Bi2O3 Flux Research Articles

Thermoluminescent Properties of Cerium-Doped Lu2SO5 and Y2SiO5 Single Crystalline Films Scintillators Grown from PbO-B2O3 and Bi2O3 Fluxes

In this work we show the influence of material preparation technology on the thermoluminescent properties of single crystalline films (SCFs) of Ce3+-doped Lu2SiO5 (LSO) and Y2SiO5 (YSO) orthosilicates. LSO:Ce and YSO:Ce SCFs were grown by the liquid phase epitaxy method from two different melt-solutions based on PbO-B2O3 and Bi2O3 fluxes. Absorption, cathodoluminescence, and thermoluminescent properties of LSO:Ce and YSO:Ce SCFs grown from the two previously mentioned types of fluxes were compared, and results of spectrally resolved thermoluminescence measurements and thermoluminescent glow curves of SCFs recorded in different spectral ranges were presented. We have found that the observed differences in thermoluminescent properties of the SCFs under study can be caused by the domination of Ce4+ and Pb2+ emission centers in LSO:Ce and YSO:Ce SCFs grown using PbO-B2O3 flux, and Ce3+ and Bi3+ emission centers in the SCFs grown from Bi2O3 flux.

ChemInform Abstract: Revised Bi/M Layered Oxo‐Sulfate (M: Co, Cu): A Structural and Magnetic Study.

AbstractReinvestigation of mixed Bi/M (M: Co, Cu) oxo‐sulfates using crystal growth in Bi2O3 flux, single crystal XRD, magnetic measurements, and DFT calculations lead to the full structural characterization of (IV) and (VII).

Revised Bi/M Layered Oxo-Sulfate (M = Co, Cu): A Structural and Magnetic Study

The combination of oxo-bismuthite slabs with counter oxo-anions main often leads to a series of layered Sillen-related compounds. For electroneutrality, it is convenient that the structure incorporates aliovalent cations such as Bi(3+)/M(2+) ions that could be confined either in the Bi/O slabs or in the interleave. In the case of SO4(2-) oxo-anions, only two compounds have been reported for M = Co, Cu, while interesting magnetic topologies emerge in absence of any prior characterization. Our reinvestigation of these systems using crystal growth in Bi2O3 flux led to the full structural characterization of [Bi2CoO3](SO4) (I) and [Bi6.2367Cu1.6O8](SO4)3 (II), which both exhibit pleated [Bi/M/O] slabs running in doubled cells comparatively to previous reports. (I) shows an interesting weak ferromagnetism (∼0.2 μB/Co) below 17 K arising from Dzyaloshinskii-Moriya interactions in Co(2+) zigzag chains, while (II) is essentially a paramagnet despite the presence of Cu2O6 dimers. Finally in the novel [Bi6O6](CoO2)(SO4)2 (III), the Co(2+) ions are ordered with sulfate in the interleaves, leading to a noncentrosymmetric crystal structure.

Luminescent and scintillation properties of Bi3+ doped Y2SiO5 and Lu2SiO5 single crystalline films

In this paper we report our follow-up research on the Bi3+ luminescence in orthosilicate compounds, focusing on absorption, luminescent and scintillation properties of YSO:Bi and LSO:Bi SCFs with the Bi concentration ranging from 0.05 to 0.18at%. For purpose of this research, single crystalline films (SCF) of Y2SiO5:Bi and Lu2SiO5:Bi have been grown by the LPE method onto YSO and LSO substrates from the melt-solution based on Bi2O3 flux.

Bi3+–Pr3+ energy transfer processes and luminescent properties of LuAG:Bi,Pr and YAG:Bi,Pr single crystalline films

Absorption, cathodoluminescence, excitation spectra of photoluminescence (PL) and PL decay kinetics were studied at 300K for the double doped with Bi3+–Pr3+ and separately doped with Bi3+ and Pr3+ Lu3Al5O12 (LuAG) and Y3Al5O12 (YAG) single crystalline film (SCF) phosphors grown by the liquid phase epitaxy method. The emission bands in the UV range arising from the intrinsic radiative transitions of Bi3+ based centers, and emission bands in the visible range, related to the luminescence of excitons localized around Bi3+ based centers, were identified both in Bi–Pr and Bi-doped LuAG and YAG SCFs. The energy transfer processes from the host lattice simultaneously to Bi3+ and Pr3+ ions and from Bi3+ to Pr3+ ions were investigated. Competition between Pr3+ and Bi3+ ions in the energy transfer processes from the LuAG and YAG hosts was evidenced. The strong decrease of the intensity of Pr3+ luminescence both in LuAG:Pr and YAG:Pr SCFs phosphors, grown from Bi2O3 flux, is observed due to the quenching influence of Bi3+ flux related impurity. Due to overlap of the UV emission band of Bi3+ centers with the f–d absorption bands of Pr3+ ions in the UV range and the luminescence of excitons localized around Bi ions with the f–f absorption bands of Pr3+ ions in the visible range, an effective energy transfer from Bi3+ ions to Pr3+ ions takes place in LuAG:Bi,Pr and YAG:Bi,Pr SCFs, resulting in the appearance of slower component in the decay kinetics of the Pr3+ d–f luminescence.

Photoluminescence and excited state structure of Bi3+-related centers in Lu2SiO5:Bi single crystalline films

Single crystalline films of Lu2SiO5:Bi, prepared by the liquid phase epitaxy method from the melt-solution based on Bi2O3 flux, are studied at 4.2–350K by the time-resolved spectroscopy methods under excitation in the 2.4–6.2eV energy range. An intense dominant ultraviolet (≈3.5eV) luminescence of Lu2SiO5:Bi is shown to arise from the radiative decay of the metastable and radiative minima of the triplet relaxed excited state (RES) of Bi3+ centers which are related to the 3P0 and 3P1 levels of a free Bi3+ ion, respectively. At T<50K, the radiative transitions from the metastable minima mainly take place. Thermally stimulated non-radiative transitions between the metastable and radiative minima of the triplet RES appear at T>50K in the temperature evolution of the emission spectrum and decay kinetics. The excitation bands of the ultraviolet emission, located at 4.2eV, 5.03eV, and 5.95eV, are assigned to the 1S0→3P1, 1S0→3P2, and 1S0→1P1 transitions of a free Bi3+ ion, respectively. The phenomenological model is proposed to describe the excited-state dynamics of Bi3+ centers in Lu2SiO5:Bi. Characteristic parameters of the triplet RES, in particular the energy separation between the excited states and the rates of the radiative and non-radiative transitions from these states, are determined. Much weaker ≈3.3eV emission is ascribed to the Bi3+ ions located in the Lu2 lattice sites. Weak broad ≈2.2eV and ≈2.3eV emission bands are assumed to arise from the Bi3+-related localized excitons.

Bi3+–Ce3+ energy transfer and luminescent properties of LuAG:Bi,Ce and YAG:Bi,Ce single crystalline films

The absorption, cathodoluminescence, excitation spectra of photoluminescence (PL) and PL decay kinetics were studied at 300K for the double Bi3+–Ce3+-doped and separately Bi3+- and Ce3+-doped Y3Al5O12 (YAG) and Lu3Al5O12 (LuAG) single crystalline film phosphors grown by liquid phase epitaxy method. Emission bands in the UV range arising from the intrinsic radiative transitions of Bi3+-based centers, and emission bands in the visible range related to the luminescence of excitons localized around Bi-based centers, were identified in both Bi–Ce and Bi-doped YAG and LuAG SCF. Energy transfers from the host lattice to Bi3+ and Ce3+ ions and from Bi3+ to Ce3+ ions were investigated. Competition between Bi3+ and Ce3+ ions in the energy transfer from the YAG and LuAG hosts was evidenced. A strong decrease of intensity of the Ce3+ luminescence both in YAG:Ce and LuAG:Ce SCF phosphors, grown from a Bi2O3 flux, is observed due to the quenching influence of Bi3+ flux related impurity. Due to overlap of the visible emission band of Bi3+ centers with the absorption band of Ce3+ ions peaking at around 450–460nm, an effective energy transfer from Bi3+ ions to Ce3+ ions takes place, resulting in the appearance of a slower component in the Ce3+ luminescence decay kinetics.

Influence of Bi2O3 flux in the structural and photoluminescence properties of SrAl2O4:Eu2+ phosphors

SrAl2O4:Eu2+ phosphors with various content of Bi2O3 flux were synthesized and analyzed. It was observed that the crystallinity and the particle size of the phosphors were increased with the addition of Bi2O3 flux. These phenomena are considered to be caused via the melting of the Bi2O3 flux particles during the synthesis of the phosphors. The melted Bi2O3 flux increased the mobility and homogeneity of solid reactants, thereby enhancing the photoluminescence intensity of the phosphors. SrAl2O4:Eu2+ phosphors with Bi2O3 as the flux exhibited a broad green emission with a peak at 520nm. The highest photoluminescence emission intensity was observed when 5mol% Bi2O3 flux was added into the phosphors. The emission is due to 4f65d→4f7 (8S7/2) transitions of the Eu2+ ions. Moreover, Bi2O3 flux extended the application of the ultraviolet excited phosphors toward the blue-light excited phosphors. Nevertheless, the influence of Bi2O3 on the afterglow and the emission color of SrAl2O4:Eu2+ phosphors were not significant. This research indicated that Bi2O3 flux is effective flux for synthesizing SrAl2O4:Eu2+ phosphors.

Synthesis, growth, crystal structure and optical properties of BaBiBO4

The single crystal of BaBiBO4 has been grown up to about 18 mm x 10 mm x 5 mm by the top-seeded solution growth method (TSSG) in the Bi2O3 flux system. BaBiBO4 crystallizes in the centrosymmetric orthorhombic space group Pnma with a = 8.5556(8) angstrom, b = 5.1569(5) angstrom, c = 9.6677(7) angstrom, Z=4. It is a three-dimensional framework structure built up of BiO5 polyhedra, BaO9 polyhedra and BO3 triangles. The BiO5 polyhedra and BO3 triangles form infinite one-dimensional chains along the crystallographic b axis. BO3 groups present in the sample were identified by Fourier transform infrared spectrum. UV-vis-IR transmittance spectrum of BaBiBO4 showed that it has a wide transmittance range from 310 nm to 3000 nm. (C) 2012 Elsevier B.V. All rights reserved.

Growth and Characterization of High Quality BiFeO3-PbTiO3 Single Crystals

Bismuth ferrite-lead titanate (BFPT) single crystals were grown using a PbO:Bi2O3 flux. Highly pure, crack free single crystals of 4 mm diameter were produced. Energy dispersive X-ray analysis (EDX) and Electron Probe Micro-Analysis (EPMA) were used to determine the chemical composition of the crystals, and scanning electron microscopy (SEM) confirmed the absence of cracks. Powder X-ray diffraction (XRD) revealed the crystal structure to be single-phase tetragonal perovskite, and high temperature studies showed the position of the Curie point (TC). Promising electrical properties are reported including capacitance, dielectric loss, dielectric strength and piezoelectric coefficient (d33).

Growth of Delafossite CuCr1−xMxO2 Systems and Their Anisotropic Magnetization

The effort to obtain a good crystalline state of delafossite CuCrO2 phase is becoming important along with their potential application and scientific important results. In this paper we report the result of crystal growth and their Magnetic and Electric Capacitance Measurements. We focused on two methods i.e. flux decomposition (FD), and Bi2O3 Flux Growth (FB). The starting materials for FD growth were K2Cr2O7 and CuO taking the advantage of the potassium dichromate’s decomposition. In case of FB flux growth, we should prepare the correct molar ratio for CuCrO2 pellet on the Bi2O3 powder in 1 : 6 ratio. It is found that both methods are possible to obtain crystalline phases along with their specific technical processes to be overcomed. We show that FB method resulted flaky shapes while FD method produced rather bulky morphology. The obtained samples were checked by CAD4 single crystal diffractometer for their lattices and MPMS-SQUID magnetometer for their magnetization for different orientation. We check also the electric capacitance at the range of 5 K to 300 K along c lattice direction. It is found that their single Neel temperature (TN) fall around 25 K. A distinct anisotropy of magnetization profiles shown by its crystal directions and planes. On the other hand the out of plane electric capacitance of Mn doped crystal did not show any transition at the range of 5 K to 300 K.

Optical, luminescence and scintillation characteristics of Bi-doped LuAG and YAG single crystalline films

Bi-doped Lu3Al5O12 (LuAG) single crystalline films (SCFs) of thickness within 8–31 µm were grown by the liquid-phase epitaxy method onto Y3Al5O12 (YAG) single crystal substrates using a melt solution based on a Bi2O3 flux. Their characteristics were compared with YAG : Bi SCFs grown at the same conditions. The concentration of Bi3+ ions in LuAG : Bi and YAG : Bi SCFs was varied by changing the growth temperature in the ranges 0.05–0.18 at% and 0.13–0.57 at%, respectively. The absorption, luminescence and scintillation properties of these SCFs noticeably depend on the Bi3+ concentration. Luminescence spectra of both LuAG : Bi and YAG : Bi SCF consist of two broad emission bands in the UV and visible (VIS) spectral ranges peaking at 4.155–4.085 eV and 2.45–2.66 eV, respectively. Both the UV and VIS luminescence show complex non-exponential decays. Under 241Am α-particle excitation the photoelectron yield of the best performing LuAG : Bi (0.18 at%) and YAG : Bi (0.13 at%) SCFs is about 15% and 21%, respectively, of that of the reference YAP : Ce single crystal.

Magnetic properties of indium-substituted BiCaVIG single crystals

Indium-substituted BiCaVIG ({Bi3−2xCa2x}[Fe2](Fe3−xVx)O12)single crystals were grown in PbO–Bi2O3 flux with indium content, y⩽0.144 per molecular formula. Desirable magnetic properties, i.e., low saturation magnetization, MS=2.38×105A∕m, and also low magnetocrystalline anisotropy field, K1∕MS=2.6×103A∕m, have been obtained. The results can be elucidated in terms of single-ion contributions to the magnetocrystalline anisotropy from the Fe3+ ions on octahedral (A) and tetrahedral (D) lattice sites of the iron garnet structure and the effect of indium substitution.

Growth and characterization of ferroelectric SrBi2Ta2O9 single crystals via high-temperature self-flux solution method

SrBi2Ta2O9 (SBT) single crystals were produced by the high-temperature self-flux solution method using a Bi2O3 flux modified with B2O3. The processing conditions were optimized to obtain large and translucent SBT crystals with a layered habit and typical dimensions of approximately 7 × 5 × 0.2 mm. X-ray diffraction and x-ray topography measurements revealed that the major faces of the crystals with natural rectangular platelet morphology are perfectly (001)-oriented with edges directed along the [110] directions. The high quality of the crystals was confirmed by rocking curves (half-width of 0.04° for the (0018) reflection) and by ferroelectric measurements. The anisotropy in the dielectric and ferroelectric properties was investigated both along the [110] (ab plane) and the [001] (c axis) directions. The growth mechanism, morphology, and dielectric anisotropy of the SBT crystal platelets are discussed based on its crystallographic structure.

Imaging of domains in single crystals of BiFeO3-PbTiO3 using various microscopy techniques

Single crystals of BiFeO3-PbTiO3 have been grown from a PbO:Bi2O3 flux by cooling at a rate of 2°C/hour from the melt. Faceted crystals of various morphologies were produced and the size of the crystals ranged from less than 0.5mm to 5mm. Initial measurements were made using the scanning electron microscope (SEM) with energy dispersive X-ray analysis (EDX) semi-quantifying the composition of the crystals as well as electron probe microanalysis (EPMA). Powder X-ray diffraction (XRD) of the crushed and sieved crystals established that the structure was rhombohedral perovskite for the (BiFeO3)0.75-(PbTiO3)0.25 composition and tetragonal perovskite for the (BiFeO3)0.50-(PbTiO3)0.50 composition and mixed phase for the (BiFeO3)0.65-(PbTiO3)0.35 and (BiFeO3)0.70- (PbTiO3)0.30. X-ray pole figures verified that the (BiFeO3)0.75-(PbTiO3)0.25 crystal had grown with a single orientation, the [100] direction. Structures that are believed to be domains have been observed through optical and electron microscopy in backscattered mode. This interim report of on going investigations seeks to eventually confirm the domain structure in the crystals with electron back-scattered diffraction (EBSD).

Growth and magnetic properties of LPE-grown (EuTbBi)3(FeAlGa)5O12 garnet films

Using the PbO–B2O3–Bi2O3 flux system, (EuTbBi)3(FeAlGa)5O12 (EuTbIG) films were grown on (GdCa)3(GaMgZr)5O12 (SGGG) substrates for optical devices by the liquid phase epitaxial (LPE) method. The grown films' growth and magnetic domain wall were observed as a function of the Fe2O3/(Al2O3+Ga2O3)(R2) molar ratio by magnetic force microscope (MFM). As the grown films decreased the R2 molar ratio, the saturation magnetization of the grown films showed a tendency to decrease from 250 to 150 Oe. Also, we observed that the R2 molar ratio did not affect the surface morphology and thickness of the grown films, but it did affect the magnetic domain wall.

Crystal Growth and Electrical Properties of Lead-Free Piezoelectric Material (Na1/2Bi1/2)TiO3–BaTiO3

Single crystals of lead-free piezoelectric material x(Na1/2Bi1/2)TiO3–yBaTiO3 (NBBT 100x/100y) have been successfully grown by the flux method and the Bridgman method. Using the flux method, crystals having an edge length of 2–8 mm were obtained using Bi2O3 flux with cooling from 1350°C to 800°C at a rate of 3.5°C/h. Using the Bridgman method, comparatively good crystal of 15 mm diameter and 50 mm length was obtained using Bi2O3 flux with the Pt crucible driven down through the heat zone at a speed of 1.0 mm/h. The resulting crystals showed single-phase perovskite structure. Inductively charged plasma (ICP) chemical analysis revealed that the composition of the pulverized powder of these crystals is NBBT 97/3, which is slightly different from the charged composition of NBBT 94/6. One of the single crystals grown by the Bridgman method showed a dielectric constant of 1230 at room temperature and a dielectric constant peak at 313°C.

Über einen Lanthanoid-Mangan-Apatit: Nd4Mn(SiO4)3O / On a Lanthanoid Manganese Apatite: Nd4Mn(SiO4)3O

Single crystals of Nd4Mn(SiO4)3O have been prepared by a Bi2O3 flux in closed copper tubes. The colourless crystals show hexagonal symmetry, space group C6h 2—P63/m, a = 9,4986(9), c = 6,944(2) Å, Z = 2. Nd4Mn(SiO4)3O crystallizes in the Apatite structure and shows Nd3+ and Mn2+ with partly statistical distribution. As a consequence of this, O(2) and O(4) are occupying split positions.

Single crystal refinements of seven Sr1−x Ca x CuO2 structures (x = 0–0.573) and of Ca2−y Sr y CuO3 (y = 0 and 0.134)

Abstract Single crystals of Sr1−x Ca x CuO2 with x = 0–0.573 have been grown by a modified Bi2O3 flux technique using different ratios of the earth alkali carbonates. Upto x = 0.573 the SrCuO2 structure type was found. The changes of the lattice constants and of the atomic parameters are given. The different temperature dependence of the atomic parameters comparing undoped and doped crystals is discussed. From reaction mixtures with an excess of Ca (Ca:Sr ≥ 2:1) crystals with the composition Ca1.866Sr0.134 · CuO3 could be obtained. They crystallize in the Ca2CuO3 structure type.

Reduction of optical absorption at a wavelength of around 0.8 ?m in LPE garnet (TmBiCa)3(FeGaPt)5O12

Liquid-phase epitaxy (LPE) garnet films (TmBiCa)3(FeGaPt)5O12 have been grown using only Bi2O3 as the flux so that the film containing Bi gives high specific Faraday rotation. The film does not contain Pb, which may affect optical absorption. The optical absorption coefficientα at 810 nm has been effectively reduced by doping Ca in the melt. Our data show that a minimum level ofα and of the anisotropy constantKu and also the maximum of the electrical resistivityϱ are achieved when Ca2+ replaces Fe2+. Fe2+ results from Pt4+ incorporation in the film due to a Bi2O3 flux attack on a Pt crucible. Using a compensated film,α of 58 cm−1 and a figure of merit of 9deg/dB were obtained.