Search Results (204)

LaNi_1-xFe_xO_3-δ (LNF) perovskite oxides are promising Sr- and Co-free materials for solid oxide fuel cell (SOFC) cathodes and energy-related catalytic applications. The Ni/Fe ratio strongly influences their electronic structure, defect chemistry, transport properties, reducibility, and structural stability. This review examines how these composition-dependent properties affect LNF synthesis and performance across different applications. For SOFC cathodes, LaNi_0.6Fe_0.4O₃ is an important reference composition because of its favorable balance of conductivity, thermal compatibility, and stability. In oxygen evolution electrocatalysis and other applications, however, the preferred Ni/Fe ratio varies substantially with the required reaction properties and operating conditions. Synthesis, microstructure, surface reconstruction, reduction, and exsolution further affect the functional state of LNF. Therefore, no universally optimal Ni/Fe ratio exists. Composition should instead be selected for the intended application, followed by appropriate synthesis and surface/interface engineering to further improve performance. Full article

Juniperus species form critical, long-lived high-mountain forest ecosystems in Central Asia, serving essential phytocoenotic and ecological functions in environmentally challenging habitats. However, the relationships between the elemental composition of these evergreen conifers and their underlying soils remain poorly understood. This study evaluated and compared the distribution of major elements (Fe, Ca, P, Mg, Al, Na, K, S), trace elements (Cu, Pb, Zn, Ni, Co, Mn, As, Cd, Cr, Mo, U, Th, Sr, Sb, Bi, V, La, Ba, Ti, B, W, Sc, Zr, Tl, Ta, Nb, Se, Te, Ga, Cs, Ge, Hf, Rb, Sn and others), and environmental pollution indices (Igeo, EF, CF, BAF) in plant tissues (leaves and cones) and canopy soils of three key juniper species (Juniperus seravschanica, J. turkestanica, and J. semiglobosa) in the Fann Mountains, Tajikistan. Soil and plant samples were collected across natural habitats and analyzed for total chemical composition using ICP-OES. The soils showed a near-neutral reaction (pH 7.02–7.42 in H₂O and 6.41–7.15 in KCl), with considerable variability in Corg. content (5.04%–21.82%) and Nt content (0.337%–1.149%) in the humus (A) horizons. Geochemical indices (Igeo up to 2.42, EF up to 35.30) indicated noticeable soil enrichment and localized contamination by arsenic (As) and cadmium (Cd), likely driven by a combination of regional industrial and mining activities alongside natural geogenic enrichment. Across all sites, elemental concentrations followed a consistent sequence: soil > leaves ≈ cones. Heavy metals in plant tissues remained well below toxic thresholds. High organ-specific partitioning was observed: K predominated in cones (K > Ca > P), whereas Ca and Fe accumulated predominantly in leaves (Ca > K). Low bioaccumulation factor values (BAF < 1) indicate limited element accumulation relative to total soil concentrations for all three species, which may be influenced by both reduced bioavailability in neutral-to-alkaline soils and potential physiological regulation. As the first data reported from this region, these findings establish an essential baseline for long-term ecological monitoring, soil–plant chemistry, conservation, and environmental risk assessment in the Fann Mountains’ juniper ecosystems. Full article

Dissolved oxygen concentration is a key parameter determining the oxidation and corrosion behavior of structural materials in lead-based fast reactor coolants. Therefore, achieving high-precision in-situ oxygen measurement in LBE systems is a fundamental technical requirement for implementing oxygen-controlled corrosion protection. Currently, nuclear-grade Bi/Bi₂O₃ solid-state electrochemical oxygen sensors have a minimum effective operating temperature of 350 °C, which prevents them from meeting the real-time oxygen monitoring needs under low-temperature conditions. This temperature limitation has become a major bottleneck for the engineering application of oxygen control technology. To address these requirements and challenges, this study develops a novel electrochemical oxygen sensor based on an 8 mol% Y₂O₃-stabilized ZrO₂ (8YSZ) solid electrolyte and La_0.6Sr_0.4Co_0.2Fe_0.8O_3±δ (LSCF) electrode system. Comparative experiments with Bi/Bi₂O₃ sensors are conducted to quantitatively assess the advantages of the LSCF/Air sensor in low-temperature applications within 205~550 °C. Furthermore, considering the irradiation environment in nuclear reactors, oxygen ion irradiation was employed as an accelerated simulation method to preliminarily investigate the electrochemical transport properties of 8YSZ after irradiation. The effects of oxygen ion irradiation on the apparent impedance and apparent oxygen ion conductivity of 8YSZ were evaluated. The results show that the LSCF/Air oxygen sensor has the potential to extend the lower operating-temperature limit of 8YSZ-based oxygen sensors in static, oxygen-saturated LBE environments. Oxygen ion irradiation increased the apparent impedance and decreased the apparent ionic conductivity of the tested 8YSZ samples. These results provide preliminary experimental data for the development of oxygen sensors for oxygen monitoring and corrosion control in liquid-metal-cooled reactor systems over a wider temperature range. Full article

Reversible solid oxide cells (ReSOCs) represent one of the most promising electrochemical technologies for sustainable energy conversion and storage, yet their large-scale deployment remains constrained by electrode materials capable of sustaining stable performance under alternating oxidizing and reducing conditions. Reversible solid oxide cells require electrode materials that combine phase stability, chemical compatibility, redox tolerance and a microstructure suitable for gas transport and surface reactions. However, the relationships among cation composition, thermal processing, phase formation and local chemical homogeneity remain insufficiently understood, particularly for compositionally complex perovskite-related oxides. In this work, this problem was addressed through a comparative physicochemical screening of three candidate electrode materials synthesized by a simple co-precipitation route: two co-doped lanthanum ferrites, (La_0.8Sr_1.2) (Fe_0.9Co_0.1)O_6+δ (LSFC) and (La_0.8Ca_1.2) (Fe_0.9Co_0.1)O_6+δ (LCFC), and one high-entropy praseodymium nickelate, Pr(Ba_0.8Ca_0.2)(Fe_0.2Co_0.2Ni_0.2Cu_0.2Zn_0.2)₂O_6+δ (PBC-HEO). DTA–TG analysis was used to determine the thermal decomposition and crystallization ranges of the precipitated precursors. Phase evolution as a function of calcination temperature was investigated by X-ray diffraction, while Raman and FTIR spectroscopy were employed to examine the local metal–oxygen environment and structural disorder. Raman spectroscopy confirmed the formation of perovskite-type metal–oxygen frameworks in all samples and revealed distinct redistributions of spectral weight between apical/equatorial (or symmetry-related) BO₆ stretching sub-modes and bending/tilting modes, reflecting different local defect-chemical mechanisms associated with A-site doping (Sr vs. Ca) in the Ruddlesden–Popper ferrites and B-site multi-cation occupancy in the double-perovskite PBC-HEO. Bulk and local elemental compositions were assessed by ICP-MS and SEM-EDS, respectively, and SEM was used to compare particle morphology and porosity. SEM-EDS analysis showed that PBC-HEO developed the most open and interconnected microstructure among the investigated powders, although accompanied by residual compositional heterogeneity. This morphology may favor gas accessibility; however, its effective impact on electrocatalytic performance requires dedicated surface area, porosimetry, electrical, and electrochemical measurements. LSFC formed a single major Ruddlesden–Popper phase only after high-temperature calcination, whereas LCFC retained calcium-containing secondary phases. PBC-HEO developed a major perovskite-related phase at 700 °C, accompanied by minor Zn-rich segregation. Under the selected processing conditions, PBC-HEO retained the finest and most interconnected porous microstructure, although it also displayed the highest local compositional heterogeneity. These results demonstrate that cation selection and thermal history jointly control phase stability, local disorder and microstructure, providing a basis for the subsequent electrochemical evaluation and optimization of perovskite-related ReSOC electrode materials. Full article

The growing demand for high-performance electromagnetic interference (EMI) shielding materials in modern communication and integrated electronics has stimulated interest in materials with tunable dielectric responses. In this study, a series of A-site-doped perovskite oxides—LaCoO₃, (La_0.5Sr_0.5)CoO₃, and (La₁/₃Sr₁/₃Ba₁/₃)CoO₃—were synthesized via a sol–gel method to investigate their dielectric behavior in the radio-frequency (RF) range. Dielectric spectroscopy reveals that LaCoO₃ exhibits a positive permittivity characteristic of semiconductors, whereas Sr substitution induces a metallic state in (La_0.5Sr_0.5)CoO₃, whose dielectric response exhibits a Drude-like dispersion behavior within the measured RF frequency range. Further incorporation of Ba into the A-site results in ternary co-doping, suggesting a reduction in effective carrier transport and a shift in the characteristic dispersion frequency toward the low-frequency region. Consequently, (La₁/₃Sr₁/₃Ba₁/₃)CoO₃ displays a near-zero permittivity at approximately 2.5 kHz, indicating a transition in the dominant reactive response from inductive-like to capacitive-like behavior, which is consistent with the impedance spectroscopy results. This work demonstrates that cation engineering at the A-site enables precise control over the RF dielectric response in perovskite oxides, offering a potential pathway for the design of tunable electromagnetic functional materials relevant to EMI shielding applications with tailored permittivity characteristics. Full article

Rock-forming minerals, olivine and pyroxene, from three ore-bearing intrusions in the Norilsk districts were studied. They are the Norilsk 1 and the Northern and Southern Maslovsky massifs with PGE-Cu-Ni ores, located in the Norilsk syncline. Trace elements such as Al, Ti, Co, Cu, Nd, Sm, Ce, Cr, V, Dy, Y, Yb, Er, Sr, and Eu were determined by LA-ICP-MS. The authors found differences in mineral compositions between picritic gabbro-dolerites from these intrusions. The parental melt of the Southern Maslovsky intrusion corresponded to tholeiitic basalt containing (wt.%) H₂O—0.65, CO₂—0.16, and B—0.004. It was concluded that parental magmas for ore-bearing intrusions had no specific features and were closed to intraplate basalts. Full article

The selective conversion of syngas (CO + H₂) to higher alcohols (C₂₊OH) via Fischer–Tropsch synthesis (FTS) is a strategically important but challenging process, requiring catalysts that can simultaneously sustain C–C chain growth and preserve C–O bonds in reactive intermediates. Over the past decade (2015–2025), perovskite-type complex oxides with the formula ABO₃ have emerged as powerful precatalysts for this application, with LaCoO₃ attracting particular attention due to its structural flexibility, controllable reducibility, and the unique catalytic role of the La₂O₃ phase formed upon reduction. This review systematically covers recent advances in synthesis strategies for LaCoO₃ and substituted perovskites, including sol–gel, co-precipitation, mechanochemical, and template-assisted (KIT-6, SBA-15) methods; effects of A-site (Sr) and B-site (Cu, Ga, Ni, Mn) substitution on reducibility, active phase dispersion, and product selectivity; alkali promotion and its interaction with the perovskite-derived active phase; mechanistic understanding of the alcohol-forming pathway, including the Co⁰/Co³⁺ bifunctional site concept, CO insertion mechanism, and the role of La₂O₃ in suppressing the Boudouard reaction; and catalyst stability and deactivation pathways under FTS conditions. Original data from LaCoO₃ catalysts prepared by co-precipitation with ethylene glycol (LCO-1: S_KOH = 90%, Y_KOH = 57 mg·g⁻¹·h⁻¹) and via citrate/KIT-6 template synthesis (LCO/KIT-6: Y_KOH = 80 mg·g⁻¹·h⁻¹, S_BET = 220 m²/g) at 240 °C and 2 MPa serve as the primary experimental reference throughout. Key challenges, including the surface area–selectivity trade-off, long-term stability under industrial conditions, and opportunities in CO₂ hydrogenation, are critically discussed. Full article

The sluggish kinetics of the OER in alkaline media demand efficient non-precious electrocatalysts. This study develops a strategy of B-site Ru doping in Sr-substituted LaCoO₃ perovskite to engineer its electronic structure, thereby activating the LOM. DFT calculations and electrochemical measurements were employed to investigate the electronic structure and catalytic performance. The synthesized La_0.6Sr_0.4Co_0.9Ru_0.1O₃ (LSCR-0.1) catalyst achieves a low overpotential of 256.8 mV at 10 mA cm⁻² and a Tafel slope of 84.88 mV dec⁻¹, along with excellent long-term stability in alkaline electrolyte. The results show that Ru doping shifts the O 2p-band center and lowers the oxygen vacancy formation energy, significantly reducing the energy barrier of the rate-determining step. This work concludes that B-site doping on A-site substituted perovskites offers a general and effective strategy for modulating their electronic structure to enhance OER performance. Full article

The electrochemical co-conversion of CO₂ and H₂O into valuable products is a promising approach toward carbon-neutral energy systems. Alloy exsolution from perovskite lattices has emerged as an effective strategy to engineer catalytic interfaces, yet the mechanistic influence of exsolved bimetallic species on CO₂/H₂O co-electrolysis remains insufficiently clarified. To address this gap, density functional theory (DFT) calculations were performed in this study to systematically examine how NiFe alloy clusters exsolved from the LSFNO (La_0.7Sr_0.3Fe_0.9Ni_0.1O_3-δ) (111) surface modify the electronic structure of the interfacial region and promote the RWGS reaction in CO₂/H₂O co-electrolysis. Our work highlights bimetallic alloy exsolution as a powerful strategy for improving co-electrolysis catalysts and offers valuable guidance for the rational design of next-generation high-entropy oxide systems. Full article

Perovskite-type oxides are among the most promising cathodes for intermediate-temperature solid oxide fuel cells (IT-SOFCs) due to their mixed ionic–electronic conductivity and compositional flexibility. Many high-performance cathodes rely on Sr substitution at the A-site, often associated with surface segregation and long-term degradation. In this work, we explore an alternative strategy based on defect engineering and phase interactions in Sr-free composites. Perovskite-fluorite composites based on LaFe_0.8Co_0.2O₃ were synthesized through a one-pot route designed to promote the formation of a perovskite phase and a limited amount of fluorite-type ceria. This approach allows the introduction of small fractions of Ce into the perovskite lattice, favoring the cooperative coexistence with La-doped CeO₂. Structural, microstructural and spectroscopic characterization indicates that Ce influences the crystallization pathway and composite defect chemistry. Variations in lattice parameters and Raman features suggest modifications of perovskite structure consistent with defect formation and lattice distortion. Reduction properties and electrical conductivity measurements indicate that Ce incorporation in the perovskite and oxide interaction affect charge transport and oxygen mobility. The electrochemical results demonstrate that the optimal trade-off between activation energy (Ea) and polarization resistance (Rp) is achieved for the sample, with a nominal cerium content, Ce/(La + Ce) of 0.16. Moreover, the electrochemical properties are found to correlate with the nominal cerium content, which regulates defect chemistry and the resulting composite composition. Overall, results suggest that the one-pot synthesis promotes beneficial interactions between the perovskite and ceria phases, allowing the development of Sr-free ferrite-based materials with enhanced functional properties, minimizing the amount of ceria in the composite. Full article

Deep-to-ultra-deep marine carbonate reservoirs represent an important frontier for hydrocarbon exploration in the Tarim Basin, yet fluid sources and accumulation processes in the Ediacaran (Sinian) succession remain poorly constrained due to extreme burial depth and complex tectono-thermal evolution. Here, we investigate fracture–vug reservoirs of the Sinian Qigebulake Formation in Well LT3 (Tabei Uplift) using an integrated dataset including petrography and cathodoluminescence, fluid-inclusion microthermometry, fluorescence and Raman spectroscopy, in situ major/trace element analysis and C–O–Sr isotope geochemistry, and LA-ICP-MS carbonate U–Pb dating of authigenic minerals. The paragenetic sequence comprises early dolomite (Dol-I), later dolomite (Dol-II), co-precipitated calcite (Cal-I) and quartz (Qtz-I), and late solid bitumen (Bit). Dolomite veins show PAAS-normalized REE patterns and 87Sr/86Sr ratios (0.70918–0.70984; average 0.70942) comparable to the surrounding Sinian marine wall rocks, indicating precipitation from diagenetic fluids dominated by closed-system water–rock interaction. In contrast, Cal-I displays LREE enrichment, pronounced positive Eu anomalies (δEu = 4.91–7.21), radiogenic ⁸⁷Sr/⁸⁶Sr ratios (0.71161–0.71417; average 0.71256), and negative δ¹⁸O_VPDB values (down to −9.439‰), suggesting a large-scale influx of deep-seated, high-temperature, Sr-rich hydrothermal fluids likely linked to fault-assisted fluid circulation. Fluid inclusions record four hydrocarbon charging episodes, evolving from lower- to higher-maturity oils and ultimately to dry gas. Dol-II hosts pale-yellow to pale-blue oil inclusions, whereas Cal-I and Qtz-I predominantly contain deep-blue oil inclusions and methane-rich gas inclusions (Raman peak near 2917 cm⁻¹). Carbonate U–Pb ages constrain dolomite precipitation to the Middle Ordovician (~468–463 Ma) and hydrothermal-related carbonate filling to the Early Triassic (~247–244 Ma). Collectively, these results support a time-resolved evolution in which early diagenetic fluid circulation in a marine carbonate system was overprinted by a later hydrothermal pulse that modified pore structures and thermal conditions, followed by late-stage deep burial leading to cracking of retained liquids, widespread bitumen formation, and methane charging. This framework provides new information on the constraints for fluid–rock interaction and hydrocarbon evolution in deep marine carbonate successions. Full article

This study reports a dual composition-interface engineering strategy for high-performance La_1−xSr_xCoO₃/NiFe-LDH hierarchical heterojunction. Porous La_1−xSr_xCoO₃ microspheres were synthesized through a gel route. Then it was used as an in situ–formed template to grow NiFe-LDH nanosheets. The hierarchical design inhibits nanosheet aggregation and ensures robust interfacial contact, mitigating the intrinsic instability of physical mixtures. The prepared composite displays superior OER performance in 1.0 M KOH, delivering an overpotential of 237.8 mV at 10 mA cm⁻² and a Tafel slope of 85.06 mV dec⁻¹. These values exceed those of the original samples and commercial RuO₂ and the composite exhibits excellent long-term stability under harsh alkaline conditions. Complemented by DFT calculations, we further indicate that Sr doping coupled with the heterointerface induces substantial electronic structure reconstruction. This effectively switches the OER mechanism from conventional AEM to the thermodynamically more favorable LOM, overcoming the intrinsic scaling relation constraints of AEM. Full article

We report, for the first time, waimirite-(Y) in Egypt. This is only the third reported occurrence of this mineral in the world. This observation arose during our study of the rare earth element (REE) mineralization associated with the Neoproterozoic rare-metal granite intrusion in Wadi Abu Rusheid in the Eastern Desert of Egypt. The principal lanthanide and yttrium (Y) hosts in the area are waimirite-(Y) and bastnäsite-(Ce) in leucogranite and bastnäsite-(Y) in adjacent metasedimentary country rock. The leucogranite is a strongly fractionated, metaluminous to weakly peraluminous (A/CNK = 0.98–1.03), medium- to high-K calk-alkaline I-type granite. The metasediments are composed of upper greenschist to lower amphibolite-grade biotite schists with variable amounts of amphibole, graphite, and garnet. Leucogranite contains accessory Li-bearing mica, garnet, zircon, fluorite, and columbite in addition to the REE minerals. It is enriched by three orders of magnitude relative to primitive mantle in Li, Rb, Th, Ta, Nb, Pb, U, and Sn; relative to these highly enriched elements the concentrations of Sr, Ba, Ga, Zr, Hf, and Y are notably low. The REE patterns of most samples show strong enrichment in heavy relative to light REE but occasional samples have light REE-enriched patterns controlled by accessory REE minerals, and all display strong negative Eu anomalies (Eu/Eu* ≤ 0.05). The whole-rock chemistry of the metasedimentary units are different; relative to average upper continental crust they show enrichments of one to two orders of magnitude in Li, Rb, Pb, Sn, Cs, and sometimes Cr and Zn. The REE patterns of the metasedimentary units are nearly flat, with some samples showing negative Eu anomalies. Waimirite-(Y), nominally YF₃, also contains several weight percent each of Yb, Dy, and Er. The empirical formula (based on one cation) is (Y_0.55Ce_0.02Pr_0.01Nd_0.02Sm_0.02Gd_0.02Dy_0.05Er_0.04Yb_0.05Th_0.05Ca_0.16Pb_0.01)_∑1.00(F_2.48O_0.52)_∑3.00. Bastnäsite-(Ce) in leucogranite samples, nominally Ce(CO₃)F, also has several weight percent each of Nd₂O₃ and La₂O₃. The REE host in metasedimentary rocks is bastnäsite-(Y), nominally Y(CO₃)F, but also rich in Nd₂O₃ (11–19 wt.%) and La₂O₃ (4–14 wt.%). It is intimately associated with fluorophlogopite. The geochemical, mineralogical, and textural evidence indicates that waimirite-(Y) and bastnäsite-(Ce) in leucogranite crystallized from granite-derived F- and CO₂-bearing hydrothermal fluids, whereas the source of Y for growth of the bastnäsite-(Y) in the metasedimentary rocks is unclear; the large negative Ce anomaly in bastnäsite-(Y) suggests an oxidizing supergene setting. Despite their proximity, if there is a genetic connection between the mineralization in the granite and in its country rocks, the relationship is not evident from elemental patterns or host mineralogy. Full article

The Yaojia Formation in the northeastern Songliao Basin is a primary target horizon for sandstone-type uranium mineralization in the area. Understanding its provenance, composition, and depositional paleoclimate is of great significance for uranium exploration in the region. This study analyzed 58 sandstone and mudstone samples using petrographic thin-section observation, elemental geochemistry, and detrital zircon U-Pb geochronology. The results show that Yaojia Formation sandstones are feldspathic lithic quartzose sandstone (averaging 47% lithics, 32% quartz, and 21% feldspar, mainly K-feldspar), with moderate sorting and predominantly angular to subangular grains, indicating rapid denudation in the source area, medium- to short-distance transport, and rapid deposition. The chemical weathering index (CIA, 52–68) and the index of compositional variation (ICV, 0.83~1.26) are generally low, indicating moderate chemical weathering. Rb/Sr, Sr/Cu, Al₂O₃/MgO, CIA, MgO/CaO ratios indicate that the Yaojia Formation was deposited under predominantly arid–semiarid conditions, with later stages being wetter than earlier ones. Rare earth element (REE) characteristics indicate light REE enrichment, heavy REE depletion, and significant negative Eu anomalies. Combined with A-CN-K diagrams and discriminant plots such as La/Th-Hf and Co/Th-La/Sc, the provenance is primarily derived from felsic magmatic rocks in a post-orogenic extensional tectonic setting. Detrital zircon U-Pb ages are mainly concentrated at 119–153 Ma (64%), 160–183 Ma (14%), and 318.3–327.7 Ma (6%), showing the highest similarity to zircon age spectra from magmatic rocks in the Great Xing’an Range. The comprehensive results indicate that the clastic rocks of the Yaojia Formation in the study area were mainly sourced from Early Cretaceous felsic magmatic rocks in the Great Xing’an Range and have undergone short- to medium-distance transport and sedimentation under arid to semi-arid paleoclimatic conditions. Full article

In this work, an A-site deficient perovskite, (La_0.3Sr_0.6Ce_0.1)_0.9Co_0.1Ti_0.9O_3−δ (LSCCoT) was applied as an additional catalytic layer on Ni–YSZ anode for biogas-fuelled SOFC. Under reducing conditions, the formation of well-dispersed, socketed Co nanoparticles was observed due to the cobalt exsolution from the perovskite lattice. The structural and microstructural characterization confirmed phase stability of the perovskite after high-temperature reduction in hydrogen and the presence of exsolved nanoparticles on the grains’ surface. Electrical conductivity measurements showed thermally activated semiconducting behavior in air (E_a = 0.582 ± 0.121 eV) and a strongly enhanced conductivity with weak temperature dependence in hydrogen (E_a = 0.057 ± 0.001 eV). Single-cell tests performed under a CH₄/CO₂ (60/40 vol%) biogas mixture revealed a 30% increase in maximum power density at 800 °C compared to the reference cell. During 100 h of operation, the modified cell exhibited reduced performance degradation, improved internal reforming activity, and a more stable outlet gas composition. Full article