Space Group Immm Research Articles

Machine learning accelerated random structure searching: Application to yttrium superhydrides.

The search for new superhydrides, promising materials for both hydrogen storage and high temperature superconductivity, made great progress, thanks to atomistic simulations and Crystal Structure Prediction (CSP) algorithms. When they are combined with Density Functional Theory (DFT), these methods are highly reliable and often match a great part of the experimental results. However, systems of increasing complexity (number of atoms and chemical species) become rapidly challenging as the number of minima to explore grows exponentially with the number of degrees of freedom in the simulation cell. An efficient sampling strategy preserving a sustainable computational cost then remains to be found. We propose such a strategy based on an active-learning process where machine learning potentials and DFT simulations are jointly used, opening the way to the discovery of complex structures. As a proof of concept, this method is applied to the exploration of tin crystal structures under various pressures. We showed that the α phase, not included in the learning process, is correctly retrieved, despite its singular nature of bonding. Moreover, all the expected phases are correctly predicted under pressure (20 and 100GPa), suggesting the high transferability of our approach. The method has then been applied to the search of yttrium superhydrides (YHx) crystal structures under pressure. The YH6 structure of space group Im-3m is successfully retrieved. However, the exploration of more complex systems leads to the appearance of a large number of structures. The selection of the relevant ones to be included in the active learning process is performed through the analysis of atomic environments and the clustering algorithm. Finally, a metric involving a distance based on x-ray spectra is introduced, which guides the structural search toward experimentally relevant structures. The global process (active-learning and new selection methods) is finally considered to explore more complex and unknown YHx phases, unreachable by former CSP algorithms. New complex phases are found, demonstrating the ability of our approach to push back the exponential wall of complexity related to CSP.

Peculiarities of the electric resistivity behavior of R3(Ce,Nd,Sm)Cu4Sn4, R(Gd,Tb,Ho)NiSn2, DyNiSi, and DyNiSi3 compounds in magnetic fields

The resistance of ternary intermetallic compounds, namely RE(Ce, Nd, Sm)3Cu4Sn4 (space group Immm), RE(Gd, Tb, Ho)NiSn2 and DyNiSi (space group Pnma) and DyNiSi3 (space group Cmmm), has been studied in the temperature range up to 0.3 K and magnetic field up to 12 Tl. The temperature dependencies of electrical resistivity evidently show the anomalies at low temperatures. The anomalies of resistance temperature dependencies observed at the absence of an external magnetic field, agree well with magnetic phase transitions. In the majority of the investigated compounds, an increase of the external magnetic field leads to an erosion of the peculiarities on the temperature dependency of resistivity, right up to complete disappearance. Such effect is caused by the corresponding magnetic order phase transitions. Magnetic field influence on the temperature dependency of resistance is treated as an influence on the magnitude of hybridization between (s-d) conductivity electrons and localized f-electrons including influence on change on the charge caries mobility due to a possible spin-compensated interaction. Electron transport properties expose peculiarities in dependency of different chemical environment vicinity in elementary cell of crystal lattice and of magnetic state of the compound.

Li5Sn, the Most Lithium-Rich Binary Stannide: A Combined Experimental and Computational Study.

From reaction of excess lithium with tin, we isolate well-crystallized Li5Sn and solve the crystal structure from single-crystal X-ray diffraction data. The orthorhombic structure (space group Cmcm) features the same coordination polyhedra around tin and lithium as previously predicted by electronic structure calculations for this composition, however differently arranged. An extensive ab initio analysis, including thermodynamic integration using Langevin dynamics in combination with a machine-learning potential (moment tensor potential), is conducted to understand the thermodynamic stability of this Cmcm Li5Sn structure observed in our experiments. Among the 108 Li5Sn structures systematically derived using the structure enumeration algorithm, including the experimental Cmcm structure and those obtained in previous ab initio studies, another new structure with the space group Immm is found to be energetically most stable at 0 K. This computationally discovered Immm structure is also found to be thermodynamically more stable than the Cmcm structure at finite temperatures, indicating that the Cmcm Li5Sn structure observed in our experiments is favored likely due to kinetic reasons rather than thermodynamics.

Magnetic ordering and magnetocalori effect of GdNiGa4, GdNi0.5Ga1.5 and GdNiGa

The polycrystalline YNiAl4-type GdNiGa4 (space group Cmcm, N 63, oC24), CeCu2-type GdNi0.5Ga1.5 (space group Imma, N 74, oI12) and TiNiSi-type GdNiGa (space group Pnma, N 62, oP12) are prepared by arc melting with following annealing. The magnetic ordering and magnetocaloric effects of these compounds have been investigated using magnetic measurements in fields up to 90 ​kOe GdNiGa4 shows field insensitive antiferromagnetic ordering below TN ​= ​12 ​K, GdNi0.5Ga1.5 demonstrate ferromagnetic ordering below TC ​= ​36 ​K and low-temperature field-sensitive ferro-antiferromagnetic ordering (Tm) in the range of 12–32 ​K, while GdNiGa exhibits ferromagnetic ordering below TC ​= ​28 ​K. The saturation magnetizations at 2 ​K indicate a collinear ferromagnetic ordering of Gd-sublattice in GdNi0.5Ga1.5 and GdNiGa. The transformation of crystal lattice from GdNi0.5Ga1.5 to GdNiGa with ordering of Ni-sublattice leads to a remarkable increasing of magnetic entropy change and magnetocaloric effect. The structural and magnetic features of ternary Gd-Ni-Ga compounds are discussed.

Affimer Tagged Cubosomes: Targeting of Carcinoembryonic Antigen Expressing Colorectal Cancer Cells Using In Vitro and In Vivo Models.

Nanomedicines, while having been approved for cancer therapy, present many challenges such as low stability, rapid clearance, and nonspecificity leading to off-target toxicity. Cubosomes are porous lyotropic liquid crystalline nanoparticles that have shown great premise as drug delivery vehicles; however, their behavior in vivo is largely underexplored, hindering clinical translation. Here, we have engineered cubosomes based on the space group Im3m that are loaded with copper acetylacetonate as a model drug, and their surfaces are functionalized for the first time with Affimer proteins via copper-free click chemistry to actively target overexpressed carcinoembryonic antigens on LS174T colorectal cancer cells. Unlike nontargeted cubosomes, Affimer tagged cubosomes showed preferential accumulation in cancer cells compared to normal cells not only in vitro (2D monolayer cell culture and 3D spheroid models) but also in vivo in colorectal cancer mouse xenografts, while exhibiting low nonspecific absorption and toxicity in other vital organs. Cancerous spheroids had maximum cell death compared to noncancerous cells upon targeted delivery. Xenografts subjected to targeted drug-loaded cubosomes showed a 5–7-fold higher drug accumulation in the tumor tissue compared to the liver, kidneys, and other vital organs, a significant decrease in tumor growth, and an increased survival rate compared to the nontargeted group. This work encompasses the first thorough preclinical investigation of Affimer targeted cubosomes as a cancer therapeutic.

Negative linear compressibility in Se at ultra-high pressure above 120 GPa.

A series of in situ synchrotron X-ray diffraction (XRD) measurements were carried out, combined with first-principles calculations, to study structural phase transitions of selenium at high pressures and room temperature. Several phase transitions were observed, among which an isostructural phase transition was found at around 120 GPa for the first time. Evolved from the rhombohedral (space group R 3 m) structure (Se-V), the new phase (Se-V') exhibited an interesting increase of lattice parameter a at pressures from 120 to 148 GPa, known as negative linear compressibility (NLC). The discovery of NLC behavior observed in this work is mainly attributed to the accuracy and fine steps controlled by the membrane system for in situ XRD data collected with an exposure time of 0.5 s. After 140 GPa, a body-centered cubic (b.c.c.) structure Se-VI (space group Im 3 m) was formed, which remains stable up to 210 GPa, the highest pressure achieved in this study. The bulk moduli of phases Se-V, Se-V' and Se-VI were estimated to be 83 ± 2, 321 ± 2 and 266 ± 7 GPa, respectively, according to the P-V curve fit by the third-order Birch-Murnaghan equation of state. The Se-V' phase shows a bulk modulus almost 4 times larger than that of the Se-V phase, which is mainly due to the effect of its NLC. NLC in a higher pressure range is always more significant in terms of fundamental mechanism and new materials discovery, yet it has barely been reported at pressures above 100 GPa. This will hopefully inspire future studies on potential NLC behaviors in other materials at ultra-high pressure.

Crystal Structures of Hexafluoridoantimonate(V) Salts of d‐block Metals in Oxidation State +2

AbstractThe crystal structures of the M(SbF6)2 salts (M=Cu, Pd) are isotypic (Type I). They crystallize in the triclinic space group , Z=1 at 150 K. M2+ cations lying in the same plane are connected via SbF6 units forming slabs. There are only van der Waals contacts of fluorine atoms between the adjacent slabs. Salts of M(SbF6)2 (M=Fe, Co, Zn) crystallize differently (Type II; space group , Z=2 at 150 K). Their crystal structures are composed of M2+ cations interconnected by [SbF6]− anions – thus forming a three‐dimensional framework. The crystal structure of Fe(SbF6)2, determined at 240 K, is currently the only representative of the Type III. The main feature of this type is also a three‐dimensional framework consisting of M2+ cations and [SbF6]− anions. However, the mode of their association differs from that observed in Type II. The crystal structures of CuFSbF6 (orthorhombic space group Imma, Z=4 at 150 K) and AgFSbF6 (orthorhombic space group Pnma, Z=4 at 150 K) are not isotypic. The crystal structures of the by‐products H3ONi(SbF6)3 (orthorhombic space group Pnma, Z=4 at 150 K) and (O2)2Ag6CuF5(SbF6)11 ⋅ 2HF (triclinic space group , Z=1 at 150 K) were determined. In the latter, HF is directly attached to an Ag(II) via a fluorine atom.

Guest-Induced Multistep-to-One-Step Reversible Spin Transition with Enhanced Hysteresis in a 2D Hofmann Framework.

The interplay of host-guest interactions and controlled modulation of spin-crossover (SCO) behavior is one of the most exploited topics regarding data storage, molecular sensing, and optical technologies. In this work, we demonstrate the experimental approach of tuning the SCO behavior via controlled modulation of the spin-state cooperativity in a 2D Hofmann coordination polymer, [FeIIPd(CN)4(L)2]·1.3MeOH (1·1.3MeOH; L = methyl isonicotinate). Removal of the solvent changes the four-step transition to a complete one-step spin transition with an enhanced hysteresis width (∼20 K). Structural analysis of solvated (1·1.3MeOH) and partially desolvated (1·0.3MeOH) compounds reveals that the crystal system changes from a monoclinic C2/c space group to an orthorhombic Imma space group, where the FeII sites are present in a more symmetrically equivalent environment. Consequently, the axial ligand-field (LF) strength and face-to-face interactions of the ligands were increased by removing the guest, which is reflected in the highly cooperative SCO in 1 (desolvated compound). Also, the shift of the CN bond stretching frequencies and decrease of their relative intensities from the variable-temperature Raman spectroscopic measurements further corroborate the SCO behavior. Besides, theoretical calculations reveal that the singlet (1Γ) LF terms decrease by removing guest molecules, enhancing the molecular population in the low-spin state at low temperature, as experimentally observed for 1. Notably, fine tuning of the SCO behavior via host-guests interactions provides a great opportunity to design potential chemosensors.

Effect of divalent transition metal ions on physical, morphological, electrical and electrochemical properties of alluaudite phases Na2M2+2Fe3+(PO4)3 (M = Mn, Co and Ni): Cathode materials for sodium-ions batteries

The limited resources of lithium stimulated the research work to develop new polyanionic cathode materials for sodium-ion batteries. The Na2M2+2Fe3+(PO4)3 (M = Mn, Ni and Co) phases were prepared by autocombustion method assisted by glycine. Structural, morphology, thermal, electrical and electrochemical properties have been investigated. Its structures were determined using Xray powder diffraction and Rietveld method refinements. The two compounds Na2M2+2Fe3+(PO4)3 (M = Mn and Co) are alluaudite-type. Both compounds crystallize in monoclinic system with the space group C2/c and similar parameters: a = 12.0337(3) Å, b = 12.6268(3) Å, c = 6.5070(1) Å, β = 114.563(2)° for Na2M2+2Fe3+(PO4)3 (NMFP) and a = 11.7597(3) Å, b = 12.4579(3) Å, c = 6.4607(1) Å, β = 113.968(1)° for Na2Co2Fe(PO4)3 (NCFP). The NaNiFe2(PO4)3 (NNFP) compounds crystallize in orthorhombic system with the space group Imma and unit cell parameters: a = 10.3993(1) Å, b= 13.1966(1) Å, c = 6.4955(1) Å. The composition and morphology of the compounds were checked by energy dispersive spectroscopy coupled with scanning electron microscope. The thermal analysis confirmed the allotropic transition of the three materials from monoclinic to orthorhombic symmetry with the changing of divalent transitions metal ion. The electrical conductivity results of indicated that NNFP has the lowest value of activation energy of value= 0.63 eV owing to the large size of open channels existed in the orthorhombic symmetry. The electrochemical cycling results showed that NMFP cathode delivered the maximum storage capacity of about 94.2 mAh/g which correspond to coloumbic efficiency of about 75.5% after the initial cycling.

New data on sulphosalts from the hydrothermal siderite-type veins in the Spišsko-gemerské rudohorie Mts. (eastern Slovakia): 4. Tennantite-(Hg) from the Vyšný Klátov ore occurrence

A new occurrence of tennantite-(Hg) was recently confirmed at the Vyšný Klátov ore occurrence, Spišsko-gemerské rudohorie Mts., Košice-okolie Co., Košice Region, Slovakia. Tennantite-(Hg) occurs as lead-gray to black grains and aggregates up to 1 cm in size, associated with cinnabar, chalcopyrite, pyrite and hematite. Reflectance data of tennantite-(Hg) are given in this paper. The refined unit-cell parameters of tennantite-(Hg) from the Vyšný Klátov (for the cubic space group I-43m) are: a 22.523(7) Å and V 3105.4(1) Å3. Empirical chemical formulae of the two studied samples of tennantite-(Hg) from the Vyšný Klátov ore occurrence, recalculated on the basis of ΣMe = 16 apfu are: (Cu5.97Ag0.03)Σ6.00[Cu3.99(Hg1.95Fe0.10)Σ2.05](As3.57Sb0.39)Σ3.96S13.21 (sample VK1, n = 21) and (Cu5.99Ag0.01)Σ6.00[Cu4.05(Hg1.91Fe0.08)Σ1.99] (As3.79Sb0.15)Σ3.94S13.26 (sample VK3, n = 29).

Dachiardit-Ca, ferrierit-Mg a sprievodná zeolitová mineralizácia v dutinách chalcedónov na lokalitách Byšta, Brezina a Kuzmice (Slanské vrchy, Slovenská republika)

An interesting zeolite association has been identified at the localities Byšta, Brezina and Kuzmice, consisting of mordenite, clinoptilolite-Ca, dachiardite-Ca and ferrierite-Mg. Dachiardite-Ca (from Byšta and Brezina) and ferrierite-Mg (from Brezina) represent first recorded occurrences in the Slovak Republic. Zeolite mineralization occurs as white to gray crystalline fillings in small chalcedony cavities and crusts, developed in strongly altered Miocene rhyolites (Byšta and Brezina) or silicified andesites (Kuzmice). Crystals of dachiardite-Ca have acicular shapes, and are grouped into the radial, spherical and sheaf-like aggregates. Their average size ranges about 1 - 3 mm. Dachiardite-Ca from Byšta and Brezina is monoclinic, space group C2/m with following unit-cell parameters refined from X-ray powder diffraction data: a 18.618(8), b 7.498(3), c 10.284(4) Å, β 108.36(3)o, V 1362.4(1.3) Å3 and a 18.616(12), b 7.492(5), c 10.271(6) Å, β 108.27(5)o, V 1360.2(2.0) Å3, respectively. Chemical analysis is corresponding to the average empirical formula (Ca1.12K0.78Na0.16)Σ3.52(Al3.52Si20.56O48)·13H2O for dachiardite-Ca from Byšta and (Ca1.37Na0.48K0.25Ba0.02Mg0.02)Σ3.65(Al3.65Si20.37O48)·13H2O for dachiardite-Ca from Brezina. Ferrierite-Mg from Brezina forms acicular crystals and spherical aggregates of average size up to 1 mm. It is orthorhombic, space group Immm with following unit-cell parameters refined from X-ray powder difraction data: a 19.084(4), b 14.151(2), c 7.4932(16) Å, V 2023.7(1) Å3. Chemical analysis of ferrierite-Mg is corresponding to the following average empirical formula: (Mg1.14Ca0.48Ba0.40K0.28Na0.16Fe0.01)Σ2.47(Al5.09 Si31.06O72)·20H2O. PXRD as well as quantitative chemical data for clinoptilolite-Ca and mordenite are also provided in this paper. The formation of studied zeolites is associated with post-magmatic fluids significantly enriched in Si, which likely circulated during the younger stages of Miocene volcanic activity in the Slanské vrchy Mts. Hydrothermal fluids were probably generated from Si-rich rocks, represented predominantly by rhyolites under low temperature conditions (120 - 250 °C).

Ferrierit-Mg a Ba bohatý heulandit z Chvaletic u Přelouče (Česká republika)

Two zeolites are described from the pyrite-manganese deposit Chvaletice near Přelouč, central Bohemia, Czech Republic. Ferrierite-Mg forms brown, up to 5 mm long flat needles, radially arranged, which grow on grey-brown fine-grained rock composed of quartz, pyrite and Mn-silicates. The unit-cell parameters of ferrierite-Mg, refined from the powder X-ray diffraction data, are a = 19.162(14), b = 14.125(13), c = 7.495(6) Å and V = 2028.8(9) Å3 (space group Immm). Chemical analyses correspond to the empirical formula (Mg2.66Ca0.44Mn0.41Fe0.30Ba0.29K0.16Na0.10Sr0.03)Σ4.39(Al7.77 Si27.96O72)·18 H2O. The Ba-rich heulandite forms aggregates up to several cm in size composed of transparent gold-brown grains with characteristic pearly luster at cleavage planes. The unit-cell parameters of heulandite, refined from the powder X-ray diffraction data, are a = 17.732(2), b = 17.823(4), c = 7.4290(15) Å, β = 116.3(2) ° and V = 2104.2(6) Å3 (space group Cm). In BSE images, its aggregates are not homogenous. Ba-poor part of analyses corresponds to heulandite-Ca and heulandite-K, Ba-rich part beside Ca- and K-dominant members also to very rare heulandite-Ba. Both studied zeolites contain a significant content of Mn, ranging between 0.32 - 0.70 apfu (ferrierite-Mg) and 0.09 - 0.28 apfu (Ba-rich heulandite).

Hydrogen storage properties, structural analysis, elastic and electronic properties of K2PdH4

Density functional theory is adopted to study phase transitions and structural, elastic, and electronic properties of hydrogen storage K2PdH4. First, the structural evolution of K2PdH4 is investigated under high pressure along with the hydrogen storage properties. In the ambient conditions, K2PdH4 crystallizes in a tetragonal structure with space group I4/mmm. As the pressure is increased gradually on the crystal, a phase transition is recorded to the orthorhombic structure with space group Immm. Subsequently, the density of states and electronic band structures are obtained for each phase. Mechanical properties such as ductility and brittleness are investigated using elastic constants which are crucial parameters for solid-state hydrogen storage materials. Moreover, several properties are analyzed using Young, shear and bulk modulus to reveal the bonding characteristics of K2PdH4.

Crystal electric field and possible coupling with phonons in Kondo lattice CeCuGa3

We investigate the magnetic and crystal electric field (CEF) states of the Kondo lattice system CeCuGa3 by muon spin relaxation (muSR), neutron diffraction, and inelastic neutron scattering (INS) measurements. A noncentrosymmetric BaNiSn3-type tetragonal crystal structure (space group I4mm) is inferred from x-ray as well as from neutron powder diffraction. The low-temperature magnetic susceptibility and heat capacity data show an anomaly near 2.3 - 2.5~K associated with long range magnetic ordering, which is further confirmed by muSR and neutron diffraction data. The neutron powder diffraction collected at 1.7 K shows the presence of magnetic Bragg peaks indexed by an incommensurate magnetic propagation vector k = (0.148, 0.148, 0) and the magnetic structure is best described by a longitudinal spin density wave with ordered moments lying in ab-plane. An analysis of the INS data based on a CEF model reveals the presence of two magnetic excitations near 4.5 meV and 6.9 meV. The magnetic heat capacity data suggest an overall CEF splitting of 20.7 meV, however the excitation between 20 and 30 meV is very broad and weak in our INS data, but could provide an evidence of CEF level in this energy range in agreement with the magnetic entropy. Our analysis of INS data based on the CEF-phonon model indicates that the two excitations at 4.5 meV and 6.9 meV have their origin in CEF-phonon coupling (i.e. splitting of one CEF peak into two peaks, called vibron), with an overall splitting of 28.16 meV, similar to the case of CeCuAl3 and CeAuAl3.

New data on gersdorffite and associated minerals from the Peloritani Mountains (Sicily, Italy)

Abstract. Gersdorffite, ideally NiAsS, and associated minerals from Contrada Zillì (Peloritani Mountains, Sicily, Italy) have been characterized through electron microprobe analysis and X-ray diffraction. Primary minerals, hosted in quartz veins, are represented by gersdorffite, tetrahedrite-(Fe), and chalcopyrite with minor pyrite and galena. Rare aikinite inclusions were observed in tetrahedrite-(Fe) and chalcopyrite. Gersdorffite occurs as euhedral to subhedral crystals, up to 1 mm in size, with (Sb,Bi)-enriched cores and (Fe,As)-enriched rims. Its chemical composition is (Ni0.79−0.95Fe0.18−0.04Co0.04−0.01)(As0.90−1.03Sb0.10−0.00Bi0.02−0.00)S0.98−0.92. It crystallizes in the space group P213, with unit-cell parameters a=5.6968(7) Å, V=184.88(7) Å3, and Z=4, and its crystal structure was refined down to R1= 0.035. Associated tetrahedrite-(Fe) has chemical formula (Cu5.79Ag0.07)Σ5.86(Cu3.96Fe1.59Zn0.45)Σ6.00(Sb3.95As0.17Bi0.03)Σ4.15S13.06, with unit-cell parameters a= 10.3815(10) Å, V=1118.9(3) Å3, and space group I-43m. Its crystal structure was refined to R1=0.027. Textural and crystallographic data suggest a polyphasic crystallization of gersdorffite under low-temperature conditions.

Sc3Ir4Si13+x and Sc4Ir7Ge6 – the perovskite-related crystal structures

Abstract The crystal structure of Sc3Ir4Si13+x (x = 0.22) [space group P m 3 ‾ n $Pm\bar{3}n$ , a = 8.4651(1) Å] is found to be a new disordered variant of the primitive cubic Yb3Rh4Sn13 Remeika prototype. The silicide is stable in the narrow temperature range of 1283–1397 °C and reveals metallic properties. The crystal structure of Sc4Ir7Ge6 [U4Re7Si6 type, space group I m 3 ‾ m $Im\bar{3}m$ , a = 8.1397(8) Å] is refined for the first time. The electronic band structure calculations reveal that the properties of this germanide can be explained based on the free electron gas model. Both compounds reveal close structural relationships to the simple perovskite structure.

Neutron Diffraction Study of the Martensitic Transformation of Ni2.07Mn0.93Ga Heusler Alloy

The martensitic transition featuring the ternary Heusler alloy Ni2.09Mn0.91Ga was investigated by neutron diffraction. Differential scanning calorimetry indicated that structural transition starts at 230 K on cooling with a significant increase in the martensitic transformation onset compared to the classical Ni2MnGa. The low-temperature martensite presents the 5M type of modulated structure, and the structural analysis was performed by the application of the superspace approach. As already observed in Mn-rich modulated martensites, the periodical distortion corresponds to an incommensurate wave-like shift of the atomic layers. The symmetry of the modulated martensite at 220 K is orthorhombic with unit cell constants a = 4.2172(3) Å, b = 5.5482(2) Å, and c = 4.1899(2) Å; space group Immm(00γ)s00; and modulation vector q = γc* = 0.4226(5)c*. Considering the different neutron scattering lengths of the elements involved in this alloy, it was possible to ascertain that the chemical composition was Ni2.07Mn0.93Ga, close to the nominal formula. In order to characterize the martensitic transformation upon increasing the temperature, a series of neutron diffraction patterns was collected at different temperatures. The structural analysis indicated that the progressive change of the martensitic lattice is characterized by the exponential change of the c/a parameter approaching the limit value c/a = 1 of the cubic austenite.

Enhanced self-host blue emission of CaSrSb2O7 materials via Bi3+ ion doping for high CRI WLEDs, security inks and flexible displays

Luminescent materials are indispensable in our daily lives and have already been widely applied in various fields. Herein, novel self-host blue-emitting CaSrSb2O7 and CaSrSb2O7:Bi3+ phosphors with orthorhombic space group Imma (74) were successfully prepared. The phase purity, elemental composition, morphology, luminescent behaviors, etc. were investigated in detail. To compare the luminescence properties of rare-earth-activated phosphors, the self-host blue-emitting CaSrSb2O7 phosphor with unique performance exhibited a good quantum yield (QY) of 39.81%, and its emission intensity and QY could also be improved by doping Bi3+ ions. The CaSrSb2O7:Bi3+ phosphor was located in the pure blue region with the Commission Internationale de I'Eclairage chromaticity coordinate of (0.151, 0.058) and good color purity of 89.35%. For identifying its potential applications, the packaged white light-emitting diode device emitted a high color rendering index value of 93.66 under a forward current of 300 mA, and it would be further applied in security inks and flexible displays owing to its strong emission by the naked eyes. These results suggest that novel self-host blue-emitting CaSrSb2O7:Bi3+ phosphors could be used in multifunctional applications.

Structure investigation and vibrational spectroscopy of two prospective hybrid perovskites based on Mn and Co

Single crystals of two organic-inorganic hybrid (OIH) perovskites containing 1,5 pentylenediammonium, [NH3-(CH2)5–NH3] MnCl3.47Br0.53 (C5MnCB) and [NH3-(CH2)5–NH3] CoCl2.72Br1.28 (C5CoCB) were grown from solution by evaporation. The structure is investigated by single crystal x-ray diffraction, and infrared and Raman spectroscopy is used to help proper space group selection. The C5MnCB hybrid perovskite crystallizes in the orthorhombic space group Ima2, with unit cell parameters a = 23.9358(11) Å, b = 7.4110(3) Å, c = 7.1765(4) Å, V = 1273.03(11) Å3 and Z = 4. In this sample two types of disorder are found: a preferential substitution of Cl by Br, and a dynamical disorder caused by the rotation of the NH3+ group. The C5CoCB hybrid perovskite crystallizes in the monoclinic space group P21/c, with unit cell parameters a = 7.1914(14) Å, b = 16.265(4) Å, c = 11.248(2) Å, β = 98.033(7)°, V = 1302.7(5) ų and Z = 4. In this compound a random Cl–Br occupancy is present. Based on UV–Vis spectroscopy and thermal stability measurements, we suggest possible photovoltaic and visible light photocatalytic applications.

Structural evolution and magnetic aspects in nanostructured (Fe92Zr8)96B4 alloys

Magnetic powder alloys (Fe92Zr8)96B4 were produced by using a combination of two synthesis techniques, casting and ball milling. Bulk samples were reached from casting while milling yield to powders to induce a homogenized structural phase. The structural analysis confirmed that initially an α-Fe phase (bcc) was formed with space group Im-3m. As the milling time goes from 0 to 36 h, small changes in the lattice parameter were noticed, going from 0.285 nm to 0.287 nm. Magnetic hysteresis loops measurements revealed that the samples are ferromagnetic at room temperature, with a maximum saturation magnetization ~ 161 emu/g for 0 h and~150 emu/g for 36 h. Likewise, the powder samples are magnetically soft at room temperature, with coercive field values below 50 Oe. Finally, through Mössbauer spectroscopy, the ferromagnetic character of the (Fe92Zr8)96B4 alloys was confirmed, where the hyperfine field sites can be associated with Fe-rich regions in which almost all the nearest neighbors are Fe atoms.