High-purity Oxide Research Articles

Local states of iron ions in Bi0.815Eu0.085La0.1FeO3 perovskite

Multiferroic Bi0.815Eu0.085La0.1FeO3 with rhombohedral structure is synthesized using the solid state method from high-purity metal oxides in air. The hyperfine magnetic fields and quadrupole and isomer shifts on 57Fe nuclei are investigated at temperatures of 87, 295, and 600–700 K by Mossbauer spectroscopy. Three nonequivalent magnetic trivalent high-spin states of iron ions exist in this perovskite at 295 and 87 K. It is also established that there is no spatial spin-modulated structure in Bi0.815Eu0.085La0.1FeO3.

Thermophysical properties of Gd2Zr2O7 powders prepared by mechanical milling: Effect of homovalent Gd3+ substitution

This contribution analyzes the thermophysical properties of Gd1.6Ln0.4Zr2O7 (Ln = La3+, Nd3+, Sm3+, Dy3+ and Er3+) ceramics synthesized at room temperature, by mechanically milling stoichiometric mixtures of high purity oxides. Regardless of chemical composition, powders milled for 27 h show XRD patterns similar to fluorite-type materials. Post-milling thermal treatments at 1500 °C, facilitates the evolution to the ordered pyrochlore derivative for Gd2Zr2O7, and the La3+-, Nd3+-, and Sm3+-containing materials. By contrast, samples containing the smaller lanthanides (Dy3+ or Er3+), maintain the fluorite structure. Thermal conductivity of the as-prepared samples was obtained as a function of temperature, from thermal diffusivity, heat capacity and density values, using sintered pellets. We found that doping has an important effect in lowering Gd2Zr2O7 thermal conductivity, with final values ranging from 1.22 to 1.94 W m−1 K−1; Nd3+- and Er3+-containing samples represent an optimum combination of defects and disordering of oxygen vacancies that generate the lowest conductivity values of all samples tested.

Determination of impurities in bismuth oxide by laser mass spectrometry

We have developed a technique for the quantitative analysis of bismuth oxide by laser mass spectrometry. The technique makes it possible to determine up to 70 impurities in the range 10−6 to 10−4 wt %. To evaluate relative sensitivity factors and obtain calibration plots, we used reference samples prepared by diluting a standard SOG-21-1 graphite sample with high-purity bismuth oxide powder.

Effects of Gamma Ray Irradiation on High Temperature Superconductors YBCO with Nanoparticles Fe<sub>3</sub>O<sub>4</sub> Addition

<p>The effects of gamma ray irradiation on high temperature superconductors YBa2Cu3O7-δ with nano particles Fe3O4 (20-30 nm) addition were investigated. YBCO superconductor powders were prepared by using high purity oxide powders via solid state reaction method. 0.01 – 0.05 wt.% of nano particles were added into YBCO. Samples were irradiated with 100 kGy gamma ray. The critical temperature (Tc) and transport critical current density (Jc) were determined by using four point probe method. The lattice parameters and morphology of the samples were characterized by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM), respectively. The results before and after gamma ray irradiation were compared. All of the samples showed increased Tc-zero after 100 kGy gamma ray irradiation. However, the Jcwas degraded after gamma ray irradiation. There is no significant variation found in the XRD patterns. The porosity of the samples was increased by the gamma ray irradiation. It can be concluded that gamma ray irradiation has enhanced the superconducting properties but degraded the transport properties.</p>

Improved compaction of ZnO nano-powder triggered by the presence of acetate and its effect on sintering

The retention of nanocrystallinity in dense ceramic materials is still a challenge, even with the application of external pressure during sintering. The compaction behavior of high purity and acetate enriched zinc oxide (ZnO) nano-powders was investigated. It was found that acetate in combination with water plays a key role during the compaction into green bodies at moderate temperatures. Application of constant pressure resulted in a homogeneous green body with superior packing density (86% of theoretical value) at moderate temperature (85 °C) in the presence of water. In contrast, no improvement in density could be achieved if pure ZnO powder was used. This compaction behavior offers superior packing of the particles, resulting in a high relative density of the consolidated compact with negligible coarsening. Dissolution accompanying creep diffusion based matter transport is suggested to strongly support reorientation of ZnO particles towards densities beyond the theoretical limit for packing of ideal monosized spheres. Finally, the sintering trajectory reveals that grain growth is retarded compared to conventional processing up to 90% of theoretical density. Moreover, nearly no radial shrinkage was observed after sinter-forging for bodies performed with this advanced processing method.

Diffused phase transitions in Pb(Zr0.65Ti0.35)O3-Pb(Fe2/3W1/3)O3 multiferroics

The solid solutions of (1−x)Pb(Zr0.65Ti0.35)O3-xPb(Fe2/3W1/3)O3 in different ratios were fabricated by a high-temperature solid-state reaction method using high-purity oxides for possible multi-ferroic applications. Structural analysis using x-ray diffraction powder patterns of the system by Rietveld refinement method exhibits the formation of rhombohedral phase with R3c space group. Detailed studies of dielectric permittivity as a function of temperature of the systems show that the frequency independent dielectric maximum temperature shifts toward room temperature on increasing x. In addition to this, the degree of diffuseness of the permittivity anomaly is more pronounced for higher content of Pb(Fe2/3W1/3)O3, implying the existence of a composition-induced diffuse phase transition for the limited range of compositional ratios. Detailed impedance spectroscopy analysis shows the contributions of grain, grain boundary, and interfacial polarizations in the resistive characteristics and conduction mechanism of the materials. The weak ferromagnetic and saturated ferroelectric loops indicate that system with x = 0.1, 0.2 have good multiferroic characteristics, and may be useful for future spintronic devices.

Enhancement of Optical Absorption, Photoluminescence and Raman Transitions in Bi2O3-GeO2Glasses with Embedded Silver Nanoparticles

The influence of silver nanoparticles (Ag-NPs) on the optical properties of Bi2O3-GeO2 glasses was investigated aiming the characterization of their potential for applications in photonic devices. The samples were prepared by the melt-quenching technique starting from high purity oxides (GeO2, Bi2O3 and AgNO3). Heat-treatment during different times was performed to nucleate Ag-NPs. A transmission electron microscope was used to confirm the presence of Ag-NPs and to determine their sizes and composition. The glass network was studied by spontaneous Raman scattering. The optical absorption spectra showed an absorption band at ca. 500 nm associated to the bismuth ions, and a 7-fold enhancement of absorption was observed in the samples with Ag-NPs. Photoluminescence (PL) spectra were obtained by exciting the samples with a 808 nm laser. Maximum enhancements of ca. 100% of the PL band centered at 1300 nm and ca. 70% of the Raman spectrum were observed due to the nucleation of the Ag-NPs. The enhanced optical response of the samples with Ag-NPs is attributed to the growth of the local field on the isolated bismuth ions and clusters that are located in the vicinity of the nanoparticles. The results illustrate the large potential of Bi2O3-GeO2 with Ag-NPs to be used in photonic devices.

ICP-AES analysis of high purity bismuth oxide

Two ICP-AES techniques for analysis of high-purity bismuth oxide are described. The direct techniques enables determination of 46 impurities in bismuth oxide with limits of detection (LODs) at the level of 10−8–10−5 wt %, and the method with separation matrix allows determination of 22 impurities with LODs at the level of 10−9-10−6 wt %.

Analysis of high-purity bismuth oxide by atomic absorption spectrometry with reactive distillation of the matrix

A procedure is developed for the analysis of bismuth oxide by electrothermal atomization atomic absorption spectrometry with matrix preseparation by reactive distillation as bismuth trichloride. The procedure allows the determination of Ag, Al, Co, Cu, Mn, Ni, Pb in bismuth oxide with limits of detection of 6 × 10−9 − 6 × 10−8 wt %.

Addressing Rare-Earth Element Criticality: An Example from the Aviation Industry

Rare-earth (RE) elements are enablers for a wide range of technologies, including high-strength permanent magnets, energy-efficient lighting, high-temperature thermal barrier coatings, and catalysts. While direct material substitution is difficult in many of these applications because of the specific electronic, optical, or electrochemical properties imparted by the individual rare-earth elements, we describe an example from the aviation industry where supply chain optimization may be an option. Ceramic matrix composite engine components require environmental barrier coatings (EBCs) to protect them from extreme temperatures and adverse reactions with water vapor in the hot gas path. EBC systems based on rare-earth silicates offer a unique combination of environmental resistance, thermal expansion matching, thermal conductivity, and thermal stability across the service temperature window. Several pure rare-earth silicates and solid solutions have been demonstrated in EBC applications. However, all rely on heavy rare-earth elements (HREEs) for phase stability. This article considers the possibility of using separation tailings containing a mixture of HREEs as a source material in lieu of using the high-purity HREE oxides. This option arises because the desired properties of RE-silicate EBCs derive from the average cation size rather than the electronic properties of the individual rare-earth cations. Because separation tailings have not incurred the costs associated with the final stages of separation, they offer an economical alternative to high-purity oxides for this emerging application.

The Effects of Nanoparticle Addition in Bi-2212 Superconductors

The effect of Y2O3 nanoparticle addition on the superconducting properties of Bi1.6Pb0.4Sr 2CaCu 2Oy have been investigated. The samples were prepared using high purity oxide powders via solid state reaction method. Y2O3 nanoparticle with 0.0-1.0 wt. % was systematically added to the well balanced Bi1.6Pb0.4 Sr2CaCu2Oy before sinter in order to trace the existense of nanoparticle addition in the system. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and critical current density, Jc. The current density measurement was done via four-point probe method under zero magnetic fields. The critical current density, Jc and superconductivity transition temperature, Tc for sample with addition of Y2O3 nanoparticle were found to be higher than the pure sample. The optimal addition of Y2O3 nanoparticle to the sample Bi-2212 system was found at 0.7 wt. %. The crystallographic structure of all samples was evidenced to be orthorhombic where a ≠ b ≠ c. Changes in superconducting properties of Y2O3 nanoparticle added Bi-2212 system were discussed.

Synthesis, Electrical And Thermal Properties Of Bi4V2-xCuxO11 (x=0.0 And 0.02) Ceramics

Polycrystalline ceramic samples of pure and Cu +2 doped Bi4V2-xCuxO11(x=0.0 and 0.02) have been synthesized by standard solid state reaction method using high purity oxides. The dielectric constant and dielectric loss and hence ac conductivity as a function of frequency and temperature have been measured. The dielectric studies indicate that the material is highly lossy and hence its ac conductivity increases with the increase of temperature. The dc conductivity of material has been measured as a function of temperature from room temperature to 653 K and its activation energy was calculated using the relation σ = σo exp (- Ea/kT). The dc conductivity increases with the substitution of Cu on the vanadium site. The Modulated Differential Scanning Calorimetry (MDSC) has been used to investigate the effect of substitution on the phase transition of the compounds. The results are discussed in detail.

Enhanced Transport Critical Current Density of NiO Nano Particles Added YBCO Superconductors

The effects of NiO nanoparticles addition in YBa2Cu3O7-δ (YBCO) superconductors had been investigated. YBCO superconductor powders were prepared by using high purity oxide powders via solid state reaction method. 0.01 0.05 wt.% of NiO nanoparticles were added into YBCO. The critical temperature (Tc) and transport critical current density (Jc) were determined by using four point probe method. The lattice parameters and morphology of the samples were characterized by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM), respectively. Tc of YBCO increased from 84 K to 87 K with 0.02 wt.% of NiO nanoparticles addition. The addition on NiO nanoparticles have significantly enhanced transport critical current density of YBCO by acting as flux pinning centers. YBCO with 0.03 wt.% of NiO nanoparticles performed the highest Jcup to 1265 mA/cm2 among the NiO-added samples. However, excessive addition of NiO nanoparticles in YBCO caused degradation in Tc and Jc.

Structural and electrical properties of Bi5Ti3FeO15 ceramics

Bi5Ti3FeO15 (BTF) is a multiferroic material of Aurivillius structural family with (perovskite) layered structure. This material has special interest and position in the family because it is a combination of multiferroic BiFeO3 and ferroelectric Bi4Ti3O12, and can be used as new magneto-electric material for devices. The compound (Bi5Ti3FeO15) was synthesized by a standard and widely used a high-temperature solid-state reaction method using high purity oxides. Preliminary structural analysis of the compound from the room temperature X-rays diffraction data confirmed the formation and good quality of the material. The nature of the microstructure (i.e., distribution, size and shape of grains, etc.) of sample recorded at room temperature using scanning electron microscopy exhibits formation of high-density sample. Studies of capacitive (permittivity and tangent loss) and resistive (impedance, electrical modulus and electrical conductivity) properties of the material as a function of frequency (1–1,000 kHz) at different temperatures (30–500 °C) using a complex impedance spectroscopy technique have provided many interesting and vital information on contribution of grains, grain boundary and interface in the material.

Zinc Oxide Production Technology of Distillation Twice Based on Scrap Miscellaneous Zinc Materials

By using scrap miscellaneouszinc materialas raw materials, a new technology with the help of two distillationsby fire method to produce zinc oxide was invented.The scrap miscellaneous zinc materialshave complex sources, containing dust, stone, iron and steel parts and other impurities, and zinc content is more than 15% over a wide range. The presence of zinc is in the form of pure metallic state, alloy state and oxidation state.Distillation process has two steps, the primary for removing the principal impurities and the second for zinc oxide purification. With less investment, low cost, simple equipment, easy operation, environmental protection and other advantages, this method is fit for production of high-purity zinc oxide and can also be used for the production of nanoscale high purity zinc oxide.

Synthesis, electrical and thermal properties of Bi4V2−xMexO11 (Me=Nb, Zr, Y and Cu with x = 0.0 and 0.06) ceramics

Polycrystalline ceramic samples of Bi4V2−xMexO11 (Me=Nb, Zr, Y and Cu and x = 0.0 and 0.06) have been synthesized by standard solid state reaction method using high purity oxides. The formation of the compounds have been analysed by X-ray diffraction method. The dielectric constant, dielectric loss and AC conductivity as a function of frequency and temperature have been measured. The dielectric studies indicate that the material is highly lossy, and hence, its AC conductivity increases with the increase of temperature. The DC conductivity of material has been measured as a function of temperature from room temperature to 723 K and its activation energy was calculated using the relation σ = σ 0exp (−E a/kT). The modulated differential scanning calorimetry has been used to investigate the effect of substitution on the phase transition (heat capacity and heat flow) of the compounds. The results are discussed in detail.

The Effect of Inclusions on the Formation of Intragranular Ferrite

In order to make a more intuitive and easier analysis the influence of different inclusions on the formation of ferrite, a layer of high purity oxide powder was added in the two parts of the Q235 steel artificially. The effect of the inclusions Ti2O3MgOZrO2 and Al2O3 on the nucleation of intragranular ferrite were studied by means of the physical simulation method. The microstructure of the micro-zone adjacent to the inclusions was observed and the elements of the micro-zone adjacent were analyzed. The results showed that the inclusions Ti2O3 and Al2O3 can form the ferrite layers at the oxides-steels interface; the inclusions Ti2O3 has an ability to induce the nucleation of intragranular ferrite; the inclusions Ti2O3 can change the chemical composition of the metal micro-zone adjacent to the inclusions, where the Mn depletion area was observed.

Synthesis, electrical and thermal properties of Bi4V2−xZrxO11 (x = 0.0, 0.02, 0.06 and 0.10) ceramics

Polycrystalline ceramic samples of Bi4V2−xZrxO11 (x = 0.0, 0.02, 0.06 and 0.10) have been synthesized by standard solid state reaction method using high purity oxides. The formation of the compounds have been checked by X-ray diffraction method. The dielectric constant, dielectric loss and ac conductivity as a function of frequency and temperature have been measured. The dielectric studies indicate that the material is highly lossy and hence its ac conductivity increases with the increase of temperature. The dc conductivity of all the materials has been measured as a function of temperature from room temperature to 673 K and its activation energy was calculated using the relation σ = σoexp (−Ea/kT). The Modulated Differential Scanning Calorimetry (MDSC) has been used to investigate the effect of substitution on the heat capacity and heat flow of the compounds. The results are discussed in detail.

DETERMINATION OF LANTHANIDES AND YTTRIUM IN HIGH PURITY DYSPROSIUM BY RP-HPLC USING α-HYDROXYISOBUTYRIC ACID AS AN ELUENT

An HPLC method is presented for the determination of lanthanides viz. lutetium (Lu), ytterbium (Yb), thulium (Tm), erbium (Er), holmium (Ho), terbium (Tb), and yttrium (Y) in high-purity dysprosium oxide (Dy2O3) matrix. In view of their similar chemical and physical properties, determination of rare-earth elements in bulk of a rare-earth element is a difficult task. Studies were carried out on C18 and C8 reversed phase columns employing α-hydroxyisobutyric acid (α-HIBA) as an eluent. n-Octane was used as an ion interaction reagent (IIR). Different chromatographic parameters e.g., ion interaction reagent, pH and concentration of α-HIBA were studied simultaneously to arrive at the optimum condition for the individual separation of lanthanides. When n-Octane sulphonate was used as the IIR, C8-based stationary phase was found to give significantly better resolution as compared to C18-based stationary phase. Under the optimized conditions, it was possible to resolve Y from Dy using α-HIBA as the single eluent. Separation and quantification of rare-earth elements were possible in samples with Dy/Tb and Dy/Y amount ratios up to 200. The method was validated using the simulated sample containing above lanthanides, Y and Dy matrix. Quantification was done using standard addition method. The method was successfully applied for the quantification of lanthanides and Y in high purity Dy2O3 sample. Concentrations of Lu, Yb, Tm, Er, Ho, Tb, and Y were found to be 74 ppmw, 432 ppmw, 22 ppmw, 57 ppmw, 3325 ppmw, 1207 ppmw, and 4463 ppmw, respectively.

Absorption Coefficient of Molten Aluminum Oxide in Semitransparent Spectral Range

A critical compilation and analysis of all the available experimental data and approximation formulas for the wavelength and temperature dependences of the absorption coefficient of molten aluminum oxide in semitransparent region are presented. The main factors and the influence of physicochemical processes on the value of the absorption coefficient are considered. Special attention is focused on possible reasons for large values of absorption of the alumina melt as compared to the crystal near melting temperature. It is shown that the available data can be divided into two groups, according to the level of absorption. The first group includes the results of the research of optical properties of solid propellant combustion products, and the second group–the results of the research of single crystal melts and some other high-purity molten aluminum oxides. Along with the detailed analysis of the absorption coefficient, also a brief analysis of available data on the refractive index has been done.