Search Results (67)

High-Temperature Proton-Exchange Membrane Fuel Cells (HT-PEMFCs) represent a promising clean energy technology and are valued for their fuel flexibility and simplified balance of plant. Their commercialization, however, is critically hindered by the prohibitive cost and resource scarcity of platinum-group metal (PGM) catalysts. The challenge is amplified in the phosphoric acid (PA) electrolyte of HT-PEMFCs, where the severe anion poisoning of PGM active sites necessitates impractically high catalyst loadings. This review addresses the urgent need for cost-effective alternatives by providing a comprehensive assessment of recent advancements in non-precious metal (NPM) catalysts for the oxygen reduction reaction (ORR) in HT-PEMFCs. It systematically explores synthesis strategies and structure–performance relationships for emerging catalyst classes, including transition metal compounds, metal–nitrogen–carbon (M-N-C) materials, and metal-free heteroatom-doped carbons. A significant focus is placed on M-N-C catalysts, particularly those with atomically dispersed Fe-Nx active sites, which have emerged as the most viable replacements for platinum due to their high intrinsic activity and notable tolerance to phosphate poisoning. This review critically analyzes key challenges that impede practical application, such as the trade-off between catalyst activity and stability, mass transport limitations in thick electrodes, and long-term degradation in the harsh PA environment. Finally, it outlines future research directions, emphasizing the need for a synergistic approach that integrates computational modeling with advanced operando characterization to guide the rational design of durable, high-performance catalysts and electrode architectures, thereby accelerating the path to commercial viability for HT-PEMFC technology. Full article

Recent archaeological sites dating to the late 19th and early 20th centuries have rarely been studied to date. Among the 500 “glassy” beads excavated from Dohouan (Côte d’Ivoire), elemental analyses reveal that fewer than half contain abnormally high alumina contents, associated with a soda–potash–lime flux (three compositional groups). The remaining beads are typical lead-based glass. The Raman spectra of the alumina-rich beads are quite complex due to their glass–ceramic nature, combining features similar to the vitreous phase of porcelain glaze with the presence of various crystalline phases (quartz, wollastonite, calcium phosphate, calcite). Organic residues are also observed. Colors are primarily produced by transition metal ions, although some specific pigments have also been identified. These characteristics suggest that the alumina-rich beads were manufactured by pressing followed by sintering, as described in patents by Richard Prosser (1840, UK) and Jean Félix Bapterosse (1844, France). A comparison is made with beads from scrap piles at the site of the former Bapterosse factory in Briare, France. This process represents one of the earliest examples of replacing traditional glassmaking with a ceramic process to enhance productivity and reduce costs. Full article

The increasing demand for critical metals has intensified efforts to recover valuable metals from various sources, including secondary waste. Zn-Pb tailings contain both major and trace metals with economic and environmental significance. This study examined the extraction of transition metals from Zn-Pb tailings using inductively coupled plasma mass spectrometry (ICP-MS) at a constant time of 30 min. Metal extraction efficiencies were evaluated using N-Methyl-N,N,N-trioctylammonium chloride (Aliquat 336), methyl salicylate (MS), di(2-ethylhexyl) phosphoric acid (D2EHPA), tributyl phosphate (TBP),2,4,6-tris(allyloxy)-1,3,5-triazine (TAOT), and triethyl phosphate (TEP). Increasing mixing rates improved mass transfer, enhancing recoveries, with Hf⁴⁺, Ti⁴⁺, and Fe³⁺ reaching 88, 56, and 50%, respectively, at 1000 rpm (mixing rate; rotation per minute) using D2EHPA. At a mixing rate of 1000 rpm, 10% TEP recovered 25% of Cu²⁺ and 34% of Mn²⁺, while 150 g/L extracted 48% of Hf⁴⁺ and 46% of V⁴⁺. Additionally, 10% TBP extracted 33% of Mn²⁺ and 35% of V⁴⁺, 10% MS recovered 41% of Mn²⁺ and 39% of V⁴⁺, while TAOT extracted 35% of V⁴⁺. At room temperature (22.5 °C) and 1400 rpm, 10% of D2EHPA recovered 80% of Hf⁴⁺, 73% of Ti⁴⁺, and 61% of Fe²⁺. However, 10% TAOT selectively recovered 50% of V⁴⁺, while 10% MS, under the same conditions, recovered 50% of V⁴⁺ with co-extraction of Mn²⁺ and Cu²⁺ (<10%). A total of 150 g/L Aliquat 336 effectively extracted Hf⁴⁺ (66%), Zn²⁺ (19%), and V⁴⁺ (56%). A total of 10% TBP recovered 53% and 47% of Mn²⁺ and V⁴⁺, respectively. A total of 10% TEP recovered Cu²⁺ (45%), Mn²⁺ (55%), Zn²⁺ (29%), V (40%), and 26% of Ni²⁺. At room temperature (22.5 °C) and 1400 rpm, pH changes significantly affected extraction, with D2EHPA (10%) demonstrating 89% efficiency for Hf⁴⁺ at pH 1.3, while other metals showed lower recoveries. TEP (10%) increased Cu²⁺ and Hf⁴⁺ recovery to 52% and 80%, respectively, at pH 1.3, while 150 g/L Aliquat 336 favored Cu²⁺ (58%), with co-extraction of 16% of Zn²⁺ at pH 1.3. TBP (10%) extracted 60% and 61% of Cu²⁺ and Fe, respectively, at pH 1.3, while 10% of MS recovered 55% and 50% of V, respectively. A concentration of 10% D2EHPA favored the recovery of 90% of Hf⁴⁺ at pH 1.3, with less than 35% co-extraction of Cu²⁺, Mn²⁺, Zn²⁺, and Fe²⁺. At 1400 rpm, temperature also influenced extraction, with D2EHPA recovering 84% of Hf⁴⁺ at 35 °C, 77% of Ti (55 °C), and 79% of Fe (55 °C) and TBP extracting 73% of Cu²⁺, 67% of Mn²⁺, 68% of Zn, 60% of V⁴⁺, and 47% of Ni²⁺ at 55 °C. A concentration of 10% MS extracted 61% of V⁴⁺and 54% of Fe²⁺, while 150 g/L recovered 61% of V⁴⁺ at 55 °C. TAOT extracted 46% of Mn and 41% of V⁴⁺, while 10% TEP recovered 60% of Mn and 32% of V⁴⁺ at 55 °C. These outcomes contribute to an improved understanding of the solvent extraction mechanisms of different ligands. Full article

Soil fungi are significantly resistant to heavy metals, which allows them to be used in biotechnologies for environmental bioremediation. In order to clarify the prospects for using the fungi in Zn-detoxifying technologies, we investigated in vitro the effect of fungal metabolism on Zn minerals formation. The cultivation of fungi with different acid-producing activities (Aspergillus niger and Penicillium chrysogenum) was carried out in a liquid Czapek–Dox nutrient medium with Zn concentrations from 250 to 2000 µmol within 28 days. The quantitates of low-molecular-weight organic acids, phosphates, and hydrophosphates ions in the medium were determined through chromatography–mass spectrometry; analysis of biomineralization products was carried out through powder X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. It was found that Zn in concentrations 250–500 μmol acts as a physiologically essential element, activating the growth of fungal mycelium, while at high concentrations (1000–2000 μmol), Zn acts as a toxic heavy metal, inhibiting fungal growth. Zn also activates the formation of oxalic acid by both species of fungi. But A. niger strongly acidified the medium, while P. chrysogenum leaves the medium pH close to neutral or slightly alkaline. Oxalate and phosphate crystallization occur with the participation of both fungal species. The ratio of biogenic oxalates and phosphates is directly dependent on the acid-reducing capacity of fungi. The solid solutions of katsarosite–glushinskite of the isodimorphic series with the general formula (Zn,Mg)C₂O₄·2H₂O (Mg ions comes from Czapek–Dox medium) were detected at all Zn concentrations in a wide range of pH (from 2 to 9.0). The transition from monoclinic (α-modifications) to orthorhombic (β-modifications) occurs at the ratio Mg/Zn > 1. Fungal zinc phosphate hopeite Zn₃(PO₄)₂·4H₂O was formed at a near-neutral pH at high Zn concentrations (1000 and 2000 µmol/L). In the Zn example, it was shown that not only oxalate but also phosphate fungal biomineralization can be used for the environment detoxification of heavy metals. The application of phosphate biomineralization seems promising in the case of severe pollutions. To create a near-neutral medium favorable for the formation of phosphates, it is advisable to use soil fungi non-producing or weakly producing organic acids (for example, P. chrysogenum). Full article

Solvent extraction of metals from Ti ore was investigated with a view of enhancing extraction yields by changing the concentration of the ligands, the rate of mixing, the pH, and the temperature of the solution. Norwegian Ti ore was leached with 5M HNO₃ alongside 10% ascorbic acid to obtain a pregnant solution containing transition metals and some rare earth elements (REEs). Part Two of the study will address the recovery of the REEs in the ore. The elemental analysis of solid and aqueous samples was done by two models of total reflection X-ray fluorescence spectrometers (S2 PICOFOX, Bruker Corporation, Berlin, Germany; and T-STAR, Bruker Corporation, Berlin, Germany). The same analysis was repeated using an inductively coupled plasma-mass spectrometer (Perkin Elmer Sciex ELAN DRC II, Perkin Elmer, Waltham, MA, USA). The extraction process and parameters were examined by ICP-MS. The extraction efficiencies were studied under different conditions through the use of various concentrations of ligands at different pHs, temperatures, and mixing rates of the solution. At pH 1.0, 22.5 °C, and a mixing rate of 1400 rpm, the selectivity of 150 g/L trioctyl methyl ammonium chloride (Aliquat 336) was 99% Ti⁴⁺, 94% V⁴⁺, and 82% Hf⁴⁺, while 99% of Co²⁺ was recovered at pH 0.8. The extraction efficiency of triethyl phosphate (10% TEP) was 58% Cu²⁺, 68% Mn²⁺, and 63% V⁴⁺ at 55 °C, 1400 rpm, and without a pH change. Tributyl phosphate (10% TBP) was able to retrieve 87% Cu²⁺ and 78% Zn²⁺ at pH 1.3, 1400 rpm, and 22.5 °C, and 80% Ti⁴⁺ at pH 1.2. A 10% solution of 2,4,6-tris (allyloxy)-1,3,5-triazine (TAOT) demonstrated 61% Mn²⁺ and 56% Hf⁴⁺ extraction at pH 1.3, 22.5 °C, and 1400 rpm. Under the same conditions, 10% methyl salicylate (MS) was able to recover 56% Hf⁴⁺ at pH 1.3. Using 1400 rpm, di (2-ethylhexyl) phosphoric acid (10% D2EHPA) was found to selectively extract 87% Hf⁴⁺ at 22.5 °C without a pH change, and around 99% Co²⁺, Ti⁴⁺, and Fe²⁺ at pH 1.3. This study provides valuable insights into optimizing solvent extraction conditions for transition metals’ recovery and serves as a precursor to future research on the extraction of REEs from Ti ores. This process is relevant from the environmental and economic perspectives since it provides the best approach to recycling metals to reduce the rate of raw ore mining. Full article

One of the priority goals of sustainable socio-economic development for the period up to 2030 is providing food for the planet’s population. This entails an increase in the output of mineral fertilizers and, consequently, an increase in the quantities of solid industrial waste. Phosphogypsum, a by-product of phosphate fertilizer production from apatite ore, is one example of such waste. The problem of solid industrial waste recycling is urgent. The present study examines the process of converting calcium sulfate, in the form of a reagent, and phosphogypsum into a composite material of calcium sulfate/sulfide. An environmentally friendly material, sucrose, is used as a reducing agent. Reduced phosphogypsum (as well as calcium sulfate) luminescence is suggested to be associated with the formation of a CaS/CaSO₄ composite material. The synthesized materials are characterized by X-ray phase analysis, X-ray photoelectron spectroscopy, elemental analysis, and calcium sulfide qualitative and quantitative content in the samples. It is shown that in the reduction process at the phase contact point, crystal grids are formed with a significant number of defects, which contributes to the convergence of some of the energy levels of the calcium cation and sulfide anion, facilitating the transitions of electrons from the valence zone to the core zone and the formation of luminescence centers (cross-luminescence). Both samples of reduced phosphogypsum and alkaline earth metal sulfates are found to exhibit luminescence properties under ultraviolet radiation. The data obtained open up broad prospects for the use of solid industrial waste for the synthesis of new materials. Full article

A stable and efficient porous nickel phosphate (p-NiPO/Ti) electrocatalyst on titanium sheets was developed via electrochemical deposition and low-temperature phosphatization. For obtaining the optimal performance of the p-NiPO/Ti electrocatalyst, the optimized experimental parameters of deposition and phosphatization were determined by parallel experiments. After the preparation, XPS and XRD were used to validate the chemical and amorphous structure, with SEM and TEM simultaneously validating a distinct nanosheet/nanocluster crosslinked microstructure. In particular, with phosphatization conditions maintained at 300 °C for 10 min, the p-NiPO/Ti produced demonstrated excellent charge transfer and catalytic characteristics in 1.0 M KOH. The electrocatalytic results revealed that the optimal p-NiPO/Ti with excellent catalytic performance and excellent stability (~24 h) needs lower HER overpotentials (128 mV at 10 mA cm⁻² and 242 mV at 100 mA cm⁻²) as inputs. This research provides a promising strategy with which to use transition metal materials as catalysts in alkaline electrocatalytic hydrogen production. Full article

A simple, sensitive and reliable sensing system based on nitrogen-rich porous carbon (NRPC) and transition metals, NRPC/Ni, NRPC/Mn and NRPC/NiMn was developed and successfully applied as electrode materials for the quantitative determination of carbendazim (CBZ). The synergistic effect of NRPC and bimetals with acceptable pore structure together with flower-like morphology resulted in producing a highly conductive and interconnected network in NRPC/NiMn@GCE, which significantly enhanced the detection performance of CBZ. The electrochemical behavior investigated by cyclic voltammetry (CV) showed improved CBZ detection for NRPC/NiMn, due to the controlled adsorption/diffusion process of CBZ by the NRPC/NiMn@GCE electrode. The influences of various factors such as pH, NRPC/NiMn concentration, CBZ concentration and scan rate were studied. Under optimal conditions, 0.1 M phosphate-buffered saline (PBS) with a pH of 7.0 containing 30 µg/mL NRPC/NiMn, a favourable linear range detection of CBZ from 5 to 50 µM was obtained. Moreover, a chronoamperometric analysis showed excellent repeatability, reproducibility and anti-interfering ability of the fabricated NRPC/NiMn@GCE sensor. Furthermore, the sensor showed satisfactory results for CBZ detection in real samples with acceptable recoveries of 96.40–104.98% and low RSD values of 0.25–3.45%. Full article

Transition metal phosphate is the prospective electrode material for supercapacitors (SCs). It has an open frame construction with spacious cavities and wide aisles, resulting in excellent electric storage capacity. However, the inferior rate behavior and cycling stability of transition metal phosphate materials in alkaline environments pose significant barriers to their application in SCs. Herein, Ni₁₁(HPO₃)₈(OH)₆/Co₃(HPO₄)₂(OH)₂ heterostructured materials synthesized through a one-step hydrothermal process exhibiting remarkable rate capability coupled with exceptional cycling endurance. Ni₁₁(HPO₃)₈(OH)₆/Co₃(HPO₄)₂(OH)₂ samples exhibit a micron-scale structure composed of sheet-like compositions and unique pore structure. The multistage pore structure is favorable for promoting the diffusion of protons and ions, enhancing the sample’s electrochemical storage capacity. Upon conducting electrochemical tests, it was observed that Ni₁₁(HPO₃)₈(OH)₆/Co₃(HPO₄)₂(OH)₂ composite electrode surpassed both the standalone Ni₁₁(HPO₃)₈(OH)₆ and Co₃(HPO₄)₂(OH)₂ electrode, achieving a remarkable specific capacity of 163 mAh g⁻¹ with exceptional stability and efficiency at 1 A g⁻¹. Notably, this electrode also exhibits superior rate performance, maintaining 82.5% and 71% of its original full capacity even at 50 A g⁻¹ and 100 A g⁻¹, respectively. Furthermore, it demonstrates superior stability in cycling, retaining a capacity of 92.7% at 10 A g⁻¹ after 5000 cycles. Moreover, Ni₁₁(HPO₃)₈(OH)₆/Co₃(HPO₄)₂(OH)₂ and porous carbon (PC) were assembled into a hybrid supercapacitor (HSC). Electrochemical tests reveal an impressive power density of up to 36 kW kg⁻¹ and an exceptional energy density of up to 47.4 Wh kg⁻¹ for the HSC. Moreover, Ni₁₁(HPO₃)₈(OH)₆/Co₃(HPO₄)₂(OH)₂//PC HSC exhibits robust capacity retention stability of 92.9% after enduring 10,000 cycles at 3 A g⁻¹, demonstrating its remarkable durability. This work imparts viewpoints into the design of transition metal phosphate heterostructured materials. Full article

Dopamine (DA) is an important catecholamine neurotransmitter in the mammalian central nervous system that affects many physiological functions. Hence, a highly sensitive and selective sensing platform is necessary for quantification of DA in the human body. In this study, ternary transition metal tellurides of CoNiTe₂ were successfully synthesized using the hydrothermal method. The proposed CoNiTe₂ nanomaterials were dispersed well in Nafion to form a well-dispersed suspension and, when dropped on a glassy carbon electrode (GCE) as the working electrode (CoNiTe₂/Nafion/GCE) for electrochemical non-enzymatic DA sensing, displayed excellent electrocatalytic activity for dopamine electrooxidation. The morphology and physical/chemical properties of CoNiTe₂ nanomaterials were characterized using field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). In order to obtain the best electrochemical response to DA from the fabricated CoNiTe₂/Nafion/GCE, the experimental conditions of electrochemical sensing, including the CoNiTe₂ loading amounts and pH values of the phosphate buffer solution (PBS), were explored to achieve the best electrochemical sensing performance. Under optimal conditions (2 mg of CoNiTe₂ and pH 6.0 of PBS), the fabricated CoNiTe₂/Nafion/GCE showed excellent electrocatalytic activity of DA electrooxidation. The CoNiTe₂/Nafion/GCE sensing platform demonstrated excellent electrochemical performance owing to the optimal structural and electronic characteristics originating from the synergistic interactions of bimetallic Co and Ni, the low electronegativity of Te atoms, and the unique morphology of the CoNiTe₂ nanorod. It exhibited a wide linear range from 0.05 to 100 μM, a high sensitivity of 1.2880 µA µM⁻¹ cm⁻², and a low limit of detection of 0.0380 µM, as well as acceptable selectivity for DA sensing. Therefore, the proposed CoNiTe₂/Nafion/GCE could be considered a promising electrode material for electrochemical non-enzymatic DA sensing. Full article

Introducing post-transition metal cations is an excellent strategy for enhancing optical properties. This paper focuses on four isomers, namely the X₂PO₄I (X = Pb, Sn, Ba, and Sr) series. For the first time, the paper’s attention is paid to the changes in electronic structure, as well as refractive indices and birefringence, with and without the inclusion of spin–orbit effects in this series. The first-principles results show that spin–orbit effects of the 5p and 6p states found in these compounds lead to splitting of the bands, narrowing of the band gap, enhancement of the lone-pair stereochemistry, and enhancement of the refractive indices and birefringence. Moreover, a comparison of the lone-pair electron phosphates, X₂PO₄I (X = Pb and Sn), and the isomeric alkaline earth metal phosphates, X₂PO₄I (X = Ba and Sr), reveals that changes in the band structure have a greater effect on the enhancement of the birefringence than the slight enhancement of the lone-pair stereochemical activity. This study has important implications for a deeper understanding of the optical properties of crystals and the design of novel optical materials. Full article

High-entropy materials (HEMs) constitute a revolutionary class of materials that have garnered significant attention in the field of materials science, exhibiting extraordinary properties in the realm of energy storage. These equimolar multielemental compounds have demonstrated increased charge capacities, enhanced ionic conductivities, and a prolonged cycle life, attributed to their structural stability. In the anode, transitioning from the traditional graphite (372 mAh g⁻¹) to an HEM anode can increase capacity and enhance cycling stability. For cathodes, lithium iron phosphate (LFP) and nickel manganese cobalt (NMC) can be replaced with new cathodes made from HEMs, leading to greater energy storage. HEMs play a significant role in electrolytes, where they can be utilized as solid electrolytes, such as in ceramics and polymers, or as new high-entropy liquid electrolytes, resulting in longer cycling life, higher ionic conductivities, and stability over wide temperature ranges. The incorporation of HEMs in metal–air batteries offers methods to mitigate the formation of unwanted byproducts, such as Zn(OH)₄ and Li₂CO₃, when used with atmospheric air, resulting in improved cycling life and electrochemical stability. This review examines the basic characteristics of HEMs, with a focus on the various applications of HEMs for use as different components in lithium-ion batteries. The electrochemical performance of these materials is examined, highlighting improvements such as specific capacity, stability, and a longer cycle life. The utilization of HEMs in new anodes, cathodes, separators, and electrolytes offers a promising path towards future energy storage solutions with higher energy densities, improved safety, and a longer cycling life. Full article

Na-V-P-Nb-based materials have gained substantial recognition as cathode materials in high-rate sodium-ion batteries due to their unique properties and compositions, comprising both alkali and transition metal ions, which allow them to exhibit a mixed ionic–polaronic conduction mechanism. In this study, the impact of introducing two transition metal oxides, V₂O₅ and Nb₂O₅, on the thermal, (micro)structural, and electrical properties of the 35Na₂O-25V₂O₅-(40 − x)P₂O₅ − xNb₂O₅ system is examined. The starting glass shows the highest values of DC conductivity, σ_DC, reaching 1.45 × 10⁻⁸ Ω⁻¹ cm⁻¹ at 303 K, along with a glass transition temperature, T_g, of 371 °C. The incorporation of Nb₂O₅ influences both σ_DC and T_g, resulting in non-linear trends, with the lowest values observed for the glass with x = 20 mol%. Electron paramagnetic resonance measurements and vibrational spectroscopy results suggest that the observed non-monotonic trend in σ_DC arises from a diminishing contribution of polaronic conductivity due to the decrease in the relative number of V⁴⁺ ions and the introduction of Nb₂O₅, which disrupts the predominantly mixed vanadate–phosphate network within the starting glasses, consequently impeding polaronic transport. The mechanism of electrical transport is investigated using the model-free Summerfield scaling procedure, revealing the presence of mixed ionic–polaronic conductivity in glasses where x < 10 mol%, whereas for x ≥ 10 mol%, the ionic conductivity mechanism becomes prominent. To assess the impact of the V₂O₅ content on the electrical transport mechanism, a comparative analysis of two analogue series with varying V₂O₅ content (10 and 25 mol%) is conducted to evaluate the extent of its polaronic contribution. Full article

Transition metals and their oxide compounds exhibit excellent chemical reactivity; however, their easy agglomeration and high cost limit their catalysis applications. In this study, an interpolation structure of a Myriophyllum verticillatum L. biochar-supported Mn/Mg composite (Mn/Mg@MV) was prepared to degrade triphenyl phosphate (TPhP) from wastewater through the activating periodate (PI) process. Interestingly, the Mn/Mg@MV composite showed strong radical self-producing capacities. The Mn/Mg@MV system degraded 93.34% TPhP (pH 5, 10 μM) within 150 min. The experimental results confirmed that the predominant role of IO3· and the auxiliary ·OH jointly contributed to the TPhP degradation. In addition, the TPhP pollutants were degraded to various intermediates and subsequent Mg mineral phase mineralization via mechanisms like interfacial processes and radical oxidation. DFT theoretical calculations further indicated that the synergy between Mn and Mg induced the charge transfer of the carbon-based surface, leading to the formation of an ·OH radical-enriched surface and enhancing the multivariate interface process of ·OH, IO₃, and Mn(VII) to TPhP degradation, resulting in the further formation of Mg PO₄ mineralization. Full article

Under hydrothermal conditions emulating natural hydrothermalites, three oxo-salts with sodium and transition metal cations were obtained in the form of single crystals. Their compositions and crystal structures were studied using scanning electron microscopy, microprobe X-ray spectral analysis, and X-ray single-crystal diffraction. The sodium cobalt silicate, i.e., Na₂CoSiO₄, a structural analog of the mineral liberite, is well known as an ionic conductor. Its crystal structure consists of a framework derived from β-tridymite, built using the Co- and Si-centered tetrahedra sharing vertices. The sodium oxocuprate phosphate chloride Na₂Cu₃O(Cu₀.₈Na₀.₂)(PO₄)₂Cl belongs to a group of compounds, including fumarolic minerals, characterized by the presence of oxo-centered pyroxene-like chains in their structures. The crystal structure of mineralogically probable sodium vanadium phosphate hydroxide (Na₃V(OH)(HPO₄)(PO₄)) is based on chains built using octahedra centered by magnetically active V³⁺. Magnetic susceptibility measurements indicate an antiferromagnetic arrangement of V³⁺ ions and no transition to an ordered state up to 2 K. Full article