Fabrication and characterization of La2O3–Fe2O3–Bi2O3 nanopowders: Effects of La2O3 addition on structure,optical, and radiation-absorption properties

In this study, we fabricated and characterized six new nanopowders representing variations of La₂O₃–Fe₂O₃–Bi₂O₃, i.e., 100Bi₂O₃, 30Fe₂O₃–70Bi₂O₃, 3La₂O₃–27Fe₂O₃–70Bi₂O₃, 7La₂O₃–23Fe₂O₃–70Bi₂O₃, 10La₂O₃–20Fe₂O₃–70Bi₂O₃, and 20La₂O₃–10Fe₂O₃–70Bi₂O₃ (represented by 100B, 30F70B, 3L27F70B, 10L20F70B, and 20L10F70B, respectively). These nanopowders were prepared by the microwave-assisted hydrothermal synthesis method. Saponin extract from soapnuts was used as the nanoparticle capping agent. The structural, optical, and gamma radiation characteristics were measured, calculated, and analysed, respectively. The chemical structures of the nanocomposites influenced their optical and radiation shielding characteristics. The optical bandgaps of the 100B, 30F70B, 3L27F70B, 7L23F70B, 10L20F70B, and 20L10F70B nanopowders were 3.16, 3.13, 3.43, 3.45, 3.46, and 3.58 eV, respectively. The ranges of the mass attenuation coefficients of the nanopowders were computed, using XCOM, to be 0.0412–5.1624, 0.0401–4.5406, 0.0401–4.5285, 0.0401–4.5129, 0.0401–0.5015, and 0.0400–4.4156 cm²/g, respectively, and the ranges of mass energy absorption coefficients were found to be 0.0232–1.7525, 0.0228–1.5484, 0.0228–1.5598, 0.0288–1.5746, 0.0228–1.5853, and 0.0227–1.6192 cm²/g, respectively, for photon energies in the range of 0.1–10 MeV. The order of the dose rate trend was as follows: 30F70B < L27F70B < 7L23F70B < 10L20F70B < 20L10F70B. Analysis of the photon interaction parameters showed that the synthesized nanopowders could function well as fillers in radiation-shielding matrices.     

Optical and structural properties of ZnO NPs and ZnO–Bi2O3 nanocomposites

Pure ZnO and ZnO–Bi₂O₃ nanocomposites with 5 wt% and 10 wt% of Bi₂O₃ content were synthesized using the co-precipitation method. Optical properties such as refractive index (n), extinction coefficient (k), bandgap (E_g), and Urbach energies, as well as the band structure, were determined by modeling the experimental transmittance and reflectance UV–Vis spectra. The deduced bandgap and Urbach energies for pure ZnO (3.758 eV) increase with the increase of the doping degree of Bi₂O₃ in ZnO–Bi₂O₃ nanocomposite films. X-ray diffraction and scanning electron microscopy (SEM) was used to study the structural and morphological properties of these nanocomposite films. Pure ZnO and nanocomposites with Bi₂O₃ exhibit crystalline domains with wurtzite hexagonal structures, and as the doping degree of Bi₂O₃ increases, the crystallite size decreases. Based on SEM micrographs, the ZnO nanoparticles (NPs) structure shows the presence of aggregation. Moreover, Bi₂O₃ NPs in the nanocomposite film led to the further aggregation in the form of large rods. The elemental and chemical properties of the nanocomposites were investigated using infrared and energy-dispersive X-ray spectroscopy. The charge transfer process in the studied system is between ZnO and Bi₂O₃ conduction bands. Density-functional theory (DFT) calculations were performed for ZnO, Bi₂O₃, and ZnO-Bi₂O₃ compounds to investigate structural, optical, and electronic properties, being in agreement with the experimental results.     

Effects of TeO2/B2O3 substitution on synthesis,physical, optical and radiation shielding properties of ZnO–Li2O-GeO2-Bi2O3 glasses

Tellurite glass is a model material having superior features for several applications. It can be considered as a potential host matrix for different oxides, and this paper aims to study the effects of TeO₂/B₂O₃ substitution on synthesis, physical, optical and radiation shielding properties of ZnO–Li₂O-GeO₂-Bi₂O₃ glasses produced by melt quenching technique. The physical and optical features of the fabricated glasses were experimentally investigated by determining pivotal parameters such as density, XRD, tellurium ion concentration (N_i), linear refractive index (n_o), polaron radius (r_p) and inter nuclear distance (r_i). Moreover, the relative radiation deposition within the glasses was assessed via the attenuation coefficients (e.g. MAC), specific gamma ray constant (ᴦ), total stopping power (TSP), neutron cross sections, and dose rate (D). Our results suggest that both TeO₂ and B₂O₃ additives have a significant effect on the fundamental properties of the ZnO–Li₂O-GeO₂-Bi₂O₃ glasses. It also found that the lower thicknesses of the present glasses are required to provide the same level of shielding than ordinary, ilmenite, steel scrap, hematic-serpentine, ilmenite-limonite and basalt-magnetite concretes, RS253-G18 and RS360 glass shields. Therefore, presently investigated glasses are promising photon shields in different technological applications of gamma- and x-rays.     

Synthesis,physical, optical,mechanical, and radiation attenuation properties of TiO2–Na2O–Bi2O3–B2O3 glasses

A series of bismo-borate (50-x)B₂O₃-xTiO₂-15Na₂O–30Bi₂O₃ glass samples (where x = 0, 2.5, 5, 7.5, and 10 wt%) doped with TiO₂ were fabricated via the melt-quenching technique. The gamma and neutron shielding, physical, optical, and mechanical properties of the prepared samples were investigated. The experimental results were measured using an HPGe detector. ¹⁵²Eu, ¹³³Ba, ¹³⁷Cs, and ⁶⁰Co radioactive sources were used with energies in the range of 81–1408 keV. The experimental results were compared with both the FLUKA code and the XCOM database. The addition of TiO₂ increased the density of the glass samples and decreased their molar volume. The mass attenuation coefficient (MAC) decreased as photon energy decreased, while it increased as TiO₂ concentration increased. The half value layer (HVL) and mean free path (MFP) of the glass samples increased when the photon energy increased and decreased as the TiO2 concentration increased. The absorbance of the present samples is enhanced by using TiO₂, meaning they can be used to protect humans from UV light. Both direct and indirect band gaps decreased as TiO₂ content increased from 0 to 10 wt %. Moreover, the electronic transition between localized states is valid in the present samples. The radiation shielding, optical, physical, and mechanical properties of the fabricated glass samples demonstrate their utility for diagnostic gamma shielding.     

ZnO – Yb2O3 composite optical ceramics: Synthesis,structure and spectral-luminescent properties

Zinc oxide optical ceramics containing 0–2 wt% ytterbium are prepared by uniaxial hot pressing of commercial oxides at 1150 and 1180 °C. The ceramics have the main crystalline phase of hexagonal wurtzite-type ZnO. Ytterbium ions do not enter the ZnO crystals but form a cubic sesquioxide phase of Yb₂O₃ located at the ZnO grain boundaries. Yb acts as an inhibitor for the ZnO grain growth. The ceramics exhibit transmittance up to 60 % in the visible. Their transmission in the infrared is determined by the free charge carrier absorption. The Yb³⁺ ions are found in C₂ and C_3i sites in Yb₂O₃ crystals. Under X-ray excitation, the ceramics exhibit intense luminescence bands in the blue (near-band-edge emission) and green (defect emission) whose positions, intensities and decay times depend on the Yb content. Yb₂O₃ causes a redistribution of luminescence intensity in favor of the near-band-edge emission and fastens the emission decay.     

Impact of TeO2–B2O3 manipulation on physical,structural, optical and radiation shielding properties of Ho/Yb codoped mixed glass former borotellurite glass

In this work, (75-x)B₂O₃-xTeO₂-11Bi₂O₃–10Li₂O-1Ho₂O₃-3Yb₂O₃ (x = 10–60 mol%) mixed glass former (MGF) glasses were prepared by using the melt-quenching method to investigate the effect of mixed glass former between B₂O₃ and TeO₂ on the structural, optical and radiation shielding properties of glass. The amorphous nature of the glass samples was confirmed through XRD measurement. Optical ultraviolet–visible light (UV–Vis) spectroscopy revealed that the direct and indirect optical band gap (E_opt) decreased as TeO₂ content increased except for the anomaly at x = 30 mol% due to the interchanging dominance of bridging oxygen (BO) and non-bridging oxygen (NBO) in the glass network. Both direct and indirect refractive indices, n posted an increment except for x = 30 mol% due to polarizability influence of BO and NBO. Urbach energy, E_u declined thus indicating lesser disorder and less defects on the glass structure. The radiation shielding properties of the glass samples were determined for 15 keV–15 MeV photon energy range by using Phy-X/PSD software. Atomic number-dependent parameters such as mass attenuation coefficient (MAC) and effective atomic number (Z_eff) demonstrated an enhanced performances caused by higher Z of Te over B. Meanwhile, density-dependent parameters such as linear attenuation coefficient (LAC), mean-free path (MFP), half-value layer (HVL) and tenth-value layer (TVL) all exhibited an improvement over TeO₂ concentration due to higher density data obtained.     

Fabrication,structural, optical,physical and radiation shielding characterization of indium (III) oxide reinforced 85TeO2-(15–x)ZnO-xIn2O3 glass system

This work aimed to evaluate the structural, optical, and physical features of several types of glasses based on 85TeO₂-(15–x)ZnO-xIn₂O₃ (x = 2, 4, 6, and 8 mol%) system. As a result, five different samples were synthesized utilizing the melting-annealing technique. The Archimedes method was used to calculate the densities of the synthesized glasses. The structural, optical, physical, and radiation interaction characteristics of the sample were determined using XRD investigations, Raman spectra, and advanced modelling methods, producing optical band gap, refractive index, and Urbach energy values. The glass densities increased from 5.6091 g cm⁻³ to 5.6754 g cm⁻³ by increasing In₂O₃ reinforcement from 2 to 8 mol %. Urbach energies increased consistently from 0.1399 to 0.1439 eV as In₂O₃ concentration increased, apart from a drop to 0.1345 eV at x = 8. The optical transmittance and absorption characteristics altered nearly monotonically with increasing In₂O₃ ratios, showing that these characteristics may be estimated and controlled using In₂O₃ additive. By substituting ZnO with In₂O₃ within the structure, the optical band gap was dramatically enlarged. Additionally, at simulated energies greater than 0.02 MeV, the gamma-ray mass attenuation coefficient grows monotonically with In₂O₃ reinforcement. As a result, it can be stated that the high concentration In₂O₃ to TeO₂–ZnO glass combination is a good synergetic tool for integrating structural, optical, and radiation properties.     

Growth and optical properties of ZnO–In2O3 heterostructure nanowires

ZnO–In₂O₃ heterostructure nanowires were grown on a Si (111) substrate using the thermal evaporation method. Scanning electron microscopy results showed that the ZnO nanowires had spherical caps. The X-ray diffraction (XRD) pattern and energy-dispersive X-ray (EDX) spectrum indicated that these caps were In₂O₃. An analysis of the early growth process revealed that indium oxide might have played a self-catalytic role. Therefore, it was plausible that the vapor–liquid–solid mechanism (VLS) was responsible for the growth of the ZnO–In₂O₃ heterostructure nanowires. The optical properties of the products were characterized using a photoluminescence (PL) technique. The PL results for the ZnO–In₂O₃ heterostructure nanowires showed a strong peak in the ultraviolet region as a result of the near band emission and a negligible peak for the visible emissions that occurred as a result of the defects. Based on these PL results, it was found that the In₂O₃ nanostructures not only introduced the caps at the tips of the ZnO nanowires but also partially passivated the nanowire surfaces, leading to an improved near band edge emission and the suppression of the defect luminescence.     

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 520 nm. The highest photoluminescence emission intensity was observed when 5 mol% Bi₂O₃ flux was added into the phosphors. The emission is due to 4f⁶5d→4f⁷ (⁸S_7/2) 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.     

Large third-order optical nonlinearity of ZnO–Bi2O3–B2O3 glass–ceramic containing Bi2ZnB2O7 nanocrystals

Homogeneous transparent optical glass–ceramics precipitated with unique nonlinear crystals are promising materials for photonic applications. We have utilized heat treatment method to prepare transparent ZnO–Bi₂O₃–B₂O₃ glass–ceramic containing Bi₂ZnB₂O₇ nonlinear nanocrystals. A large third-order nonlinear susceptibility χ⁽³⁾ of glass–ceramic is measured by Z-scan technique, which mainly attributed to unique [BiO₆] and [B₂O₅] units in Bi₂ZnB₂O₇ crystal structure and the quantum size effect of nanoparticles. The discovery is of great potential in the application of nonlinear optical integrated devices.     

Synthesis,structural and electrical properties of novel pyrochlores in the Bi2O3–CuO–Ta2O5 ternary system

A series of non-stoichiometric cubic pyrochlores with general formula, Bi_3?xCu_1.8Ta_3+xO_13.8+x (BCT) was successfully prepared by solid state reaction at the firing temperature of 950 °C over 2 days. The solid solution mechanism is proposed as one-to-one replacement of Bi³⁺ for Ta⁵⁺, together with a variation in oxygen content in order to achieve electroneutrality. The solid solution limit is confirmed by X-ray diffraction technique (XRD) for which linear variation of lattice constants is observed at 0 ≤ x ≤ 0.6. The refined lattice constants are found to be in the range of 10.4838 (8) Å–10.5184 (4) Å and the grain sizes of these samples determined by scanning electron microscopy (SEM) fall between 1 and 40 μm. Meanwhile, thermal analyses show no physical or chemical change for the prepared pyrochlores. The relative densities of the densified pellets for AC impedance measurements are above 85% and the measured relative permittivity, ?′ and dielectric loss, tan δ for composition, x = 0.2 at ambient temperature are ～60 and 0.07 at 1 MHz, respectively. The calculated activation energies are 0.32–0.40 eV and the conductivity values, Y′ are in the order of 10^?3 at 400 °C. The conduction mechanisms of BCT pyrochlores are probably attributed to the oxygen non-stoichiometry and mixed valency of copper within the structure.     

Microstructure and electrical properties of ZnO–ZrO2–Bi2O3–M3O4 (MCo,Mn) varistors

Phase evolution, microstructure and the electrical properties of ZrO₂-added pyrochlore-free ZnO–Bi₂O₃–M₃O₄ (MCo, Mn) varistors have been studied as functions of ZrO₂ content up to 10 vol% and the sintering temperature between 900 and 1300 °C. Zirconia remained as intergranular second phase particles up to 1100 °C, which retarded densification and inhibited the grain growth of ZnO. At higher temperatures, on the contrary, ZrO₂ particles began to be entrapped in ZnO grains and irreversibly transform from monoclinic to stable cubic phase dissolving transition metal ions. The grain size of ZnO decreased with increasing ZrO₂ content, and increased with the increase of the sintering temperature. Accordingly breakdown voltage changed with both ZrO₂ content and the sintering temperature as was expected. Nonlinear coefficient (α) depended primarily on the sintering temperature: it increased to >40 up to 1000 °C, and significantly decreased to <30 at higher temperatures probably due to the volatilization of Bi₂O₃. While the specimens sintered at 1200 °C or above had relatively high leakage current (I_L) and large clamping ratio (C_R), those with ZrO₂ content of 0.5–5.0 vol% and sintered below 1200 °C revealed low I_L of ⩽20 μA/cm² and C_R well below 2.0. In spite that varistor characteristics of ZrO₂-added system could not match those of commercial ZnO varistors, its low temperature sinterability and ease of breakdown voltage control via ZrO₂ content without a serious loss of its figures of merit are worth noticing, particularly for multi-layered chip varistor (MLV) application.     

Ytterbium (III) oxide reinforced novel TeO2–B2O3–V2O5 glass system: Synthesis and optical,structural, physical and thermal properties

Different samples of xTeO₂.(25-y)B₂O₃.zV₂O₅.yYb₂O₃ (or TBVY) new glass material were synthesized by the classical melt-quenching method. Structural, optical, physical, and thermal analyses of the synthesized glasses were performed in addition to Monte Carlo simulation to test radiation shielding properties. The results showed that increasing ratios of Yb₂O₃ (y = 0.0, 0.5, 1.0, and 1.5 mol%) produced monotonic density values of the synthesized glasses ranging from 4.70058 g cm^?3 to 5.01038 g cm^?3. XRD and FTIR analyses were used to confirm the glass structure of all samples. Optical transmittance and absorption parameters varied almost monotonically with increasing ratios of Yb₂O₃ indicating the ability to predict and control these properties using Yb₂O₃ additive. Furthermore, simulated radiation interaction parameters, such as attenuation coefficients and half-value layer, exhibited well-behaved dependence on the concentration ratio of the Yb₂O₃ additive. This approach to glass material synthesis demonstrate the useful synergetic effect of combining structural, optical, and radiation characteristics.     

Relationship of structural phase transformations and properties of sol-gel films in the Bi2O3 — TiO2 — Fe2O3 system

It is shown that the structure and properties of gel-sol oxide films depend on the total mass content of film-forming oxides in the solution and are determined by the different degrees of nonequilibrium of the physicochemical processes. The existence of quite clear relationships between the solution viscosity, the specifics of the microstructure, and certain properties of the film is established. Translated from Steklo i Keramika, No. 4, pp. 11 – 14, April, 2000.     

Influence of Cr2O3 on highly nonlinear properties and low leakage current of ZnO–Bi2O3 varistor ceramics

ZnO–Bi₂O₃–Sb₂O₃–Co₂O₃–MnO₂–xCr₂O₃ (ZBSCM–xCr₂O₃, 0≤x≤0.6 mol%) varistors were fabricated through the conventional solid state method, and the effects of Cr₂O₃ on the microstructures and electrical properties were investigated. Results showed that the secondary phases CrBi₁₈O₃₀ and Co₂Cr_0.5Sb_0.5O₄ emerged when x ranges from 0.2 to 0.4. In these compositions, Cr₂O₃ acted as a donor and decreased the electrical properties of ZBSCM. For samples with x=0.5, the secondary phases transformed to MnCr₂O₄ and the electrical properties increased significantly: the nonlinear coefficient α sharply increased up to 80.71 and the barrier height ϕ_b reached 3.88 eV. This indicates that the donor effect of Cr₂O₃ disappeared. In addition, with the increase of Cr₂O₃, the average grain size of ZnO decreased from 7.48 μm to 5.46 μm, which in turn resulted in an increase of breakdown voltage E_1mA from 216.17 V/mm to 362.50 V/mm. Besides, all the samples showed the low value of leakage current of lower than 0.1 μA. This varistor might be a promising candidate for highly effective applications.     

Effect of ZnO on the structural,physio-mechanical properties and thermal shock resistance of Li2O–Al2O3–SiO2 glass-ceramics

The composition of lithium aluminosilicate (LAS) with different zinc oxide-magnesium oxide (ZnO–MgO) contents that ranged from 0 to 1.45 wt percent (wt%) was investigated to determine the thermal shock resistance properties of the glass-ceramics. The LAS glasses were melted in an alumina crucible at 1550 °C for 5 h, and the green compact samples were then heat-treated at 1100 °C for 3.5 h. The presence of zinc oxide (ZnO) in the compositions did not change the major crystal phase of β-spodumene. However, the addition of ZnO shifted the pronounced peak to a lower angle and increased the percentage of crystallinity from 55% to 59%. Additionally, the function of ZnO in LAS glass-ceramics as the network modifier was confirmed through Fourier Transform Infrared Spectroscopy (FTIR) analysis. The physio-mechanical properties were improved when 1.45 wt% ZnO was added to the LAS glass-ceramics. The results showed increased density (2.42 g/cm³), low porosity (0.85%), high flexural strength (125.23 MPa), and low coefficient of thermal expansion (25–800 °C) (CTE_{(25–800 °C)}) value of 1.73 × 10^?6 °C^?1. Meanwhile, the thermal shock resistance properties evaluation of the LAS glass-ceramics at different ZnO contents were conducted at different thermal shock temperatures of 200 °C, 500 °C, and 800 °C. The critical temperature of the LAS specimens with 1.45 wt% ZnO demonstrated the ability to withstand a thermal shock at 800 °C while preserving 87% of their initial strength of 108.40 MPa, exemplifying the best LAS glass-ceramics properties for rapid high-temperature change applications.     

Radiation attenuation properties of Bi2O3–Na2O– V2O5– TiO2–TeO2 glass system using Phy-X / PSD software

The purpose of this work is to investigate the effect of increasing Bi₂O₃ mol% on the radiation shielding parameters of tellurite glass system with the formula Bi₂O₃–Na₂O– V₂O₅– TiO₂–TeO₂ by using Phy-X/PSD computer software between 15 keV and 10 MeV. The results showed that the attenuation factor is very large at 15 keV. The mass attenuation coefficient (μ/ρ) at 15 keV lies within the range of 55.96–67.03 cm²/g for the selected samples. The μ/ρ for the investigated samples at 10 MeV is in the range of 0.0365–0.0392 cm²/g. The results also revealed that the addition of Bi₂O₃ enhances the effective atomic number (Z_eff) and the sample corresponding to the lowest and highest amount of Bi₂O₃ (coded as TeBTi1 and TeBTi6) has the lowest and highest Z_eff. Moreover, Z_eff has high values between 15 keV and 0.1 MeV and the maximum Z_eff occurs at 0.1 MeV (equal to 61.01, 62.67, 64.10, 65.34, 66.44 and 67.41 for TeBTi1– TeBTi6 samples respectively). The half value layer (HVL) increased when the energy changes from 15 keV to 10 MeV and the lowest HVL occurs at 15 keV for the sample coded as TeBTi6 and equal to 0.0025 cm, while the HVL at this energy for TeBTi1 is 0.0056 cm. Also, we calculated the tenth value layer (TVL) for the present system and we found that TVL reduces with the increment of Bi₂O₃ content, and the sample corresponding to 22 and 0 mol% of Bi₂O₃ and TiO₂ respectively namely TeBTi6 possesses the lowest value of TVL, thus has the best radiation attenuation performance in comparison to other selected glasses. Also, we evaluated the effective removal cross-sections of fast neutrons (∑_R) for the investigated glass system and we found that the ∑_R values increase with increase the concentration of Bi₂O₃.     

Synthesis,structural and electrical properties of Bi1−xDyxFeO3 multiferroic ceramics

Polycrystalline ceramic samples of dysprosium (Dy³⁺) doped bismuth ferrite of general formula Bi_1?xDy_xFeO₃ (x=0.00, 0.01, 0.05 and 0.1) have been prepared by standard solid state reaction method. Powder X-ray diffraction (XRD) analysis reveals that all the samples crystallize in the rhombohedral structure with noncentrosymmetric R3c space group. The refined lattice parameters decrease with the increase of Dy concentration within the same structure symmetry. The bond lengths among atoms for all the compounds were calculated by the Rietveld analysis. The frequency and temperature dependent dielectric constants (real and imaginary parts) have been measured. The real part of dielectric constant reveals that the Neel temperature decreases with the increase of Dy-substitution down to ～200 °C for 10% substitution to the Bi site.