Progress in Solid State Chemistry最新文献

The undesirable capacity degradation of LiMnPO₄ upon cycling at high temperatures is a challenge to its practical application. Herein, a lattice doping strategy is adopted to improve the high-temperature cycling stability of LiMnPO₄, and the comparative study reveals that Al³⁺ doping into LiMnPO₄ in a form of Li_0.98Al_0.02MnPO₄ is highly beneficial to the cycling performance of LiMnPO₄ and the capacity retention can be significantly improved from 67.4 % to 93.4 % after 100 cycles at 1C at 60 °C, because Al³⁺ doping can effectively reduce passivation products deposition on the cathode and manganese dissolution in the electrolyte, which thus improve the cathode/electrolyte interface and stabilize the structure of LiMnPO₄ at high temperatures.

Chromophores at different coordinations can give rise to different colors; usually, chromophores at non-centrosymmetric coordinations are preferred for intense pigments. Different solid solutions M_2-xCo_xM’O₄ (M = Mg/Zn, and M’ = Ti/Sn) with inverse spinel structure were synthesized with the goal of understanding color variation with site distribution, as the chromophore Co²⁺ in these solid solutions can occupy either the tetrahedral or octahedral sites or both depending on the composition. Another goal was to develop environmentally friendly and cheap blue pigments by reducing the carcinogenic cobalt to obtain a similar color to that of commercially available cobalt blue, which uses a significant amount of Co²⁺ (33.31 % by mass). For Mg_2-xCo_xTiO₄ series, turquoise blue hues were observed for low cobalt content, and different shades of blue were observed for Mg_2-xCo_xSnO₄ series with a color similar to cobalt blue, including just 4.90% of cobalt by mass. While for Zn_2-xCo_xTiO₄, and Zn_2-xCo_xSnO₄ series, different shades of brown and different shades of green, respectively, were observed. One of the main reasons behind the major difference in color for the Mg and Zn containing solid solutions, regardless of the same chromophore in the same structure is related to the chromophore site distribution in the system. For the Mg-containing solid solutions, different shades of blue are observed as Mg has no preference for any of the sites, Co²⁺ mostly goes to tetrahedral sites. In contrast, for the Zn-containing solid solutions, no blue shades were observed because of the strong preference of Zn for the tetrahedral sites owing to the sp³ hybridization, which in turn forces Co²⁺ to occupy the octahedral sites. Neutron refinement proves that Co²⁺ occupies mainly tetrahedral sites in the Mg-containing solid solutions and mostly octahedral sites in the Zn-containing solid solutions.

With the increasing maturity of lithium-ion battery (LIB) research and large-scale commercial application, the shortage of lithium resources has gradually emerged. Sodium-ion batteries (SIB) have become a potential choice for secondary battery energy storage systems due to their abundant resources, high efficiency, and ease of use. The cathode materials of sodium-ion batteries affect the key performance of batteries, such as energy density, cycling performance, and rate characteristics. At present, transition metal oxides, polyanion compounds, and Prussian blue compounds have been reported as cathode materials. This paper summarizes the classification, performance characteristics, and research progress of main cathode materials for sodium-ion batteries, and prospects the potential research directions.

Infrared nonlinear optical (IR-NLO) crystals with excellent properties are in extensive demand due to their important role in IR laser technology. Currently, it remains a great challenge to obtain IR-NLO materials with both high second harmonic generation (SHG) response and large laser-induced damage thresholds (LIDTs). Some structural design strategies such as ‘structural/functional regions’ have been adopted to develop new high-performance NLO materials. The covalent structural region producing SHG signals has been extensively investigated, whereas the hard cations (alkali, alkaline-earth, and rare-earth metal ions) which are responsible for improving LIDTs, have been relatively neglected. Utilizing the concept of structural/functional regions, we focus on the relation between structural regions and SHG properties in chalcogenides. Combining different kinds of hard cations can change the dimension of structures and affect the stacking of NLO-active groups. Introducing more hard cations and constructing more complex ion regions help to increase the laser damage threshold. Based on the mentioned structural strategies, guidance will be provided for developing high-performance multiple-cation materials for IR NLO applications.

The primary objective of this study is to explore the relationship between the composition, structure, and thermal characteristics of M-Al-Si-O-N glasses, with M representing sodium (Na), magnesium (Mg), or calcium (Ca). The glasses were prepared by melting in a quartz crucible at 1650 °C and AlN precursor (powder) was utilized as a nitrogen source. The measured thermal properties studied were glass transition temperature (T_g), crystallization temperature (T_c), glass stability, viscosity, and thermal expansion coefficient (α). The findings indicate that increasing the aluminum content leads to higher glass transition, crystallization temperatures, and viscosities. In contrast, fragility values increase with the Al contents, while modifier elements and silicon content influence thermal expansion coefficient values. FTIR analysis revealed that in all glasses, the dominant IR bands are attributed to the presence of Q² and Q³ silicate units. The effect of Al is observed as a progressive polymerization of the silicate network resulting from the glass-forming role of Al₂O₃. In most samples, the Q⁴ silicate mode was also observed, strongly related to the high Al content. Overall, the study shows that the complexity of composition-property correlations where the structural changes affect the properties of Mg/Ca-based oxynitride glasses has potential implications for their use in various technological fields.

Two-dimensional (2D) materials have attracted much research attention in the last ten years, resulting in significant advancements in their theoretical and technical understanding. Since the successful fabrication of 2D graphene, various types of graphene-like 2D materials, such as transition metal dichalcogenides (TMDCs), metal carbides or nitrides (MXenes), hexagonal boron nitride (h-BN), layered double hydroxides (LDHs), and halide perovskites, have drawn significant attention and developed into the most promising semiconductor materials in the area of optoelectronic devices. Recently, several studies have been reported indicating the exciting optoelectronic properties of these 2D materials. In this review, the properties and applications of different 2D materials, including TMDCs, halide perovskites, and MXenes, are discussed briefly. Firstly, the basic properties of these 2D materials, particularly those pertaining to optoelectronic properties, are described. Then, the most recent studies on 2D-based optoelectronic applications, such as solar cells, photodetectors, and LEDs, are studied. The conclusion provides some viewpoints on the current challenges and potential future applications of these 2D materials. This article provides a comprehensive, authoritative, critical, and accessible review of general interest to the materials science research community, including beginners and experts. Its comprehensive approach, mechanistic insights, real-world applications, and relevance to materials science justify its value as an authoritative and accessible resource.

The present study aims to describe the role of the grain size on the properties of submicron- and nano-structured Ba_0·8Sr_0·2TiO₃ (BST) ceramics. Dense (1 − 2% porosity) ceramics with average grain sizes in the range of (77 − 234) nm were consolidated under different spark plasma sintering conditions starting from nanopowders with a mean particle size of 70 nm, synthesized via the acetate variant of the sol-gel method. The structural analysis based on XRD data revealed a mixture of cubic and tetragonal modifications at room temperature for the precursor powders and for all the investigated ceramics. The structural heterogeneity of the individual ceramic grains with coexistence of cubic and tetragonal polymorphs was confirmed by HR-TEM investigations. Accordingly, a “brick-wall" model with cubic grain boundary regions and tetragonal grain cores is proposed. By increasing the grain size, from 77 to 234 nm, a decrease of the phase transitions diffuseness accompanied by an increase of the permittivity maxima (from 650 to 4500) and dielectric losses (from 5 to 7.5%, at 100 Hz), was detected by broadband dielectric spectroscopy. No variation of the Curie temperature in the investigated Ba_0·8Sr_0·2TiO₃ ceramics was detected, unlike typically reported for BaTiO₃ ceramics with similar grain sizes. The Curie-Weiss temperature and the Curie constant decrease when grain size is diminished, indicating an overall reduction of the ferroelectric active volume, as a scaling effect. The ferroelectric switching was demonstrated for all the selected fine-grained BST ceramics, either at nanoscale or macroscopically, with an increased ferroelectric character for the coarser submicron-structured ceramics, with respect to the nanocrystalline one. The observed properties of the fine-grained Ba_0·8Sr_0·2TiO₃ ceramics are explained in the frame of multiphase coexistence and ferroelectricity “dilution” due to the increasing role of non-ferroelectric grain boundaries when reducing grain size and complete the knowledge on the scale-dependent properties of dense fine-grained BaTiO₃-based ceramics.

Cemented carbides have enjoyed widespread applications as a function of their outstanding properties during the past 100 years. Despite the advantages, however, recently there have been concerns about the challenges associated with traditional cemented carbides, i.e. the conflict of properties (hardness and toughness, strength and wear resistance) as well as the instability of reliability in service, necessitating the development of functional gradient cemented carbides (FGCCs). Although recent decades, investigations have seen explosive growth in FGCCs, there is still a lack of comprehensive review on FGCCs. Herein, the current study applies towards summarize the progress of FGCCs during the past 60 years, emphasizing the demand in FGCCs with tailored properties and customized requirements for specific applications. We initially introduce basic cognition of FGCCs, subsequently, comprehensively elucidate the gradient formation mechanisms of carburization, decarburization, nitridation, denitrification, infiltration process, and construction methods (solid-phase sintering, graphene doping and additive manufacturing etc.), then summary processing techniques and mechanical properties of FGCCs. In addition, the impart of additive on further improving the properties of FGCCs is discussed. Afterward, the possible applications of FGCCs at different areas are proposed. At the end of this paper, a summary of concluding remarks and potential developed direction of state-of-the-art FGCCs is provided.

Solar water-splitting using particle photocatalysts is a promising approach to sustainably produce hydrogen. LaTiO₂N is an auspicious visible light absorbing photocatalyst regarding the oxygen evolution reaction. In this work, the topotactic growth mechanism of LaTiO₂N particles is investigated by varying the precursor material and the synthesis conditions during thermal ammonolysis. Their influence is discussed in regard to structure, composition, morphology, optical, and functional properties. Using the conventional, layered perovskite oxide, La₂Ti₂O₇, as precursor resulted in brick-shaped porous LaTiO₂N particles with a high degree of crystallinity and a high surface area. When adding flux, the increased mobility during thermal ammonolysis leads to larger morphology changes resulting in non-porous, perforated particles with skeletal features. In a novel, alternative approach, LaTiO₂N is prepared via the topotactic conversion of a double-layered Sillén-Aurivillius type oxyhalide material, La_2·1Bi_2·9Ti₂O₁₁Cl. The facile formation of LaTiO₂N results in a perforated porous structure exhibiting skeletal features whilst maintaining a high surface area due to the presence of pores. By alternating the morphology of the material in this matter the oxygen evolution under one sun illumination is improved by around 10% or 30% depending on whether thermal ammonolysis of La₂Ti₂O₇ is performed with or without flux, respectively.

The last two decades have seen a growing trend towards sizable single crystals of REBa₂Cu₃O_7−δ (RE123, RE = rare earth elements) with fine quality, which have been attracting considerable interest in the study of superconductivity. As an advanced and classic method, top-seeded solution-growth (TSSG) is the only technique to date for producing RE123 single crystals with dimensions of 2 cm, e.g., a Y123 single crystal of 19.8 × 19.5 mm² in a-b plane and 16.5 mm in height. Recently, novel approaches were developed such as crystal-pulling combined with continual cooling for rapid growth to attain a large-sized RE123 crystal, and the utilization of dopant-added crucibles for continuous growth to produce highly-uniform doped-Y123 crystals. Consequently, researchers from several tens of physical laboratories worldwide have been benefiting from TSSG-produced RE123 single crystals and generating excellent collaborative work. This paper provides an overview of the progress and achievements on the growth of superior RE123 single crystals by TSSG for fundamental studies and practical applications, focusing on three aspects including crystal enlargement, RE123 stoichiometry control and cation doping. The mechanism of crystal growth and the correlation between phase formation and superconducting properties are comprehensively elucidated on the basis of distinctive features of phase diagrams of RE–Ba–Cu–O systems.