Solid State Sciences最新文献

As a novel cathode material for sodium-ion batteries, Na₃MnTi(PO₄)₃ (denoted as NMTP) has received great attention because of its abundant natural resources, excellent safety, low toxicity as well as three-electron reactions. Unfortunately, the pure NMTP cathode displays a bad conductivity, resulting in an inferior electrochemical performance for sodium energy storage. Herein, we introduce a good route to fabricate the nitrogen-doped graphene-decorated NMTP@C (denoted as NG-NMTP@C) composite with superior rate property and superior cycle stability for the first time. In this fabricated material, the nitrogen-doped graphene nanosheets are dispersed into the NMTP@C particles. Compared to NMTP@C, the prepared NG-NMTP@C cathode possesses better cycle stability and higher capacity. It shows the capacity of 173.1 mAh g⁻¹ at 0.1 C and presents the high capacity retention of around 97.1 % at 10.0 C over 400 cycles. Therefore, this fabricated NG-NMTP@C nanocomposite can be employed as the novel positive electrode in sodium-ion storage.

In depth understanding of the magnetic, structural and electrical properties of Heusler alloys are crucial to achieve potential applications in spin-based device. Wherein, we report the synthesis of Cr₂MnAl Heusler alloy nanoparticles (NPs) via co-precipitation method and also demonstrated their transport properties. Interestingly X-ray analysis confirms the cubic phase of the synthesized Heusler alloy NPs and transmission electron microscopy (TEM) analysis reveals that the Cr₂MnAl as particle size of 10 ± 2 nm. Moreover, this particle size has adverse effect on symmetry of Cr₂MnAl Heusler alloy due to their higher surface to volume ratio that significantly changes their magnetic and electrical properties. These NPs exhibit soft ferromagnetic properties with a Curie temperature (Tc) of 25 K. Besides, resistivity measurements indicate the semiconducting nature and also we report the observation of anomalous Hall effect. In addition, we support our experimental results by studying the electronic and magnetic properties of alloy using first principle calculations. This density functional theory reveals that Cr₂MnAl has half metallic characteristics with high spin polarization. In light of above, this material can be used as intermediate layer to decouple the two ferromagnetic layers which acts as spin-polarized carriers in spin-based device.

A new Mg-containing disordered quaternary telluride Mg_1.2(1)In_1.2(1)Si₂Te₆ is prepared at 1223 K by direct fusion of elements. This mixed metal telluride adopts a trigonal (P$\bar{3}$1m space group) structure having refined cell constants of a = b = 7.0603(3) Å and c = 7.1681(4) Å. Four unique crystallographic sites are filled in the structure: one disordered metal site (In1/Mg1), one partially filled Mg2, one Si1, and one Te1. Each metal ion (In and Mg) in the structure sits at the center of a distorted octahedron of Te1 atoms. Two Si atoms are involved in forming an ethane-like Si₂Te₆ unit with the help of a Si−Si bond. The local coordination environment around each Si atom can be described as a distorted tetrahedron comprising one Si1 and three Te1 atoms. A polycrystalline sample with the loaded composition of Mg_1.2In_1.2Si₂Te₆ shows an optical bandgap of 1.02(2) eV. The p-type semiconducting nature of the Mg_1.2In_1.2Si₂Te₆ sample was established from the positive values of the Seebeck coefficient (S) and resistivity studies. The complex structure of the Mg_1.2In_1.2Si₂Te₆ phase, which features heavy elements (In and Te), helps to achieve ultralow total thermal conductivity (k_tot) of 0.33 W/mK at 773 K.

The Ni-doped CoFe₂O₄ graphene composites (Ni-CFO/RGO) have been successfully prepared using the microwave-assisted method. The substance is a novel nanocomposite structure in which CoFe₂O₄ nanoparticles are tightly and uniformly attached to graphene hybrid nanosheets. The synergistic effect of Ni doping and CoFe₂O₄ can reduce the volume expansion of CoFe₂O₄ in the reaction process and inhibit the stacking of graphene. Because the Ni-CFO/RGO composite is structurally stable during the electrochemical reaction, it has a good theoretical capacity. Excellent carbon composite can further enhance the electron transport performance and structural stability of the material, thereby improving the electrochemical performance and cycle life of the material. Doping Ni²⁺ into metal oxides can not only form oxygen vacancies, and improve the transport capacity of sodium ions, but also broaden the electron transport channel. In addition, the catalyst can form a composite structure with metal oxide, which can effectively inhibit its volume expansion. At the same time, reacting with carbon materials, can also effectively reduce the accumulation of carbon, thereby reducing its resistance. After 200 cycles at a current density of 0.05 A g⁻¹, it can provide a high sodium storage capacity of 380.6 mAh g⁻¹, which still keeps 203.4 mAh g⁻¹ at 1.5 A g⁻¹.

In layered perovskites with the Carpy-Galy structural type, similar structural phase transitions occur under high pressure. These structural changes, which are crucial for the pressure-induced phase transition in layered perovskite, were analyzed based on experimental X-ray diffraction data. The tilting of the Ti-O₆ octahedra and the distortion of the arrangement of rare-earth atoms were studied in detail. Changes in these structural features in layered perovskite serve as common indicators of the phase transition to the monoclinic phase that occurs under high pressure application.

The conversion of CO₂ into fuel using photocatalytic technology is critical in reducing greenhouse gas emissions and addressing the energy issue. In this paper, type II heterojunctions of 2D/2D BiOIO₃/Bi-MOF were built using the solvothermal approach. The materials were characterized utilizing methods such as XRD, SEM, TEM, XPS, UV–vis diffuse reflection, and an electrochemical workstation. Under 300 W Xenon lamp irradiation, BiOIO₃/Bi-MOF-30 (BOIOB-30) produced 21.26 μmol/g/h of CO, 1.95 times greater than pure BiOIO₃. This improvement is related to the alteration of BiOIO₃ with lamellar Bi-MOF, which provides more reactive sites and significantly increases the composite's photocatalytic activity.

In this study, Na_1/3Cd_1/3(Bi_1-xY_x)_1/3Cu₃Ti₄O₁₂ (NCBYCTO, x = 0−0.20) ceramics were successfully prepared via solid state method. Their microstructure along with the optical, dielectric, and non-Ohmic properties were investigated systemically. It was shown that Y³⁺ doping caused the decrease in cation vacancy concentration and the increase in optical energy band. With the increase of Y³⁺ content, ceramics exhibited a more stable structure, while their average grain size increased from 6.80 μm to 9.12 μm and then decreased to 2.17 μm with the dopant amount. The relative density increased from 94.7 % for the undoped specimen to 95.6 % for the specimen with x = 0.20. The giant dielectric constant (ɛ′ = 44200) at a relatively low dielectric loss (tanδ = 0.048) at 10 kHz was obtained in the specimen with x = 0.08, being more than three times that of undoped sample and demonstrating the outstanding frequency stability in the range of 40−10⁶ Hz. The giant dielectric constant below 10⁶ Hz originated from Maxwell–Wagner relaxation related to the insulating grain boundaries (GBs) and followed the internal barrier layer capacitor model. Besides that, Y³⁺ doping improved the nonlinearity properties of NCBYCTO ceramics. The specimen with x = 0.20 had the largest nonlinearity coefficient α (∼9.60) and breakdown field strength E_b (∼7.15 kV/cm). At last, the nonlinear J-E characteristics were closely related to the GB conductivity activation energy.

Photocatalysis is a promising strategy for the production of H₂O₂, but the promotion of 2e⁻ ORR selectivity remains a challenging goal in this field. Herein, Potassium (K⁺), cyano groups (-C≡N) and porous ultrathin structures were introduced into g-C₃N₄ simultaneously by the hyphenated technique of gas template method and molten salt-assisted method. The K⁺ and –C≡N can broaden the light absorption range, improve the reduction ability and promote electron transfer of the catalyst. Additionally, the presence of a permeable ultrathin structure plays a crucial role in improving the specificity of the 2e⁻ oxygen reduction reaction (ORR). Benefiting from the multiple advantages, the H₂O₂ yield of K⁺ intercalated cyano-rich porous ultrathin g-C₃N₄ (KUCN) reached 781.39 μM with an extraordinary 2e⁻ ORR selectivity of 94.5% (0.30 V vs. RHE). Overall, this study presents a practical approach for designing catalysts based on g-C₃N₄ that exhibit a high selectivity for the 2e⁻ ORR reaction.

The aim of this work is to establish the relationship between the electrochemical performance of the Pr_1.6Cа_0.4Ni_0.6Cu_0.4O_4+δ-based electrodes and the properties of the electrode powders, conditioned by their synthesis history, as well as the electrode design and the sintering conditions of the electrode layers. The Pr_1.6Cа_0.4Ni_0.6Cu_0.4O_4+δ (PCNCO) powders are synthesized by combustion of salt compositions using different fuels: glycine, polyvinyl alcohol and citric acid. The influence of the composition of the redox mixture on the synthesis process, the phase composition of the obtained powders and their properties have been studied. The microstructure of the PCNCO electrodes formed from the powders with different dispersions is studied by electron microscopy. The electrochemical performance of the electrodes in contact with the Ce_0.8Sm_0.2O_1.9 (SDC) electrolyte is studied by impedance spectroscopy. Based on the correlations established between the chemical stability and dispersion of the powders and the microstructure and polarization resistance of the corresponding electrodes, the optimal parameters for the synthesis of the PCNCO complex oxide for the use as a cathode material have been determined. The lowest polarization resistance equal to 0.38 Ω cm² at 700 °C is obtained for the bilayer electrode with the PCNCO functional layer synthesized by the citrate-nitrate combustion and sintered at 1050 °C, and the LaNi_0.6Fe_0.4O_3–δ oxide collector sintered at 900 °C. The developed synthesis procedure and electrode design can be recommended as promising for the fabrication of air electrodes in the intermediate-temperature electrochemical devices.

Sulfide (ZnS)(Ag₂S)_x heteronanostructures of various composition were obtained by co-deposition from water colloidal solutions of silver and zinc nitrates using sodium sulfide as a sulfidizer and sodium citrate as a stabilizer. The formation of (ZnS)(Ag₂S)_x heteronanostructures was confirmed using the XRD, HAADF-STEM, SEM, EDX and Raman spectroscopy. The size of ZnS and Ag₂S nanoparticles in heteronanostructures (ZnS)(Ag₂S)_x with x ≤ 0.01 is 2–4 and no more than 3 nm, respectively. Raman spectroscopy showed that addition of silver sulfide nanoparticles into (ZnS)(Ag₂S)_x heteronanostructures leads to Ag₂S deposition onto the surface of ZnS nanoparticles. Doping ZnS with only 1 mol.% of colloidal Ag₂S nanoparticles is sufficient to produce a silver sulfide shell on the surface of ZnS nanoparticles.