Orthorhombic Space Group Pnma Research Articles

Electrical Conduction and Relaxation in Perovskite Oxide SrCe0.98Na0.02O3 Synthesized by Solid‐State Route

AbstractPowder of SrCe0.98Na0.02O3 is synthesized by calcination at 1000 °C for 8 h via solid‐state ceramic route. The ceramic/pellet of this compound is obtained by sintering at 1200 °C for 12 h. X‐ray diffraction (XRD) technique is used to confirm single‐phase formation. Rietveld refinement of the XRD pattern of sintered powder has confirmed orthorhombic crystal structure and space group Pnma as reported for SrCeO3. Further, the purity of the synthesized compound is ensured using Raman and Fourier transform infrared spectroscopy analysis. Scanning electron microscopic studies have reflected dense microstructure and spherical shape grains with an average size of 1.80 µm. Complex plane impedance and spectroscopic analysis are employed to study electrical conduction and relaxation mechanisms in the temperature range 300–600 °C and frequency range 20 Hz to 2 MHz. The activation energy for DC conduction (Econ) and relaxation (Erelx) is found to be the same (0.77 eV). Based on the numerical value of activation energies, conduction and relaxation mechanisms are attributed to migration of doubly ionized oxygen vacancies (VO••).

Spin phonon coupling in Mn doped HoFeO3 compounds exhibiting spin reorientation behaviour

An investigation has been carried out on the spin phonon coupling in a series of isostructural polycrystalline orthorhombic (Space group Pnma) compounds HoFe1−XMnXO3 (x ⩽ 0.6) exhibiting spin reorientation below Néel temperature (TN), using magnetization, neutron diffraction, and Raman scattering techniques. Mn doping leads to an anomalous increase in the spin reorientation temperature (TSR), shifting it close to room temperature from TSR ~ 60 K for x = 0 sample, and concomitant lowering of TN. The TSR is absent in samples for x ⩾ 0.5. The magnetic structure undergoes a transition at TSR from Γ4 → Γ1 in the Mn doped compounds as against Γ4 → Γ2 observed in HoFeO3 sample. In the region T < TN an anomalous softening of Raman phonon modes viz., B2g(5) and B3g(3), identified with the stretching motion and breathing mode, respectively, of Fe/Mn–O6 octahedra, is observed in compounds exhibiting spin-reorientation behaviour, indicating a spin-phonon coupling in these compounds. A quadratic correlation between the deviation of phonon frequency and variation of antiferromagnetic moment (Δω M2) is observed in these compounds. The temperature evolution of the M2+ mode obtained from the analysis of neutron diffraction data based on symmetry adapted mode decomposition of the Pnma structure further corroborates the mode softening observation.

Development of Sensor Based on Copper(II) Thiocyanate Pyridine Polymeric Complex for Detection of Catechol

The reaction of copper(I) thiocyanate with triphenylphosphine, in pyridine, in air and at room temperature, led to the formation of the copper(II) thiocyanate pyridine polymeric complex [Cu2( $\mu _{\text {3}}$ CO3)(NCS)2(Py)4]n in the form of deep blue needle-like crystals. Fourier transform infrared spectroscopy (FTIR), elemental analysis (EA), thermogravimetric analysis (TGA) and single crystal X-ray diffraction analysis (XRD) were performed in order to reveal the identity of the obtained complex. The complex is a coordination polymer that crystallizes in the orthorhombic space group Pnma and has a one-dimensional linear structure running along the crystallographic ${a}$ axis. Here, we report the investigation of the electrochemical properties of this polymeric compound, collected in acetonitrile solution and KClO4 as electrolyte, by cyclic voltammetry and square wave voltammetry. The voltammograms showed four peak pairs related to redox processes of copper ion and electroactive ligands. Moreover, we used this compound as modifier of carbon paste electrodes, whose electrochemical properties were studied in different electrolytes and electrochemical redox probes. These studies demonstrate the valuable electrochemical and electrocatalytic properties of the [Cu2( $\mu _{\text {3}}$ -CO3)(NCS)2(Py)4]npolymerimmobilized in the carbonaceous matrix. The sensor developed by using the carbon paste method has shown excellent sensitivity for catechol, good repeatability, selectivity, stability, and applicability in detection of catechol in water samples.

LiLa4N2I7 as the first lithium-containing nitride halide of the lanthanides: Synthesis, crystal structure and spectroscopic characterization

Initially, the quaternary nitride iodide LiLa4N2I7 was synthesized at 600 °C by a partial metathesis reaction of lithium nitride (Li3N) and lanthanum triiodide (LaI3) within 7 days. Single-phase samples were obtained through annealing of the corresponding binary compounds (LiI, LaN and LaI3) for 20 days overall (4 days at 600 °C prior to 16 days at 500 °C). The title compound crystallizes in the orthorhombic space group Pnma with four formula units per unit cell (a = 1374.17(9), b = 1213.45(8), c = 1079.91(7) pm at 100 K). The dominating structural features are trans-edge shared [NLa4]9+ tetrahedra building up {[NLa4/2e]3+}∞1 chains running along [010]. The linkage of these chains via iodide anions leads to a three-dimensional framework, which embeds isolated trigonal bipyramids [LiI4+1]4– with one long besides four short Li+–I– contacts. Infrared spectra of crystalline samples show four main bands between 300 and 600 cm−1, which can probably be assigned as vibrational modes of the condensed [NLa4]9+ tetrahedra. 7Li-MAS NMR spectroscopy reveals a different coordination sphere of Li+ in rocksalt-type LiI than in LiLa4N2I7, but no significant lithium-cation mobility.

Polyhedral characteristics of the cosalite-type crystal structures

Abstract The crystal structure of cosalite from the Trepča orefield was refined in the orthorhombic space group Pnma [a = 23.7878 (9), b = 4.0566 (3), c = 19.1026 (8) Å, V = 1843.35 (17) Å3, Z = 2] from single-crystal data (MoKα X-ray diffraction, CCD area detector) to the conventional R1 factor 0.031 for 1516 unique reflections with I &gt; 2σ(I). The chemical formula (Cu0.15Ag0.24)+(Fe0.19Pb7.20)2+(Bi7.06Sb1.06)3+S20, calculated on the basis of 20 S atoms per formula unit, was determined by WDX. The unit cell contains 18 + 2 symmetrically nonequivalent atomic sites: 10 occupied by S; two by pure Pb (Pb3 and Pb4); one by pure Bi (Bi1); two by a combination of Bi and small amounts of Sb (Bi2/Sb2, Bi4/Sb3); two by Pb and Bi, and in one of these also by a small amount of Ag [Me1 = Pb2 &gt;&gt; Bi5 &gt; Ag1, Me3 = Pb1 &gt;&gt; Bi3]; and finally one site, Me2 (Bi6 &gt;&gt; □), is partly occupied by Bi and partly split into an additional two adjacent trigonal planar “interstitial positions”, Cu1 and Cu2, where small amounts of Cu, Ag, and Fe can be situated. All atoms are at 4c special positions at y = 0.25 or 0.75. The structure consists of slightly to moderately distorted MeS6 octahedra sharing edges, bicapped trigonal PbS8 coordination prisms, and fairly distorted Cu1S6 and Cu2S4 polyhedra. The effects of the cation substitutions, bond valence sums, and the polyhedral characteristics are compared with other published cosalite-type structures. Among known cosalite-type structures, the largest volume contraction is shown by sample 4 (Altenberg) and involves the replacement of large cations (Bi3+ and Pb2+) by the smaller Sb3+, as well as Cu+ and Ag+. These replacements are reflected in the variations of individual Me–S bond distances, which are accompanied by variations in average Me–S distances. The degree of polyhedral distortion, Δ, progressively increases for the four Bi-hosting sites of nine cosalite-type structures: Me2 &lt; Bi2 &lt; Bi1 &lt; Bi4. The Bi4 and Me3 are the most and the Me1 and Me2 are the least distorted octahedral sites of the nine cosalite-type structures.

Double Jonscher response and contribution of multiple mechanisms in electrical conductivity processes of Fe-PrCaMnO ceramic

In this work, the ceramic Fe-PrCaMnO manganite was synthesized by means of standard high-temperature solid-state reaction technique. X-ray diffraction of Pr0.7Ca0·3Mn0·95Fe0·05O3 was indexed to a perovskite single phase. Then, all reflections appearing in the diffraction patterns were indexed and assigned to the orthorhombic Pnma space group. Electrical investigations show that the sample presents two dissimilar behaviours. A semiconductor character was observed at low temperature region [80K–250K]. Then, a metallic behaviour was detected beyond T = 250K. Then, a saturation region was marked. At low temperature region, ac-conductivity analysis shows the coexistence of two frequency dependent conduction mechanisms. The Correlated Barrier Hopping (CBH) mechanism was observed at the intermediate frequency range and a Non-Small Polaron Tunneling (NSPT) one was detected at high frequency side. In the temperature range [140K–170K], a signature of a Quantum Mechanical Tunneling (QMT) conduction mechanism was noticed. Then, beyond T = 170 K, the CBH mechanism dominated the transport properties. A double Jonscher response and the contribution of multiple mechanisms in electrical conductivity processes of Fe-PrCaMnO system were confirmed. Then, the frequency dependence of ac-conductance has been clarified by several conduction Models (CBH, NSPT and QMT).

Li2Ca5Tb(BO3)5: An orthoborate with large spherical hollow cages

A new rare-earth orthoborate Li2Ca5Tb(BO3)5 with an unusual 3D framework structure has been successfully obtained from a high-temperature solution in a platinum crucible. It crystallizes in the orthorhombic space group Pnma (62) with lattice parameters of a = 19.264(4) Å, b = 10.408(2) Å, c = 6.5336(13) Å and Z = 4. Its structure consists of near spherical hollow cages with size of dmax = 7.897, dmid = 6.532 and dmin = 5.643 Å built by (CaǀTb)O8, CaO8, CaO6, LiO5 and BO3 polyhedra. Furthermore, the thermal stability was investigated using differential scanning calorimeter (DSC). It shows strong green luminescence due to the characteristic emission 5D4 to 7F5 transitions of Tb3+ ions.

Mixed-metal borate FeVBO4 of tunnel structure: Synthesis and electrochemical properties in lithium and sodium ion batteries

Transition borates exhibit various functions due to their diverse components and structures. Herein, a new mixed-metal borate, FeVBO4 with rhombic and triangular tunnels for ionic transportation, is first synthesized at 800 °C subsequent to a sol-gel routine. The new compound FeVBO4 crystallizes in an orthorhombic space group (Pnma, #62), with cell parameters of a = 9.2367(5) Å, b = 3.1772(1) Å, and c = 9.3912(6) Å. Furthermore, the electrochemical properties of carbon-coated FeVBO4 (FeVBO4/carbon) is evaluated as intercalated anode for rechargeable Li and Na batteries. The Na storage of FeVBO4/carbon via conversion reaction exhibits very low reversible capacity (46 mAh g−1). However, the Li storage of FeVBO4/carbon revealing high capacity is worth to investigate. The Li ions first insert the rhombic tunnels to form the LixFeVBO4 (0 < x ≤ 1) solid solution, and then squeeze into the triangular tunnel and activate a conversion reaction accomplished by delivering a high discharge capacity of 621.6 mAh g−1 (theoretical capacity 737.9 mAh g−1) and showing a reversible recharge capacity of 387.3 mAh g−1. Our study has unlocked the great potential of borate-type anode in rechargeable batteries, and the new compound FeVBO4 with unique structure and mixed metallic elements could be extended to other application area.

β-Eu(BO2)3 – a new member of the β-RE(BO2)3 (RE=Y, Nd, Sm, Gd–Lu) structure family

Abstract The title compound β-Eu(BO2)3 was synthesized in a high-pressure/high-temperature experiment at 4 GPa and 1473 K. The europium borate crystallizes in the orthorhombic space group Pnma (no. 62) with the lattice parameters a = 16.071(2), b = 7.440(4), and c = 12.362(5) Å. The structure is isotypic to the already known meta-borates β-RE(BO2)3 (RE = Y, Nd, Sm, Gd, Dy–Lu) and is built up of approximately triangular ribbons of BO4 tetrahedra. The compound was further characterized by X-ray powder diffraction, vibrational spectroscopy and shows a typical Eu3+ line emission upon excitation at 448 nm.

Peculiar magnetocaloric properties and critical behavior in antiferromagnetic Tb3Ni with complex magnetic structure

A study on the magnetocaloric properties of a Tb3Ni single crystal (which crystallizes in the orthorhombic Pnma space group) has been undertaken and combined with the study of the character and critical behavior of its magnetic transitions. It presents two important magnetocaloric effects in the temperature range 3–90 K due to the richness and variety of its temperature and magnetic field induced phase transitions. There is a conventional (direct) magnetocaloric effect with a maximum at 65 K and very competitive properties: |ΔSMpk| = 16.6 J/kgK, RCFWHM = 432 J/kg, with a 50 K span, for μ0ΔH = 5 T, which is due to the transition from a magnetically ordered state to the paramagnetic (PM) state with a combined antiferromagnetic to ferromagnetic (AFM-FM) metamagnetic transition. Besides, it also presents an inverse magnetocaloric effect at very low temperature for which the presence of metamagnetic transitions between AFM and FM states is responsible (ΔSMpk=19.9 J/kgK, RCFWHM = 245 J/kg, with a 15 K span, for μ0ΔH = 5 T). At low field (<2 T), the character of the AFM-PM transition which takes place at ≈ 61 K has been well established to be second order and governed by short range order interactions, as the critical parameters α, A+/A- obtained from the specific heat at μ0H = 0 T point to the 3D-Heisenberg universality class. Conversely, the metamagnetic transitions between AFM and FM states, which appear for magnetic fields higher than 2 T, have a first order character, as proved by the magnetization behavior as a function of field and temperature. These properties make this material extremely interesting for magnetic refrigeration applications in the gas liquefaction range 4–77 K.

Effect of acceptor Na1+ doping on the properties of perovskite SrCeO3

The aim of this work is to study the effect of Na doping on the structural, microstructural and electrical properties of SrCeO3. With this goal, SrCe1−xNaxO3 (x = 0, 0.02, 0.04, 0.06 and 0.10) polycrystalline ceramics have been prepared using the solid-state route. The phase and structure of the synthesized samples were confirmed using X-ray diffraction technique. Rietveld refinement of the XRD profile confirmed that all the samples have orthorhombic structure and space group Pnma. Further, the purity of the synthesized samples was checked using Raman and Fourier transformation infrared (FTIR) spectroscopy techniques. The optical bandgap was calculated using UV–Vis technique, and the values were found 3.01 and 3.12 eV for pristine and Na doped samples. Scanning electron microscopic studies of fractured surfaces of the sintered pellets have indicated that dopant Na has played a significant role in grain growth. Grain size and morphology of Na doped samples is different from pristine SrCeO3. DC conductivity of Na doped samples is lower than undoped SrCeO3.

True Polymorphic Phase Transition or Dynamic Crystal Disorder? An Investigation into the Unusual Phase Behavior of Barbituric Acid Dihydrate

Crystalline barbituric acid dihydrate (BTADH) was previously thought to undergo a subtle temperature-dependent phase transition from a high-temperature orthorhombic Pnma space group to a nonmerohedrally twinned monoclinic P21/n phase below a transition temperature of ∼217 K. Questions remain on the true nature of the unusual transformation and the structure of the high-temperature crystal phase due to difficulties in resolving the Pnma structure from X-ray diffraction data and because of the subtlety of the structural transition. In this study, terahertz (THz) spectroscopy and solid-state density functional theory (DFT) were utilized to explore this suspected phase transition and uncover the principle physical mechanisms contributing to this anomalous transition. Our findings suggest that at temperatures above the previously reported phase transition temperature of 217 K, the crystal does not exist in the Pnma space group configuration. However, two equivalent favorable energetic states with P21/n symmetry related by the twinning plane lie on either side of the proposed Pnma structure. It is these same local potential energy minima that guide the crystal system to a nonmerohedrally twinned configuration identified in the low-temperature crystal structures. At temperatures above 217 K, the system possesses the thermal energy necessary to readily transition between these degenerate states separated by the low-lying Pnma structural barrier. The evidence acquired by THz spectroscopy and DFT indicate the absence of a true temperature-dependent phase change, and rather a system that exists in a tenuous thermally disordered state above the previously alleged transition temperature.

A Series of Lanthanide-Based Metal-Organic Frameworks Derived from Furan-2,5-dicarboxylate and Glutarate: Structure-Corroborated Density Functional Theory Study, Magnetocaloric Effect, Slow Relaxation of Magnetization, and Luminescent Properties.

Herein, through a dual-ligand strategy, we report eight isorecticular lanthanide(III) furan-2,5-dicarboxylic acid metal-organic frameworks (Ln-MOFs) with the general formula {[Ln(2,5-FDA)0.5(Glu)(H2O)2]· xH2O} n [Ln = Sm (1), Eu (2), Gd (3), Tb (4), Dy (5), Ho (6), Er (7), and Yb (8); 2,5-FDA2- = furan-2,5-dicarboxylate and Glu2- = glutarate; x = 0.5 for 1, 2, and 4 and x = 0 for 3 and 5-8], synthesized under solvothermal conditions by using an N, N'-dimethylformamide/H2O mixed solvent system. Crystallographic data reveal that all eight Ln-MOFs 1-8 crystallize in the orthorhombic Pnma space group. All of the MOFs are isostructural as well as isomorphous with distorted monocapped square-antiprismatic geometry around the Ln1 metal center. In Ln-MOFs 1-8, the 2,5-FDA2- and Glu2- ligands exhibit μ2-κ4,η1:η1:η1:η1 and μ3-κ5,η2:η1:η1:η1 coordination modes, respectively. Topologically, assembled Ln-MOFs 1-8 consist of the 2D cem topological type. The designed Ln-MOFs 1-8 are further explored for structure-corroborated density functional theory study. Meanwhile, room temperature photoluminescence properties of Ln-MOFs 2 and 4 and magnetic properties of Ln-MOFs 3 and 5 have been explored in detail. A highly intense, ligand-sensitized, Ln3+ f-f photoluminescence emission is exhibited by Ln-MOFs 2 [Eu3+ (red emission)] and 4 [Tb3+ (green emission)]. Magnetic studies suggest weak antiferro- and ferromagnetic interactions between adjacent GdIII ions in Ln-MOF 3, thereby displaying a large magnetocaloric effect. The magnetic data measured at T = 2 K and Δ H = 30 kOe depict that the -Δ Sm value per unit mass reaches 32.1 J kg-1 K-1, which is larger than most of the GdIII-based complexes reported. The alternating-current susceptibility measurements on Ln-MOF 5 revealed that out-of-phase signals are frequency- and temperature-dependent under both 0 and 2 kOe direct-current fields, thereby suggesting a typical slow magnetic relaxation behavior with two relaxation processes. This is further supported by the Cole-Cole plots at 2.4-6 K.

Tailoring the Chemical Composition of LiMPO4 (M = Mg, Co, Ni) Orthophosphates To Design New Inorganic Pigments from Magenta to Yellow Hue.

New inorganic pigments with intense and saturated coloration have been prepared by a solid-state route and exhibit a large color scale from magenta to yellow. Indeed, yellow and magenta are two of the three subtractive model's colors with wide application in printing or displays as e-book readers. To develop yellow and magenta hue, we focused on cobalt- and nickel-based orthophosphates thanks to the chemical stability, low density, low price, and easy preparation of such a pigment class. All of these orthophosphates crystallize with the well-known olivine-type structure (orthorhombic Pnma space group) where transition metals are stabilized in a distorted octahedral site. This paper deals with the optical absorption properties of various orthophosphates, the correlations with structural features, and their colorimetric parameters (in L*a*b* color space). The LiCo1- xMg xPO4 series show near-magenta color with tunable luminosity, while the LiNiPO4 compound exhibits a frank yellow coloration. Co2+ (4T1) and Ni2+ (4A2) chromophore ions occupy a more or less distorted octahedral site, leading to tuning of the intensity of the d-d electronic transitions in the visible and near-IR ranges and providing a subtractive color scale; i.e., a LiCo1- xNi xPO4 solid solution possesses a very rich panel of colors between the two yellow and magenta extremes. It is worth noting that the crystal-field splitting and B Racah parameter have been estimated in a first approximation on the basis of the Tanabe-Sugano diagram and lead to the conclusion of a slightly higher crystal-field splitting of around 0.9 eV for Ni2+ ions and similar β covalent parameters, despite the same crystallographic sites of both of these transition metals.

Structure and properties evolution with inorganic and organic acids of a new organo-chlorocadmate compound (C6H20N3)2[Cd2Cl10]: Theoretical approach

This work describes the theoretical studies of the reactivity, electrical and thermodynamic properties of a novel organo-chlorocadmate complex (C6H20N3)2[Cd2Cl10] and its inorganic and organic acid derivatives. The synthesis and crystal structure are described, with the compound crystallizing in the orthorhombic (Pnma) space group with unit cell parameters: a = 7.25494(11) Å, b = 29.3000(5) Å, c = 7.33927(13) Å. The semi-empirical calculations reveal that not only are all of the derivatives semiconductors, but also that the inclusion of acids in the structure alter the electrical and thermodynamic properties significantly, demonstrating a systematic and easy method for tuning the materials reactivity along with other desirable properties.

La2USe3S2: A Serendipitously Grown Lanthanide/Actinide Chalcogenide from a Eutectic Halide Flux

La2USe3S2, exact composition La2USe2.96S2.04, crystallized from a reaction between USe2 and La2S3 in a molten CsCl/KCl eutectic flux and was characterized by single crystal X-ray diffraction. La2USe3S2 crystallizes in the orthorhombic space group Pnma in the U3S5 structure type with lattice parameters a = 12.3284(3) A, b = 8.4028(2) A, and c = 7.3452(2) A. In La2USe3S2 all the anion sites have mixed S and Se occupancy and, henceforth, will be simply referred to as Q sites. The compound exhibits sigmoidal sheets built from LaQ8 (Q = S, Se) bicapped trigonal prisms that edge-share down the a-axis forming rectangular-shaped channels or tunnels. These tunnels are occupied by UQ6 (Q = S, Se) octahedra that edge-share to form infinite, one-dimensional chains running down the b-axis. X-ray diffraction quality single crystals of La2USe3S2 were grown from a molten CsCl/KCl eutectic flux at 950 °C and used for structure determination using single crystal X-ray diffraction. The compound crystallizes in the orthorhombic space group Pnma in the U3S5 structure type.

Crystal Structures of α- and β-Nitrogen Trifluoride.

The crystal structures of α-NF3 and β-NF3 are reported for the first time. As shown by powder neutron diffraction, the low-temperature α-NF3 crystallizes in the orthorhombic space group Pnma ( oP16) with lattice parameters a = 6.71457(13) Å, b = 7.30913(14) Å, c = 4.55189(8) Å, V = 223.396(7) Å3, and Z = 4 at T = 6 K. The intramolecular atom distances in α-NF3 are 1.3639(16) and 1.3677(11) Å for N-F, and 2.1216(16) and 2.120(2) Å for F···F. The F-N-F bond angles are 101.92(7)° and 101.63(10)°. All data are in excellent agreement with quantum-chemical predictions and previously reported experimentally obtained gas-phase data. The high-temperature β-NF3 is a plastic crystal, space group P42/ mnm ( tP120), with the lattice parameters a = 15.334(6) Å, c = 7.820(3) Å, V = 1838.6(12) Å3, and Z = 30 at T = 60 K. Its crystal structure is closely related to that of the Frank-Kasper sigma phase.

ASc[SeO3]2 (A = Na – Cs): Pure Alkali‐Metal Scandium Oxoselenates(IV) and Their Representatives With Mixed Alkali‐Metal Occupation

Alkali‐metal scandium oxoselenates(IV) ASc[SeO3]2 (A = Na – Cs) are known since a few years and a hydrothermal synthesis was used to obtain them. In our new studies we applied a flux‐supported solid‐state reaction and produced colorless single crystals as well. All representatives ASc[SeO3]2 with A = Na – Cs crystallize in the orthorhombic space group Pnma, in contrast to earlier reports for hexagonal RbSc[SeO3]2. Furthermore we have extended this field with some crystals showing a mixed occupation on the alkali‐metal site, namely (K,Na)Sc[SeO3]2, (Rb,K)Sc[SeO3]2, and (Cs,Rb)Sc[SeO3]2. Since all of them contain [ScO6]9– octahedra and [SeO3]2– ψ1‐tetrahedra the diverse connectivity of the distinct alkali‐metal centered oxygen polyhedra differentiates the compounds with the smaller alkali metals (A′ = Na and K) from those with the bigger ones (A′′ = Rb and Cs). For the mixed crystals the amount of smaller or bigger alkali metal is responsible, which design is chosen by the system. This forces the mixed crystal (Rb,K)Sc[SeO3]2 with a higher amount of potassium instead of rubidium to crystallize isotypically with KSc[SeO3]2 and NaSc[SeO3]2, whereas the pure rubidium compound RbSc[SeO3]2 adopts the CsSc[SeO3]2‐type structure. These findings are supported by single‐crystal Raman spectroscopy.

Pb4S3I2–A high-pressure phase in the PbS-PbI2 system

The reaction of a stoichiometric ratio of Pb, S and PbI2 at 4 GPa and 600 °C yields Pb4S3I2, a compound that has not been reported in the ambient pressure PbS-PbI2 system. Its crystal structure, determined from single crystal X-ray diffraction data, is orthorhombic (space group Pnma) with a = 8.1293(6) Å, b = 15.5613(11) Å, c = 8.1820(6) Å, and Z = 4 at ambient temperature and pressure. The structure consists of sheets of distorted edge-sharing lead-centered polyhedra and saw-tooth-shaped lead-lead bonded chains. Density Functional Theory based band structure calculations suggest Pb4S3I2 to be an indirect band gap semiconductor, and, consistently, a band gap value of approximately 1.6 eV is determined by diffuse reflectance measurements. The material is diamagnetic above 1.8 K.

Influence of silver (Ag) doping on a crystal structure of La0.7Ag0.1Ca0.2MnO3 and La0.65Ag0.15Ca0.2MnO3 manganites synthesized by sol-gel method

Perovskite manganite material has been extensively investigated because it has many attractive properties. In this paper, crystal structure of La0.7Ag0.1Ca0.2MnO3 (LACMO1) and La0.65Ag0.15Ca0.2MnO3 (LACMO15) materials will be reported. LACMO1 and LACMO15 materials were synthesized by sol-gel method with sintering temperature 900°C for 24h. Structural properties of LACMO1 and LACMO15 materials were characterized using X-Ray Diffractometer (XRD). The characterized results show a crystal structure transition from orthorhombic (Pnma spacegroup) to rhombohedral ( space group) along with increasing the concentration of Ag doping. The crystal structure transition show there is a distortion of the material structure caused by Ag-doping. Increasing the concentration of Ag doping may affect the tolerance factor (t) that used to measure the degree of distortion of a perovskite.