (CSMO) and BaMnO3 (BSMO) was investigated. ...CSMO and BSMO were prepared by citrate-nitrate autocombustion and coprecipitation synthesis, pressed into pellets and sintered. Since the oxygen nonstoichiometry in CSMO was uniform, the increase in electrical conductivity was primarily caused by the increase in Sr content. On the other hand, the oxygen nonstoichiometry in BSMO was more pronounced and it decreased with Sr-doping. Therefore, the highest conductivities were obtained for the undoped BaMnO3 samples. The electrical conductivities of CSMO were similar to those of widely investigated rare-earth manganites and more than 104 times higher than those of BSMO. Therefore, CSMO has the potential to be a low-cost cathode material in solid oxide fuel cells.
•Both autocombustion and coprecipitation are suitable for CSMO and BSMO preparation•Autocombustion synthesis yielded materials of higher electrical conductivity•CSMO possess electron conductivity comparable to the LSMO•BSMO crystal structure is without distortions, resulting in low conductivity•Oxygen vacancies have the main role in the conductivity of BSMO
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•The concept of dual-function photovoltaic humidity sensors was first introduced.•CdSe semiconductor was implemented in cellulose microfibrils to form composite films.•To increase the ...conductivity of hybrid films CdSe filler size was brought to QD.•Quantum confinement phenomena proved viable for swelling-type humidity sensors.•A functional device comprising QD-cellulose PV absorbing-sensing film was assembled.
A great demand exists for the customisation and downsizing of gas sensors. Materials of interest commonly utilise some sort of charge transport phenomena to allow a sensing response, f.e. increase or decrease of the electric signal. Here we implemented sensing principles into solar cells (SC) and presented a novel concept of two-in-one SC and humidity sensor. Potentially, this could also allow the adjustment of SC performance according to humidity conditions. To better display the application potential, we modified solely the SC photoactive layer, which was prepared by infusion of CdSe quantum dots (QDs) into cellulose microfibrils, following a newly compiled synthetic route. When semiconductive fillers are implemented in composite materials, the sensing response usually consists only of the swelling of composite material, but with successful implementation, we have promoted more complex mechanisms due to multiple contributions. All of the segments were stabilised sufficiently to prepare devices and characterised in detail. We showed it is possible to boost and tailor the sensing performance of photoactive semiconducting materials based on swelling sensors by implementing the quantum confinement phenomena. In conclusion, the novel QD-microfibrils within a thin-film SC proved viable for a dual-functioning photovoltaic swelling-type semiconductor-organic hybrid gas sensor.
Molybdenum coordination complexes are widely applied due to their biological and pharmacological potential, as well as their performance in different catalytic processes. Parent dioxidomolybdenum ...Schiff base complexes were prepared via the reaction of MoO
(acac)
with a hydrazone Schiff-base tetradentate ligand. A new hydrazone-Schiff base (H
L
) and its corresponding mononuclear and polynuclear dioxidomolybdenum(VI) complex were synthesized and characterized by spectroscopic methods and elemental analyses, and their thermal behavior was investigated by thermogravimetry. The crystal and molecular structures of H
L
ligands and the complexes MoO
(L
)(H
O), MoO
(L
)(H
O), MoO
(L
)(MeOH)∙MeOH, MoO
(L
)(EtOH)∙EtOH, MoO
(L
)(2-PrOH)∙2-PrOH, and MoO
(L
)
were determined by single-crystal X-ray diffraction. Using the in situ impedance spectroscopy method (IS), the structural transformations of chosen complexes were followed, and their electrical properties were examined in a wide range of temperatures and frequencies.
This work provides new insights into the nature of the polaronic transport in xV2O5–(100−x)P2O5, 41 ≤ x ≤ 89 mol% glasses from analysis of their conductivity over a wide range of frequencies and ...temperatures, and correlation of the electrical parameters to the structural models of these materials. The results show that the linear increase in direct current (DC) conductivity with the increase in V2O5 could be related to the formation of a vanadate subnetwork, which is characterized by a length distribution of V–O bonds and variations in linkages between different vanadate units. Such a structurally complex network offers multiple conduction pathways which are favorable for polaron hopping. The Summerfield scaling of conductivity spectra reveals a temperature‐invariant mechanism of polaron transport for all glasses and the same local structural environment of polarons at higher V2O5 contents due to the same ratio of vanadate units present in the network. Also, this study highlights the similarities and differences in the nature of the polaronic transport of vanadate–phosphate glasses and other polaronically conducting phosphate glasses containing WO3, MoO3, and Fe2O3, and pins down a pivotal role of the glass structure in electrical processes in these materials.
