BaBi Research Articles

Study of Eu3+–Gd3+ co-doped Ba–Bi–B glasses for red-laser applications: Physical, structural, photoluminescence and time-resolved spectral characteristics

A series of Eu3+ and Eu3+/Gd3+ co-doped barium-bismuth-borate (Ba–Bi–B) glasses were prepared by melt-quench technique. And deliberated the physical, structural, and spectroscopic properties of all glasses and explored the energy transfer process from Gd3+ to Eu3+ ions. The density of glasses increased with increasing of Gd3+ concentration in co-doped glasses. Characteristics of steady-state and time-resolved photoluminescence (PL) of Eu-doped and Eu3+-Gd3+ co-doped glasses under different excitation wavelengths suggested the prospects of the investigated glass system for display device applications. PL spectrum displays a strong red emission peak centered at 612 nm due to the Eu3+: 5D0→ 7F2 transition. Less intense emissions centered at 577 nm (7F0), 590 nm (7F1), 651 nm (7F3) and 700 nm (7F4) are also observed from the radiative transitions of the excited state 5D0 of Eu3+ions. The values of radiative parameters such as transition probability, branching ratios, and stimulated emission cross-sections were obtained from Judd–Ofelt theory analysis and indicated the aptness of the Ba–Bi–B glasses for optical devices. A 5-fold enhancement in the PL intensity was observed in 1.0 mol% Eu3+ and 3.0 mol% Gd3+ co-doped glass under λExci. = 394 nm excitation. The calculated commission Internationale de l'eclairage color coordinates and correlated color temperature values show that the Ba–Bi–B glasses are useful for red-laser and display device applications.

Geochemical study of the Ashele Copper-Zinc Deposit using portable X-ray fluorescence spectrometry based on matrix effect correction, Northwest China

Because the Ashele Cu–Zn deposit is located deep below and core samples are difficult to obtain, portable X-ray fluorescence spectroscopy (pXRF), which can be used for rapid and non-destructive analysis in the field, was chosen as the testing instrument. However, the testing accuracy and precision of elements are significantly affected by matrix effects. In this study, 170 samples from the deposit were measured, and the data was corrected using the matrix effect correction (MEC) method instead of the simple linear regression (SLR) method to enhance the data quality, followed by geochemical and correspondence analysis of the data. The results show that calibration data corrected by the MEC method was of greater quality than those corrected by the SLR method, particularly for elements such as Co, Cr, Mo, Sn, Ba, and W. The Ashele Cu–Zn deposit is formed in multi-phase hydrothermal superposition mineralization and is rich in Mg, Fe, and S but deficient in Al, Si, K, and Ca. The main mineralized zones are located at 400–500 m and 200–300 m. Cu, Zn, and Pb are significantly enriched in the mineralization, with the axial zoning sequence of the primary halo (Pb–Zn–Mn–As–Cu–Cd–Sn–Ba–Bi–Sb–Co–W–Mo) showing inverse zoning. The correspondence analysis results also show a clear distinction between non-metallogenesis and metallogenesis. Also, the application of pXRF based on MEC in the Ashele Cu–Zn deposit is effective and can be extended to other types of deposit studies.

Low-Temperature Synthesis of K–Ba–Bi–O Oxides in KOH Solution

The reaction of KBiO3–δ with Ba2+ ions at a Ba : Bi ratio of 0.5‒1.6 (mol.) in a 10 M. KOH solution under reflux (~140°C) has furnished oxides, which composition and structure have been studied by X-ray diffraction, energy dispersive X-Ray, and chemical analysis. Pseudo cubic (а = 4.271‒4.285 A) perovskite-like phases of barium‒bismuth(III,V)‒potassium oxides with insignificant impurity of sodium have been formed in the KBiO3–δ‒Ba2+‒OH–‒H2O system during 1 h. The products have been characterized by an average oxidation state of bismuth –Bi = 4.36‒4.59. Barium content in the resulting oxides has increased with an increase in its concentration in the charge. According to the Ba–Bi ratio, the resulting phases can be classified as non-superconducting oxides of homologous series МxBamBim+nOy (x <n), МxBamBim+nOy, and (М, Ba)m+nBimOy (m = 1, 2, ...; n = 0, 1, 2, ...), M = K, Na.

Effect of phase structures and substrate temperatures on NTC characteristics of Cu-modified Ba–Bi–O-based perovskite-type thermistor thin films

Based on the formula of BaBi0·92Cu0·08O3, Cu-modified Ba–Bi–O-based perovskite-like negative temperature coefficient (NTC) thermistor thin films were successfully prepared by radio frequency (RF) magnetron sputtering method with the various deposition temperatures (25 °C, 100 °C, 200 °C and 250 °C). The effects of the substrate temperatures on the phase structures and electrical properties were respectively characterized and investigated by X-ray diffraction (XRD), resistance-temperature measurement, and complex impedance analysis for the Ba–Bi–O-based thin films. Additionally, the cross-sectional microstructures and grain morphologies of the BaBi0·92Cu0·08O3 thin films were analyzed by scanning electron microscope (SEM) and atomic force microscope (AFM). The XRD patterns results showed that the perovskite monoclinic structure with a small amount of BaBiO2.5 s phase could be obtained for the BaBiO3 thin film deposited at 200 °C, and also, the main crystalline phase was transferred from BaBiO2.82 to BaBiO2.5 when the BaBi0·92Cu0·08O3 thin films were deposited at 200 °C and 250 °C, respectively. Temperature dependent complex impedance spectroscopy was carried out to make clear the resistance contribution of grain (Rg), grain boundary (Rgb) and contact (Rs) response for the conduction mechanisms in the Ba–Bi–O-based thin film deposited at a given substrate temperature. Compared with the electrical properties of the BaBiO3 thin film deposited at 200 °C [such as the room-temperature resistivity (ρ25 ~ 1548 Ω cm) and the thermistor constant (B25/85–3245 K)], the better NTC characteristics of a lower ρ25 value of about 956 Ω cm and a higher B value of approximately 3480 K were found in the BaBi0·92Cu0·08O3 thin film deposited at a same temperature (200 °C). It is believed that the phase structures and electrical properties of the BaBiO3 perovskite-type NTC thermistor thin films could be adjusted and optimized by a trace amounts of Cu-ions substitutions and depositing at an appropriate substrate temperature, which also showed that such as these novel BaBiO3-based thin films are feasible with the extensive of actual applications for the NTC thermistors.

Bab I

latar belakang

Babi Yar

e ravin de Babi Yar, à la périphérie de Kiev, est resté inscrit dans la mémoire collective comme le tragique point de départ de l’Holocauste. Employé par les Nazis comme lieu d’exécution durant les deux années d’occupation de la ville, près de 100.000 personnes, issues de divers groupes ethniques, politiques et sociaux, y ont trouvé la mort entre 1941 et 1943. Cet article analyse le devenir de Babi Yar après la guerre ainsi que les facteurs qui ont empêché sa transformation, à commencer par le contexte défavorable de l’ère stalinienne, suivi d’un dégel partiel dans les années 1960-1970, et d’une libéralisation mémorielle entachée d’incohérences au cours de la période postcommuniste. Il s’agit ici d’explorer les transformations du ravin de Babi Yar à travers ces différentes époques et de passer en revue les divers enjeux d’une commémoration qui demeure, sinon impossible, du moins problématique et semée d’embûches.

Soft X-ray absorption spectroscopy study of multiferroic Bi-substituted Ba1−x Bi x Ti0.9Fe0.1O3

The electronic structures of multiferroic oxides of Ba(1-x)Bi(x)Ti(0.9)Fe(0.1)O(3) (0 < x < 0.12) have been investigated by employing photoemission spectroscopy and soft x-ray absorption spectroscopy (XAS). The measured Fe and Ti 2p XAS spectra show that Ti ions are in the Ti4+ states for all x and that Fe ions are Fe2+-Fe3+ mixed-valent for x > 0. The valence states of Fe ions are found to be nearly trivalent for x=0, and decreases with increasing x from being nearly trivalent (v(Fe)~ 3) for x=0 to v(Fe)~ 2.6 for x=0.12. The valence states of both Ti and Ba ions do not change for all x < 0.12. Based on the obtained valence states of Fe ions, the electronic and magnetic properties of Ba(1-x)Bi(x)Ti(0.9)Fe(0.1)O(3) are explored.

On hydrolysis of Ba–Bi–O and K–Ba–Bi–O oxide systems

Fundamentally different behavior of Ba–Bi–O (Ba : Bi = 11 : 4, 1 : 1, 2: 3, and 1 : 5 mol/mol) and K n Ba m Bi m+n O y (m = n = 1, 2,...; exhibiting superconducting properties with T c = 28–32 K) oxides and BaO2 in hydrolysis reactions has been revealed by means of potentiometry and chemical analysis. Products of the oxides treatment with water do not contain H2O2, evidencing the absence of peroxide ions in their structure. The perovskite-type barium-bismuth(III) oxides are completely hydrolyzed into Ba(OH)2 and Bi2O3 at room temperature.

Investigation into the extremely low thermal conductivity in Ba heavily doped BiCuSeO

Heavily doped Bi0.875Ba0.125CuSeO alloys were found to exhibit the highest ever ZT value in oxygenous thermoelectric systems, attributed to the extremely low thermal conductivity. In this report, we investigated the microstructural reason of the thermal conductivity in Ba- heavily doped BiCuSeO through scanning transmission electron microscopy (STEM). We found a large amount of nano-scale BaSeO3 precipitates dispersed widely in BiCuSeO matrix grains; besides, for the first time, we provide visual evidence of Ba substituting Bi atoms in Bi–O layers. Combined with DFT calculations, we conclude that intrinsic lattice vibration anharmonicity, together with Ba–Bi alloying and excess BaSeO3 precipitation, is responsible for the observed low lattice thermal conductivity in experiments.

Syntheses, structural and characterizations of a new anhydrous mixed-metal phosphate

A new mixed-metal phosphate of BaBi2CoP2O10 was synthesized by high temperature solution growth (HTSG) method and structurally characterized by X-ray single crystal diffraction and powder diffraction for the first time. The title compound crystallizes in the monoclinic system with space group P2(1)/c and represents the first compound in the Ba–Bi–M–P–O (M=transition metal) quinary anhydrous system, which structure features a novel 2D open framework which can be considered as building from the layers of [Bi2CoP2O10]2−∞ parallel to the bc plane interconnected by corner or bridge sharing of BiO5, BiO7, CoO6, and PO4 groups, where Ba2+ cations are located in the space between two adjacent layers. It is worth to note that the Bi3+ cations containing two kinds of coordinations (5 and 7) show stereochemically activities of their 6s2 lone pairs. The results of magnetic property measurements evidence on the antiferromagnetic property of BaBi2CoP2O10.

Organic reagents for the identification of Bi(V) and O 2 2– in Ba–Bi–O and K–Ba–Bi–O oxides using field test methods

We investigated the interaction of aromatic amines, such as diphenylamine (DPA), Arnold’s base (AB), benzidine (B), and o-tolidine (OT), and dyes, namely, Methyl Red (MR), Chromazurol S (CA), Arsenazo III (A), Indigo Carmine (IC), and Thoron (T), with Bi2O3, Bi2O4.09, NaBiO3, BaBiO3, BaBi3O5.55, BaBi5O8.5, and KnBamBim + nOy (n = 1–3; m = 1, 3–5) oxides, having superconducting properties (Ts = 28–32 K), and BaO2 and H2O2 peroxides. Among the studied amines, only Arnold’s base is not oxidized by peroxides and can serve as a reagent for the identification of peroxide dioxygen O 22–and Bi(V). It was found that Bi(V), unlike O 22–, oxidizes acidic solutions of Methyl Red, Chromazurol S, Arsenazo III, Thoron, and Indigo Carmine, decolorizing them; that is, these dyes may be used in the test methods for identifying Bi(V) and O 22–. It was found that, in reactions with amines and dyes, Bi(V) is a stronger oxidant than O 22–. The detection limits for Bi(V) with DPA, Arnold’s base, benzidine, o-tolidine, Methyl Red, Indigo Carmine, and Thoron are determined.

Distribution of chemical elements in soils and stream sediments in the area of abandoned Sb–As–Tl Allchar mine, Republic of Macedonia

The aim of this study was to investigate the distribution of some toxic elements in topsoil and subsoil, focusing on the identification of natural and anthropogenic element sources in the small region of rare As–Sb–Tl mineralization outcrop and abandoned mine Allchar known for the highest natural concentration of Tl in soil worldwide. The samples of soil and sediments after total digestion were analyzed by inductively coupled plasma–mass spectrometry (ICP–MS) and inductively coupled plasma–atomic emission spectrometry (ICP–AES). Factor analysis (FA) was used to identify and characterize element associations. Six associations of elements were determined by the method of multivariate statistics: Rb–Ta–K–Nb–Ga–Sn–Ba–Bi–Li–Be–(La–Eu)–Hf–Zr–Zn–In–Pd–Ag–Pt–Mg; Tl–As–Sb–Hg; Te–S–Ag–Pt–Al–Sc–(Gd–Lu)–Y; Fe–Cu–V–Ge–Co–In; Pd–Zr–Hf–W–Be and Ni–Mn–Co–Cr–Mg. The purpose of the assessment was to determine the nature and extent of potential contamination as well as to broadly assess possible impacts to human health and the environment. The results from the analysis of the collected samples in the vicinity of the mine revealed that As and Tl elements have the highest median values. Higher median values for Sb are obviously as a result of the past mining activities and as a result of area surface phenomena in the past.

Upconversion fluorescence of bismuth doped silica fibers

We investigated the upconversion fluorescence characteristics of bismuth doped silica fibers with and without Al co-dopant (BA fiber and BI fiber). Unusual upconversion fluorescence was discovered in both of these fibers when excited by pump lasers. After more experiments, it was found that the BI fiber showed a more complicated and distinct upconversion spectrum than the BA fiber, but with different and weaker NIR emission, as we reported before. Moreover, it was implied that the upconversion fluorescence must be mainly responsible for the Bi2+ ions in which the BI fiber was rich. Thus, properly improving the Al co-doping concentration could alleviate the upconversion fluorescence, thus improving the efficiency of the NIR band fluorescence. Besides, the complicated upconversion fluorescence bands may be helpful to clarify the energy levels of the Bi ions in silica materials.

Synthesis, structures, and phase transitions of barium bismuth iridium oxide perovskites Ba 2BiIrO 6 and Ba 3BiIr 2O 9

The Ba–Bi–Ir–O system is found to contain two distinct perovskite-type phases: a rock-salt ordered double perovskite Ba 2BiIrO 6; and a 6H-type hexagonal perovskite Ba 3BiIr 2O 9. Ba 2BiIrO 6 undergoes a series of symmetry-lowering phase transitions on cooling Fm 3 ¯ m → R 3 ¯ c → 12 / m ( C 2 / m ) → I 1 ¯ ( P 1 ¯ ) , all of which are second order except the rhombohedral→monoclinic one, which is first order. The monoclinic phase is only observed in a 2-phase rhombohedral+monoclinic regime. The transition and 2-phase region lie very close to 300 K, making the room-temperature X-ray diffraction patterns extremely complex and potentially explaining why Ba 2BiIrO 6 had not previously been identified and reported. A solid solution Ba 2Bi 1+ x Ir 1− x O 6, analogous to Ba 2Bi 1+ x Ru 1− x O 6, 0≤ x≤2/3, was not observed. The 6H-type phase Ba 3BiIr 2O 9 undergoes a clean second-order phase transition P6 3/ mmc→ C2/ c at 750 K, unlike 6H-type Ba 3LaIr 2O 9, the P6 3/ mmc structure of which is highly strained below ∼750 K but fails to distort coherently to the monoclinic phase.

Lone electron-pair enhancement of SHG responses in eulytite-type compounds: AII3MIII(PO4)3(A = Pb, M = Bi; A = Ba, M = Bi, La)

A new eulytite-like orthophosphate Pb(3)Bi(PO(4))(3), was synthesized by the high temperature solution growth (HTSG) method and characterized by X-ray single crystal diffraction, powder diffraction and electron microscopy. It crystallizes in the acentric cubic space group (I4[combining macron]3d). The pure-phase powders of Pb(3)Bi(PO(4))(3), Ba(3)La(PO(4))(3) and Ba(3)Bi(PO(4))(3) were also prepared by the high temperature solid reaction method. Second harmonic generation (SHG) measurements revealed that the optical response signals of Pb(3)Bi(PO(4))(3) and Ba(3)Bi(PO(4))(3) are about 3.0 and 0.5 times that of KH(2)PO(4) (KDP), respectively, and both are phase-matchable. The SHG signal of Ba(3)La(PO(4))(3) is very weak. Our studies indicate that the enhancement of the nonlinear optical response is mainly due to the contribution from the irregular PbO(6) and BiO(6) octahedra due to the 6s(2) lone electron-pair stereochemical activity in eulytite-like orthophosphates. Additionally, the calculated band structure and density of states also provide evidence that the charge transfers within irregular octahedral of Pb/BiO(6) make a significant contribution to the nonlinear optical response.

Cation Substitution Effects in the System Sr2−xBaxBi3 (0 ≤ x ≤ 1.3): Structural Distortions Induced by Chemical Pressure

Crystals of the composition Sr(2-x)Ba(x)Bi(3) (0 < or = x < or = 1.3) have been synthesized from the elements and were characterized by single-crystal and powder X-ray diffraction methods. The compounds crystallize for x = 0, 0.45, 0.86, 1.08, 1.28 in the structure type of the parent compound Sr 2Bi 3 with space group Pnna (No. 52) and Z = 4. Substitution of Sr by Ba leads to a site preference for Ba. The anionic Bi substructures in the pseudoternary system simultaneously distort under remarkable elongation of one distinct Bi-Bi contact. Magnetic measurements for samples with x = 0, 0.45 and 1.08 reveal superconducting transitions at low temperatures. Linear muffin-tin orbital band structure calculations of Sr(2)Bi(3) show strong cation-anion interactions that greatly stabilize the structure. Besides showing characteristics of a typical metal, the band structure plot unveils the co-instantaneous occurrence of flat and steep bands around the Fermi level indicative for superconductivity.

Phonons, electronic charge response and electron–phonon interaction in the high‐temperature superconductors

AbstractWe investigate the complete phonon dispersion, the phonon induced electronic charge response and the corresponding self‐consistent change of the crystal potential an electron feels as a direct measure of the electron–phonon interaction in the high‐temperature superconductors within a microscopic model in the framework of linear response theory. Moreover, dielectric and infrared properties are calculated. The experimentally observed strong renormalization of the in‐plane oxygen bond‐stretching modes which appears upon doping in the high‐temperature superconductors is discussed. It is shown that the characteristic softening, indicating a strong nonlocal electron–phonon interaction, is most likely a generic effect of the CuO plane and is driven by a nonlocal coupling of the displaced ions to the localized charge‐fluctuations at the Cu and the Oxy ions. At hand of the oxygen bond‐stretching modes it is illustrated how lattice‐, charge‐ and spin‐degrees of freedom may act synergetically for anisotropic pairing in the high‐temperature superconductors. The different behaviour of these modes during the insulator‐metal transition via the underdoped phase is calculated and from a comparison of these generic modes in the different phases conclusions about the electronic state are drawn. For the non‐cuprate potassium doped high‐temperature superconductor Ba–Bi–O also a very strong and anisotropic renormalization of the oxygen bond‐stretching modes is predicted. In another investigation c‐axis polarized infrared‐ and Raman‐active modes of the HTSC's are calculated in terms of charge fluctuations and anisotropic dipole‐fluctuations. Mode assignments discussed controversially in the literature are proposed. Finally, interlayer phonons propagating along the c‐axis and their accompanying charge response are investigated. Depending on the strength of the interlayer coupling calculations are performed ranging from the static, adiabatic response regime to the non‐adiabatic regime where dynamical screening of the bare Coulomb interaction and phonon–plasmon coupling becomes relevant within a certain region around the direction of the c‐axis. A comparison with the experimental situation is given. Both, the oxygen bond‐stretching modes calculated in adiabatic approximation and the non‐adiabatic coupled c‐axis phonon–plasmon modes are found to be important for pairing via lattice‐ and charge‐degrees of freedom. Favouring aspects to achieve high‐temperature superconductivity are also discussed. (© 2005 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Valence compounds versus metals. Synthesis, characterization, and electronic structures of cubic Ae(4)Pn(3) phases in the systems Ae = Ca, Sr, Ba, Eu; Pn = As, Sb, Bi.

The isostructural compounds Sr(4)Bi(3), Ba(4)Bi(3), and Ba(4)As( approximately )(2.60) were prepared by direct reactions of the corresponding elements and their structures determined from single-crystal X-ray diffraction data as anti-Th(3)P(4) type in the cubic space group I43d, Z = 4 (a = 10.101(1) A, 10.550(1) A, 9.973 (1) A, respectively). The two bismuth compounds are stoichiometric, and the arsenide refines as Ba(4)As(2.60(2)). Only unrelated phases are obtained for all binary combinations among the title components for either Ca or Sb. The magnetic susceptibility and resistivities of Ba(4)Bi(3) and Eu(4)Bi(3) show that they are good metallic conductors ( approximately 40 microomega.cm at 298 K), whereas Ba(4)As(2.60) exhibits rho(150) > 1000 microomega.cm. The electronic structures of Sr(4)Bi(3), Ba(4)Bi(3), and Ba(4)As(3) were calculated by TB-LMTO-ASA methods. Mixing of cation d states into somewhat disperse valence p bands on Bi results in empty bands at E(F) and metallic behavior, whereas the narrower valence band in the electron-deficient Ba(4)As(3) leads to vacancies in about 11% of the anion sites and a valence compound.

Preparation and Characterization of Sol-Gel Derived (Sr,Ba)Bi 2 (Ta,Nb) 2 O 9 Thin Films for Ferroelectric-Gate FET Applications

We have fabricated (Sr,Ba) 0.8 Bi 2.2 (Ta,Nb) 2 O 9 (SBBTN) thin films by the sol-gel technique to obtain a small remanent polarization and a large coercive field for ferroelectric-gate FET applications. Ba and Ta compositions are varied from 0 to 0.2 and from 0 to 0.5, respectively. It is demonstrated that the coercive field becomes large by the partial replacement of Ta with Nb atoms and that the Ba doping results in slight decrease of the remanent polarization. A remanent polarization as small as 5 w C/cm 2 and a coercive field as large as 100 kV/cm can be obtained for Sr 0.6 Ba 0.2 Bi 2.2 Ta 1.5 Nb 0.5 O 9 thin films, which were crystallized at 850°C.

HREM Study of Compounds in the Bi-Rich Part of the Ba–Bi–O System

A series of perovskite-like compounds with general composition BanBin+mOy(m, n—integer) has been studied by means of electron diffraction and high-resolution electron microscopy. For a number of simple, discrete values of the cation composition ratio Ba:Bi the structures were found to be Ruddlesden–Popper–like derivatives of the perovskite structures of BaBiO3, with composition-dependent long periods. For more complicated values of the cation composition ratio the perovskite blocks are further fragmented by planar interfaces into a two-dimensional periodic island structure. This fragmentation gives rise to complicated local structures formed by a mosaic of square or (and) rectangular islands, which often produce incommensurate diffraction patterns. Such diffraction patterns are interpreted in the framework of the “fractional shift” method for interface modulated structure. Structure models and compositions can be made compatible by assuming that substitution of barium ions by bismuth ions must take place, predominantly along the island boundaries.