Room Temperature Electrical Conductivity Research Articles

Fabrication of highly conducting undoped ZnO ceramics by flash sintering

Highly conducting undoped ZnO ceramics were fabricated by flash sintering using commercial pure ZnO powder as a model system. The flash-sintered samples with diameters of 15 mm and heights of 2 mm exhibited relative densities ranging from 93.6% to 97.1% and room-temperature electrical conductivities between 205 and 590 S/cm. X-ray diffraction and Raman spectra indicated a high concentration of oxygen vacancies and zinc interstitials in the flash-sintered samples, increasing the carrier concentration. Detailed microstructural analyses show that clean grain boundaries and the morphology and distribution of impurities in flash-sintered samples are favorable for improving carrier mobility. Additionally, flash sintering has the advantage of reducing conditions, which reduces acceptor defects at ZnO grain boundaries, lowers Schottky barriers, and increases carrier mobility. The results show that flash sintering can synergistically enhance the carrier concentration and mobility in ZnO ceramics, making it a promising technique for fabricating highly conducting ZnO ceramics.

Water-induced strong isotropic MXene-bridged graphene sheets for electrochemical energy storage.

Graphene and two-dimensional transition metal carbides and/or nitrides (MXenes) are important materials for making flexible energy storage devices because of their electrical and mechanical properties. It remains a challenge to assemble nanoplatelets of these materials at room temperature into in-plane isotropic, free-standing sheets. Using nanoconfined water-induced basal-plane alignment and covalent and π-π interplatelet bridging, we fabricated Ti3C2Tx MXene-bridged graphene sheets at room temperature with isotropic in-plane tensile strength of 1.87 gigapascals and moduli of 98.7 gigapascals. The in-plane room temperature electrical conductivity reached 1423 siemens per centimeter, and volumetric specific capacity reached 828 coulombs per cubic centimeter. This nanoconfined water-induced alignment likely provides an important approach for making other aligned macroscopic assemblies of two-dimensional nanoplatelets.

Phase composition and thermoelectric properties of Cu–Ag–Se films with different Ag content

In this study, a series of Cu–Ag–Se films were prepared on Si (100) substrate by magnetron sputtering. The phase composition, micro-structure and thermoelectric properties were studied. The results showed that the phase composition of deposited Cu–Ag–Se films varied from β-Cu2-xSe and a small amount of CuAgSe phase to majority β-Cu2-xSe and minority CuAgSe phase, minority β-Cu2-xSe and majority CuAgSe phase, CuAgSe and a small amount of β-Cu2-xSe phase, Ag2Se and a small amount of CuAgSe +β-Cu2-xSe phase as Ag content increased from 0.4 to 17.0, 20.8, 29.5, 41.4 at.%, respectively. In the deposited Cu–Ag–Se films, the carrier concentration first decreased and then increased and the mobility displayed an opposite trend with increasing CuAgSe content (decreasing β-Cu2-xSe content). The room temperature electrical conductivity and absolute value of room temperature Seebeck coefficient gradually increased with increasing CuAgSe content for the deposited Cu–Ag–Se films. The power factor of 29.5 at.% Ag samples (CuAgSe phase films) at whole measured temperature was the highest in all samples due to high Seebeck coefficient and high electrical conductivity, resulting in the highest PF value of 2.05 mW m−1 K−2 at 62 °C. However, due to its high thermal conductivity of 10.93 W m−1K−1, the room temperature ZT value of this sample was only 0.05 even if it possessed a higher PF value. Ag2Se phase films possessed the lowest PF value due to their lower Seebeck coefficient even if they possessed higher electrical conductivity.

Formation, Enhanced Crystallization, Optical Absorption and Electrical Conduction in Copper Indium Selenide Thin Films Prepared via Pulse Laser Welding Technique

AbstractIn this study, thin films of CuInSe2 (CIS) are expeditiously fabricated within 1 s utilizing the pulsed laser welding (PLW) technique. Preceding the PLW process, thin films of InSe (500 nm) are coated with Cu nanosheets of 60 and 120 nm thicknesses using vacuum coating systems. The optimal PLW parameters leading to the formation of CIS films include a pulse width of 1.0 ms, a spot diameter of 2.0 mm, and a repetition frequency of 10 Hz. The resulting CIS films exhibited a well‐crystalline cubic structure with lattice parameters of 5.265 Å. Surface morphology analyses revealed the preferential formation of porous films with varying stoichiometry, a characteristic that can be manipulated by adjusting laser welding parameters. The energy band gap and room temperature electrical conductivity display values of 1.80 eV and 2.06 × 10−5 (Ωcm)−1, respectively. Cu‐rich samples exhibit a wider energy band gap of 1.94 eV and lower electrical conductivity values of 4.78 × 10−7 (Ωcm)−1. The CIS film demonstrates n‐type conductivity attributed to the formation of donor levels centered at 0.24 and 0.10 eV. This study presents an ultrafast method for fabricating CIS films with physical properties compatible with those produced using traditional methods.

Enhancing the Properties of Yttria-Stabilized Zirconia Composites with Zeolitic Imidazolate Framework-Derived Nanocarbons.

Ceramic matrix composites (CMCs) reinforced with nanocarbon have attracted significant interest due to their potential to enhance mechanical, thermal, and electrical properties. Although the investigation of carbon-based materials such as graphene and carbon nanotubes as additives for advanced ceramics has been widespread, the utilization of metal-organic framework (MOF)-derived nanocarbons in CMCs remains largely unexplored. We extended our previous proof-of-concept investigations by demonstrating the effectiveness of a different type of MOF-derived carbon as a reinforcing phase in an alternative ceramic matrix. We employed spark plasma sintering (SPS) to consolidate yttria-stabilized zirconia (YSZ) and zeolitic imidazolate framework (ZIF-67) powder blends at 1300 °C and a uniaxial pressure of 50 MPa. YSZ serves as the ceramic matrix, whereas ZIF-67 serves as the nanocarbon source. The composite exhibits a highly significant improvement in fracture toughness with an increase of up to 13% compared to that of the YSZ monolith. The formation of ZIF-derived nanocarbon interlayers is responsible for the observed enhancement in ductility, which can be attributed to their ability to facilitate energy dissipation during crack propagation and inhibit grain growth. Furthermore, the room-temperature electrical conductivity of the sintered samples demonstrates a substantial improvement, primarily due to the in situ formation of nanocarbon-based fillers, reaching an impressive 27 S/m with 10 wt % ZIF-67 content. Based on the results, it can be inferred that the incorporation of in situ MOF-derived nanocarbons into CMCs leads to a substantial improvement in both the mechanical and electrical properties.

Influence of Si content on thermoelectric properties of Mg2(Sn,Si) films by sputtering

Mg2(Sn,Si) films with different Si content were prepared by magnetron sputtering. The phase composition, surface and cross-sectional morphology, chemical composition and element distribution, carrier concentration, carrier mobility, electrical conductivity, Seebeck coefficient and power factor of the deposited Mg–Sn–Si films were studied. The results show that the deposited films are composed of Mg2(Sn,Si) solid solution phase and a small amount of metal Mg phase. The room temperature carrier concentration decreases and mobility increases with increasing Si content in deposited Mg–Sn–Si films, respectively. The room temperature electrical conductivity and Seebeck coefficient decreases and increases with increasing Si content, respectively. The deposited Mg2(Sn,Si) films with moderate Si content possess the maximum power factor value of 2.76 mW m−1 K−2 at 303 °C and its room temperature figure of merit reaches the highest value of 0.44. The thermal conductivity decreases with increasing Si content, indicating that the lattice distortion caused by Si doping can reduce the thermal conductivity of the deposited films.

Effects of Pb nanosheets substrates on the optical and electrical properties CrSe thin films

Herein the effects of lead nanosheets substrates on the optical and electrical properties of chromium selenide thin films were studied. Chromium selenide thin films were grown by vacuum thermal evaporation technique onto glass and 100 nm thick lead nanosheets substrates. The effects of Pb nanosheets on the structural, morphological, compositional, optical and electrical properties was explored. While films grown onto glass substrates showed compositional stoichiometry forming CrSe2 phase those coated onto Pb substrates preferred the growth CrSe phase. Both films were of amorphous structure and exhibited direct and indirect allowed optical transitions. Pb nanosheets enhanced the optical absorption of chromium selenide in the visible and ultraviolet ranges of light. Formation of films onto Pb nanosheets resulted in band gaps and band tails narrowing and decreased the room temperature electrical conductivity () as well. Deep analyses of the variations in the range of 25–340 K showed that the electronic transport is dominated by the thermal excitation and variable range hopping of charge carriers. It was observed that Pb nanosheets increased the average hopping energy and hopping range, decreased the density of localized states near the Fermi level and increased the degree of state disorder. The features of glass/CrSe2 and Pb/CrSe films are promising for using then in optoelectronic technology.

Probing the Electro-Chemical and Thermal Properties of Polyaniline/MWCNT Nanocomposites

The tremendous interest for robust, clean energy storage devices to comprehend the growing needs of modern gadgets has led to exploration of materials having unprecedented electrochemical and interfacial properties. Here, the present study deals with the synergistic effects of multi walled carbon nanotubes and polyaniline nanocomposites on the electro-chemical and thermal properties for wide-range of applications. The microstructural, structural, and optical characterizations have been evaluated through scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and UV-Vis spectrophotometry. The thermal stability of the product was also studied through thermal gravimetric analysis (TGA) and the room temperature electrical conductivity was also measured. An exceptional enhancement in thermal stability and conductivity has been observed apparently due to interfacial properties of polyaniline (PANI) and multiwalled carbon nanotubes (MWCNTs). Further, in present study we are going to report a comparative analysis of thermal and electrical properties of PANI/MWCNT nanocomposites with different loadings of MWCNTs. The room temperature conductivity as calculated for 1%, 2%, 4% and 8% MWCNT loading is around 2.019, 3.075, 4.48, 8.73 S/cm respectively. The mechanism for thermal and electrical enhancements in PANI-coated MWCNT nanocomposites is also expounded.

Synthesis and characterization of ternary layered i‐MAX (Mo2/3Y1/3)2AlC ceramics fabricated by spark plasma sintering

AbstractIn this paper, the i‐MAX phase (Mo2/3Y1/3)2AlC ceramic with high purity of 98.29 wt% (1.13 wt% Y2O3 and 0.58 wt% Mo2C) and high relative density of 98.59% was successfully synthesized by spark plasma sintering (SPS) at 1500°C with the molar ratio of n(Mo):n(Y):n(Al):n(C) = 4:2:3.3:2.7. The positions of C atoms in the crystal of (Mo2/3Y1/3)2AlC were determined. Microstructure and physical and mechanical properties of (Mo2/3Y1/3)2AlC ceramic were systematically investigated. It was found that the obtained (Mo2/3Y1/3)2AlC ceramic had an average grain size of 32.1 ± 3.1 μm in length and 14.2 ± 1.7 μm in width. In terms of physical properties, the measured thermal expansion coefficient (TEC) of (Mo2/3Y1/3)2AlC was 8.99 × 10−6 K−1, and the thermal capacity and thermal conductivity at room temperature were 0.43 J·g−1·K−1 and 13.75 W·m−1·K−1, respectively. The room temperature electrical conductivity of (Mo2/3Y1/3)2AlC ceramic was measured to be 1.25 × 106 Ω−1·m−1. In terms of mechanical properties, Vickers hardness under 10 N load was measured as 10.54 ± 0.29 GPa, while flexural strength, fracture toughness, and compressive strength were determined as 260.08 ± 14.18 MPa, 4.51 ± 0.70 MPa·m1/2, and 855 ± 62 MPa, respectively, indicating the promising structural applications.

Boosting the Ceramics with In Situ MOF-Derived Nanocarbons

Metal–organic framework (MOF)-derived nanocarbons have emerged as promising materials for energy and environmental applications owing to their high surface area, structural and chemical tunability, and hierarchical porosity. Although various carbon-based materials such as graphene and carbon nanotubes have been extensively used as secondary sintering additives to develop advanced ceramics with improved mechanical, thermal, and electrical properties, the potential of MOF-derived nanocarbon-based materials has not been explored. Here, we report the first use of MOF-derived nanocarbons as a reinforcement phase in ceramic composites. To this end, Al2O3 and zeolitic imidazolate framework (ZIF-8) are used as the ceramic matrix and nanocarbon source, respectively. The ceramic composites are produced by densifying Al2O3 and ZIF-8 powder mixtures using spark plasma sintering (SPS) at 1550 °C and uniaxial pressure of 50 MPa. The fracture toughness of the composite increases up to 67% in comparison to an alumina monolith as ZIF-derived nanocarbons form interlayers to assist the dissipation of energy during the crack propagation and inhibit grain growth. The room-temperature electrical conductivity of the sintered samples drastically increases with the in situ formed nanocarbon-based fillers, reaching as high as 1410 S/m for 10 wt % ZIF-8 content. These results constitute an excellent initial step toward boosting the mechanical and electrical properties of ceramic matrix composites with in situ MOF-derived nanocarbons.

Relationship Between Mass Loss and Fruit Quality of Sweet Orange at Two Different Storage Conditions.

Mass loss from fresh produce is linked to areduction of its aesthetic value. However, arelationship between mass loss and biochemical quality parameters at different storage conditions has not been widely explored. Therefore, the current study is designed with the objectives to determine the behavior of fruit quality parameters and arelationship between fruit mass loss and fruit quality at two different storage conditions. Sweet orange fruit stored in azero energy cool chamber (ZECC) had greater shelf-life of more than 15 days, fruit size (62.40 mm) and peel (35.15%) and lower mass loss (4.94%), juice (32.19%) and electrical conductivity (EC) (2.06 S/m) as compared to ambient conditions in laboratory during 25 days of storage. In ZECC, only EC was positively correlated (r = 0.57) with mass loss, whereas at room temperature EC (r = 0.76), total soluble solids (TSS) (r = 0.60) and fruit internal temperature (r = 0.64) were positively and peel (%) (r = -0.52) and fruit diameter (r = -0.49) were negatively correlated with mass loss. Correlation of combined storage conditions revealed that EC (r = 0.47) and TSS (r = 0.50) were positively and peel (%) (r = -0.77) and fruit diameter (r = -0.55) were negatively correlated with mass loss (%). The principal component analysis (PCA) revealed that the scores of room temperature were strongly associated with TSS, pH, EC, mass loss (%), juice (%) and internal temperature (°C), whereas scores ofZECCwere strongly associated with pulp (%), ascorbic acid (mg 100 mL-1), acidity (%), and fruit diameter (mm).

One-step post-treatment boosts thermoelectric properties of PEDOT:PSS flexible thin films

• High power factor of 64.4 µW m −1 K −2 is achieved in PEDOT:PSS films at 360 K. • 80 vol.% DMAC solution boosts the electrical conductivity from 5 to 964 S cm −1 . • 0.5 mol L −1 LAA improves the Seebeck coefficient from 18.7 to 25 µV K −1 . • Mott variable range hopping model explains the thermoelectric transport behavior. Developing high-performance poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) significantly widens the practical applications of flexible organic thermoelectric devices, while the water-based co-solvent dopants and/or post-treatments are still rarely studied so far. Here, we develop a one-step post-treatment to improve the power factor of PEDOT:PSS films by using a water-based solution, which is composed of co-solvent (polar solvent dimethylacetamide (DMAC) and deionized water) and organic reducing agent L-ascorbic acid (LAA). The 80 vol.% DMAC solution significantly boosts the room-temperature electrical conductivity of the films from 5 to 964 S cm −1 , while the Seebeck coefficient can be further enhanced from 18.7 to 25 µV K −1 by treating with 0.5 mol L −1 LAA, contributing to a significantly improved power factor of 55.3 µW m −1 K −2 . The boosted electrical conductivity is ascribed to the separated PEDOT and PSS phases triggered by the high dielectric constant and polarity of DMAC; while the improved Seebeck coefficient is attributed to the reduced oxidation degree of PEDOT from the reducing agent LAA, both confirmed by the comprehensive structural and morphological characterizations. Furthermore, a maximum power factor of 64.4 µW m −1 K −2 can be achieved at 360 K and the observed temperature-dependent electrical transport behavior can be well explained by the Mott variable range hopping model. Besides, a flexible thermoelectric device, assembled by the as-fabricated PEDOT:PSS films, exhibits a maximum output power of ∼23 nW at a temperature difference of 25 K, indicating the potential for applying to low-grade wearable electronics.

Continuous intercalation compound fibers of bromine wires and aligned CNTs for high-performance conductors

This work presents macroscopic fibers of aligned double-walled carbon nanotubes (DWCNTs) intercalated with long-range ordered bromine, with a stoichiometry close to C17Br. Tribromide ions lie inside interstitial sites between hexagonally-packed DWCNTs and extend parallel to their axis as ordered supramolecular “wires”. First-principles simulations confirm this structure and a transfer of 0.13 electrons per Br atom. The structure of nested bundles of CNTs with a homogeneous distribution of bromine species in the interstitial sites of the superlattice is directly imaged by cross-sectional HRTEM, showing full intercalation of highly dense and aligned fibers. The presence of Br2 and Br3– is confirmed by Raman spectroscopy, and their supramolecular organization is resolved by 2D wide-angle X-ray scattering. Intercalation increases room-temperature longitudinal electrical conductivity by a factor of 8.4. Through low-temperature transport measurements in the longitudinal and transverse directions, we show that the intercalate reduces the tunneling-dominated resistance associated with transport between adjacent CNTs, rather than exclusively acting as a dopant that increases conductance of individual CNTs. By preserving the separation between CNTs, the exceptional mechanical properties of the CNT fiber host are retained. The combined tensile strength above 2.46 GPa and conductivity of 10.68 MS/m makes intercalated CNT fibers attractive lightweight conductors with combined properties superior to metals and graphite intercalation compounds.

Structural, Optical, Magnetic and Electrical Properties of Sputtered ZnO and ZnO:Fe Thin Films: The Role of Deposition Power

Structural, optical, magnetic, and electrical properties of zinc oxide (henceforth, ZO) and iron doped zinc oxide (henceforth, ZOFe) films deposited by sputtering technique are described by means of Rutherford backscattering spectrometry, grazing incidence X-ray diffraction, scanning electron microscope (SEM), UV–Vis spectrometer, vibrating sample magnetometer, and room temperature electrical conductivity, respectively. GIXRD analysis revealed that the films were polycrystalline with a hexagonal phase, and all films had a preferred (002) c-axis orientation. The lattice parameters a and c of the wurtzite structure were calculated for all films. The a parameter remains almost the same (around 3 Å), while c parameter varies slightly with increasing Fe content from 5.18 to 5.31 Å throughout the co-deposition process. The optical gap for undoped and doped ZO was obtained from different numerical methods based on the experimental data and it was increased with the increment of the concentration of Fe dopant from 3.26 eV to 3.35 eV. The highest magnetization (4.26 × 10−4 emu/g) and lowest resistivity (4.6 × 107 Ω·cm) values of the ZO films were found to be at an Fe content of 5% at. %. An explanation for the dependence of the optical, magnetic, and electrical properties of the samples on the Fe concentrations is also given. The enhanced magnetic properties such as saturated magnetization and coercivity with optical properties reveal that Fe doped ZO thin films are suitable for magneto-optoelectronic (optoelectronic and spintronics) device applications.

RCoO3 {R=Pr, Nd and Sm} electrode-based for efficient solid-state symmetric supercapacitor

Tunable electrical conductivity and energy storage ability have been achieved by controllable rare earth substitution at the A-site in hydrothermally synthesized single perovskite oxides. Controlling the electrochemical performance of these electro-active materials has been attractive for futuristic energy storage devices. Crystallographic analysis confirmed a distorted orthorhombic Pnma structure for PrCoO3 (PCO), NdCoO3 (NCO) and SmCoO3 (SCO). The morphology of the materials showed significant changes in size, texture and porosity; with shape morphology varied from rectangular shaped crystallites in SCO and NCO to spherical shaped crystallites in PCO. The comparison of room temperature electrical conductivity shows good correlation with the structural features. A gradual decrease in the activation energies, obtained from the small polaron hopping (SPH) model, was observed as a function of the increasing ionic radii (Pr3+>Nd3+>Sm3+). The electrochemical properties are systematically investigated by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectra (EIS) analysis. The charge storage mechanism in PCO, NCO and SCO is clearly demonstrated to be a diffusion controlled process. An effective correlation is drawn between the electrical and electrochemical parameters and their inherent structural disorder. PCO based materials show superior electrochemistry with a specific capacitance of ∼557 F/g at 1 A/g and ∼88% capacity retention even after 10,000 charging and discharging cycles. Based on its superior 3-electrode performance, a solid-state symmetric supercapacitor (SSC–P) was fabricated using PCO-based electrodes. It shows an energy and power densities of ∼40 W-h/Kg and ∼5574 W/kg respectively retaining 81% stability even after 5000 operational cycles. Finally, our fabricated solid-state symmetric supercapacitor (SSC–P) illuminated a LED for 3 min after 1 min charging, which shows its applicative potential for optimal smart energy storage device applications.

CVD nanocrystalline multilayer graphene coated 3D-printed alumina lattices

3D printing technologies have expanded the possibilities of fabricating new composite materials with tailored properties, which depend on both the materials selected and the structural design at multiple length scales. Here, a catalyst-free CVD method has been used to produce hybrid materials based on 3D printed cellular α-Al2O3 substrates decorated by either nanocrystalline graphene or nanocrystalline graphitic films of tunable number of layers. Graphene-based coatings of variable thickness and crystallinity have been controlled by the alteration of the parameters of CVD processing, performed under CH4/H2 flux. Transmission electron microscopy has confirmed the effective growth of nanocrystalline graphene layers on the scaffolds due to the penetration of CVD gases into the open pores. The fully-connected and highly conductive 3D pathways have displayed a room temperature electrical conductivity in the range of 101–103 S m−1. Furthermore, the thermal conductivity has also increased by 50% for the specimen decorated with a 20 nm thick graphitic coating as compared to a bare 3D ceramic scaffold. The developed structures open up new possibilities for expanding the field of application of graphene/ceramic composites for conditions requiring dielectric substrates of various shapes coated with conductive films or graphene-based catalytic supports with good structural stability.

Oriented Thiophene‐Extended Benzotrithiophene Covalent Organic Framework Thin Films: Directional Electrical Conductivity (Adv. Funct. Mater. 47/2022)

Covalent Organic Frameworks In article number 2205949, Dana Dina Medina, Ralf Thomas Weitz, Timothy Clark and co-workers describe the synthesis of covalent organic frameworks (COFs) based on a thiophene-extended benzotrithiophene (BTT) building block. Oriented thin films of the BTT COFs show room-temperature in-plane electrical conductivity of up to 10−4 S m−1 and a trap-dominated charge transport via a hopping mechanism. Moreover, electrical conductivity of the COF films is directional with a strong preference for the in-plane over the out-of-plane direction.

Transforming an Insulating Metal–Organic Framework (MOF) into Semiconducting MOF/Gold Nanoparticle (AuNP) and MOF/Polymer/AuNP Composites to Gain Electrical Conductivity

Transforming permanently porous but electrically insulating metal–organic frameworks (MOFs) into electrically conducting materials is key to expanding their utility beyond traditional guest storage, separation, and delivery applications into the realms of modern electronics and energy technologies. To this end, herein, we have converted a highly porous but intrinsically insulating NU-1000 MOF into semiconducting NU-1000/gold nanoparticle (AuNP) and NU-1000/polydopamine/AuNP composites via MOF- and polymer-induced reduction of infiltrated Au3+ ions into metallic AuNPs. The NU-1000/AuNP and NU-1000/PDA/AuNP composites not only gained significant room temperature electrical conductivity (∼10–7 S/cm), which was ca. 104 times greater than any MOF/metal nanoparticle (MNP) composites exhibited thus far under the same conditions, i.e., without photoinduction and thermal induction, but also retained sizable porosity and surface areas (1527 and 715 m2/g, respectively), which were also larger than most intrinsically conducting 3D MOFs developed to date. The markedly higher conductivities of the NU-1000/AuNP and NU-1000/PDA/AuNP composites can be attributed to more efficient charge hopping or tunneling through well-dispersed AuNPs embedded inside the crystalline MOF matrix, which pristine NU-1000 lacked. Thus, this work presented an effective new strategy to transform porous but nonconducting MOFs into electrically conducting MOF/MNP composites with considerable porosity, which could be useful in future electronics, electrocatalysis, and energy storage devices.

Structure and Electrical Properties of Carbon-Rich Polymer Derived Silicon Carbonitride (SiCN)

This article reports on the structure and electronic properties of carbon-rich polysilazane polymer-derived silicon carbonitride (C/SiCN) corresponding to pyrolysis temperatures between 1100 and 1600 °C in an argon atmosphere. Raman spectroscopy, X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), Scanning Electron Microscopy (SEM) and Hall measurements were used to support the structural and electronic properties characterization of the prepared C/SiCN nanocomposites. A structural analysis using Raman spectroscopy showed the evolution of sp2 hybridized carbon phase that resulted from the growth in the lateral crystallite size (La), average continuous graphene length including tortuosity (Leq) and inter-defects distance (LD) with an increase in pyrolysis temperature. The prepared C/SiCN monoliths showed a record high room temperature (RT) electrical conductivity of 9.6 S/cm for the sample prepared at 1600 °C. The electronic properties of the nanocomposites determined using Hall measurement revealed an anomalous change in the predominant charge carriers from n-type in the samples pyrolyzed at 1100 °C to predominantly p-type in the samples prepared at 1400 and 1600 °C. According to this outcome, tailor-made carbon-rich SiCN polymer-derived ceramics could be developed to produce n-type and p-type semiconductors for development of the next generation of electronic systems for applications in extreme temperature environments.

Non-metal/metalloid modification of perovskite oxide enables lattice oxygen participation in accelerating oxygen evolution activity

Perovskite oxides, with structural and compositional flexibility, have been extensively used as electrocatalysts in alkaline solutions for the oxygen evolution reaction (OER) which is a key factor in determining the overall efficiency of metal-air batteries or hydrogen evolution from electrochemical water splitting. The cation-doping approach is widely used to generate novel perovskite oxides with boosted electrocatalytic activity, while non-metal and metalloid modifications have received far less attention. Herein, we show a simple non-metal/metalloid alteration method to make efficient OER electrocatalysts with low overpotential and good stability. The developed SrCo0.95M0.05O3−δ (M = P, S, and Si) catalysts exhibit greatly improved OER activity and stability in comparison to the pristine hexagonal SrCoO3−δ. SrCo0.95Si0.05O3−δ achieves the lowest OER overpotential of 0.41 V at 10 mA cmdisk−2 and the lowest Tafel slope of 63 mV dec−1, while SrCoO3−δ exhibits 0.46 V and 95 mV dec−1 under identical conditions. SrCo0.95Si0.05O3−δ further demonstrates improved stability when compared to SrCoO3−δ. The creation of a stable cubic perovskite structure with an increased amount of oxygen vacancy facilitates oxygen diffusivity, thus maximizing the lattice oxygen participation. Furthermore, the surface evolution and the enhanced room-temperature electrical conductivity jointly contribute to the improvement of the electrocatalytic OER activity of SrCo0.95M0.05O3−δ. Our present findings offer a simple and viable strategy for creating highly efficient perovskites for OER.