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The Ruddlesden–Popper (R–P) bilayer nickelate, La 3 Ni 2 O 7 , was recently found to show signatures of high-temperature superconductivity (HTSC) at pressures above 14 GPa (ref.  1 ). Subsequent investigations achieved zero resistance in single-crystalline and polycrystalline samples under hydrostatic pressure conditions 2 – 4 . Yet, obvious diamagnetic signals, the other hallmark of superconductors, are still lacking owing to the filamentary nature with low superconducting volume fraction 2 , 4 , 5 . The presence of a new 1313 polymorph and competing R–P phases obscured proper identification of the phase for HTSC 6 – 9 . Thus, achieving bulk HTSC and identifying the phase at play are the most prominent tasks. Here we address these issues in the praseodymium (Pr)-doped La 2 PrNi 2 O 7 polycrystalline samples. We find that substitutions of Pr for La effectively inhibit the intergrowth of different R–P phases, resulting in a nearly pure bilayer structure. For La 2 PrNi 2 O 7 , pressure-induced orthorhombic to tetragonal structural transition takes place at P c  ≈ 11 GPa, above which HTSC emerges gradually on further compression. The superconducting transition temperatures at 18–20 GPa reach T c onset = 82.5 K and T c zero = 60 K , which are the highest values, to our knowledge, among known nickelate superconductors. Importantly, bulk HTSC was testified by detecting clear diamagnetic signals below about 75 K with appreciable superconducting shielding volume fractions at a pressure of above 15 GPa. Our results not only resolve the existing controversies but also provide directions for exploring bulk HTSC in the bilayer nickelates. Bulk high-temperature superconductivity observed in pressurized tetragonal La 2 PrNi 2 O 7 was testified by detecting clear diamagnetic signals below about 75 K with appreciable superconducting shielding volume fractions at a pressure of above 15 GPa.

Future quantum networks will enable the distribution of entanglement between distant locations and allow applications in quantum communication, quantum sensing and distributed quantum computation 1 . At the core of this network lies the ability to generate and store entanglement at remote, interconnected quantum nodes 2 . Although various remote physical systems have been successfully entangled 3 – 12 , none of these realizations encompassed all of the requirements for network operation, such as compatibility with telecommunication (telecom) wavelengths and multimode operation. Here we report the demonstration of heralded entanglement between two spatially separated quantum nodes, where the entanglement is stored in multimode solid-state quantum memories. At each node a praseodymium-doped crystal 13 , 14 stores a photon of a correlated pair 15 , with the second photon at telecom wavelengths. Entanglement between quantum memories placed in different laboratories is heralded by the detection of a telecom photon at a rate up to 1.4 kilohertz, and the entanglement is stored in the crystals for a pre-determined storage time up to 25 microseconds. We also show that the generated entanglement is robust against loss in the heralding path, and demonstrate temporally multiplexed operation, with 62 temporal modes. Our realization is extendable to entanglement over longer distances and provides a viable route towards field-deployed, multiplexed quantum repeaters based on solid-state resources. Robust heralded entanglement between two solid-state quantum memories with temporal multiplexing is realized using photons at telecommunication wavelengths.

Pr-144 isotope is one of the most favorable antineutrino sources for short-baseline experiments aimed at sterile neutrino search. These experiments require precise theoretical knowledge of the antineutrino spectrum. We calculate antineutrino spectrum of Pr-144 taking into account various corrections with emphasis on corrections due to atomic effects.

Visible-light and infrared-light persistent phosphors are extensively studied and are being used as self-sustained glowing tags in darkness. In contrast, persistent phosphors for higher-energy, solar-blind ultraviolet-C wavelengths (200–280 nm) are lacking. Also, persistent tags working in bright environments are not available. Here we report five types of Pr 3+ -doped silicates (melilite, cyclosilicate, silicate garnet, oxyorthosilicate, and orthosilicate) ultraviolet-C persistent phosphors that can act as self-sustained glowing tags in bright environments. These ultraviolet-C persistent phosphors can be effectively charged by a standard 254 nm lamp and emit intense, long-lasting afterglow at 265–270 nm, which can be clearly monitored and imaged by a corona camera in daylight and room light. Besides thermal-stimulation, in bright environments, photo-stimulation also contributes to the afterglow emission and its contribution can be dominant when ambient light is strong. This study expands persistent luminescence research to the ultraviolet-C wavelengths and brings persistent luminescence applications to light. Ultraviolet-C radiation sources are important for disinfection and photochemical water purification, but development of persistent phosphors is needed for other applications. Here the authors report praseodymium-doped silicate ultraviolet-C persistent phosphors for self-sustained glowing tags in bright light.

Aurivillius BaBi2Nb2O9 and Ba1-xPrxBi2Nb2O9 ceramics were successfully synthesized by a simple solid state reaction method. Ceramics were prepared from reactants: Nb2O5, Bi2O3, BaCO3 and Pr2O3. The microstructure, structure, chemical composition, and dielectric properties of the obtained materials were examined. Dielectric properties were investigated in a wide range of temperatures (T = 20–500 °C) and frequencies (f = 0.1 kHz–1 MHz). The obtained ceramic materials belong to the group of layered perovskites, crystallizing in a tetragonal structure with the space group I4/mmm. Modification of the barium niobate compound with praseodymium ions influenced its dielectric properties and introducing a small concentration of the dopant ion causes a slight increase in the value of electric permittivity and shifts its maximum towards higher temperatures.

Imitation gemstone glass has numerous characteristics, including low cost, rich colour, stable colouring, and the formation of colour-changing effects that can meet the jewellery market demand for beautiful gemstones of middle and low grades. In this study, four types of gem-imitating glass were prepared by the elemental substitution of praseodymium, neodymium and chromium elements based on rare earth glass and examined by combining refractive index, density, spectral characteristics and colour parameters. Sample 1 contained only Pr6O11 and showed a golden-yellow colour like chrysoberyl. Sample 2 contained only Nd2O3 and showed a blue-purple colour like amethyst. Sample 3 contained Pr6O11 and Nd2O3 and appeared green under D65 light source and red under A light source, with a colour-change effect like alexandrite. Sample 4 contained Pr6O11, Nd2O3 and Cr2O3 and showed a highly saturated green colour like emerald because of the strong colouring effect of Cr3+ in the glass. The findings revealed that all four samples are transparent, with a refractive index greater than 1.5 and a density higher than 2.6 g/cm3. The comprehensive performance of the four imitation gemstone glasses can be found in the corresponding natural gemstones, which has a certain practical value.

The oxygen incorporation and evolution reactions (OIR/OER) at air electrodes are key challenges limiting the performance of reversible solid oxide cells (SOCs). Surface modification using binary oxides has emerged as a promising strategy to enhance OIR/OER kinetics, with PrO x as a popular choice of the modification layer. However, the mechanisms behind this improvement of reaction kinetics remain unclear. In this study, we combine insights from electrochemical measurements and operando X-ray absorption spectroscopy to reveal that interfacial charge transfer plays a pivotal role in enhancing the OIR/OER activity in La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3−δ (LSCF) with PrO x surface modification. The charge transfer increases the hole concentration in LSCF, which can be quantitatively correlated with accelerated OIR/OER kinetics (up to ~70 times enhancement) over a broad range of oxygen chemical potential. We further demonstrate this mechanism in realistic SOCs devices, showing enhanced performance in both fuel cell and electrolysis modes. Our work provides critical insights into the role of interfacial charge transfer and defect chemistry in surface-modified SOCs electrodes, offering a pathway to optimize SOCs performance through surface modifications. Solid oxide cells are limited by slow oxygen exchange reaction kinetics at the oxygen electrode. Operando X-ray absorption and electrochemical analysis show that surface modification with a praseodymium oxide layer induces interfacial charge transfer and accelerates the surface kinetics.

Nickelates are a rich class of materials, ranging from insulating magnets to superconductors. But for stoichiometric materials, insulating behavior is the norm, as for most late transition metal oxides. Notable exceptions are the 3D perovskite LaNiO 3 , an unconventional paramagnetic metal, and the layered Ruddlesden-Popper phases R 4 Ni 3 O 10 , (R = La, Pr, Nd). The latter are particularly intriguing because they exhibit an unusual metal-to-metal transition. Here, we demonstrate that this transition results from an incommensurate density wave with both charge and magnetic character that lies closer in its behavior to the metallic density wave seen in chromium metal than the insulating stripes typically found in single-layer nickelates like La 2- x Sr x NiO 4 . We identify these intertwined density waves as being Fermi surface-driven, revealing a novel ordering mechanism in this nickelate that reflects a coupling among charge, spin, and lattice degrees of freedom that differs not only from the single-layer materials, but from the 3D perovskites as well. Layered Ruddlesden-Popper structure nickelates R 4 Ni 3 O 10 ( R  = La,Pr) show an unusual metal-to-metal transition, but its origin has remained elusive for more than two decades. Here, the authors show that this transition results from intertwined density waves that arise from a coupling between charge and spin degrees of freedom

The growing dependence of society on rare-earth elements poses a challenge to achieving a just low-carbon transition globally. While circular economy strategies have gained attention, their specific impacts remain unmeasured. Here we present an integrated model that quantifies how circular economy strategies can reshape global supply chains of the critical rare-earth elements such as neodymium, praseodymium, dysprosium and terbium. The model considers both in-ground and in-use stocks across ten regions from 2021 to 2050. The projections include the full deployment of three widely accepted climate scenarios. We find a considerable mismatch between in-ground stocks, supply and demand at specific region and element levels, with the mismatch for heavy rare-earth elements as a key obstacle for achieving net-zero emissions targets. We suggest that, as in-ground stocks decline among mineral suppliers, the accumulation of in-use stocks in consuming regions can foster a more balanced and less polarized geopolitical landscape for rare-earth elements, and circular economy strategies can lead to an increase of 701 kt secondary supply and a decrease of 2,306 kt demand within the next three decades. Implementing these circular economy strategies will require international cooperation in the governance of rare-earth elements amid sustainable transition. Mobilization of in-use rare-earth element stocks in regions of high consumption can ease dependence on regions of rare-earth extraction, according to dynamic integrated modelling combining material flow and scenario analysis.