Orthorhombic Space Group Pnma Research Articles

Synthesis, structure and photocatalytic performance of {[Bi6(tza)5(NO3)2(OH)5O3]·H2O}n and its derivatives

A polynuclear metal-organic framework, {[Bi6(tza)5(NO3)2(OH)5O3]·H2O}n (Htza=1H-tetrazole-1-acetic acid), was successfully synthesized and characterized, and its photocatalytic properties, along with those of its derivatives, were investigated. The crystal structure of the compound was determined to belong to the orthorhombic space group Pn ma, featuring a 3D framework comprising cage-like [Bi6(µ3-O)3(µ3-OH)5]7+ clusters. {[Bi6(tza)5(NO3)2(OH)5O3]·H2O}n demonstrated significant photocatalytic activity with UV light response within the pH range of 6.0–8.0 and a band gap energy of 3.32 eV. Under optimal conditions, a reduction in chemical oxygen demand (COD) and total organic carbon (TOC) (from 126.90 mg/L to 4.57 mg/L) clearly validated the efficient methyl orange degradation. The main active groups in the degradation process were h+, ·O2− and ·OH, and the catalyst demonstrated reusability for up to six cycles. Moreover, it was hydrolyzed to Bi2O2CO3 and BiOCl under alkaline (pH=9.0–11.0) and acidic (pH=1.0–5.0) conditions, respectively, thus serving as a valuable precursor. Notably, the Bi2O2CO3 and BiOCl derivatives exhibited higher catalytic activities than catalysts synthesized using alternative methods under the same experimental conditions. Therefore, within the pH range of 1.0–11.0, {[Bi6(tza)5(NO3)2(OH)5O3]·H2O}n, along with its in situ derivatives BiOCl and Bi2O2CO3, were highly efficient UV light-driven photocatalysts.

Diffusion dominant thermal transport in mixed valent Ba4Sn4Se9

New material developments are of paramount importance from the perspective of developing a fundamental understanding of material properties as well as transitioning from materials to devices. Among the different classes of materials of interest, mixed valence Sn compositions have been known to display technologically important properties and are of interest for the design and synthesis of novel compositions for targeted applications. Herein, we report on electronic, optical and thermal properties of the previously unexplored mixed valence composition Ba4Sn4Se9, a material with a direct optical band gap of 2.36 eV. As revealed by single crystal synchrotron X-ray diffraction, Ba4Sn4Se9 crystallizes in the orthorhombic space group Pnma with a large unit cell comprised of 58 atoms. Heat capacity data reveals a low Debye temperature with many low frequency optic modes. Our low temperature thermal conductivity data and analyses show that thermal diffusion dominates thermal transport above 80 K. Furthermore, high lattice anharmonicity contributes to the very low thermal conductivity. Our results and analyses will motivate further investigations of this as well as other compositions in the Ba-Sn-Se system, as well as other mixed valence chalcogenides for technological applications.

Pentanary Oxythiogermanates Ba3MGe3O2S8 (M = Ca, Zn) Featuring [Ge3O2S8]8- Trimers and {[MGe3O2S8]6-}∞ Chains: Structural Chemistry and Physical Properties.

Oxychalcogenides are increasingly attracting wide attention because they contain multiple anions that may combine the advantages of oxides and chalcogenides. In this work, two new pentanary oxythiogermanates, Ba3MGe3O2S8 [M = Ca (1), Zn (2)], were synthesized by a high-temperature solid-state reaction. They crystallize in the orthorhombic space group Pnma, and their structures contain isolated [Ge3O2S8]8- units constructed by one [GeO2S2] and two [GeOS3] tetrahedra that link with M2+ ions to build the {[MGe3O2S8]6-}∞ chain, representing a new type of oxythiogermanate. Notably, a [ZnS5] square pyramid exists in 2. Their structural chemistry and relationship with relevant structures are analyzed. 1 and 2 exhibit wide band gaps of 3.93 and 2.63 eV, birefringences of 0.100 and 0.089 at 2100 nm, respectively, and also obvious photocurrent responses. This work may be extended to a family of AE3MIIMIV3O2Q8 (AE = alkali-earth metal; MII = Ca, Zn, Cd, Hg; MIV = Si, Ge, Sn; Q = S, Se), and further systematic survey on them can be performed to enrich the study of multifunctional oxychalcogenides.

Growth, spectroscopy and laser operation of Tm,Ho:GdScO3 perovskite crystal

We report on the growth, polarized spectroscopy and first laser operation of an orthorhombic (space group Pnma) Tm3+,Ho3+-codoped gadolinium orthoscandate (GdScO3) perovskite-type crystal. A single crystal of 3.76 at.% Tm, 0.35 at.% Ho:GdScO3 was grown by the Czochralski method. Its polarized absorption and fluorescence properties were studied revealing a broadband emission around 2 µm. The parameters of the Tm3+ ↔ Ho3+ energy transfer was quantified, P28 = 1.30 × 10−22 cm3µs-1, and P71 = 0.99 × 10−23 cm3µs-1, and the thermal equilibrium lifetime was measured to be 3.5 ms. The crystal-field splitting of Tm3+ and Ho3+ multiplets in Cs symmetry sites of the perovskite structure was determined by low-temperature spectroscopy and the mechanism of spectral line broadening is discussed. The continuous-wave Tm,Ho:GdScO3 laser generated 1.16 W at ∼2.1 µm with a slope efficiency of 50.5%, a laser threshold of 184 mW, a linear laser polarization ( E || c ) and a spatially single-mode output. The Tm,Ho:GdScO3 crystal is promising for broadly tunable and femtosecond mode-locked lasers emitting above 2 µm.

MoO3/MeMoO4 (Me = Cu, Ni, Co, Fe, Mn, and Cr) composites as materials for prospective optical and electrical applications

The composite MoO3/MeMoO4 (Me = Cu, Ni, Co, Fe, and Mn) ceramics were obtained by standard high-temperature sintering. Their structure was tested using XRD, SEM, EDS, and XPS. The occurrence of two phases was determined. The main MoO3 phase exhibited an orthorhombic Pnma space group related to the ceramic grain of micrometre size. The second phase was induced by doping with the Me atom. It showed various monoclinic structures and a smaller grain size. The XPS test confirmed the coexistence of the phases, which was reflected in several lines in the patterns. The valence band of the undoped MoO3 was located ∼3.3 eV below the Fermi level. An additional subband attributed to the Me 3d state was detected within the energy gap. The MoO3/MeMoO4 composites showed a valence band shifted toward the Fermi level and overlapped with the subband, originating from hybridized Mo 4d – Me 3d states. Magnetic susceptibility showed an antiferromagnetic state below ∼20 K for the Ni- and Fe-doped composites. The estimated magnetic moment magnitudes indicated the contribution from Me2+ and Me3+ ions that marked the occurrence of oxygen vacancies. Diffuse reflectance spectra exhibited anomalies in the Vis (∼500–650 nm) and the NIR (∼700–850 nm) ranges and tails in the ∼900–1000 nm range. The estimated magnitudes of energy gaps were attributed to defect-induced states. They corresponded to deduced oxygen vacancies (2.05–2.38 eV) and states or subbands induced by the introduced Me atoms (1.34–1.89 eV). Electric dc resistivity temperature dependence showed thermally activated dependence. The estimated activation energy varied from 0.27 eV to 0.58 eV, depending on the doping of the Me atom. The electric features were consistent with the electronic structure determined using XRD and XPS tests.

Optimizing energy storage under low electric field in A-site dysprosium modified BiFeO3-BaTiO3 ceramics

Electric recoverable energy density and dielectric breakdown strength are crucial factors in the high power-density capacitors. This study highlights the A-site dysprosium (Dy) substituted perovskite 0.5(Bi1−xDyx)FeO3-0.5BaTiO3 relaxor ferroelectric ceramics (x = 0–0.30) in O2-atmosphere sintering. An overall pseudo-cubic structure with a major cubic Pm-3m symmetry was observed in all compositions accompanied by multiple lattice symmetries. Anti-polar orthorhombic Pbam space group and non-polar orthorhombic Pnma symmetry gradually increase while ferroelectric tetragonal P4mm symmetry decreases as Dy content approaches x = 0.3. Recoverable energy densities (Wrec) of 4.8 J/cm3 and 3.6 J/cm3, storing efficiencies (η) of 68% and 75%, and recoverable energy storage intensities (ρ) of ∼3.2×10−2 J/kV·cm2 and ∼2.1×10−2 J/kV·cm2 were attained at x = 0 and 0.10 at electric fields of 150 and 175 kV/cm, respectively. The breakdown strength is improved from 150 to 200 kV/cm as x increases from 0.0 to 0.30. This study suggests that grain boundaries and local nanoclusters may act as barriers to inhibit charge transport and consequently increase the breakdown strength.

Structural, optical, and impedance spectroscopy of the pseudobrookite Pb0·5Ba0·5Fe2O5 synthesized by sol–gel route

Pseudobrookite of general formula Pb0·5Ba0·5Fe2O5 was synthesized by the sol–gel route. X-ray diffraction confirms the orthorhombic Pnma space group of our sample. UV–Vis absorption spectroscopy was used to characterize this material's optical properties. We used the Tauc model and absorption measurements to estimate the direct optical band gap at 3.53 eV. We also calculate the Urbach energy, the optical extinction coefficient, and the refractive index. In addition, the skin depth, optical conductivity, and Cauchy parameters were investigated in relation to the incident photon's wavelength. Electrical conductivity data flow the Jonscher's power law and show that PBFO has two different conducts; Semiconductor behavior in the temperatures region [400 K–520 K]. Then, a metallic trend was detected beyond TS-M = 520 K. The correlated barrier hopping (CBH) model is the appropriate model to describe the conduction process in low temperature range. On the other hand, the conduction is ensured by the non-overlapping small polaron tunneling (NSPT) at high temperature zone. The scaling study shows that the conductivity spectra deviate from Summerfield and Ghosh scaling. The random barrier model (RBM) is employed to correct the Summerfield approach and we note that the conductivity isotherms are combined into a single master curve. The estimated activation energies values from dc-conductivity, hopping frequency and relaxation time are very close. The behavior of dielectric parameters was examined using the Maxwell-Wagner theory of interfacial polarization. The dielectric-relaxation phenomenon is shown by the behaviors of imaginary parts of impedance (Z″) and modulus (M″). The ideal electrical equivalent circuit for simulating the Nyquist curves (i.e. Z′′(Z′)) for our pseudobrookite is (Rg + Rgb//CPEgb). Finally, the entropy (ΔS), and enthalpy (ΔH) were established as thermodynamic parameters.

Synthesis, structures and properties of two new nitrate optical materials: Rb3ZnNO3Cl4 and Rb5Na(NO3)4Cl2

Two new nitrates Rb3ZnNO3Cl4 and Rb5Na(NO3)4Cl2 have been synthesized by hydrothermal method, and they are crystallized in orthorhombic space group Pnma (no. 62) and tetragonal space group P4/mnc (no. 128), respectively. ZnCl4 and RbO3Cl6 polyhedron, NaO4Cl2 and RbO8Cl2 polyhedron are connected by sharing O or Cl atoms to construct three-dimensional (3D) frameworks with trigonal plane NO3 units as pseudo-layers, in which different types of channels are presented. In addition, Rb5Na(NO3)4Cl2 exhibits a perovskite-related framework, and Rb3ZnNO3Cl4 crystals is grown with dimensions up to 5×4.5×1 mm3. Notably, these two compounds have short UV cut-off edge (below 222 nm and 238 nm, respectively). Theoretical calculations indicate that the birefringence enhancement is mainly derived from π-conjugated NO3 units.

Synthesis and Characterization of High-Energy Anti-Perovskite Compounds Cs3X[B12H12] Based on Cesium Dodecahydro-Closo-Borate with Molecular Oxoanions (X- = [NO3]-, [ClO3]- and [ClO4]-).

Three novel anti-perovskite compounds, formulated as Cs3X[B12H12] (X- = [NO3]-, [ClO3]-, and [ClO4]-), were successfully synthesized through the direct mixing of aqueous solutions containing Cs2[B12H12] and CsX (X-: [NO3]-, [ClO3]-, [ClO4]-), followed by isothermal evaporation. All three compounds crystallize in the orthorhombic space group Pnma, exhibiting relatively similar unit-cell parameters (e.g., Cs3[ClO3][B12H12]: a = 841.25(5) pm, b = 1070.31(6) pm, c = 1776.84(9) pm). The crystal structures were determined using single-crystal X-ray diffraction, revealing a distorted hexagonal anti-perovskite order for each. Thermal analysis indicated that the placing oxidizing anions X- into the 3 Cs+ + [B12H12]2- blend leads to a reduction in the thermal stability of the resulting anti-perovskites Cs3X[B12H12] as compared to pure Cs2[B12H12], so thermal decomposition commences at lower temperatures, ranging from 320 to 440 °C. Remarkably, the examination of the energy release through DSC studies revealed that these compounds are capable of setting free a substantial amount of energy, up to 2000 J/g, upon their structural collapse under an inert-gas atmosphere (N2). These three compounds represent pioneering members of the first ever anti-perovskite high-energy compounds based on hydro-closo-borates.

Characterizations of structural, optical, and dielectric properties of oxynitride perovskites ACa0.2M0.8O2.6N0.4 (A= Sr, Ba; M = Nb, Ta)

Perovskite-type oxynitrides ACa0.2M0.8O2.6N0.4 (A = Sr, Ba; M = Nb, Ta) were synthesized via the ammonolytic reaction between A5M4O15 and CaCl2, where the Ca2+ insertion and O2−/N3− substitution occurred cooperatively. In terms of the average structure, SrCa0.2Nb0.8O2.6N0.4 and SrCa0.2Ta0.8O2.6N0.4 belong to the orthorhombic Pnma space group, and BaCa0.2Nb0.8O2.6N0.4 and BaCa0.2Ta0.8O2.6N0.4, the primitive cubic Pm3‾m group. The comparison between the experimental lattice volume and the summed ionic volume suggested that ACa0.2M0.8O2.6N0.4 have higher degrees of ionicity than AM'0.2M0.8O3−xNx (M′ = Li, Mg, Mn), but are more covalent than ANa0.2M0.8O2.8N0.2. Despite the significant mismatches of size and charge between Ca2+ and Nb5+ (or Ta5+), no cation ordering was detected on the octahedral site. On the other hand, the O/N distribution appeared to depend on the bonding geometry around the anion sites in a way N favors the straighter bonding connectivity of M−N−M. The band gap energies of ACa0.2M0.8O2.6N0.4 were estimated to be 1.9–2.25 eV depending on A and M. The band gaps and color properties of AMO2N and AM'0.2M0.8O3−xNx (A = Sr, Ba; M = Nb, Ta; M′ = Li, Na, Mg, Ca, Mn) are compared. Thermogravimetry and differential scanning calorimetry were conducted in the air to assess the oxynitride stability. The electrical behaviors were studied by the equivalent circuit analysis of the impedance spectrum using compacted polycrystalline specimens, where BaCa0.2Ta0.8O2.6N0.4 was found to possess a bulk dielectric constant of 4550 along with an electrical conductivity of ≈10−6 S/cm at 27 °C. It remains, however, necessary to assess the extrinsic effects arising from the non-ideal sintering to interpret thoroughly the electrical property of BaCa0.2Ta0.8O2.6N0.4.

Synthesis, Characterization, Fluorescence and Antibacterial Activities Studies of Transition Metals Complexes with a Macro Acyclic Schiff Base Ligand

The reactions of the Schiff base 2,2’-[(2-hydroxypropane-1,3-diyl) bis-(imino-methane diyl)] bis-(4-bromophenol) (H3L), with metal transition ions (Mn(II), Ni(II), Cu(II), Zn(II), and Cd(II),) afforded one type of complex formulated as [M(HL)(H2O)2].nH2O. These compounds have been characterized by elemental analysis, UV–Vis, FTIR, 1H and 13C NMR spectroscopies, molar conductivity and room temperature magnetic measurements. The structure of nickel (II) complex has been determined by X-ray crystallography. The complex crystallizes in the orthorhombic space group Pnma with a = 7.7702(4) Å, b = 23.1921(15) Å, c = 10.6853(5) Å, V = 1925.57(15) Å3, Z = 8, R1 = 0.043 and wR2 = 0.107, Dcalc = 1.893 Mg m−3. The ligand acts in tetradentate fashion in its di-deprotonated form. Two coordinated water molecules complete the coordination sphere. The environment around the Ni(II) center is best described as an octahedral geometry. In the crystal structure of the Schiff base ligand, the existence of a strong intramolecular O-H•••O hydrogen bonding [O2W-H2W 0.80(3) Å, H2W •••O1 1.915(3) Å, O2W••• O1 2.6258(19) Å, O2W-H2W•••O1 148(3)°] and [O1W-H1W 0.73(3), H1W•••O1 2.15(4) Å, O1W•••O1 2.836(2)Å, O1W-H1W•••O1 156(4)°] are observed. Antibacterial activity study shows that the cadmium (II) complex is more active than the free ligand on.

Synthesis and crystal structure of the zinc borate Zn6B22O39·H2O

Abstract The synthesis and crystal structure of Zn6B22O39·H2O are described. This new zinc borate was synthesized at 7 GPa and 1523 K in a multianvil device. It crystallizes in the orthorhombic space group Pnma (no. 62) with the lattice parameters a = 818.77(4), b = 768.42(3), c = 1744.82(9) pm, V = 1.09777(9) nm3, and two formula units per unit cell (Z = 2). The structure is closely related to those of M 6B22O39·H2O (M = Fe, Co, Ni, Cd) and features non-planar (BO3) units as demonstrated by single-crystal and powder X-ray diffraction techniques.

Effect of A-site ionic disorder on structure, magnetic and magnetocaloric properties of La0.85-xNdxAg0.15-yKyMnO3 manganites

In this paper, the effect of A-site ionic disorder (σ2) on the structure, magnetic and magnetocaloric properties in La0.85-xNdxAg0.15-yKyMnO3 have been investigated. X-ray diffraction analysis using Rietveld refinement shows that the crystal structure of the perovskite manganites changes from rhombohedral (space group R3 ͞C) to orthorhombic (space group Pnma) structure with the increasing in σ2. Magnetization measurements showed that, upon increasing σ2, ferromagnetic double exchange interaction of the perovskite manganites diminishes, and as a result, Curie temperature (TC) of the samples decrease linearly. The inverse of susceptibility shows a downturn with decreasing temperature before TC indicating the existence of the Griffiths phase for La0.62Nd0.23Ag0·099K0·051MnO3 (σ2 = 0.004). The magnetic phase transitions of all the samples are belongs to second order transition.

A first-principles study of ternary metal chalcogenides [formula omitted][formula omitted] for efficient thermoelectric applications empowered by machine-learning interatomic potential

Metal chalcogenides have already been recognized as promising candidates for thermoelectric applications in the past decade. This study systematically analyzes the ternary metal chalcogenide Ba2MnX3 (X = Te,Se,S) materials to check their suitability for thermoelectric applications. Ba2MnX3 materials belong to the orthorhombic and centrosymmetric Pnma space group, with Ba atoms distributed inside the three-dimensional framework of MnX4 tetrahedron units, forming a quasi-one-dimensional crystal structure. The electronic band structures of the materials investigated using density functional theory (GGA+U) reveal that the materials have direct band gaps ranging between 1.3 eV to 1.9 eV. The structural stability and phonon transport properties are studied using a combination of density functional theory and machine-learning approach. The study shows that all Ba2MnX3 materials possess low lattice thermal conductivity (κL). For Ba2MnTe3, at 700 K κL∼0.45Wm−1K−1 is the lowest achieved κL in this work. The thermoelectric transport parameters of the materials are estimated by working out the semiclassical Boltzmann transport equation. Finally, the Figure of merit (ZT) and thermoelectric conversion efficiency values of the materials are calculated. The maximum ZT≈ 0.74 at 700 K at a carrier concentration of 2.43×1020cm−3, and an efficiency ∼8% in the temperature interval 300 – 700 K is achieved for Ba2MnSe3.

Impurity, host and defect-related luminescence of CsLaSiS4 thiosilicate crystals doped with Ce3+ ions

Ce+3 doped CsLaSiS4 single crystals were synthesized using high-temperature flux synthesis. XRD analysis showed that the products are isostructural to CsLaSiS4 and crystallize in orthorhombic space group Pnma. Absorption spectra were studied at room temperature, and photoluminescence properties were examined in the temperature range of 5–310 K. The energy of interband transitions Eg = 3.75 eV was determined at room temperature in the Tauc model. At room temperature, only a non-elementary d → f emission band of Ce+3 ions was observed in the 520 nm region. The luminescence kinetics upon excitation by a pulsed cathode beam or X-ray synchrotron radiation exhibited a dominant nanosecond component. Decay time, as well as build-up time, decreased with increasing concentration of Ce+3 ions. Concentration quenching of Ce+3 emission was not observed up to 11.9 mol% of Ce+3 ions. At a low temperature of 5 K, new wide emission bands at 422 and 688 nm appeared in the photoluminescence spectrum. It is shown that the 422 nm band in the photoluminescence spectrum corresponds to host emission, specifically the luminescence of self-trapped excitons (STE). The 688 nm emission band corresponds to defect-related luminescence. STE emission is quenched according to the Mott law at temperatures above 26 K with an activation energy of 20 meV. An efficient energy transfer channel from the STE to the Ce+3 ion via the radiative resonance mechanism is observed. The emission of Ce+3 ions and defect-related luminescence can be excited by the intracenter way, due to electron-hole recombination, or by the creation of defect bound excitons. Based on the obtained spectroscopic data, a band scheme illustrating the processes of relaxation of electronic excitations at T = 5 K in Ce+3 doped CsLaSiS4 crystals is proposed.

Improvement on Magnetocaloric Effect through Structural Evolution in Gadolinium Borate Halides Ba2Gd(BO3)2X (X = F, Cl).

A new Gd3+-containing borate Ba2Gd(BO3)2F has been successfully grown via the high-temperature solution method using BaF2-NaF-B2O3 flux. Ba2Gd(BO3)2F crystallizing in the orthorhombic space group Pnma is with lattice parameters a = 7.571(4) Å, b = 10.424(5) Å, c = 8.581(4) Å, α = β = γ = 90°, and Z = 2. Its three-dimensional framework was constructed from interesting pinwheel-like [Gd(BO3)F]∞ layers bridged by sharing [BO3]3-, which is different from the [Gd(BO3)]∞ layer in the model structure Ba2Gd(BO3)2Cl. The magnetic measurements indicated that Ba2Gd(BO3)2F has a larger magnetocaloric effect with -ΔSm,max = 27.82 J·kg-1·K-1at 2 K and 9 T than that of Ba2Gd(BO3)2Cl under the same conditions. Moreover, thermal stability, infrared spectrum (IR), and ultraviolet-visible-near-infrared diffuse reflectance spectrum were carried out to characterize the title compounds. The first-principles computations also looked into the electronic band structures, densities of states, and refractive indices.

Crystal structure of the quaternary lithogallate Sr2LiGaO4

Abstract The new quaternary lithogallate Sr2LiGaO4 was prepared by conventional solid-state synthesis in a welded tantalum ampoule at T = 850 °C. Single-crystal X-ray diffraction was used to elucidate the crystal structure of the compound, which crystallizes in the orthorhombic space group Pnma (no. 62) with the lattice parameters a = 11.2434(4), b = 5.6879(2), and c = 6.6983(2) Å. The phase composition of the powder sample was determined by Rietveld refinement based on X-ray diffraction data. The crystal structure is composed of layers of corner-sharing LiO4 and GaO4 tetrahedra with alternating orientation parallel to the crystallographic bc plane. The eightfold coordinated strontium atoms are arranged in a zigzag manner between the layers forming two types of double-capped trigonal prismatic SrO8 units with common faces. The crystal structure of Sr2LiGaO4 is isotypic to that of the lithoaluminate derivate Sr1.85Ba0.15LiAlO4.

Optimal Selection Role of Chelating Agents in the Synthesis of YFeO3 Nanomaterials Prepared via Sol-gel Technique

The present paper focuses on the selection of the optimal composition of YFeO3 polycrystalline materials which were prepared by using the sol-gel technique in the presence of different chelating agents, such as glycine, ethylene diamine tetraacetic acid (EDTA), urea and starch. The chelating agents used in the synthesis of YFeO3 were selected based on the good to excellent physical and magnetic properties that they demonstrated. The structural phase purity of YFeO3 formed with different chelating agents was examined with the help of the X-ray diffraction (XRD) technique. The synthesized compounds exhibited orthorhombic structure and Pnma space group, which was further confirmed with the help of Rietveld refinement. The surface morphology of these compounds with different chelating agents showed the particles with different sizes within the range of 750 nm to 940 nm. The surface areas of YFO materials (Glycine, Urea, and Starch) were found to be almost similar within a close range of 4.34 m2 g−1. But in the case of YFO (EDTA) material, a value of 7.34 m2 g−1 was noticed, which is quite higher as compared to the other chelating agents used in this study. The desired property of magnetization (1.80 emu g−1) and coercive field (54.83 Oe) for the YFO (EDTA) material showed decent values as compared with glycine, urea, and starch as chelating agents for YFO. The optical band gap for the synthesized compounds was estimated with the help of a Tauc plot considering the indirect band gap, which is comparable with the existing values as mentioned in the standard reports. The optical band gap was found to be in the range of 2 eV. It was observed that YFO (EDTA) material acted as a better chelating agent, which was confirmed with the help of the above results.

K2Mn3O(OH)(VO4)(V2O7) with Sawtooth Chains of Multivalent Manganese Triangular Trimer Units: Magnetic Susceptibility Shrouding a Long-Range Antiferromagnetic Order of Ferromagnetic Triangles.

ortho-Pyrovanadate (or ortho-diorthovanadate) K2Mn23+Mn2+O(OH)(VO4)(V2O7) synthesized hydrothermally crystallizes in the orthorhombic space group Pnma with a = 17.9155(5), b = 5.8940(2), c = 10.9971(3) Å, V = 1161.23(6) Å3, and Z = 4. Its crystal structure features linear chains of edge-sharing Mn3+O6 octahedra with every second pair of Mn3+O6 octahedra condensed with a Mn2+O6 octahedron on one side of a chain in a sawtooth pattern so that each sawtooth chain consists of a triangular trimer. These sawtooth chains, running parallel to the b axis and linked by the VO4 and V2O7 groups, form a framework with channels populated by K atoms. The new compound is a structural analogue of the mineral zoisite Ca2Al3O(OH)(SiO4)(Si2O7), showing a striking example of very different chemical compositions. K2Mn3O(OH)(VO4)(V2O7) undergoes a phase transition into an ordered antiferromagnetic (AFM) state at TN = 14.4 K, which was detected by high-frequency electron spin resonance as well as by both specific heat Cp and Fisher's specific heat d(χT)/dT measurements. However, this phase transition was not detected by magnetic susceptibility measurements. The origin of this puzzling observation was resolved by evaluating the spin exchanges of K2Mn3O(OH)(VO4)(V2O7), which revealed that each triangular trimer is a ferromagnetically coupled cluster, and the observed ordering involves an AFM ordering between the ferromagnetic (FM) clusters. This ordering is shrouded in magnetic susceptibility measurements due to the susceptibility contributions from the individual FM triangular trimers even below TN. We showed that the magnetic susceptibility of K2Mn3O(OH)(VO4)(V2O7) between ∼30 K and room temperature is satisfactorily described by an AFM chain made up of ferromagnetically coupled triangular clusters, as described by a few spin-exchange parameters.

Disordered Crystal Structure and Anomalously High Solubility of Radium Carbonate.

Radium-226 carbonate was synthesized from radium-barium sulfate (226Ra0.76Ba0.24SO4) at room temperature and characterized by X-ray powder diffraction (XRPD) and extended X-ray absorption fine structure (EXAFS) techniques. XRPD revealed that fractional crystallization occurred and that two phases were formed─the major Ra-rich phase, Ra(Ba)CO3, and a minor Ba-rich phase, Ba(Ra)CO3, crystallizing in the orthorhombic space group Pnma (no. 62) that is isostructural with witherite (BaCO3) but with slightly larger unit cell dimensions. Direct-space ab initio modeling shows that the carbonate oxygens in the major Ra(Ba)CO3 phase are highly disordered. The solubility of the synthesized major Ra(Ba)CO3 phase was studied from under- and oversaturation at 25.1 °C as a function of ionic strength using NaCl as the supporting electrolyte. It was found that the decimal logarithm of the solubility product of Ra(Ba)CO3 at zero ionic strength (log10 Ksp0) is -7.5(1) (2σ) (s = 0.05 g·L-1). This is significantly higher than the log10 Ksp0 of witherite of -8.56 (s = 0.01 g·L-1), supporting the disordered nature of the major Ra(Ba)CO3 phase. The limited co-precipitation of Ra2+ within witherite, the significantly higher solubility of pure RaCO3 compared to witherite, and thermodynamic modeling show that the results obtained in this work for the major Ra(Ba)CO3 phase are also applicable to pure RaCO3. The refinement of the EXAFS data reveals that radium is coordinated by nine oxygens in a broad bond distance distribution with a mean Ra-O bond distance of 2.885(3) Å (1σ). The Ra-O bond distance gives an ionic radius of Ra2+ in a 9-fold coordination of 1.545(6) Å (1σ).