Progress in Solid State Chemistry最新文献

Titanium Nitride (TiN) is widely used in many industrial sectors for its outstanding performances including its mechanical properties, high chemical and thermal stability. Associated with its plasmonic behavior, TiN thin films are very promising for the manufacturing of optical metasurfaces devices or new plasmonic materials. Among the processes that make it easy to obtain metal nitride coatings, nitriding of metal oxide films has become increasingly popular in recent years. A multitude of synthesis processes can be used to obtain TiO₂ films, with different crystalline states (amorphous, anatase or rutile) depending on the technique used, which can then be converted into TiN coatings. In this paper, the effect of the initial crystalline state of TiO₂ layers was investigated on the structural properties, plasmonic properties and the friction behavior of TiN thin films obtained by Rapid Thermal Nitridation (RTN). The results indicate that, regardless of the crystalline state of the starting TiO₂ film, the RTN process leads to complete nitridation of TiN coating. Moreover, even though surface morphology and friction properties differ slightly, depending on the crystallization of the starting TiO₂, plasmonic properties remain very similar, thus highlighting the great versatility and uniformity of this nitriding technique, enabling TiN to be produced for a wide range of applications.

Among the Material of Institute Lavoisier (MIL) compounds, MIL-125 has been proved to be potentially high photoactive electrode in the photoelectrochemical (PEC) devices. The great progress has been achieved in the preparation, structural optimization and applications of MIL-125, especially in the PEC technology, as witnessed by the quick increase in the number of published papers. Consequently, a comprehensive review of the current research status of MIL-125 based electrodes in PEC is warranted. This review provides an in-depth analysis of various PEC applications employing MIL-125 based photoelectrodes, such as sensing (including PEC biosensors, organic pollutant detection, and heavy metal ion sensing), water splitting for hydrogen production, photovoltaic cells (including dye-sensitized solar cells, quantum dot-sensitized solar cells, perovskite solar cells, and organic solar cells), photoelectrocatalysis, and photocathodic protection. Particular emphasis is placed on the signal amplification strategies, modification design, and reaction mechanisms of MIL-125 for PEC applications. Finally, the development opportunities and unsolved challenges associated with MIL-125 based materials in the PEC field are also highlighted. This comprehensive review is expected to expand the knowledge of recent advancements in MIL-125 and its derivatives modified electrodes and encourage researchers to promote the construction of efficient PEC systems.

Transition metal nitrides (TMNs), in some cases referred as metallic ceramics, have unique physical and chemical properties, thanks to their ceramic-metallic nature, and are considered an attractive alternative to noble metals for electrochemical processes. In particular, theoretical work predicts TMNs as promising electrocatalysts towards the nitrogen reduction reaction (NRR). However, recent experimental studies under realistic conditions, have shown the release of lattice nitride to ammonia in a noncatalytic process, suggesting inherent instability of these materials. TMNs stability can be increased by the incorporation of a second metal in the lattice, to form bimetallic systems. Herein, we present a robust approach to prepare nonprecious transition multi-metallic nitride nano-catalysts, followed by a comprehensive study on their stability. The stability of the as-prepared catalysts was tested in electrolytes relevant for electrocatalysis, showing a higher chemical resistance of the bimetallic catalysts over the monometallic ones. This study suggests a novel approach to matching electrolyte pH and catalyst to ensure chemical stability in the electrochemical environment.

This article investigates the densification of AlN ceramics through both Gas Pressure Sintering (GPS) and Spark Plasma Sintering (SPS) methods, employing cerium aluminates (CeAlO₃) as sintering aids and comparing their influence to that of the usual cerium oxide (CeO₂). While sintering aids like CeO₂ promote densification, CeAlO₃ exhibited lower reactivity during both SPS and GPS sintering. Chemical reactions between cerium oxide and aluminium oxide primarily involved the reduced phase as cerium sesquioxide (Ce₂O₃). On the basis on the Ce₂O₃–Al₂O₃ pseudo-binary system, the formation of secondary phases, such as CeAlO₃ and CeAl₁₁O₁₈, during sintering was explained and confirmed by XRD. From complementary characterizations, it has been shown that sintering significantly impacted secondary phase composition and distribution. By employing specific densification cycles, SPS yielded smaller grains and thicker secondary phase cordons which led to enhanced electrical conductivity. Conversely, GPS produced coarser microstructures including larger grains and a network of secondary phases and some agglomerations at the triple points. These modifications influenced the overall conductivity. SPSed samples with 3 wt.% CeO₂ and short dwelling times demonstrated higher electrical conductivity, exceeding by about 6 orders of magnitude the electrical conductivity of those obtained by GPS.

We present a range of inverse perovskite nitrides with an elpasolite-type superstructure. (Ca₃N_0.682(9))Sn and (Ca₃N_0.559(7))Pb are variants of the previously described (Ca₃N)Sn and (Ca₃N)Pb which contain less nitrogen and crystallize in $Fm\bar{3}m$. (Ba₃N_0.5)Sn and (Ba₃N_0.5)Pb resemble the previously reported perovskites (Ba₃N_x)Sn and (Ba₃N_x)Pb, but with both the superstructure and octahedral tilting, resulting in space group $R\bar{3}$. (Ca₃N_0.77(2))Si, (Ca₃N_0.669(6))Ge, (Sr₃N_0.5)Ge and (Ba₃N_0.5)Ge all crystallize in P2₁/n. Among these, only (Ca₃N_x)Ge has been previously described as (Ca₃N)Ge. (Ca₃N_0.77(2))Si is notably the first compound in which mutually isolated N³⁻ and Si⁴⁻ ions coexist. There also exists a version with composition (Ca₃N_0.86(6))Si, which crystallizes in the cubic perovskite aristotype structure with space group $Pm\bar{3}m$. Similarly, there are versions of (Sr₃N_0.5)Ge, (Ba₃N_0.5)Sn and (Ba₃N_0.5)Pb with elevated nitrogen contents, less strongly tilted octahedra and no apparent superstructure. Electronic structure calculations indicate a metallic nature of the title compounds, with rather narrow improper band gaps for the strontium and barium compounds.

From crystal chemistry and density functional theory DFT calculations, a stepwise rationale is proposed for the transformation from standalone distorted tetrahedron α-C₅ favored over standalone regular tetrahedron β-C₅ to high density – ultra hard orthorhombic α-C₆ and β-C₆ with qtz (quartz-based) topology characterized by 3D arrangements of distorted tetrahedra to lower density dia-C topology (diamond-like, with regular C4 tetrahedra). Progressive C insertions into orthorhombic α-C₅, α-C₆, and lastly into C₇ were operated leading to ultimate C₈ stoichiometry identified as diamond-like. C₇ was also used as template to devise C₃N₄ carbonitride with exceptional mechanical properties. The induced structural and physical changes are supported with elastic properties pointing to ultra-hardness, larger for qtz α,β-C₆ than dia C₈ and inferred dynamic stability for all stoichiometries from the phonons band structures. The thermodynamic quantities as the specific heat were compared with diamond experimental C_V. The electronic band structures reveal semi-conducting C₆, metallic C₇ characterized by diamond-defect structure, and insulating C₈. The results are meant to help further systemic understanding of tetrahedral carbon allotropes.

Interest in perovskite solar cell (PSC) research is increasing because PSC has a remarkable power conversion efficiency (PCE), which has notably risen to 28.3 %. However, commercialization of PSCs faces a significant obstacle due to their stability issues. This review article primarily focuses on several key aspects of PSCs, including different types of solar cells, their construction and operational mechanisms, efficiency, and overall stability. It explains the structure and functioning of PSCs, covering materials and components used for absorber layer, electron-transport layer, hole-transport layer, and electrodes. This review emphasized stability challenges associated with PSCs and discussed various factors and issues contributing to the degradation of these solar cells over time. It then provided a concise overview of different strategies and ongoing efforts taken to enhance the stability of PSCs. It also summarized various approaches used to improve their durability. In summary, this article offers a comprehensive exploration of PSCs, encompassing their construction, operation, improvement in efficiency, and obstacles related to their long-term stability. Furthermore, it addresses factors influencing PSC stability and outlines future challenges, focusing on prolonging their lifespan and enhancing stability for broader applications. Finally, this article has tackled various possible solutions to address the challenges encountered by the PSCs.

Fe³⁺-activated near-infrared (NIR) luminescent materials have attracted growing research interests for their tunable broadband emission and extensive application potentials in the fields of night vision, biomedical imaging, nondestructive food analysis, etc. Deep insight into the relation between crystal structure and luminescence performance plays a significant role in developing novel efficient NIR functional materials. In this review, after a brief introduction, we first discuss the mechanism of Fe³⁺ luminescence in octahedral and tetrahedral crystal fields based on the Tanabe-Sugano energy level diagram. Next, the research progress of Fe³⁺-doped NIR luminescent materials, including structure, property and potential application, is summarized, followed by the strategies to enhance NIR steady-state luminescence, persistent luminescence and mechanoluminescence performances. Then we conduct a comparison of luminescence efficiency and luminescence thermal stability of Fe³⁺-doped NIR materials. At last, we propose several challenges and outlooks in the research of Fe³⁺-activated NIR luminescent materials. This review is aimed to provide a deeper understanding of not only Fe³⁺ luminescence mechanism but also the current research progress of Fe³⁺-doped materials, so as to provide constructive strategy in the exploitation of efficient Fe³⁺-activated NIR luminescent materials.

This review presents an overview on the structures and electrical properties of B-site deficient hexagonal perovskite oxides, which have been receiving increasing attention as key components as dielectric resonators in microwave telecommunications, as well as solid-state oxide ion and proton conductors in solid oxide fuel cells. The structural evolution and stability, order-disorder of cation and anions, and mechanisms underlying the dielectric and ionic conduction behaviors for the B-site deficient hexagonal perovskites are summarized and the roles of the B-site deficiency on the structural stability and option, ion order-disorder and electrical performance are highlighted. This provides useful guidance for design of new hexagonal perovskite oxide materials and structural control to enhance their electrical properties and discover new functionality as dielectric resonators and solid-state ionic conductors.