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Lead-free Cs3Cu2I5 metal halides have garnered significant attention recently due to their non-toxic properties and deep-blue emission. However, their relatively low photoluminescence quantum efficiency and poor stability have limited their applications. In this work, sodium iodide (NaI) is used to facilitate the synthesis of Cs3Cu2I5 nanocrystals (NCs), demonstrating improved photoluminescence intensity, photoluminescence quantum yield, and stability. Systematic optoelectronic characterizations confirm that Na+ is successfully incorporated into the Cs3Cu2I5 lattice without altering its crystal structure. The improved Photoluminescence Quantum Yield (PLQY) and stability are attributed to the strengthened chemical bonding, which effectively suppresses vacancy defects in the lattice. Additionally, light-emitting diodes (LEDs) based on 10% NaI-doped Cs3Cu2I5 NCs were assembled, emitting vibrant blue light with a maximum radiant intensity of 82 lux and Commission Internationale de l'Eclairage (CIE) chromaticity coordinates of (0.15, 0.1). This work opens new possibilities for commercial lighting display applications. [ABSTRACT FROM AUTHOR]

This study investigates the enhancement of Li2TiSiO5 anode material through Na doping via two routes: melt-quenching (route I) and subsequent heat treatment (route II). A 5 % Na-doped ceramic sample significantly improves Li-ion mobility and discharge capacity (215 mA h g−1 at 10 mA g−1), sustaining 45 mA h g−1 at a high rate of 1 A g−1. However, higher doping levels hinder performance, indicating Li-ion path obstruction and non-conductive impurities. Intriguingly, undoped Li2TiSiO5 glass exhibits superior electrochemical performance, with a discharge capacity of 340 mA h g−1 at 10 mA g−1 and high-rate endurance (81 mA h g−1 at 1 A g−1). This research provides insights into phase-dependent optimization, highlighting the glass phase's inherent benefits for Li-ion diffusion. It addresses a significant research gap, offering critical understanding for advancing high-energy-density anode materials in next-generation batteries.

Lead-free Cs3Cu2I5 metal halides have garnered significant attention recently due to their non-toxic properties and deep-blue emission. However, their relatively low photoluminescence quantum efficiency and poor stability have limited their applications. In this work, sodium iodide (NaI) is used to facilitate the synthesis of Cs3Cu2I5 nanocrystals (NCs), demonstrating improved photoluminescence intensity, photoluminescence quantum yield, and stability. Systematic optoelectronic characterizations confirm that Na+ is successfully incorporated into the Cs3Cu2I5 lattice without altering its crystal structure. The improved Photoluminescence Quantum Yield (PLQY) and stability are attributed to the strengthened chemical bonding, which effectively suppresses vacancy defects in the lattice. Additionally, light-emitting diodes (LEDs) based on 10% NaI-doped Cs3Cu2I5 NCs were assembled, emitting vibrant blue light with a maximum radiant intensity of 82 lux and Commission Internationale de l’Eclairage (CIE) chromaticity coordinates of (0.15, 0.1). This work opens new possibilities for commercial lighting display applications.

This study aims to investigate the effect of Na doping on the structure, electrical, and electrochemical properties of lithium-rich cathode material. Pristine Li1.2Ni0.13Mn0.54Co0.13O2 (LNMC) and Na-doped Li1.17Na0.03Ni0.13Mn0.54Co0.13O2 (Na-LNMC) layered lithium-rich/manganese-rich compounds are prepared by the sol-gel method. The structural and morphological characterization reveals that the Na doping leads to an ordered structure with regular cubic morphology and enlarged Li layer spacing. This enlargement facilitates the diffusion of lithium ion inside the bulk lattice. Electrochemical impedance spectroscopy (EIS) shows that doping by a small amount of Na (3 mol%) decreases the impedance by more than three orders of magnitude and enhances the diffusion of lithium ions in the same proportion. This remarkable improvement in the conductivity and diffusion coefficient of lithium ions of Na-LNMC improves its capacity retention. In addition, this structure and mode of preparation results in “U-shaped” capacity vs. cycle curves, similar to the curves observed for transition metal oxide electrodes, resulting in an exceptional cycle life, tested for up to 400 cycles at 2C.

[Display omitted] • An in-situ programmed electrostatic spraying approach was developed. • Na doping into the Co 3 O 4 lattice led to structural distortion and charge imbalance. • Both Na doping and oxygen vacancies in Co 3 O 4 provided abundant OER active sites. • An overpotential of 360 mV@10 mA·cm−2 and at least 200 h stability were realized. • This electrocatalyst enabled a current density of 100 mA·cm−2 at 1.62 V in PEMWE. The daunting challenge to establish a trade-off among the activity, durability, and cost of electrocatalysts for oxygen evolution reaction (OER) with sluggish reaction kinetics impedes the practical green energy conversion. Hereby, a non-noble metal-based electrocatalyst (i.e., Na-doped Co 3 O 4) was in-situ prepared by programmed electrostatic spraying as an advanced alternative to the costly and scarce state-of-the-art IrO 2 and RuO 2 -based electrocatalysts. The utilization of this sprayer facilitates intimate contact with the substrate electrode and provides short ion diffusion paths, facilitating efficient electron transport. Additionally, the doping of Na ions into the Co 3 O 4 structure results in structural distortion and charge redistribution, leading to the generation of oxygen vacancies (OVs). These OVs enhance the activity of lattice oxygen atoms, thus enabling rapid and durable oxygen evolution in an acidic media (0.5 M H 2 SO 4). The optimal Na-Co 3 O 4 (AA) exhibits a notably low overpotential of 360 mV@10 mA·cm−2 and at least 200 h stability. In addition, density functional theory (DFT) calculations confirm that the incorporation of Na ions significantly elevates electrical conductivity by decreasing the energy band gap and reduces the free energy barrier for the conversion of *O to *OOH, thereby improving the intrinsic OER activity. Finally, by implanting the catalyst in a single-cell proton exchange membrane water electrolyzer (PEMWE), the current density of 100 mA·cm−2 is achieved at a voltage of 1.62 V. This innovative non-noble metal catalyst holds great potential for scalable PEMWE anodes. [ABSTRACT FROM AUTHOR]

This study investigates the enhancement of Li 2 TiSiO 5 anode material through Na doping via two routes: melt-quenching (route I) and subsequent heat treatment (route II). A 5 % Na-doped ceramic sample significantly improves Li-ion mobility and discharge capacity (215 mA h g -1  at 10 mA g -1 ), sustaining 45 mA h g -1  at a high rate of 1 A g -1 . However, higher doping levels hinder performance, indicating Li-ion path obstruction and non-conductive impurities. Intriguingly, undoped Li 2 TiSiO 5 glass exhibits superior electrochemical performance, with a discharge capacity of 340 mA h g -1  at 10 mA g -1 and high-rate endurance (81 mA h g -1  at 1 A g -1 ). This research provides insights into phase-dependent optimization, highlighting the glass phase's inherent benefits for Li-ion diffusion. It addresses a significant research gap, offering critical understanding for advancing high-energy-density anode materials in next-generation batteries., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Authors.)

This study aims to investigate the effect of Na doping on the structure, electrical, and electrochemical properties of lithium-rich cathode material. Pristine Li1.2Ni0.13Mn0.54Co0.13O2 (LNMC) and Na-doped Li1.17Na0.03Ni0.13Mn0.54Co0.13O2 (Na-LNMC) layered lithium-rich/manganese-rich compounds are prepared by the sol-gel method. The structural and morphological characterization reveals that the Na doping leads to an ordered structure with regular cubic morphology and enlarged Li layer spacing. This enlargement facilitates the diffusion of lithium ion inside the bulk lattice. Electrochemical impedance spectroscopy (EIS) shows that doping by a small amount of Na (3 mol%) decreases the impedance by more than three orders of magnitude and enhances the diffusion of lithium ions in the same proportion. This remarkable improvement in the conductivity and diffusion coefficient of lithium ions of Na-LNMC improves its capacity retention. In addition, this structure and mode of preparation results in "U-shaped" capacity vs. cycle curves, similar to the curves observed for transition metal oxide electrodes, resulting in an exceptional cycle life, tested for up to 400 cycles at 2C. [ABSTRACT FROM AUTHOR]

• CO 2 sorption on Na-doped Li 4 SiO 4 was explored by experimental and DFT study. • Doped Li 4 SiO 4 trapped more CO 2 than pure Li 4 SiO 4 even below the melting point. • The Na doped at Li site and created quasi Li 2 O groups on Li 4-x Na x SiO 4. • This doping showed larger sorption energies and stronger CO 3 2– bond. • A new and unified sorption mechanism was proposed regardless of "melting layer". The addition of molten Na 2 CO 3 can drastically accelerated the extremely slow sorption kinetics of Li 4 SiO 4 -based CO 2 sorbents in the sorption enhanced reforming process. However, the lack of a unified consensus about the effect of doped Na 2 CO 3 on the CO 2 capture process, now delays the development of more-effective Li 4 SiO 4 sorbents. Here, sorption tests, sturactural characterzations and periodic density functional theory calculations were combined to develop a better mechanistic understanding CO 2 sorption on Na-doped Li 4 SiO 4. The Na-doped Li 4 SiO 4 exhibited a better CO 2 capture performance than pure Li 4 SiO 4 even below the melting point of any eutectic mixtures. Structural characterizations revealed that rather than generating physical favorable characteristics, the Na doping substituted at the Li site and created lithium–sodium orthosilicates (Li 4-x Na x SiO 4). Theoretical calculations agreeing with experimental results further demonstrated that Li 4-x Na x SiO 4 presented a weaker Na-O bond and generated more active phases (quasi Li 2 O groups) for larger sorption energies, more charge transfers and stronger CO 3 2– bond formation, in turn providing more reactive sites for enhanced CO 2 chemisorption as comparing with pure Li 4 SiO 4. Finally, we propose a new and unified sorption mechanism independent of the traditional "melting layer" explanation. [ABSTRACT FROM AUTHOR]

The applications of LiNi1/3Co1/3Mn1/3O2 (LNCM111) can be expanded if its electrochemical performance is improved. In this study, LNCM111–xNa samples with different Na-doping concentrations were successfully prepared by solid-phase and hydrothermal methods as a cathode material for Li-ion batteries. The effect of Na doping on the structures and electrochemical properties of the resultant layered oxide cathode materials was then investigated. The crystalline structure and morphology of the materials were characterized by powder X-ray diffraction and scanning electron microscopy, respectively. The results of these analyses indicated that all of the synthesized materials were free of impurities and Na doping did not change the LNCM111 structure. Moreover, a proper doping concentration can reduce the degree of cation mixing in the samples. These findings collectively indicate that LNCM111–0.1Na is a promising material with potential applications in high-performance batteries. [ABSTRACT FROM AUTHOR]

• Fabrication of CZTS:Na/CdS with Na doping on the surface using spin coating method. • The typical cliff-like CBO were obtained to 0.25 eV for CZTS/CdS heterojunction and 0.1 eV for CZTS:Na/CdS. • Sodium doping improves the performance of CZTS solar cells. Alkali doping can suppress deleterious antisite defects in kesterite Cu 2 ZnSnS 4 (CZTS) and improve the open-circuit voltage. In this study, the effects of light Na-doping on the performance and the band alignment of CZTS/CdS thin-film solar cells were investigated. CZTS:Na thin films were fabricated by the spin coating with 10% Na doping on the surface of CZTS. The Na-doping led to the narrower FWHM and larger grain size. The hole concentration and the conductivity were improved due to the Na Zn shallow acceptor defects. In addition, Na-doping can improve the band alignment of absorber/buffer interface and inhibit SRH recombination by the Na passivation effect and the suppression of Sn Zn defects. The typical cliff-like conduction band offset (CBO) was reduced from 0.25 eV in CZTS:Na/CdS to 0.1 eV in CZTS/CdS heterojunction. CZTS:Na device exhibited a higher Voc of 653 mV than that of CZTS/CdS device. The maximum conversion efficiency reached 7.46%, increased by 44% after Na-doping. These results clarify the effect of Na-doping on the band structure of the heterojunction in CZTS solar cells and support a new aspect that synthesis of a surface-doping CZTS:Na absorber has great potential for future research. [ABSTRACT FROM AUTHOR]

Semiconducting manganese selenide (MnSe), crystalizing in a cubic structure with a wide band gap, is focused on in this work for its potential as an ecofriendly thermoelectric material. Pristine MnSe exhibits a low carrier concentration of ∼1.3 × 1017 cm−3 at room temperature, which can be dramatically increased to ∼2.6 × 1021 cm−3 primarily resulting from the Mn-vacancy introduced by Na-doping at Mn site. The broad range of carrier concentration not only enables a reliable prediction of the electrical transport properties using a single parabolic band (SPB) model with the acoustic scattering, but also provides a well understanding of its underlying material physics. Such a doping and the simultaneously induced Mn-vacancies provide additional phonon scattering, leading to a reduced lattice thermal conductivity of ∼1.2 W/m-K at high temperatures. • A systematic investigation is carried out on thermoelectric properties of MnSe. • SPB model enables a well prediction on electronic transport properties. • Introduced point defects and precipitates effectively reduce the κ L. • Underlying physics of MnSe are well understood by the SPB model. [ABSTRACT FROM AUTHOR]

Lithium-ion battery cathode materials Li1.2Ni0.2Mn0.6O2 and Li1.15Na0.05Ni0.2Mn0.6O2 were synthesized using different Na source through a facile ball-milling method. The XRD results reveal that all the cathode materials display a layered structure of solid solution. Charge/discharge tests demonstrate that the Li1.15Na0.05Ni0.2Mn0.6O2 electrode using LiAC and NaAC as raw materials shows an excellent electrochemical performance including high reversible discharge capacity (232 mAhg−1 at 0.2 C), enhanced rate capability (109 mAhg−1 at 5 C), and superior cycling stability (96.64% capacity retention after 80 cycles). Furthermore, EIS results also support that better raw materials can effectively decrease the charge transfer resistance and facilitate the Li diffusion coefficient of the as-prepared cathode material. It is also confirmed that the better electrochemical performance of the Na-doped sample Li1.15Na0.05Ni0.2Mn0.6O2 mainly come from the Na-doping process which stabilizes the host layered structure by suppressing the conversion from layered to spinel structure during cycling. [ABSTRACT FROM AUTHOR]

Na-doped lithium vanadates Li 3− x Na x VO 4 ( x  = 0, 0.03, 0.05, and 0.08) were synthesized as anode materials for lithium-ion batteries by a simple sol-gel method. The structural and morphological characterizations reveal that Na-doping in Li 3 VO 4 leads to slightly expanded lattice and suppressed particle agglomeration with relative uniform morphology and the doped Na + ions distributed uniformly throughout Li 3 VO 4 grains. The Na-doped Li 3 VO 4 electrodes present enhanced cycling stability, better rate performance and lower charge transfer resistance, especially for the Li 2.95 Na 0.05 VO 4 electrode. It delivers the highest initial charge capacity of 523.4 mAh/g at 0.1C in the series electrodes. After 150 cycles at 1C, Li 2.95 Na 0.05 VO 4 electrode maintains a charge capacity of 398.3 mAh/g, which is almost the same with that of the initial one. In addition, Li 2.95 Na 0.05 VO 4 electrode also exhibits a much better rate capability with 364 and 284 mAh/g at 2C and 4C, respectively, superior to that of Li 3 VO 4 . The excellent electrochemical performance of the Na-doped samples is suggested to originate from the much higher lithium diffusion coefficient induced by the expanded lattice, the much smaller polarization and charge transfer resistance. [ABSTRACT FROM AUTHOR]

Series Li1.2Ni0.2Mn0.6O2 (LNMO) cathode materials have been synthesized by an improved one-step solvothermal method. Structural characterization reveals that all samples are composed of layered and spinel phases and the spinel phase content can be easily tuned by Na-doping or reducing lithium in the LNMO materials. The spinel phase content increases from 2.6% for the x = 0.02 Na-doped sample to 9.2% for the deficient lithium sample. Electrochemical performance measurement shows that the electrochemical performance of the series samples is closely related to the spinel phase content. The deficient lithium sample with the largest spinel phase content has the most excellent cyclic and rate performance. The deficient lithium sample displays a high discharge capacity of 118.9 mAh g−1 at 5 C rate and much more stable capacity retention of 89.4% after 50 cycles at 0.1 C rate, whereas the corresponding values are 66.7, 27.4, and 2.7 mAh g−1 at 5 C rate and 69.4, 58.7, and 37.8% at 0.1 C rate for the Na-doped samples with x = 0, 0.01, and 0.02. The excellent cyclic and rate performance of the electrodes with higher spinel phase content originated from more 3D Li-ion diffusion channels in spinel framework and the relatively stable layered structure improved by an appropriate spinel phase integration. [ABSTRACT FROM AUTHOR]

Band‐edge photoluminescence of zinc oxide materials reveals a phonon‐assisted ultraviolet emission enhanced by Na doping. We report the synthesis of ZnO and Na‐doped ZnO, the changes in structure and optical properties as a function of doping concentration and synthesis temperature. The obtained samples are nanoneedles, microparticles, and microwires. The structural effect of Na doping is studied by X‐ray diffraction and Raman spectroscopy. Room temperature photoluminescence reveals a contribution of band bending at the surface of the nanostructures, decreasing with Na concentration. Franz–Keldysh effect predicts strong electric field localized in the depletion region and appears to be the cause of red‐shift in UV band emission of nanoneedles in comparison to microwires. Our results indicate that Na doping introduces an acceptor level between 150 and 200 meV above the valence band. [ABSTRACT FROM AUTHOR]

Polycrystalline CZTS is an emerging candidate for photovoltaic, optoelectronic and gas sensing applications due to its availability and environment-friendly nature and also favorable light harvesting properties. The properties of polycrystalline materials depend upon the grain size. Grain size can be increased by increasing the annealing time, but this may lead to increased cost and also evaporation of certain volatile and low melting materials. Adding some growth enhancing elements is one of the novel methods to improve the grain size of polycrystalline materials. In this study, we studied Na induced CZTS film prepared by sputtering method. Before sulfurization, NaF (∼30 nm) thin layer was deposited on deposited CZT film using thermal evaporation method. UV-Visible, XRD and SEM/EDS analysis were used for studying optical, structural, elemental and morphological properties of CZTS films. [ABSTRACT FROM AUTHOR]

The Na-doped TiO 2 compounds, i.e Ti 1 − x Na x O 2 0 ≤ x ≤ 0.12 were synthesized via the solid-state synthesis method. The formation of single rutile phase with tetragonal structure was identified through the structural study by recording the XRD patterns. The analyses of the XRD patterns further indicate that Na+ ions are likely being substituted at the interstitial site of Ti4+ ions. The microstructural study using SEM revealed the homogeneous morphology of all compounds, with the particle size in the range of 1–2 μ m. The room temperature magnetization versus field measurement reveals a ferromagnetic behavior for all Na-doped compounds with coercivity values ranging from 100 to 930 Oe. The saturation magnetization was observed to be maximum for Ti 0.97 Na 0.03 O 2 compound but thereafter it decreases. According to optical property measurements, the bandgap reduces from 2.94 to 2.71 eV as the concentration of Na doping increases. The maximum transmittance value 91% was noted for Ti 0.97 Na 0.03 O 2 compound. The Hall effect measurements indicate that the carrier concentration of all Na-doped TiO 2 ranged from 1.077 × 10 15 to 7.579 × 10 15 /cm3, and it grew monotonically with the increase of Na-doping concentration. The value of the ac conductivity and dielectric constant were observed to enhance with increasing Na-doping concentration; indicating that transport occurs via hopping of the charge carrier. Further, the dielectric properties observation reveals lossless nature in the produced sample, which suggests that this material could be employed in high-frequency optoelectronic devices. [Display omitted] • Room temperature d 0 Ferromagnetism has been observed in Na-doped rutile TiO 2 compounds. • Hysteresis loops with a maximum saturation magnetization of 0.038 µ B per Na-ion was observed for 3% Na-doped compound. • Optical band-gap narrowing and carrier concentration enhancement was observed with the increase of Na doping concentration. • Very high optical transmittance value i.e., 83% (for TiO 2) to 91% (for 3% Na-doped TiO 2) was observed. • Zero dielectric loss was observed for all Na-doped compounds. • The dielectric constant and ac conductivity were found to increase with Na-doping. • These materials can be used for potential application for spintronics and optoelectronics devices. [ABSTRACT FROM AUTHOR]

Introducing the Na ion into the Ni-rich LiNi 0.6 Co 0.2 Mn 0.2 O 2 , Li 1- x Na x Ni 0.6 Co 0.2 Mn 0.2 O 2 ( x = 0, 0.01, 0.03) has been synthesized by high-temperature solid method. The effect of Na dopants on the structure, morphology, electrochemical properties, Li ion diffusion coefficient and the activation barriers has been extensively studied. Rietveld refinement results reveal that Na doping suppress cation mixing degree effectively and enlarge Li slab space. Electrochemical testing shows that Na-doped electrodes exhibit higher initial coulombic efficiency, good capacity retention and superior rate capability. Using experiments combined with first-principles calculations, we confirmed that the Na doping has enlarged Li slab space and then made the activation barrier of Li migration be reduced resulting higher Li + diffusion coefficients. [ABSTRACT FROM AUTHOR]

In this paper, we show that a reactive co-sputtering process using metallic CuGa and In targets; an Ar:H2Se atmosphere is well suited for the deposition of photoactive Cu(In,Ga)Se2 (CIGSe) absorber layers for thin-film solar cells in a single process step. The achievement of single-phase and well-crystallized layers is thereby no major problem if a sufficiently high H2Se content and substrate temperatures in the range of 400-500 °C are used. However, in order to achieve the desired Cupoor film stoichiometry, which is crucial for the device performance, it has to be considered already that, at moderate substrate temperatures in the range of 400-500 °C, indium has a strong tendency to re-evaporate from the film surface if the film composition is Cu-poor. If excess indium is supplied, this effect can lead to a self-adjustment of the film composition. This allows a very wide process window in a one-stage process concerning the supply ratio from the two targets of [Cu]/([In] + [Ga])supply0.35-0.8. However, the maximum efficiencies achievable with such a process are limited to 11.7% because an adequate Cu-poor composition can only be achieved with significant Cu-poor conditions, which allow only a low material quality. By using an improved process with an intermediate Cu-rich composition and a final Cupoor stage, the absorber quality could be significantly improved; efficiencies of up to 14.3% have been achieved with CIGSe films prepared on Na-doped Mo back contacts. [ABSTRACT FROM AUTHOR]

This paper reports the effect of Na doping Cu 2 ZnSnS 4 powders on the structural, morphological and optical properties. CZTS powders were synthesized by direct melting method of the constituent elements with different sodium doping concentrations from 0.5% to 2%. The resulting CZTS:Na powders were characterized by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, scanning transmission electron microscopic and UV–visible–NIR spectrophotometer. X-ray diffraction and scanning transmission electron microscopic analysis confirmed the formation of CZTS:Na with kesterite structure and preferential orientation along (112) plane. SEM results shown the microstructure with large grains with increasing the Na doping concentration. Optical measurements revealed that the band gap of CZTS decreases from 1.66 to 1.53 eV by increasing Na-doping. In addition, electrical investigations indicated that all ingots exhibit p-type conductivity. • Polycrystalline Na-doped CZTS powder was successfully obtained by direct fusion. • XRD patterns revealed that crystalline quality has been improved with Na diffusion. • CZTS:Na samples have band gap in the range 1.53–1.66 eV with p-type conductivity. [ABSTRACT FROM AUTHOR]

Peaks with anomalous abundance found in the mass spectra are associated with ions with enhanced stability. Among the scientific community focused on mass spectrometry, these peaks are called 'magic peaks' and their stability is often because of suggestive symmetric structures. Here, we report findings on ionised Na-acetic acid clusters [Na+-(AcA)n] produced by Na-doping of (AcA)n and UV laser ionisation. Peaks labelled n = 2, 4, 8 are clearly distinguishable in the mass spectra from their anomalous intensity. Ab initio calculations helped elucidate cluster structures and energetic. A plausible interpretation of the magic peaks is given in terms of (AcA)n formed by dimer aggregation. The encasing of Na+ by twisted dimers is proposed to be the origin of the enhanced cluster stability. A conceivable dimer-formed tube-like closed structure is found for the Na+-(AcA)8. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

To improve the density and electrochemical performance of LiFePO4, Na-doping modified Li0·95Na0·05FePO4 cathode material was synthesised through co-precipitation method, using a spherical sample prepared by microwave heating as precursor. The morphology, structure, electrochemical performance and the tap density of the materials were characterised by scanning electron microscope, x-ray diffraction, cyclic voltammetry, constant current charge-discharge experiment and the tap density measurement. The results indicated that the samples have rules spherical or similar spherical morphology and simple pure olive-type phase. The Na-doped Li0·95Na0·05FePO4 material showed excellent performance with a tap density of 1·63 g cm−3. At room temperature, its initial discharge capacities reached 164·2, 151·5 and 130·5 mAh g−1 at 0·2, 1 and 2 C current rates, respectively. [ABSTRACT FROM AUTHOR]

By simultaneous sputtering from metallic CuGa and In targets in an Ar:H 2 Se atmosphere onto heated substrates, single phase and well crystallized Cu(In,Ga)Se 2 thin films can be directly deposited in a single process step. However, the preparation of Cu-poor films, which are needed for high solar cell efficiencies, is impeded by the re-evaporation of excess indium, which occurs readily at moderate substrate temperatures in the range of 400 °C to 500 °C. Therefore, a significant In-excess is necessary during the second deposition stage in order to transform the final film composition into the desired Cu-poor regime ([Cu]/([In] + [Ga]) < 0.95). Higher open circuit voltages and efficiencies are achieved for absorbers produced with an intermediate Cu-rich composition and/or by using Na containing precursor films (NaF or Mo:Na). A best cell efficiency of 12.9% is achieved, which demonstrates the high potential of the investigated reactive magnetron sputtering process for solar cell manufacturing, as it is well suited for large-area, industrial applications. [ABSTRACT FROM AUTHOR]

A potential Lithium-ion battery anode material Li4-xNaxTi5O12 (0≤x≤0.15) has been synthesized via a facile hydrothermal method with short processing time and low temperature. The XRD and FE-SEM results indicate that samples with Na-doped are well-crystallized and have more homogeneous particle distributions with smaller overall particle size in the range of 300-600nm. Electrochemical tests reveal that Na-doped samples exhibit impressive specific capacity and cycle stability compared to pristine Li4Ti5O12 at high rate. The Li3.9Na0.1Ti5O12 electrode deliver an initial specific discharge capacity of 169mAh/g at 0.5C and maintained at 150.4mAh/g even after 40 cycles with the reversible retention of 88.99%. Finally, a simple solvothermal reduction method was used to fabricate Li3.9Na0.1Ti5O12/graphene(Li3.9Na0.1Ti5O12/G) composite. Galvanostatic charge-discharge tests demonstrate that this sample has remarkable capacities of 197.4mAh/g and 175.5mAh/g at 0.2C and 0.5C rate, respectively. This indicates that the Li3.9Na0.1Ti5O12/G composite is a promising anode material for using in lithium-ion batteries.

The sodium-sizer is a device for the measurement of size-distributions of neutral molecular aggregates with sizes in the nanometer range (<20 nm). This work provides a quantitative correction for the size-dependent overall detection efficiency for this instrument. Four processes contribute to the overall detection efficiency: the Na-capture, the Na-sticking, the photoionization, and the detection efficiency at the micro-channel plate detector. We demonstrate that the Na-sticking and the photoionization efficiencies are not size-dependent and thus do not require corrections. Size-dependent corrections, however, are needed for the capture and the micro-channel plate detection efficiencies. Expressions for corresponding corrections are provided. Our results show the importance to operate the sodium-sizer under single Na-doping conditions and at high ion acceleration voltages to ensure that the raw data are of sufficient quality so that the corrections can be applied. [ABSTRACT FROM AUTHOR]

Highlights: [•] Na-doped Li3V2(PO4)3/C cathode materials for Li-ion batteries were synthesized via a rheological phase reaction method. [•] Li2.95Na0.05V2(PO4)3 exhibited good rate capability and excellent cycle stability. [•] Li2.95Na0.05V2(PO4)3 sample had lower charge transfer resistance compared with the undoped Li3V2(PO4)3 sample. [Copyright &y& Elsevier]

Abstract: The chemical composition, crystalline structure, surface morphology and photoluminescence spectra of Na-doped ZnO thin films with different heat treatment process were investigated by X-ray photoelectron spectroscopy, X-ray diffraction, atomic force microscopy and a fluorescence spectrometer. The results show that preferred orientation, residual stress, average crystal size and surface morphology of the thin films are strongly determined by the preheating temperature. The effects of preheating temperature on microstructure and surface morphology have been discussed in detail. The photoluminescence spectra show that there are strong violet & UV emission, blue emission and green emission bands. The violet & UV emission is ascribed to the electron transition from the localized level below the conduction band to the valence band. The blue emission is attributed to the electron transition from the shallow donor level of oxygen vacancies to the valence band, and the electron transition from the shallow donor level of interstitial zinc to the valence band. The green emission is assigned to the electron transition from the level of ionized oxygen vacancies to the valence band. [Copyright &y& Elsevier]

Na-doped YBa1.9Na0.1Cu3Oy+40 mol%Y211 (YBNCO) and Na-free YBa2Cu3Oy (YBCO) samples were fabricated by the melt-textured growth (MTG) method to study the effect of doped Na ion on flux pinning. The effective pinning energy (U(T,Hdc,J)), irreversibility line (Hirr(T)) and critical current density (jc(Hdc)), were determined by measurement of ac susceptibility (acs) as well as hysteresis loop measurements for the samples, where T, Hdc and J are temperature, dc magnetic field and current density, respectively. It is found that Hirr(T) was shifted to lower temperatures while Jc(Hdc) and U(T,Hdc,J) of YBNCO became smaller than that of YBCO. Hence, the doping Na ion plays a negative rule on enhancing flux pinning in YBCO. The appearance of the second peak in Jc(Hdc) relation and the enhancement of anisotropy in YBNCO is a further support to the conclusion. [Copyright &y& Elsevier]

We have prepared Na-doped YBa2Cu3Oy (YBa1.9Na0.1Cu3Oy+40 mol% Y211) (YBNCO) and Na-free YBa2Cu3Oy (YBCO) samples by the melt-textured growth method to study the effect of doped Na ion on flux pinning. The ac susceptibility curves as well as the hysteresis loops were measured for the samples. Then the effective pinning energy (U(T,Hdc,J)), irreversibility line (Hirr(T)) and critical current density (jc(Hdc)) were determined, where T, Hdc and J are temperature, dc magnetic field and current density, respectively. We found that, with Na doping, the Hirr(T) line shifted to lower temperatures while the Jc(Hdc) and U(T,Hdc,J) became smaller. Hence Na ions play a negative role in the flux pinning of YBCO. The appearance of the second peak in the Jc(Hdc) curves and the enhancement of anisotropy in YBNCO further support this finding. [Copyright &y& Elsevier]

• ZnWO 4 with Na-doping and oxygen vacancies was prepared by a facile one-step hydrothermal strategy via adding Na 2 WO 4. • ZnWO 4 with Na-doping and oxygen vacancies exhibits higher photocatalytic benzene removal efficiency. • The Na-doping and OVs could activate H 2 O and O 2 molecules to generate a large number of reactive radicals. • The Na-doping and OVs could enhance the adsorption and activation of reactants. • The photocatalytic benzene oxidation mechanism is proposed. Metal ion doping and vacancy-engineering are effective strategies to promote photocatalytic performance. ZnWO 4 is an important inorganic photocatalytic material. Herein, ZnWO 4 with Na-doping and oxygen vacancies (OVs) was prepared by a facile one-step hydrothermal strategy via adding Na 2 WO 4. Due to the synergistic effects of Na-doping and OVs, the photocatalytic benzene removal rate of the ZnWO 4 samples is much higher than that of pure ZnWO 4. According to the characterization results, the Na-doping and OVs not only promote the migration of electrons but also activate H 2 O and O 2 molecules to generate a large number of reactive radicals. The results of in situ DRIFT spectroscopy and DFT calculations clearly demonstrate that the Na-doping and OVs enhance the adsorption and activation of reactants and intermediates. The photocatalytic benzene oxidation mechanism is proposed. Benzene is completely oxidized following the order of phenol, catechol (quinol), benzoquinone, and small molecule organics such as acetic acid, eventually producing H 2 O and CO 2. The work could provide new mechanistic understanding for photocatalytic VOCs decomposition. [ABSTRACT FROM AUTHOR]

• A novel sodium doped g-C 3 N 4 nanotubes (Na-CNTs) was first prepared via a microwave heating method. • The Na-CNTs exhibited a unique branch-like tubular morphology. • The Na-CNTs photocatalyst showed enhanced photocatalytic activity, with a degradation rate of nearly 91.43 % in just 20 min. • The mechanism of the formation process of Na-CNTs was deduced. The wide applications of nanotubes in many fields including catalysis have attracted considerable interest. Herein, we designed a simple and facile synthesis route to synthesize sodium-doped g-C 3 N 4 nanotubes (Na-CNTs), by means of the hydrothermal synthesis of intermediate and the subsequent treatment via microwave irradiation heating. This approach utilizes the self-assembly between melamine and cyanuric acid in the NaOH solution to form Na-doped melamine cyanaurate supramolecular intermediate. Then the supramolecular intermediate is heated under direct microwave irradiation with carbon fibers which are acted as microwave absorbents. The results of comprehensive characterizations indicate that Na-CNTs in the form of uniform one-dimensional (1D) nanotubes can be obtained conveniently, and the doping of sodium can be successfully realized by direct microwave irradiation heating. Moreover, sodium doping can enhance the charge attractive force between layers and induce more structural defects in Na-CNTs. The photodegradation result of rhodamine B (RhB) demonstrates that the as-obtained Na-CNTs exhibit enhanced photocatalytic performance, with a degradation rate of nearly 91.43 % in just 20 min, and the corresponding photodegradation velocity of Na-CNTs is 3.2 times higher than that of pure g-C 3 N 4 (PCN). [ABSTRACT FROM AUTHOR]

Current study is first ever computational study to predict optical and electronic properties of Na doped CdS system. A good comparison among optical properties of pure CdS and its doping with various Na concentrations (3.12%, 6.25%, 9.37%) is shown in our study. Cd atoms are substituted with Na atoms and a change in optical properties is studied while size of supercell (1 × 2 × 2) is kept constant for all cases. In comparison to absorption of pure CdS, the absorption shows blueshift upon increase in Na concentrations and refractive index first increase and then decreases for higher Na concentration (9.37%). Absorption increases in the visible region while for UV region it somehow shows oscillatory trend. Entire study has been executed using Wien2k code by employing PBE-GGA approximation and the manuscript is furnished with detailed discussions regarding plausible applications of CdS:Na system which highlight future directions of this material. Moreover, insight into optical properties of CdS:Na system shows surprising results which appeal candidacy of this material to be potentially used for device fabrication in the field of optoelectronics, non-linear optics, dielectrical electronics, functional microelectronics, electrostatic capacitors and piezoelectric transducers. [ABSTRACT FROM AUTHOR]

The processes involved in the photoionization of sodium-doped clusters are complex, not fully understood for many systems and still strongly debated, especially because of the discrepancy between experimental results and predicted cluster structures. We have performed a study on sodium doped formic acid clusters based on UV photoionization spectroscopy and DFT/TDDFT calculations. Apart from the monomer, all the predicted structures show vertical ionization potential values higher than those obtained by the photoionization measurements. We have calculated the absorption spectra and found many Rydberg-like states near the adiabatic ionization potentials and, crucially, in the UV range where the clusters appearance energies fall. This finding supports the hypothesis of adiabatic contributions in the measured ionization potentials for these clusters., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)