Nb Ions Research Articles

Structural and Optical Properties of SrTiO3-Based Ceramics for Energy and Electronics Applications

A series of Sr1−xDyxTi1−yNbyO3−δ (0.05 ≤ x, y ≤ 0.10) samples were fabricated using cold compaction, followed by sintering in a (95% N2 + 5% H2) reducing atmosphere. We studied the crystal structure and optical properties of Sr1−xDyxTi1−yNbyO3−δ using X-ray diffraction (XRD) with Rietveld refinement, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and ultraviolet−visible−near-infrared (UV−VIS−NIR) spectroscopy. The sintered Sr1−xDyxTi1−yNbyO3−δ had a tetragonal structure (I4/mcm space group). In the sintered samples, Ti ions existed as a mixture of Ti3+ and Ti4+, and Nb ions existed as a mixture of Nb4+ and Nb5+. The band-gap energies decreased with increasing Dy/Nb concentrations. The incorporation of Ti and Nb ions, the formation of both Ti3+ and Nb4+ ions, and the reduction in band-gap energies are likely highly effective for increasing the electron concentration and the corresponding electrical conductivity. Sr1−xDyxTi1−yNbyO3−δ with high electrical conductivity is suitable for energy and electronics applications.

Nb(V)-containing saponite: A versatile clay for the catalytic degradation of the hazardous organophosphorus pesticide paraoxon under very mild conditions

A synthetic saponite clay containing structural Nb(V) metal centres (NbSAP) was investigated in the abatement of paraoxon-ethyl, an anti-cholinergic organophosphorus pesticide, under mild conditions (neutral pH, room temperature and ambient pressure) in heterogenous phase, without additional basic additives. The material was selected according to its high surface acidity and ease of preparation through a one-step hydrothermal synthesis. The presence of Nb(V) ions played a crucial role in efficiently catalysing the degradation of aggressive chemical substrates. A niobium(V) oxide with very low surface acidity was also tested as a reference material. The study employed a multi-technique approach to monitor the pesticide degradation pathway and by-products formed during abatement experiments in polar non-protic and aqueous solvents. Notably, in water, the concentration of paraoxon-ethyl significantly decreased by 82 % within the first hour of contact with the clay. Additionally, NbSAP demonstrated a good performance after three repeated catalytic cycles and subsequent reactivation.

Structural, optical, photocatalytic and thermal behaviour of (Nb, Ta) co-doped WO3 nanoparticles and its application in photocatalytic degradation of MG and RhB dyes

In this communication, eco-friendly, cost effective and facile hydrothermal route was adopted to synthesize pure WO3, Nb-doped WO3 and (Nb, Ta) co-doped WO3 nanoparticles. Phase, lattice constants, crystallite size and crystallinity have been evaluated through X-ray diffraction. The insertion of Nb and Ta ions into WO3 nanoparticles was confirmed by XPS, FTIR and EDS studies. HRTEM and SAED micrographs exhibited highly nanocrystalline nature of samples. UV–visible studies was carried out to analyse nature of band gap, band gap energy, extinction coefficient, refractive index, Urbach energy and optical conductivity of prepared samples. Optical band gap was narrowed from 2.94 to 2.49 eV and Urbach energy was extended from 0.08 to 0.35 eV through co-doping of (Nb, Ta) ions into WO3 NPs. Reduction in PL intensity revealed that electron-hole pair recombination rate was decreased with co-doping of (Nb, Ta) ions. The photo-degradation efficiency of (Nb 5 %, Ta 5 %) co-doped WO3 nanophotocatalysts was 93.12 % against MG and 90.11 % against RhB dyes. The rate constant was found to be increased from 0.0107 to 0.0203 min−1 for MG and 0.0086 to 0.0174 min−1 for RhB. Thermal results exhibited the weight loss in three phase degradation processes, and thermal stability. The results showed that (Nb 5 %, Ta 5 %) co-doped WO3 NPs is a potential candidate for practical applications in environmental remediation (organic dyes degradation).

Deciphering the piezoelectric and conductive mechanisms of Nb-doped Bi3Ti1.5W0.5O9 high-temperature piezoelectric ceramics

The study utilizes Bi3Ti(1.5-x)NbxW0.5O9 (BTW-xNb, x=0.00, 0.01, 0.02, 0.04, 0.06) bismuth layered piezoelectric ceramics synthesized via a conventional solid-phase reaction process. This is the study to investigate the impact of B-site Nb ion doping on the structural and electrical properties of BTW-xNb ceramic. The results show that all ceramics have a single bismuth layer structure, with reduced lattice distortion according to Rietveld refinement findings. The presence of oxygen vacancies in the ceramic is the main factor that affects the high temperature conductivity of the samples. The XPS results, the increase in the activation energy of AC and DC conductivity confirm that doping with Nb5+ ions reduces oxygen vacancy concentration. The ceramics with the highest overall electrical performance are the BTW-0.02 Nb ceramics. Notably, the DC resistivity at 500 °C was enhanced from 9.16 × 105 Ω·cm (x = 0.00) to 8.24 × 106 Ω·cm. The TC was enhanced from 730 °C(undoped) to 743 °C. At 500 °C, tanδ decreases from 21.1 % to 8.2 %. The ceramic's increased resistivity increases the polarization voltage, resulting in more complete polarization. The d33 is increased from 7.5 pC/N (undoped) to 13 pC/N. Furthermore, the piezoelectric properties remain stable up to 700°C, suggesting that the material has considerable potential for use at elevated temperatures.

Optimized Nb‐Doped TiO2/rGO Nanocomposites for Assessment of Photovoltaic Performance With Metal‐Free Dye and Polymer Gel Electrolyte

AbstractThis research presents the development of niobium (Nb)‐doped titania (TiO2)/reduced graphene oxide (rGO) nanocomposites (NTR NCs) for dye‐sensitized solar cells (DSSCs). The novelty lies in two aspects: introducing Nb (V) ions into TiO2/rGO nanocomposites via an in‐situ sol‐gel method with doping concentrations from 1.0 to 3.0 mol %, and fabricating photoanodes using the doctor blade technique, sensitized with a Co2+/Co3+‐based PEO‐PEG polymer gel electrolyte‐assisted D‐π‐A carbazole metal‐free (SK3) dye. Detailed investigations into the optoelectrical, structural, and morphological properties were conducted using various spectral and analytical tools. Notably, DSSCs based on Nb‐doped TiO2/rGO nanocomposites with 2.0 mol % Nb (NTR‐2) achieved a remarkable solar efficiency (η) of 5.48 % under AM 1.5 solar simulation, significantly outperforming devices based on bare TiO2 nanoparticles and undoped TiO2/rGO NCs by factors of 4.15 and 2.97, respectively. The substantial enhancement in photovoltaic performance is attributed to superior charge transfer properties and higher carrier density, as revealed by electrochemical impedance spectroscopy (EIS) and Mott‐Schottky (M–S) analysis. Nb‐doping results in an energetic surface nature, improved optical absorption, and reduced charge transfer resistance, collectively boosting the overall efficiency of DSSCs. This work underscores the potential of Nb‐doped TiO2/rGO NCs as effective photoanode materials in enhancing DSSC performance.

Structure and electrical properties of (1-x)Bi3TiTaO9-xNa0.5Bi2.5Nb2O9 piezoelectric ceramic

The lead-free piezoelectric ceramics (1-x)Bi3TiTaO9–xNa0.5Bi2.5Nb2O9 [(1-x)BTT–xNBN; x = 0.0; 0.2; 0.5; 0.7; 1.0] were prepared using the traditional solid-state method, and the microstructure and electrical properties of the novel solid solution (1-x)BTT–xNBN were studied. XRD data and Raman spectroscopy analysis indicated that Na ions and Nb ions had been incorporated into the designed lattice, forming a stable solid solution. The piezoelectric performance of the (1-x)BTT–xNBN ceramics was improved for two reasons: on one hand, the incorporation of NBN could suppress the leakage current caused by Ti ions, effectively reducing the contribution of oxygen vacancies to the direct current resistivity, thereby increasing the ceramic's direct current resistivity (ρdc); on the other hand, the orthorhombic distortion was reduced, and the remanent polarization was enhanced. Among them, the 0.3Bi3TiTaO9-0.7Na0.5Bi2.5Nb2O9 ceramic demonstrated excellent comprehensive performance: the values of d33, Tc, and Pr were 14.4 pC/N, 777.8 °C, and 9.82 μC/cm2, respectively. Specifically, at 500 °C, tanδ and ρdc were 0.67 % and 1.01 × 108 Ω∙cm, respectively, and after depolarization at 750 °C, its d33 remained at 97.92 % of the original value.

Features of electronic states in the vicinity of band gap and atomic structure of Ta- and Nb-doped Li7La3Zr2O12

Li7La3Zr2O12 is one the most promising materials for Li-conducting solid electrolytes. The incorporation of Ta5+ and Nb5+ into the Zr4+ sites stabilizes its cubic structure and significantly enhances Li-conductivity, due to the formation of Li vacancies. In this research, we have studied the band gap features of Ta and Nd-doped Li7La3Zr2O12. Our findings indicate that Nb ions are present not only in the +5 valence state, but also in the +4 state, leading to the formation of oxygen vacancies. In the case of the Ta-doping, such an effect was not observed. This could be the reason for the approximately one order of magnitude higher lithium conductivity observed in the case of the Ta doping, in comparison to the Nb doping.

Strong Local Polarization Fluctuations Enabled High Electrostatic Energy Storage in Pb-Free Relaxors.

Electrostatic energy-storage ceramic capacitors are essential components of modern electrified power systems. However, improving their energy-storage density while maintaining high efficiency to facilitate cutting-edge miniaturized and integrated applications remains an ongoing challenge. Herein, we report a record-high energy-storage density of 20.3 J cm-3 together with a high efficiency of 89.3% achieved by constructing a relaxor ferroelectric state with strongly enhanced local polarization fluctuations. This is realized by incorporating highly polarizable, heterovalent, and large-sized Zn and Nb ions into a Bi0.5Na0.5TiO3-BaTiO3 ferroelectric matrix with very strong tetragonal distortion. Element-specific local structure analysis revealed that the foreign ions strengthen the magnitude of the unit-cell polarization vectors while simultaneously reducing their orientation anisotropy and forming strong fluctuations in both magnitude and orientation within 1-3 nm polar clusters. This leads to a particularly high polarization variation (ΔP) of 72 μC cm-2, low hysteresis, and a high effective polarization coefficient at a high breakdown strength of 80 kV mm-1. This work has surpassed the current energy density limit of 20 J cm-3 in bulk Pb-free ceramics and has demonstrated that controlling the local structure via the chemical composition design can open up new possibilities for exploring relaxors with high energy-storage performance.

Enhancing Structural Rigidity of Ultrahigh-Ni Oxide Through Al and Nb Dual-Bulk-Doping for High-Voltage Lithium-Ion Batteries.

The pursuit of high energy densities propels the design of next-generation nickel-based layered oxide cathodes. The utilization of low-cobalt, ultrahigh-nickel layered oxide cathodes, and the extension of operating voltages promise enhanced energy density. However, stability and safety face challenges associated with nickel content, including structural degradation, lattice oxygen evolution, and thermal instability. In this study, a promising strategy of Al and Nb dual-bulk-doping is presented in high-Ni cathode materials of LiNi0.96Co0.04O2 (NC) to stabilize the bulk structure, suppress oxygen release, and attain superior electrochemical performance at high voltages. The introduction of Al and Nb effectively raises the migration energy of Ni2+ into Li sites and stabilizes lattice oxygen through strengthened Al─O and Nb─O bonds. Furthermore, the substitution of high-valence Nb ions reduces the charge depletion of lattice oxygen and induces an ordered microstructure. The Al and Nb dual-bulk-doping strategy mitigates strain and stress associated with the H2↔H3 phase transition, reducing the generation and propagation of microcracks. The resulting Li(Ni0.96Co0.04)0.985Al0.01Nb0.005O2 (NCAN) cathode exhibits superior cycling stability, with a capacity retention of 77.8% after 300 cycles, even when operating at a high-voltage of 4.4V, outperforming the NC (48.5%). This work provides a promising perspective for developing high-voltage and high-Ni cathode materials.

Progress of the laser ion source upgrade (LION2) for RHIC and NSRL program at Brookhaven National Laboratory

At Brookhaven National Laboratory (BNL), the LION2 ion source is being constructed to replace an existing laser ion ablation ion source (LIS) at the EBIS facility, which provides heavy ion beams of multiple ion species for the operation of NASA Space Radiation Laboratory (NSRL) and Relativistic Heavy Ion Collider (RHIC). The LION1 ion source currently provides singly charged ions of Li, B, C, O, Al, Si, Ca, Ti, Fe, Cu, Zr, Nb, Ag, Tb, Ta, W, Au, Bi, and Th with a rapid-species-change capability. An electron beam ion source, Extended-EBIS captures, confines, and ionizes the ions to high charge state, suitable for injection and acceleration by an RFQ accelerator. Typically, single pulses of the LIS ion species for NSRL are changed sequentially during Galactic Cosmic Ray experiments, while multiple pulses of a given ion beam are provided quasi-simultaneously for RHIC. LION2 will have the same capability of the rapid-species-change with improved beam performance and reliability. LION2 is being constructed in a remote assembly location and is expected to finish in December 2023. The removal of LION1 and installation of LION2 is planned during the December 2023 or summer 2024 shutdown.

Theoretical Study of the Magnetic and Optical Properties of Ion-Doped LiMPO4 (M = Fe, Ni, Co, Mn).

Using a microscopic model and Green's function theory, we calculated the magnetization and band-gap energy in ion-doped LiMPO4 (LMPO), where M = Fe, Ni, Co, Mn. Ion doping, such as with Nb, Ti, or Al ions at the Li site, induces weak ferromagnetism in LiFePO4. Substituting Li with ions of a smaller radius, such as Nb, Ti, or Al, creates compressive strain, resulting in increased exchange interaction constants and a decreased band-gap energy, Eg, in the doped material. Notably, Nb ion doping at the Fe site leads to a more pronounced decrease in Eg compared to doping at the Li site, potentially enhancing conductivity. Similar trends in Eg reduction are observed across other LMPO4 compounds. Conversely, substituting ions with a larger ionic radius than Fe, such as Zn and Cd, causes an increase in Eg.

Cation doping and oxygen vacancies in the orthorhombic FeNbO4 material for solid oxide fuel cell applications: A density functional theory study.

The orthorhombic phase of FeNbO4, a promising anode material for solid oxide fuel cells (SOFCs), exhibits good catalytic activity toward hydrogen oxidation. However, the low electronic conductivity of the material specifically in the pure structure without defects or dopants limits its practical applications as an SOFC anode. In this study, we have employed density functional theory (DFT + U) calculations to explore the bulk and electronic properties of two types of doped structures, Fe0.9375A0.0625NbO4 and FeNb0.9375B0.0625O4 (A, B = Ti, V, Cr, Mn, Co, Ni) and the oxygen-deficient structures Fe0.9375A0.0625NbO3.9375 and FeNb0.9375B0.0625O3.9375, where the dopant is positioned in the first nearest neighbor site to the oxygen vacancy. Our DFT simulations have revealed that doping in the Fe sites is energetically favorable compared to doping in the Nb site, resulting in significant volume expansion. The doping process generally requires less energy when the O-vacancy is surrounded by one Fe and two Nb ions. The simulated projected density of states of the oxygen-deficient structures indicates that doping in the Fe site, particularly with Ti and V, considerably narrows the bandgap to ∼0.5eV, whereas doping with Co at the Nb sites generates acceptor levels close to 0eV. Both doping schemes, therefore, enhance electron conduction during SOFC operation.

Highly Selective and Reversible Detection of Simulated Breath Hydrogen Sulfide Using Fe-Doped CuO Hollow Spheres: Enhanced Surface Redox Reaction by Multi-Valent Catalysts.

The precise and reversible detection of hydrogen sulfide (H2S) at high humidity condition, a malodorous and harmful volatile sulfur compound, is essential for the self-assessment of oral diseases, halitosis, and asthma. However, the selective and reversible detection of trace concentrations of H2S (≈0.1ppm) in high humidity conditions (exhaled breath) is challenging because of irreversible H2S adsorption/desorption at the surface of chemiresistors. The study reports the synthesis of Fe-doped CuO hollow spheres as H2S gas-sensing materials via spray pyrolysis. 4 at.% of Fe-doped CuO hollow spheres exhibit high selectivity (response ratio ≥ 34.4) over interference gas (ethanol, 1ppm) and reversible sensing characteristics (100% recovery) to 0.1ppm of H2S under high humidity (relative humidity 80%) at 175 °C. The effect of multi-valent transition metal ion doping into CuO on sensor reversibility is confirmed through the enhancement of recovery kinetics by doping 4 at.% of Ti- or Nb ions into CuO sensors. Mechanistic detailsof these excellent H2S sensing characteristics are also investigated by analyzing the redox reactions and the catalytic activity change of the Fe-doped CuO sensing materials. The selective and reversible detection of H2S using the Fe-doped CuO sensor suggested in this work opens a new possibility for halitosis self-monitoring.

THE POWDER OF Co64Nb30B6 OBTAINED BY MECHANICAL ALLOYING

This work aims to synthesize the alloy Co64Nb30B6 through mechanical alloying using a planetary ball mill. A disc rotation per minute and a ball/powder weight ratio of 300 rpm and 10:1 were used, with a milled time of 10 h, respectively. The characterization of the Co64Nb30B6 alloy was performed by X-ray diffraction (XRD), examined by scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDS), thermoanalytical techniques (TGA/DTA), vibrating sample magnetometer (VSM) and confirmed by Braunauer, Emmet e Teller (BET) method type IV isotherms with a hysteresis loop for mesoporous materials. The results indicated that the evolution of the amorphous phase in the Co64Nb30B6 composition through the mechanical alloying process exhibited good soft magnetic properties with the addition of the metalloid element B and its excellent unique ferromagnetic properties. Through thermoanalytical analysis (TGA/DTA), it was shown that at higher temperatures, Co and Nb ions are oxidized by the environment and, therefore, the mass can be slightly increased to 14.9% and a probable contribution of boron in evolution stability thermal and magnetic in the amorphous phase, respectively. This suggests that the newly developed high-performance amorphous alloy Co64Nb30B6 has great application potential.

A Near Dimensionally Invariable Electrode Material: Li8/7Ti2/7V4/7O2

Our group has reported that Li-excess V-based oxide with Nb ions, Li1.25Nb0.25V0.25O2, delivers a large reversible capacity of over 250 mA g-1 with V3+/V5+ two-electron redox reaction.[1] Recently, Li8/7Ti2/7V4/7O2 has been also synthesized and examined as high-capacity positive electrode materials with V cationic redox.[2] Nanosized Li8/7Ti2/7V4/7O2 was also synthesized by high-energy mechanical milling. Nanosized Li8/7Ti2/7V4/7O2 delivers a high reversible capacity of ~300 mA h g-1 with no capacity deterioration for 100 cycles, which originates from a near dimensionally invariable nature as high-capacity electrode materials. Moreover, Li8/7Ti2/7V4/7O2 is used for as positive electrode materials for all-solid-state batteries with argyrodite-type electrolyte, Li6PS5Cl. An all-solid-state cell with Li8/7Ti2/7V4/7O2 and Li6PS5Cl delivers a large reversible capacity of 300 mA h g-1 with excellent retention for 700 cycles. From these results, the importance of a near dimensionally invariable character is discussed in detail.[1] M. Nakajima and N. Yabuuchi, Chem. Mater., 29, 6927 (2017)[2] I. Konuma et al. and N. Yabuuchi, Nat. Mater., 22, 225 (2023)

Niobium doping effect on electrical and optical properties of ZnO nanorods produced by ultrasonic spray pyrolysis

Niobium metal doped ZnO nanorods were fabricated on a glass substrate using an ultrasonic spray pyrolysis system in two steps. The structural, morphological, and optical properties of the produced samples were investigated via an x-ray diffractometer (XRD), a field emission scanning electron microscopy (FE-SEM) combined with energy dispersive x-ray spectroscopy (EDX), and a spectrophotometer, respectively. The XRD patterns were indexed in the hexagonal (wurtzite) unit cell type for all the ZnO samples. In addition, according to the XRD peaks, the crystals grew in the c-axis (002) direction. The morphological features of the obtained thin films were examined. From the SEM micrographs, it was observed that ZnO thin films doped with Nb had a nanorod structure in the c-axis direction. The presence of Nb ions in the samples was proved via EDX analysis. The electrical conductivity values of the pristine and 10 % mol Nb-doped ZnO samples were 3.16 x 10−9 and 3.98 x 10−7 (ohm−1.cm−1) at 25 °C; and 7.08 x 10−7 and 5.01 x 10−5 (ohm−1.cm−1) at 300 °C, respectively. The optical transmittances of the samples were measured at wavelengths of 350–1000 nm. It was observed that the produced films had high optical transparency. The average optical transmittance value of the samples was 90 %.

New BaTi0.96Cu0.02X0.02O3 (X = V, Nb) Photocatalysts for Dyes Effluent Remediation: Broad Visible Light Response

The problem of industrial dyes depollution has pushed the scientific research community to identify novel photocatalysts with high performance. Herein, new photocatalysts composed of BaTiO3, BaTi0.96Cu0.04O3, BaTi0.96Cu0.02V0.02O3 and BaTi0.96Cu0.02Nb0.02O3 powders were prepared by solid-state reaction. The structural analysis of the samples confirmed the formation of the BaTiO3 structure. The splitting of (002) and (200) planes verified the formation of the tetragonal phase. The XRD peaks shifted, and the unit cell volume expansion verified the substitution of the Ti4+ site by Cu2+, V4+ and Nb5+ ions. The morphological measurements showed that the addition of (Cu, V) and (Cu, Nb) ions changes the particles’ morphology of BaTiO3, reducing its grains size. After the incorporation of (Cu, V) and (Cu, Nb) ions, the band gap of BaTiO3 was reduced from 3.2 to 2.84 and 2.72 eV, respectively. The modification of BaTiO3 by (Cu, Nb) ions induced superior photocatalytic properties for methyl green and methyl orange with degradation efficiencies of 97% and 94% during 60 and 90 min under sunlight irradiation, respectively. The total organic carbon results indicated that the BaTi0.96Cu0.02Nb0.02O3 catalyst has a high mineralization efficiency. In addition, it possesses a high stability during three cycles. The high photodegradation efficiency of Bi0.96La0.02Gd0.02FeO3 was related to the wide-ranging visible light absorption.

The Surface Modification of ZrO2 Film by Zr/Nb Ion Implantation and First-Principles Calculation

Zirconium dioxide (ZrO2) possesses numerous advantages such as high mechanical strength, a low friction coefficient, excellent optical properties, and an extended lifespan. Consequently, ZrO2 has a broad research foundation and practical significance in functional films and wear-resistant coatings. However, it suffers from brittleness and low ductility when used as a bio-coating material. In this study, a ZrO2 film was fabricated on Si (100) and titanium alloy substrates using a magnetron sputtering system. Subsequently, Zr and Nb ions were implanted into the film at varying doses, but with consistent energy levels. The analysis focused on the film’s microstructure, mechanical properties, hydrophilicity, and corrosion resistance. The results demonstrate a significant improvement in the hydrophilicity and corrosion resistance of the ZrO2 film following the implantation of Zr and Nb ions. First-principles calculations based on density functional theory (DFT) principles indicated that, with increasing doping concentrations of Zr and Nb in the ZrO2 model, the stability of the model increased gradually, thereby enhancing its corrosion resistance. The developed product has propelled rapid advancements in fields such as biomedical implants.

Features of the Phase Formation of Cr/Mn/Fe/Co/Ni/Cu Codoped Bismuth Niobate Pyrochlore

The phase formation process of Bi2Cr1/6Mn1/6Fe1/6Co1/6Ni1/6Cu1/6Nb2O9+Δ containing 3d-ions of transition elements in equimolar quantities was studied in a wide temperature range (400–1050 °C). The complex oxide crystallizes in the structural type of pyrochlore (sp. gr. Fd-3m:2, a = 10.4937(2) Å). The investigation of the multi-element pyrochlore phase formation process showed that the synthesis goes through a series of successive stages, during which the transition from Bi-rich to Bi-depleted compounds takes place. The predecessor of the pyrochlore phase is bismuth orthorhombic modification orthoniobate (α-BiNbO4) with an equimolar ratio of Bi(III)/Nb(V) ions. The pyrochlore phase is formed as a result of bismuth orthoniobate doping with transition element ions. The complex oxides Bi14CrO24, Bi25FeO40, BiNbO4, and Bi5Nb3O15 appeared as intermediate phases during the synthesis. The interaction between the initial oxide precursors is fixed at temperatures above 500 °C. The phase transition of α-Bi2O3 into β-Bi2O3 near 500 °C is observed. Varying the heat treatment duration at each synthesis step did not qualitatively change the phase composition of the sample but had an effect on the quantitative phase ratio. Phase-pure pyrochlore of the given composition by solid-phase synthesis method can be obtained at a temperature no lower than 1050 °C. Ceramics are characterized by low-porous dense microstructure with blurred outlines of grain boundaries.

Ion formation in thermionic-emission-assisted hot magnetron sputtering discharge

We report an abrupt Nb ion formation in a direct current hot magnetron sputtering discharge as a result of target temperature increase to a certain point (1900 K in our case). The effect is explained by a significant thermionic emission from the target surface, leading to an enhanced electron impact ionization in plasma volume. The phenomenon is especially pronounced for Nb (refractory metal), for which higher target temperatures can be reached. The volume density mapping is undertaken for Nb neutrals and ions (by laser-based spectroscopy), emphasizing the found effects.