Polycrystalline Samples Research Articles

Perovskite-related structures of Ba2YAlO5 and the β and α phases of Ba6Y2Al4O15 containing AlO4 tetrahedra.

Single crystals of Ba2YAlO5 and of the α and β phases of Ba6Y2Al4O15 suitable for X-ray structure analysis were obtained via grain growth of polycrystalline samples prepared by solid-state reactions. Ba2YAlO5 was found to have a monoclinic crystal structure, with lattice parameters a= 7.2333 (7), b= 6.0254 (5), c= 7.4294 (7) Å and β= 117.249 (3)°, and to belong to the space group P21/m, while α-Ba6Y2Al4O15 was determined to be monoclinic, with a= 5.9019 (2), b= 7.8744 (3), c= 9.6538 (3) Å and β= 107.7940 (10)°, and the space group Pm, and β-Ba6Y2Al4O15 was found to be monoclinic, with a= 7.8310 (2), b= 5.8990 (2), c= 18.3344 (6) Å and β= 91.6065 (11)°, and the space group P2/c. In each of these compounds, BO6 octahedra in ABO3 perovskite-type structures were replaced by AlO4 tetrahedra and YO6 octahedra. Polycrystalline samples in which some Y atoms were replaced with Eu exhibited orange-red luminescence in the range 580-730 nm in response to exposure to radiation having a wavelength of approximately 250 nm.

Effect of Ce infusion on the structural, dielectric, optical, transport and polarization behavior of Nd-modified triple-layered Aurivillius phase ceramic Bi3NdTi3O12

Herein, the effect of cerium substitution on the structural, dielectric, optical, impedance and leakage current characteristics of Nd modified triple layered Aurivillius phase compound of chemical composition Bi3NdTi3-xCexO12 is investigated. The polycrystalline samples are synthesized via ceramic fabrication technology. Room temperature X-ray analysis confirms their orthorhombic symmetry. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) analysis affirm microstructure and elemental composition of the compounds. The temperature-dependent dielectric study indicates diffused phase transition (DPT) behavior possibly induced by compositional fluctuations and random occupancy of equivalent crystallographic sites. Signature peaks pertaining to metal-oxide bond vibrations are also identified by FTIR study. Impedance spectroscopic study unravels negative temperature coefficient of resistance (NTCR) and non-Debye type relaxation in the samples. UV–Visible spectroscopy reveals a reduction in band-gap from 3.1 eV to 2.83 eV with cerium infusion from x = 0 to x = 0.3. It is due to the introduction of localized mid-gap states thus, suggesting the possibility of photovoltaic applications. Further analysis of electric modulus and impedance characteristics propounds prominent short-range carrier hopping with higher cerium percentage. The room temperature I–V study suggests an increase in the voltage-dependent non-linearity with cerium incorporation. Leakage current analysis reveals a transition from Ohmic to space charge limited conduction (SCLC) type behavior with high electric field. Room temperature polarization study confirms their ferroelectric property. Frequency dependent ac conductivity obeys Jonscher double power law clearly indicating the presence of two dispersive regions dominated by grain and grain boundary effects. Reduced bandgap, enhanced voltage dependent non-linearity, NTCR type property and saturated P-E loops observed in the sample unravel the multifunctional aspects of the fabricated compound.

A Luminescent MOF Based on Pyrimidine-4,6-dicarboxylate Ligand and Lead(II) with Unprecedented Topology

In the present work, we report on a 3D MOF of {[Pb5(μ3-OH)(μ3-NO3)3(μ6-pmdc)3]·H2O}n formula (pmdc = pyrimidine-4,6-dicarboxylate) synthesized by an oven-heated, solvent-free procedure. The large connectivity afforded by the three ligands in their coordination to lead(II) ions grows cubic building units characterized by a central Pb atom with an unusual coordination index of 12 and 6 pmdc ligands occupying the faces. These cubic units are linked to one another giving rise to a quite condensed structure that represents an unprecedented topology showing the (4·62)6(43)2(45·610)3(45·68·82)6(46·69)6(612·83) point symbol. The crystalline material has been characterized by routine physico-chemical techniques to confirm its purity, and its thermal behaviour has been also studied by thermogravimetric and thermodiffractometric analyses. The solid presents a greenish blue photoluminescent emission based on pmdc ligands, as revealed by time-dependent density-functional theory (TDDFT) calculations, which is substantially more intense than in the free H2pmdc ligand according to its improved quantum yield. The emissive capacity of the material is further analysed according to decreasing temperature of the polycrystalline sample, finding that sizeable, long-lasting phosphorescence is present.

Effect of crystal morphology of ultrahigh-nickel cathode materials on high temperature electrochemical stability of lithium ion batteries

Higher nickel content endows Ni-rich cathode materials LiNixCoyMn1−x−yO2 (x > 0.6) with higher specific capacity and high energy density, which is regarded as the most promising cathode materials for Li-ion batteries. However, the deterioration of structural stability hinders its practical application, especially under harsh working conditions such as high-temperature cycling. Given these circumstances, it becomes particularly critical to clarify the impact of the crystal morphology on the structure and high-temperature performance as for the ultrahigh-nickel cathodes. Herein, we conducted a comprehensive comparison in terms of microstructure, high-temperature long-cycle phase evolution, and high-temperature electrochemical stability, revealing the differences and the working mechanisms among polycrystalline (PC), single-crystalline (SC) and Al doped SC ultrahigh-nickel materials. The results show that the PC sample suffers a severe irreversible phase transition along with the appearance of microcracks, resulting a serious decay of both average voltage and the energy density. While the Al doped SC sample exhibits superior cycling stability with intact layered structure. In-situ XRD and intraparticle structural evolution characterization reveal that Al doping can significantly alleviate the irreversible phase transition, thus inhibiting microcracks generation and enabling enhanced structure. Specifically, it exhibits excellent cycling performance in pouch-type full-cell with a high capacity retention of 91.8% after 500 cycles at 55 °C. This work promotes the fundamental understanding on the correlation between the crystalline morphology and high-temperature electrochemical stability and provides a guide for optimization the Ni-rich cathode materials.

High-pressure reactions between the pnictogens: the rediscovery of BiN.

We explore chemical reactions within pnictogens with an example of bismuth and nitrogen under extreme conditions. Understanding chemical reactions between Bi and N, elements representing the first and the last stable elements of the nitrogen group, and the physical properties of their compounds under ambient and high pressure is far from being complete. Here, we report the high-pressure high-temperature synthesis of orthorhombic Pbcn BiN (S.G. #60) from Bi and N2 precursors at pressures above 40GPa. Using synchrotron single-crystal X-ray diffraction on the polycrystalline sample, we solved and refined the compound's structure and studied its behavior and compressibility on decompression to ambient pressure. We confirm the stability of Pbcn BiN to pressures as low as 12.5(4)GPa. Below that pressure value, a group-subgroup phase transformation occurs, resulting in the formation of a non-centrosymmetric BiN solid with a space group Pca21 (S.G. #29). We use ab initio calculations to characterize the polymorphs of BiN. They also provide support and explanation for our experimental observations, in particular those corresponding to peculiar Bi-N bond evolution under pressure, resulting in a change in the coordination numbers of Bi and N as a function of pressure within the explored stability field of Pbcn BiN.

Single-crystal quality data from polycrystalline samples: finding the needle in the haystack.

Multi-grain crystallography, traditionally performed at synchrotron sources in association with high-pressure studies, has new relevance with respect to laboratory single-crystal X-ray diffraction, in which crystals can be grown rapidly in situ, and a preliminary dataset analysed and solved in a matter of minutes. Subsequently, a full-sphere of IUCr-quality data can then be collected in a few hours. To demonstrate the applicability of laboratory multi-grain crystallography with Cu Kα X-rays, co-crystals of hexafluorobenzene and pyrrole were grown rapidly by cooling a 1:1 liquid mixture in an X-ray capillary on the diffractometer. The software is able to identify a single unit cell from as few as 10% of the diffraction spots from a small number of diffraction frames. Once a unit cell is identified, a full crystal structure solution is rapidly obtained by collecting a small amount of data to a resolution of ca 1 Å. The co-crystal obtained from the 1:1 mixture showed that hexafluorobenzene and pyrrole crystallize in a 3:4 ratio, in contrast to the columnar 1:1 adduct structures typified by hexafluorobenzene and benzene. The generality of our multi-grain approach for samples that are liquid at room temperature (and form a polycrystalline solid mass on cooling) is further demonstrated by investigating and solving the 1:1 co-crystal formed between hexafluorobenzene and pyridine.

Optimization of Sintering Temperature for the Synthesis of n-type Mg<sub>3</sub>SbBi<sub>0.99</sub>Te<sub>0.01</sub> Thermoelectric Materials

Mg<sub>3</sub>Sb<sub>2</sub>-based materials are promising candidates to replace n-type Bi<sub>2</sub>Te<sub>3</sub> for cooling and power generation at low temperatures. Generally, the thermoelectric performance of a material is sensitively affected by synthesis process parameters, and among them, sintering temperature (<i>T<sub>s</sub></i>) is a critical one. In this study, n-type Mg<sub>3</sub>SbBi<sub>0.99</sub>Te<sub>0.01</sub> polycrystalline samples were fabricated by mechanical alloying and spark plasma sintering (SPS), and the effects of varying <i>T<sub>s</sub></i> (923 – 1073 K) on the thermoelectric properties were investigated. Sintering Mg<sub>3</sub>SbBi<sub>0.99</sub>Te<sub>0.01</sub> at an elevated temperature of 1073 K resulted in a notable increase in electrical conductivity at low temperatures below about 423 K. This is ascribed to a sharp reduction in carrier scattering by ionized impurities. For the same reason, the carrier mobility increased sharply at a <i>T<sub>s</sub></i> of 1073 K, which is a critical temperature for sintering in this study. Moreover, the Seebeck coefficient increased and thermal conductivity decreased simultaneously by raising <i>T<sub>s</sub></i>, resulting in the maximum power factor (<i>PF<sub>max</sub></i>) of 2.2 × 10<sup>-3</sup> W m<sup>-1</sup>K<sup>-2</sup> and the maximum dimensionless figure of merit (<i>zT<sub>max</sub></i>) of 1.20 in the sample sintered at 1073 K. Therefore, when <i>T<sub>s</sub></i> was raised from 923 K to 1073 K, the <i>PF<sub>max</sub></i> and <i>zT<sub>max</sub></i> increased by 29 % and 64 %, respectively. This improvement in performance is attributed to the annihilation of defects generated during the mechanical alloying process, which was confirmed by microstructure analysis by transmission electron microscopy (TEM).

Two new multinary chalcogenides with (Se2)2− dimers: Ba8Hf2Se11(Se2) and Ba9Hf3Se14(Se2)

Two multinary selenides, Ba8Hf2Se11(Se2) and Ba9Hf3Se14(Se2), with unprecedented structure types have been prepared using high-temperature synthesis techniques and represent the first known compounds in the Ba-Hf-Se system. Their structures were determined from single crystal X-ray diffraction (XRD) data. The Ba8Hf2Se11(Se2) compound crystallizes in the monoclinic C2/c space group with a = 12.3962(15) Å, b = 12.8928(15) Å, c = 18.1768(17) Å, and β = 90.685(4)°, while Ba9Hf3Se14(Se2) forms in the rhombohedral R3‾ space group with a = b = 19.4907(6) Å and c = 23.6407(11) Å. Both have pseudo-zero-dimensional structures with homoatomic Se–Se bonding in the form of (Se2)2− at distances of 2.400–2.402 Å. The structure of Ba8Hf2Se11(Se2) is comprised of [Hf2Se11]14−, Ba2+, and (Se2)2− dimers. Conversely, the Ba9Hf3Se14(Se2) structure contains a novel perovskite-type cluster constructed from eight octahedrally-coordinated Hf cations, i.e., [Hf8Se36]40−, and isolated [HfSe6]8− units which are separated by (Se2)2− dimers and Ba2+ cations. Polycrystalline Ba8Hf2Se11(Se2) is synthesized at 1073 K using a two-step solid-state synthesis method, with the co-formation of a small amount of a BaSe secondary phase. A direct bandgap of 2.2(2) eV is obtained for the polycrystalline sample of Ba8Hf2Se11(Se2), which is consistent with its yellow color. Density functional theory calculations reveal their bandgap transitions stem from predominantly filled Se-4p to empty Hf-5d at the edges of the valence bands (VB) and conduction bands (CB), respectively. The optical absorption coefficients are calculated to be relatively large, exceeding ∼105 cm−1 at about >2.0 eV with effective masses in the CB varying from ∼0.5 me (Γ → A) in Ba8Hf2Se11(Se2) to ∼1.0 me (Γ → L) in Ba9Hf3Se14(Se2). Thus, their optoelectronic properties are shown to be competitive with existing perovskite-type chalcogenides that have been a focus of recent research efforts.

Tunable inversion degree of MnIn2S4 thiospinels prepared by high-pressure synthesis, and its implication in the optical and magnetic properties

Indium thiospinels (AIn2S4, A= transition metals) have attracted significant attention due to their potential for manipulating magnetic and optoelectronic properties through changes in chemical composition. Defined in the cubic space group Fd-3 m (No. 227), the crystal structure consists of a framework of edge-sharing InS6 octahedra (Oh symmetry), with A cations coordinated tetrahedrally (Td symmetry) to sulfur. In this study, we describe a rapid high-pressure synthetic method (3.5 GPa) to prepare MnIn2S4 polycrystalline samples, with tunable degree of inversion (λ) or Mn-In antisite, meaning that some Mn occupy the octahedral sites and some In atoms are located at the tetrahedral positions. We found that λ closely depends on the synthesis temperature. Notably, the refinement of the crystal structure from X-ray diffraction data reveals positive correlations between the inversion degree and different properties such as the band gap, expanding its spectral coverage, and the magnetic behavior, depending on the occupancy rate of the octahedral or tetrahedral sites by the strongly magnetic Mn2+ ions. Whereas the paramagnetic behavior is not affected by the inversion degree, for higher λ values (30%<λ < 38%), achieved at synthesis temperatures as high of 800ºC, the random distribution of Mn2+ ions between Td and Oh sites accounts for a spin-glass state with a clear cusp in the magnetic susceptibility (ac and dc), based on the strong short-range antiferromagnetic interactions.

Promising elastocaloric properties of sintered polycrystalline NiMnGa produced by open die pressing

AbstractThe increasing interest in the development of multicaloric materials for solid-state cooling applications is giving rise to the investigation of elastocaloric performance of ferromagnetic Shape Memory Alloys (FeSMA). Moreover, some sintering processes have been proposed to overcome the well-known brittleness of these alloys. In this context, a novel application of the open die pressing (ODP) method for the preparation of NiMnGa polycrystalline samples sets the chance to have interesting mechanical properties, until now never reported in literature. In this work, a tunable optimization of microstructure is presented and the elastocaloric properties are investigated by different mechanical approaches and direct measurement of adiabatic ΔT values. It is observed, for the first time, a polycrystalline NiMnGa alloy that exhibits an extremely stable mechanical and thermal response upon 200 adiabatic compression cycles. The best performance consisted in a ΔS peak of 35 J/(kg °C) and an adiabatic ΔT value of ± 4 °C in the first 10 cycles and + 3,75 / − 4 °C in stabilized conditions over 200 cycles.

Revival of Ferromagnetic-Metallic Phase and Emergence of Griffiths Phase via Ni and Cr Substitution in Charged-Ordered Pr0.75Na0.25MnO3 Manganite

Polycrystalline samples of Pr0.75Na0.25Mn1-xAxO3 (A = Ni, Cr; x = 0, 0.03) were prepared using conventional solid-state method and their structural and magnetic properties were investigated. Monovalent-doped Pr0.75Na0.25MnO3 exhibits insulating behavior which is related to the strong localization of charge carriers due to the presence of charge ordering (CO). The substitution of different types of magnetic ions, A, which are Ni2+ and Cr3+, at a concentration of x = 0.03 at the Mn site in the CO Pr0.75Na0.25Mn1-xAxO3 manganite, has been found to dramatically modify its structural and magnetic properties. X-ray diffraction patterns showed that all samples were present in single phase and crystallized in orthorhombic structure with Pnma space group. The Rietveld refinement analysis showed that the unit cell volume increased due to Ni2+ substitution, while it decreased due to Cr3+ substitution, which may be attributed to the different ionic radii of both ions. The suppression of the CO state and the induction of the ferromagnetic-metallic state in the Ni-substituted and Cr-substituted samples are suggested to be due to the induction of double-exchange interaction involving Ni2+–O–Mn4+ and Mn3+–O–Cr3+, respectively. The variation in magnetic properties between the Ni-substituted and Cr-substituted samples is suggested to be due to the existence of different strengths of ferromagnetic interaction between Ni2+–O–Mn4+ and Mn3+–O–Cr3+. In addition, the deviation of the temperature dependence of the inverse magnetic susceptibility curves from the Curie-Weiss law suggests the existence of Griffith’s phase-like behaviour for both substitution samples. The Ni-substituted sample induced a greater GP effect than the Cr-substituted sample due to the larger difference of TC and TG value (TC-TG).

The Co2＋-Ir5＋ orbital hybridization in LaCaCoIrO6 double perovskite

Here, we report on the structural, electronic, and magnetic properties of a polycrystalline sample of the LaCaCoIrO6 double-perovskite investigated by means of synchrotron x-ray powder diffraction, x-ray absorption spectroscopy, and x-ray magnetic circular dichroism at the Co and Ir L2,3 edges, magnetometry, and electrical transport. Our results indicate a configuration of nearly Co2+/Ir5+ configuration for the transition-metal ions, with spin canting within the Co antiferromagnetic superstructure responsible for the ferromagnetic-like behavior observed below 100 K. The highly insulating character of LaCaCoIrO6 and its positive magnetoresistance further suggest that this antiferromagnetic superexchange interaction occurs through an indirect hybridization between the Co eg orbitals.

Determination of single crystal thermal expansion in Uranium-6wt%Niobium shape memory alloy using in-situ diffraction and modeling of textured polycrystalline samples

In-situ neutron diffraction and ex-situ dilatometry experiments were performed on a chemically banded, quenched uranium-6wt% niobium shape memory alloy to study the impact of deformation-(detwinning-) induced texture on the evolution of thermally induced strains (and associated stresses). Thermal heating and cooling cycles between 5K and 473K were performed in-situ with neutron diffraction, and the lattice strain evolution is reported for the observed monoclinic α″ phase. Comparisons between the measured diffraction strains and macroscopic dilatometry experiments reveal relationships between micro- and macro-level thermal expansion. Softening of the texture during heating suggests that twin boundary motion can accommodate the large internal thermal strains which are approximately 2% greater than that typically observed during the 175K heating interval used to age more randomly oriented polycrystalline material. Assuming weak constraint of neighboring grains in randomly textured polycrystals, the single crystal thermal expansion tensor is extracted from measurements of lattice strains over the range 5K to 473K. Predictions of polycrystalline thermal expansion, based upon this single crystal thermal expansion tensor, are shown to compare favorably with bulk thermal expansion observations of the as quenched microstructure. However, such a lower-bound estimate is insufficient to explain all aspects of the behavior of the textured material, where the matrix is not isotropic. It is hypothesized that relaxation processes which occur within the quenched microstructure during heating are responsible for the distinct thermal expansion behavior observed during the initial heating cycle compared to cooling and subsequent cycling.

Comparative analysis of crystallographic phase stability of single and poly-crystalline lead nitrate at dynamic shocked conditions

In the present work, we report the crystallographic structural stability of the poly-crystalline lead nitrate samples at shocked conditions with which a systematic comparison is made for the previously reported single-crystalline lead nitrate crystal at shocked conditions. X-ray diffractometry (XRD) and Raman spectroscopic measurements have been performed to assess the crystallographic structural stability of poly-crystalline Pb(NO3)2 samples at shocked conditions and the observed XRD and Raman results disclose that the title poly-crystalline samples retain the original crystallographic structure even at 100 shocked conditions interacting with the shock waves of 2.2 Mach number. But the single crystals of Pb(NO3)2 undergo crystalline to amorphous phase transition at shocked conditions. Based on the observed results, poly-crystalline samples have higher-structural stability than that of single crystals. The outcome of this work provides glimpses of possible further contributions to crystal engineering for the design of new materials with specific physical and chemical properties.

Excellent cycling performance of high-nickel single-crystal cathode material by a well-tailored binary molten-salt method

Nickel-rich LiNixCoyMnzO2 (x + y + z = 1) cathode materials have been extensively studied due to their improved energy density and reduced cost in comparison to conventional layered oxides (LiCoO2) and perovskite-type compounds (LiFePO4). However, the further commercialization of polycrystalline nickel-rich layered cathodes are severely hampered by entrenched particle microcracking that evolves mainly from the randomly oriented grain boundaries in the primary particles. Herein, an environmental-friendly LiOH⋅H2O/Li2CO3 binary molten-salt method is introduced to synthesize single-crystal LiNi0.88Co0.09Mn0.03O2 with good crystallinity and dispersion, and the possible growth mechanism of the particles is inferred. The sample prepared at a lithium ratio of 1.7 (SC1.7) shows a lower degree of cation mixing and larger lithium layer spacing compared to control polycrystalline sample (PC), and the residual alkali is effectively removed from the surface of single crystal particles. These features enable SC1.7 to maintain robust structural stability during cycling, with the cycle retention at 1C rate and a voltage of 4.5 V to be 86.73% after 100 cycles. The desirable performance is rationally derived from the significant inhibition of microcracks in particles, and reduction of parasitic reactions. The unique binary molten-salt strategy provides a new avenue for the design of high-performance high-nickel cathode materials in lithium-ion batteries.

Investigation of role of antisite disorder in pristine cage compound FeGa$_3$

The role of controlled Fe antisite disorder in the narrow gap semiconductor FeGa_33 has been investigated. Polycrystalline samples were synthesized by the combination of arc-melting furnace and successive annealing processes. Deviations from occupation numbers of Fe and Ga sites expected in the pristine compound were obtained from X-ray data using Rietveld refinement analysis. Besides that, electrical transport and magnetization measurements reveal that hierarchy in Fe and Ga site disorder tunes the ground state of FeGa_33 from paramagnetic semiconductor to a magnetic metal. These findings are discussed inside the framework of Anderson localization in the vicinity of metal-semiconductor transitions and spin fluctuations.

Observation of spin-glass behavior in 1111-type magnetic semiconductor (La, Ba)(Zn, Mn)SbO

We report the successful fabrication of a new 1111-type bulk magnetic semiconductor (La,Ba)(Zn,Mn)SbO through the solid solution of (La,Ba) and (Zn,Mn) in the parent compound LaZnSbO. The polycrystalline samples (La,Ba)(Zn,Mn)SbO crystallize into ZrCuSiAs-type tetragonal structure, which has the same structure as iron-based superconductor LaFeAsO1–δ . The DC magnetization measurements indicate the existence of spin-glass ordering, and the coercive field is up to ∼11500 Oe (1 Oe = 79.5775 A⋅m−1). The AC magnetic susceptibility further determines that the samples evolve into a conventional spin-glass ordering state below the spin freezing temperature T f. In addition, the negative magnetoresistance (MR ≡ [ρ(H)–ρ(0)]/ρ(0)) reaches −88% under 9 T.

Correlating Corrosion to Surface Grain Orientations by Scanning Electrochemical Cell Microscopy

The study of grain-dependent corrosion behaviors of practical polycrystalline metals remains challenging due to the difficulty in eliminating the influences of other microstructural features, such as intermetallic particles and grain boundaries. In this work, we performed thousands of microscopic potentiodynamic polarization measurements on a polycrystalline alloys using the spatially resolved oil-immersed scanning electrochemical cell microscopy measurement. This work highlights the capability of oil-immersed scanning electrochemical cell microscopy in resolving small electrochemical differences, which will greatly promote the study of grain-dependent behaviors of practical polycrystalline samples.

Synthesis of possible room temperature superconductor LK-99: Pb9Cu(PO4)6O

The quest for room temperature superconductors has been teasing scientists and physicists, since its inception in 1911 itself. Several assertions have already been made about room temperature superconductivity, but have never been verified or reproduced across the labs. The cuprates were the earliest high transition temperature (T c) superconductors, and it seems that copper has done the magic once again. In July 2023, a Korean group synthesized a lead apatite based compound LK-99, showing a T c of above 400 K (Lee et al 2023 arXiv: 2307.12008; 2023 arXiv: 2307.12037; Lee et al 2023 J. Korean Cryst. Growth Cryst. 33 61). The signatures of superconductivity in the compound are very promising, in terms of resistivity (ρ = 0) and diamagnetism at T c. Although, the heat capacity (C p) did not show the obvious transition at T c. Inspired by the interesting claims of the above room temperature superconductivity in LK-99, in this article, we report the synthesis of polycrystalline samples of LK-99, by following the same heat treatment as reported in Lee et al (2023 arXiv: 2307.12008; 2023 arXiv: 2307.12037) using a two-step precursor method. The phase is confirmed through x-ray diffraction measurements, performed after each heat treatment. The room temperature diamagnetism is not evidenced by the levitation of a permanent magnet over the sample or vice versa. The isothermal magnetization measurement at 280 K shows that as synthesized sample of LK-99 is paramagnetic. Further measurements for the confirmation of bulk superconductivity in variously synthesized samples are underway. Our results on the present LK-99 sample, synthesized at 925 °C, as of now do not confirm the appearance of bulk superconductivity at room temperature. Further studies with different heat treatments are underway.

Single-crystal quality data from polycrystalline samples: finding the needle in the haystack

Single-crystal quality data from polycrystalline samples: finding the needle in the haystack