Effect Of Ta Doping Research Articles

The thermodynamic properties of ZrCo hydrogen isotopes storage: The effect of Ta doping

ZrCo alloy exhibits distinct advantages in the storage of hydrogen and its isotopes. In this study, the phonon dispersion relation of ZrCo and ZrCoMx (M = H, D, T) is calculated. Subsequently, the thermodynamic properties of ZrCo and ZrCoMx compounds are investigated. Furthermore, an analysis is conducted on the temperature-dependent variations in the thermodynamic properties during hydrogen (deuterium, tritium) absorption reactions. Additionally, the impact of Ta doping (Zr0·875Ta0·125Co) on the thermodynamics of hydrogen storage (deuterium tritium) in ZrCo is discussed. The results indicate that H in the octahedral void leads to a higher thermodynamic value and a more stable system compared to H in the tetrahedral interstice. When ZrCo alloy store deuterium and tritium, there is an increase in ZPE, △H and △G of the system. At 300 K, the △H of ZrCo reacting with hydrogen, deuterium and tritium to form ZrCoM3 (M = H, D and T) are 85.94 kJ/mol, 90.09 kJ/mol and 92.16 kJ/mol, respectively. The ZPE and the △H of reaction are reduced upon Ta doping, thereby facilitating hydrogen (deuterium and tritium) circulating storage capabilities of alloy.

Effect of oxygen vacancies in Ta2O5-doped SnO2 ceramics on thermal conductivity and varistor characteristics

The effects of Ta doping on the thermal and electrical properties of SnO2 varistors were researched. The results showed that the thermal conductivity is 2.01 WK−1m−1, the nonlinearity coefficient is 43, and the leakage current density is 0.7 μA/cm2 when the Ta doping level reaches 0.2 mol%. According to the measurement results of the EPR, SEM/EDS, and XRD, the Ta dopant can reduce the oxygen vacancy concentration, which was generated during the sintering. The decline of the oxygen vacancy concentration reduces the phonon scattering, then the thermal conductivity of the varistors is improved. On the other hand, the reduction of the oxygen vacancy concentration elevates the barrier height, so the nonlinearity coefficient is improved and the leakage current density is declined.

High-performance solar-blind photodetectors based on Ta-doped ZnSnO3 single crystal thin films

High-quality Ta-doped ZnSnO3 single crystal thin films were grown on LiTaO3 substrates by pulsed laser deposition (PLD) method, and the effects of Ta doping on the lattice structure, surface morphology, electronic structure and photodetector performance of ZnSnO3 thin films are studied in detail. When the Ta doping content is 1 %, the [0001]-oriented ZnSnO3 thin film present the highest quality, which the optical band gap (3.75 eV), the smoothest surface roughness (0.83 nm), and the biggest carrier concentration (4.03 × 1019 cm−3). For the solar-blind photodetectors (PDs), based on these excellent characteristics, the 1 % Ta-doped ZnSnO3 PD exhibits large light-to-dark current ratio (>103), responsivity (21.37 A/W), detectivity ((3.63±0.71) ×1011 Jones) and external quantum efficiency (∼1.04× 104 %) under 254 nm UV light at an applied bias of 5 V. This study suggests that Ta doping can effectively improve the optoelectronic performance of ZnSnO3 PDs, laying the foundation for their application.

Tantalum-doped tin oxide thin films using hollow cathode gas flow sputtering technology

SnO2 and tantalum doped SnO2 (TTO) thin films were prepared using reactive hollow cathode gas flow sputtering (GFS) on glass substrates. An in-situ heating process under vacuum preceded the sputtering. The resistivity of the tin oxide films was reduced to a remarkable low of 2.02 × 10−3 Ω cm, with a carrier concentration of 2.55 × 1020 cm−3 and a mobility of 12.11 cm2V−1s−1. As the substrate temperature increased, the film resistivity decreased. Notably, at a substrate temperature of 270 °C, the effect of Ta doping on the film resistivity and carrier concentration was significantly stronger compared to higher temperatures. Elevating the substrate temperature and Ta doping resulted in a lower refractive index (n). This effect was consistently strong at higher temperatures, attributed to the higher film-free carrier concentration (4.54 × 1020 cm−3) compared to lower temperatures (2.35 × 1020 cm−3). The film's structure was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and atomic force microscope (AFM). The preferred direction of film growth was discussed. The successful and reproducible fabrication of tin oxide films underscores the advantages of gas flow sputtering (GFS) technology. GFS offers stable operating conditions across various oxygen flow levels without requiring target oxidization control, as is required in magnetron sputtering when managing gas status and film quality.

Enhanced conduction and phase transition reversibility of O3-type NaNi1/3Fe1/3Mn1/3O2 cathode via Ta doping for high-performance sodium-ion battery

The complex phase transition that occurs during the charge/discharge process leads to poor rate and cycling performance of O3-type NaNi1/3Fe1/3Mn1/3O2 (NFM). In this paper, we propose a novel modification strategy for NFM that involves doping its transition metal layer with Ta5+ ions of higher valence and stronger binding energy to oxygen than the transition metal. The effects of Ta doping on the crystal structure, transition metal valence states, activation barrier energy, and bandgap of NFM were investigated, and the modification mechanisms were explored. The capacity retention of NFM-Ta0.01 (80.15 %) was higher than that of NFM (35.44 %) after 200 cycles. This improvement is attributable to the strong bonding energy effect of TaO, which stabilized the crystal structure of NFM, delayed the transition of the material from the hexagonal O3 phase to the hexagonal P3 phase beyond 3.2 V, and enhanced the phase transition reversibility of NFM. Moreover, Ta introduction increased the sodium layer spacing and reduced the Na+ activation barrier energy of the material from 0.773 to 0.692 eV, and the band gap from 1.7416 to 1.5951 eV, leading to a significant improvement in electronic conductivity. Owing to the synergistic effect of these factors, the discharge capacity of NFM-Ta0.01 at a 5C rate (100.6 mAh g−1) was considerably higher than that of NFM (79.3 mAh g−1). This work presents a proven modification strategy for achieving structurally stable and improved rate performance for NFM.

Solution-processed Ta doped heterojunction structure ITO/ZTO thin film and application for high electrical and stable TFTs

Here, the solution-processed heterojunction structure Ta doped ZnSnO/InSnO (TaZTO/ITO) semiconductor thin film and TFTs have been fabricated on atomic layer deposition deposited Al2O3. The effects of Ta doping on the structure, thickness, thermal decomposition, contact angle, surface morphology, transmittance, chemical bond states and electrical characteristics of ZTO back-channel layer have been investigated by glancing angle incidence X-ray diffraction (GIXRD), cross sectional transmission electron microscopy (TEM), thermogravimetric analysis (TGA), contact angle meter, atomic force microscopy spectrometer (AFM), spectrometer, X-ray photoelectron spectroscopy (XPS) and semiconductor characterization system, respectively. Moreover, the influence of Ta doping in the electrical property and stability of heterojunction structure TaZTO/ITO TFTs has been also analyzed. A proper Ta concentration in the TaZTO back-channel layer can realize stable, dense film and good electrical and stable heterojunction structure TFTs due to inhibiting the generation of defects originated from oxygen vacancies. The heterojunction structure TaZTO/ITO TFTs with 1%mol Ta doping shows the best electrical property with the mobility (μ) of 4.72 cm2/Vs and the best stability with the threshold voltage shift of 0.95 V under positive bias stress. The strategy has coordinated the relationship between μ and stability effectively, and provide a new way for the development of oxide TFTs technology in the future.

Fabrication of Lead-Free Bismuth Based Electroceramic Compositions for High-Energy Storage Density Applications in Electroceramic Capacitors

Lead-based electro-ceramic compositions are excellent energy storage materials used for high-energy storage density applications in dielectric ceramic capacitors. However, these materials have lead contents in their compositions, making them toxic, with a negative impact on human health and the environment. For this reason, we synthesized a lead-free bismuth-based electro-ceramic perovskite, 0.80(0.92Bi1/5Na1/5TiO3-0.08BaTiO3)-0.20(Na0.73Bi0.09NbO3−xTa2O5), abbreviated (BNT-BT-NBN1−xTx), from mixed oxides with doping of tantalum (Ta) at different concentrations, using a conventional solid-state reaction method. The effects of Ta doping on the phase evolution, microstructure development, and energy storage applications were investigated. Detailed powder X-ray diffraction analysis revealed a pure perovskite phase with Ta doping at ≤0.05. Furthermore, it was observed that excessive addition of Ta has been resulted in secondary phase generation. Scanning electron microscopy validated the development of dense microstructures with a reduced grain size for the Ta concentration of ≤0.01. Electrochemical analysis revealed a maximum polarization (Pm) of ~22 µC/cm2 and a recoverable energy density of 1.57 J/cm3 with 80% efficiency for Ta doping at 0.05 with an applied field of 175 kV/cm. These results demonstrate the development of enhanced ferroelectric characteristics in an as-synthesized electro-ceramic perovskite for high-energy storage density applications in electro-ceramic capacitors.

Effect of Ta Doping on the Microstructure and Thermoelectric Properties of Bi2O2Se

In this study, Bi2−xTaxO2Se (x = 0, 0.02, 0.04, 0.06, and 0.08) ceramics were prepared using a synthesis method combining high-energy ball milling and cold pressing. Furthermore, the effects of tantalum (Ta) doping on the microstructure and thermoelectric properties of Bi2O2Se were systematically investigated. The results indicate that Ta doping effectively improves the carrier concentration and mobility, thus increasing the electrical conductivity from 8.75 S cm−1 to 39.03 S cm−1 at 323 K. Consequently, the power factor is improved, reaching a maximum value of 124 μW m−1 K−2 for the Bi1.92Ta0.08O2Se sample at 773 K. Moreover, the thermal conductivity of Bi1.96Ta0.04O2Se is reduced to 0.50 Wm−1 K−1. Finally, the maximum dimensionless figure of merit (ZT) value of the Bi1.94Ta0.06O2Se sample reached 0.18, which was 64% higher than that of Bi2O2Se (0.11). These results indicate that Ta doping and high-energy ball milling can optimize the electrical and thermal properties and thus improve the thermoelectric properties of ceramics.

Gas adsorption performance of Ta doped MoSe2 based on first principles

In this paper, the effect of Ta doping on the gas sensitivity of two-dimensional MoSe2 is studied by first-principles calculation, it is found that Ta atoms can be stably doped in Se vacancies on two-dimensional MoSe2 supercells. The adsorption properties of four toxic gases CO, H2S, SO2 and HCN on Ta doped MoSe2 were also studied. Four initial adsorption sites were selected before and after doping to explore the best adsorption sites for the four gases. The adsorption energy, transfer charge, adsorption distance, recovery time and other parameters were calculated and the adsorption type and sensitive gas were determined. The results show that Ta doping improves the adsorption capacity of two-dimensional MoSe2 to gas molecules, the electron interaction between gas molecules and substrate surface is enhanced. Thus, the gas sensitivity of two-dimensional MoSe2 is improved.

Thermoelectric Properties of Ta-doped Zr0.6-xTi0.4TaxNiSn n-type Half-Heusler Materials

Half-Heusler (HH) thermoelectric materials are promising for mid- to high-temperature applications, and MNiSn (M = Ti, Zr, Hf) is a representative n-type HH alloy. In general, the M sites are mixed with isoelectronic elements Ti, Zr, and Hf, to lower the lattice thermal conductivity, and the Sn sites are doped with Sb to adjust the electron concentration. However, Hf is a rare element in earth’s crust, and the volatility of Sb makes it difficult to maintain the initial Sb amount during material synthesis. In this study, as an alternative, Ta was added in the M sites along with the host elements Ti and Zr to produce Hf-free Zr0.6-xTi0.4TaxNiSn alloys (0 ≤ x ≤ 0.04), and the effects of Ta doping on the thermoelectric properties were analyzed. The electrical conductivity of Zr0.6-xTi0.4TaxNiSn increased with Ta content, and the electron concentration increased almost linearly, reaching 5.6 × 1020 cm -3 at x = 0.04. By adding Ta, the maximum power factor also increased by approximately 17% to 3.94 × 10-3 W m-1K-2 at x = 0.02. The lowest lattice thermal conductivity (κlat) was observed at x = 0.02, reaching approximately 1.9 W m-1K-1 at 723 K, but overall, a dramatic decrease in κlat was not observed with Ta doping in Zr0.6-xTi0.4TaxNiSn. This is probably due to the existing effect of Zr/Ti mixing at the M sites, which enhances phonon scattering. A maximum figure of merit (zT) of 0.91 was obtained in Zr0.58Ti0.4Ta0.02NiSn at 873 K, which is a high value for ZrNiSn-based Hf-free HH materials. In conclusion, Ta doping is a viable method to replace Sb doping in ZrNiSn-based HH alloys.

Improving the glass-forming ability and plasticity of a TiCu-based bulk metallic glass composite by minor Ta doping

The effects of Ta doping on the glass-forming ability and the mechanical behavior of a B2 phase formable Ti-Cu-Ni-Zr bulk metallic glass composite have been investigated. The doped Ta causes the morphology change of in-situ precipitated B2 phase, from patch-like shapes to homogeneously distributed spherical shapes. The solid-dissolved Ta in the matrix improves the glass-forming ability, suppressing the precipitation of unexpected brittle Ti2Cu phase. Doping Ta with 2 at% generates a homogeneously distributed spherical B2 phase without other crystalline phases, and shows the best mechanical property, including a fracture strength of 1804 MPa and plastic strain of 3.2%. The precipitated B2 phase could hinder the rapid propagation of the main shear band, causing branching, stopping and multiplication of it. The multiplied shear bands accommodate the improved plasticity. The present study provides an important insight into tailoring the phase formation and plasticity of in-situ bulk metallic glass composites via minor alloying.

Effect of Ta doping on the properties of β-Ga2O3 heteroepitaxial films prepared on KTaO3(100) substrates

β-Ga2O3 single-crystal films with Ta doping concentrations of 0–1.4 at.% were prepared on KTaO3(100) substrates by metal–organic chemical vapor deposition. Herein, we investigated the influence of Ta doping concentration on the structural and electrical properties of the films. X-ray diffraction results showed that the crystalline quality of the films slightly deteriorated with the increase of doping concentration, and the epitaxial relationship was identified as β-Ga2O3(100)//KTaO3(100) with β-Ga2O3[001]//KTaO3 . The chemical composition and surface morphology of the films were characterized using X-ray photoelectron spectroscopy, and atomic force microscopy, respectively. Hall effect measurement determined that the resistivity and carrier concentration of the films were in the range of 14.8 ~ 5.01 × 103 Ω cm and 3.85 × 1016 ~ 3.97 × 1018 cm−3, respectively, whereas the film with 0.2 at.% Ta doping concentration presented the highest Hall mobility of 4.56 cm2 V−1 s−1.

Effect of Ta-Doping on LLZO Garnet Solid Electrolytes for Solid State Batteries Applications

Compared with conventional lithium-ion batteries, all-solid-state lithium batteries based on inorganic solid electrolytes have shown advantages over conventional lithium-ion batteries, such as explosion resulted from flammable liquid electrolyte, low energy density. Therefore, solid state batteries are considered a promising candidate with better safety features. Among oxide electrolytes, garnet-type LLZO electrolyte exhibits high ionic conductivity and electrochemical potential window. However, it is reported that there are difficulties to prepare Li7La3Zr2O12(LLZO) pellets with high relative density. In this study, LLZO containing Ta ion as a dopant is expected to show more Li vacant sites to enhance its conductivity and density. The LLZO powder calcined at 1200 °C with a cubic phase was confirmed by X-ray diffraction (XRD). The sintered Ta-LLZO pellets exhibit relative density of 88.45% and ionic conductivity of 1.04*10-4 S/cm at room temperature and good electrochemical stability with Li metal. After assembling LiCoO2/Ta-LLZO/Li battery, the discharge capacity reached 105.2 mAh/g for the first cycle.

Structural and electrical properties of lead-free Na0.685K0.315Nb1–yTayO3 (0 ≤ y ≤ 0.05) ceramics

Piezoceramic Na0.685K0.315Nb1–yTayO3 (NKNT) (where y ≤ 0.05) samples were prepared via a solid-state reaction using double sintering. The effects of Ta-doping on the phase structure and electrical properties of the NKNT ceramics were investigated. The temperature dependence of the dielectric constant, loss tangent, and dielectric conductivity of the prepared samples was measured from RT to 500 °C at 10 kHz and 1 MHz. High temperature X-ray diffraction (HT- XRD) measurements were carried out on the prepared samples between RT and ~200 °C, 200 and 380 °C, 380 and 460 °C, and above 460 °C, which showed monoclinic, tetragonal, tetragonal, and cubic phases, respectively. In Na0.685K0.315Nb1–yTayO3, all the transition peaks were observed to gradually shift towards lower temperatures upon increasing the Ta concentration at y ≤ 0.05 in the temperature range from RT to 500 °C.

Effects of Ta doping and irradiation with He+ ions on photoluminescence of MgAl2O4 spinel ceramics

Photoluminescence (PL) properties of pristine and Ta-doped MgAl2O4 spinel ceramics prepared via spark plasma sintering technique and irradiated with He+ ions were studied. The results indicate strong influence of the grain boundaries on PL spectra. Ta doping promotes the formation of O and Al vacancies at the grain boundaries leading to an increased number density of F+ centres. The ionised irradiation forms antisites preferentially at the grain boundaries, which inhibit excitonic PL and exciton energy transfer while do not affect proper PL of lattice defects. A weak PL excitation band at 7.25 ± 0.25 eV may belong to excitons localised near bulk antisites. In the Ta-doped ceramics, the electronic transitions between 5.75 eV and 7.0 eV belong to an intermediate state situated at the grain boundaries and structurally linked to Ta, which readily transfers energy to F and F+ centres; it was assigned to the nucleated Mg4Ta2O9 phase.

Magnetic Properties, Phase Transition Temperatures, Intergranular Exchange Interactions and Microstructure of Ta-Doped Nd-Ce-Fe-B Nano ribbons

The effects of Ta doping on the magnetic properties, temperature stabilities, phase constituents, intergranular exchange interactions, and microstructures of (Nd0.8Ce0.2)13.5Fe80.5−xTaxB6 (x = 0–1.5) nanoribbons are investigated in this paper. It is found that Ta doping increased the coercivity of the alloys, while the remanence remained nearly unchanged. The temperature stability of the alloys improved significantly as the absolute value of temperature coefficient of coercivity β enhanced from 0.48%/K for Ta-free alloy to 0.38%/K for the alloys with 0.3–1.5 at.% Ta addition. The lattice constants (a, c), unit cell volume, and phase transition temperatures (Tsr, TC) of the alloys changed by adding Ta into the alloys. Comprehensive best magnetic properties of Hcj = 16.0 kOe, Br = 7.65 kG, and (BH)max = 12.60 MGOe are obtained in (Nd0.8Ce0.2)13.5Fe79.6Ta0.9B6 ribbon. The improvement in magnetic properties is mainly attributed to refined and uniform microstructure of the Ta-doped alloys.

Effects of Tantalum Doping on Electrical Characteristics of High-Mobility Zinc Oxynitride Thin-Film Transistors

The effects of Ta doping on the electrical characteristics of high-mobility zinc oxynitride (ZnON) thin-film transistors (TFTs) are investigated. With increasing Ta content ( ${C}_{\text {Ta}}$ ) in ZnON, the threshold voltage ( ${V}_{\text {th}}$ ) of Ta-doped ZnON TFTs increases from negative to positive values, and the subthreshold swing ( SS ) becomes smaller, leading to significantly improved switching characteristics as compared with those for undoped ZnON TFTs. Furthermore, Ta doping effectively suppresses the negative ${V}_{\text {th}}$ shift with time. However, excess Ta doping is found to degrade the field-effect mobility ( $\mu _{\text {fe}}$ ). To elucidate the mechanism behind these results, the bonding states of Ta in ZnON are analyzed using X-ray photoelectron spectroscopy. Through the optimization of ${C}_{\text {Ta}}$ , a high $\mu _{\text {fe}}$ of 49 cm2/Vs is achieved, together with a less negative ${V}_{\text {th}}$ , a smaller SS , and a better long-term ${V}_{\text {th}}$ stability. In addition, the annealing temperature dependence of the properties of Ta-doped ZnON TFTs is investigated. When the annealing temperature is increased to 250 °C, a considerable decrease in the on-current is observed, which is attributed to nitrogen desorption from ZnON, as confirmed by thermal desorption spectroscopy.

Effect of Ta-doping on functional properties of K0.51Na0.49NbO3

K.51Na.49Nb1−xTaxO3 (0.05 ≤ x ≤ 0.30) ceramics were prepared using a conventional solid-state sintering route. XRD of this system showed the crystal structure shifted gradually from orthorhombic to tetragonal phase. SEM images revealed that grain morphology remained the same in all compounds. At room temperature, relative permittivity has its highest value at x = 0.20, while tanδ remained less than 5% for all compositions at 100 kHz. For x > 0.05, double peaks were observed in relative permittivity versus temperature data. Saturated and symmetrical ferroelectric loops were obtained at an applied electric field of 60 kV cm−1. Remanent polarization (Pr) decreased with increasing x, however coercive field (Ec) was almost independent of composition. Isovalent doping of Ta5+ () marginally improved d33 at low concentrations (i.e., maximum d33 = 135pC/N, at x = 0.10). However, the broadening of peaks observed in dielectric data due to inhomogeneity may open new applications in microwave dielectrics or relaxor type applications in smart ceramics.

Enhanced electrocatalytic activity and CO2 tolerant Bi0.5Sr0.5Fe1-Ta O3- as cobalt-free cathode for intermediate-temperature solid oxide fuel cells

Abstract One of the significant motivations in developing intermediate-temperature solid oxide fuel cells (IT-SOFCs) is to design cobalt-free cathodes with high electrocatalytic activity and CO 2 tolerance ability. In this work, iron-based perovskite materials Bi 0.5 Sr 0.5 Fe 1- x Ta x O 3- δ are investigated as potential cathodes for IT-SOFCs. The effects of Ta doping on crystal structure, thermal expansion coefficients and electrocatalytic activities are systematically evaluated. Among the Ta-doped oxides, Bi 0.5 Sr 0.5 Fe 0.9 Ta 0.1 O 3- δ exhibits the highest electrochemical performance with the lowest polarization resistance ( R p ) of 0.124 Ω cm 2 at 700 °C in air. The peak power density of the single cell with Bi 0.5 Sr 0.5 Fe 0.9 Ta 0.1 O 3- δ cathode reaches 1.36 W cm −2 at 700 °C. Compared to Bi 0.5 Sr 0.5 FeO 3- δ , the improved CO 2 tolerance of Ta-doped oxides can be attributed to the high acidity of Ta 5+ cations and the increased average metal bond energy (ABE) within the material. Further study proves that the adsorption-dissociation process of molecular oxygen is the limiting step for oxygen reduction reaction (ORR) on Bi 0.5 Sr 0.5 Fe 0.9 Ta 0.1 O 3- δ cathode.

Structural, photoelectrical and photoluminescence properties of Ta-doped SnO2 monocrystal films grown on MgF2 (110) substrates

Epitaxial Ta-doped SnO2 films with Ta concentrations from 0 to 8 at.% have been deposited on MgF2 (110) substrates by the metal-organic chemical vapor deposition (MOCVD) method. The effects of Ta doping on the structural, photoelectrical and photoluminescence (PL) properties of the obtained films were studied in detail. The results showed that the single crystal rutile SnO2 films were obtained and the heteroepitaxial relationship was SnO2 (110) || MgF2 (110) with SnO2 [001] || MgF2 [001]. The highest Hall mobility of 74.2 cm2 V−1 s−1 was achieved for the 5 at.% Ta-doped SnO2 film and the minimum resistivity as low as 2.5 × 10−4 Ω cm was obtained at 6 at.% of Ta-doping. In the visible region, all the obtained films had average transmittances exceeding 87%. As the Ta concentration increased from 0 to 8 at.%, the optical band gap of the films rose from 3.89 to 4.32 eV. The room temperature PL spectra of Ta-doped SnO2 films showed intense green emission, weak violet and yellow emissions. The corresponding PL mechanisms were discussed.