Progress in Solid State Chemistry最新文献

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.

Perovskite-type oxynitrides are a new class of inorganic materials that have potential applications as photocatalysts, inorganic pigments and dielectrics. Design of the morphology in conjunction with new synthesis methods is essential for their practical use. In this review, we present the formation of fine particles via a low temperature and ammonia-free synthesis method, the morphology of the oxynitride perovskites obtained using metal carbodiimide, and the toughness of the sintered ceramics in relation to their microstructure.

Making highly efficient and stable perovskite solar cells (PSCs) are often based on the processing techniques, band gap of the material and effective interface charge separation. The efficiency of PSCs can be enhanced through several methods including the utilization of a solar-friendly absorber, interface passivation and the implementation of multi-junction spectrally matched absorbers or bilayered phase homojunction (BPHJ) consisting of identical absorbers. Here, we demonstrated BPHJ concept by stacking identical compositions of highly efficient and stable FA_0.15MA_0.85PbI₃ perovskite absorbers adopting solution process (SP) and thermal evaporation (TEV) techniques. We successfully achieved FA_0.15MA_0.85PbI₃ (SP)/FA_0.15MA_0.85PbI₃-(TEV) based BPHJ normal n-i-p devices, which significantly crossing 22.

% PCE. These improvement stems from effective deposition method for achieving high-quality FA_0.15MA_0.85PbI₃-based BPHJ enabling smooth charge transfer at the interfaces. The resulting BPHJ-based champion device achieve a 22.13 % PCE and retain >95 % its original efficiency over 1000 hours.

Lithium-rich manganese-based transition metal oxide Li_1.2Ni_0.2Mn_0.6O₂ (LNMO) can achieve high energy density due to the interaction of anionic redox kinetics in Li₂MnO₃. However, the irreversible release of oxygen and migration of Mn ions during deep de-lithiation disrupts the layer structure of LNMO, leading to a decrease in voltage and capacity. Herein, we confine oxygen anion through Zr and Al co-doping. Combined analysis of structure refinement, XPS and XAS, the co-doped strategy effectively prohibits cation disordering of Li/Ni, inhibits the Jahn-Teller effect and reduces the transition metal (TM) and oxygen hybridization. As a result, the Zr and Al co-doping LNMO sample (ZA-LNMO) possesses a capacity retention of 92% after 100 cycles and 86% after 200 long-term cycles, much higher than the value of the undoped sample (79% for 100 cycles and 58% for 200 cycles). Even at the harsh conditions such as ultra-high current rate (10 C) or high temperature (60 °C), ZA-LNMO also maintains 70% retention after 200 cycles. Our findings provide an insight into the synergistic effect of cation co-doping and help to design layered oxides for future applications.

Perovskite-type oxynitrides ACa_0.2M_0.8O_2.6N_0.4 (A = Sr, Ba; M = Nb, Ta) were synthesized via the ammonolytic reaction between A₅M₄O₁₅ and CaCl₂, where the Ca²⁺ insertion and O²⁻/N³⁻ substitution occurred cooperatively. In terms of the average structure, SrCa_0.2Nb_0.8O_2.6N_0.4 and SrCa_0.2Ta_0.8O_2.6N_0.4 belong to the orthorhombic Pnma space group, and BaCa_0.2Nb_0.8O_2.6N_0.4 and BaCa_0.2Ta_0.8O_2.6N_0.4, the primitive cubic Pm $\bar{3}$ m group. The comparison between the experimental lattice volume and the summed ionic volume suggested that ACa_0.2M_0.8O_2.6N_0.4 have higher degrees of ionicity than AM'_0.2M_0.8O_3−xN_x (M′ = Li, Mg, Mn), but are more covalent than ANa_0.2M_0.8O_2.8N_0.2. Despite the significant mismatches of size and charge between Ca²⁺ and Nb⁵⁺ (or Ta⁵⁺), no cation ordering was detected on the octahedral site. On the other hand, the O/N distribution appeared to depend on the bonding geometry around the anion sites in a way N favors the straighter bonding connectivity of M−N−M. The band gap energies of ACa_0.2M_0.8O_2.6N_0.4 were estimated to be 1.9–2.25 eV depending on A and M. The band gaps and color properties of AMO₂N and AM'_0.2M_0.8O_3−xN_x (A = Sr, Ba; M = Nb, Ta; M′ = Li, Na, Mg, Ca, Mn) are compared. Thermogravimetry and differential scanning calorimetry were conducted in the air to assess the oxynitride stability. The electrical behaviors were studied by the equivalent circuit analysis of the impedance spectrum using compacted polycrystalline specimens, where BaCa_0.2Ta_0.8O_2.6N_0.4 was found to possess a bulk dielectric constant of 4550 along with an electrical conductivity of ≈10⁻⁶ S/cm at 27 °C. It remains, however, necessary to assess the extrinsic effects arising from the non-ideal sintering to interpret thoroughly the electrical property of BaCa_0.2Ta_0.8O_2.6N_0.4.

Ferroelectric ceramics, which exhibit the phenomenon of reversible spontaneous polarization, have been utilized in multiple conventional applications including sensors, actuators, nano-generators, micro-electromechanical systems (MEMS), memory storage systems, energy harvesting devices, etc. Recently, ferroelectric ceramics have been employed for catalysis-induced applications. One of such catalysis process is known as ‘pyrocatalysis’, which makes use of pyroelectric materials to execute catalysis reactions using temperature fluctuation-derived waste thermal energy/heat. This new and evolving pyrocatalysis process has shown promising potential in new and exciting applications including water-cleaning, water-splitting, bacterial disinfection, tooth whitening, carbon-dioxide reduction, tumor therapy, etc. In principle, ferroelectric ceramics are always pyroelectric in nature, which enables them to be utilized for pyrocatalytic applications. High pyrocatalytic performances of ferroelectric ceramics have been reported by various reports in multiple applications. This review starts with the basic introduction to ferroelectric ceramics, pyroelectric effect, and pyrocatalysis process. Further, it provides the review of recent studies utilizing ferroelectric ceramics for pyrocatalytic applications. The strategies to improve pyrocatalytic performance of ferroelectric ceramics are discussed in detail. At last, this review provides insights to new future directions for researchers working on ferroelectric pyrocatalysts.

Being a highly proficient material for electrochemical energy storage systems, MXene is gaining popularity. MXene pseudocapacitive charge storage system with electric double layer behaviour has improved the efficiency of supercapacitors. Furthermore, the proper interlayer spacing and distinct chemistry have enabled batteries to attain high capacity while enabling quick charge-discharge. Such breakthroughs are a result of MXene inherent characteristics, including its strong electrical conductivity, well defined layered structure, and capacity for modification, which allows it to customize electrodes to a particular purpose. Additionally, MXenes have shown their value by allowing supercapacitors and batteries to defy convention and explore the world of hybrid capacitors, micro-supercapacitors (MSCs), and batteries other than Li-ion. This article covers the MXene-based supercapcitor electrodes and difficulties associated with them. By using logical analysis, we also present several important directions for future study that could assist in resolving these issues and enabling the family of MXene materials to reach its full potential.