Effect Of Ti-doping Research Articles

Ultrahigh Power Factor of Sputtered Nanocrystalline N-Type Bi2Te3 Thin Film via Vacancy Defect Modulation and Ti Additives.

Magnetron-sputtered thermoelectric thin films have the potential for reproducibility and scalability. However, lattice mismatch during sputtering can lead to increased defects in the epitaxial layer, which poses a significant challenge to improving their thermoelectric performance. In this work, nanocrystalline n-type Bi2Te3 thin films with an average grain size of ≈110nm are prepared using high-temperature sputtering and post-annealing. Herein, it is demonstrated that high-temperature treatment exacerbates Te evaporation, creating Te vacancies and electron-like effects. Annealing improves crystallinity, increases grain size, and reduces defects, which significantly increases carrier mobility. Furthermore, the pre-deposited Ti additives are ionized at high temperatures and partially diffused into Bi2Te3, resulting in a Ti doping effect that increases the carrier concentration. Overall, the 1µm thick n-type Bi2Te3 thin film exhibits a room temperature resistivity as low as 3.56 × 10-6 Ω∙m. Notably, a 5µm thick Bi2Te3 thin film achieves a record power factor of 6.66mWmK-2 at room temperature, which is the highest value reported to date for n-type Bi2Te3 thin films using magnetron sputtering. This work demonstrates the potential for large-scale of high-quality Bi2Te3-based thin films and devices for room-temperature TE applications.

Fine microstructure tuning via titanium doping in ultrahigh-nickel cathodes to enhance the reversibility of the H2/H3 phase transition and reduce micro-cracks

Due to increasing demands for electric vehicles with high energy density and low costs, ultrahigh-nickel LiNixCoyM1-x-yO2 (x≥0.9, M=Mn/Al) cathodes have attracted increasing attention. However, the preparation of ultrahigh-nickel cathode materials with satisfactory cycle stability remains challenging because of their structural and interface instability. In this study, the effects of Ti-doping on the performance of Li(Ni0.95Co0.05Mn0.01)1-xTixO2 (NCMT) were systematically investigated. Titanium doping enlarged the spacing between the lithium layers and increased the c/a ratio, thereby improving the structural stability of the cathode materials. In situ X-ray diffraction showed that the anisotropy change was significantly reduced after Ti doping. The reversibility of the H2/H3 transition was enhanced and the initiation of microcracks caused by the anisotropy change was restrained. Moreover, the emission structure induced by Ti doping effectively mitigated stress accumulation and restrained the propagation of microcracks. Therefore, the optimal NCMT cathode (with 1 mol.% of Ti doping) demonstrated an outstanding rate performance and cycle stability without capacity loss. Compared with the retentions of the pristine cathode without Ti doping (89.73 % in a coin cell and 51.16 % in a pouch cell), the NCMT cathode with 1 mol.% Ti maintained a capacity retention of 92.45 % in a coin cell after 100 cycles at 0.5 C and 70.49 % in a pouch cell after 1000 cycles at 1 C. This study provides an effective solution to realize stable cyclability without capacity loss in ultrahigh-nickel cathode materials.

Study on the effects of VO and Hi on the absorption spectrum and conductivity of Ti doped β-Ga2O3

β-Ga2O3 has many excellent properties, but poor electrical conductivity limits its application in optoelectronic devices. At present, some progress has been made in the study of Ti doping on the photoelectric properties of β-Ga2O3. However, few studies on the effects of Ti doping and VO-Hi co-existence on photoelectric properties of β-Ga2O3. Defects (VO) and unintentional impurities (Hi) will inevitably exist during the preparation of β-Ga2O3. Given these problems, the effects of Ti doping and VO-Hi co-existence on photoelectric properties of β-Ga2O3 were studied using first-principles GGA+U method. The electronic structure, dielectric function, absorption spectrum, effective mass, mobility, and conductivity of the system were calculated and analyzed. The results indicate that with the increase of Ti doping concentration, the bandgap of the Ti doped β-Ga2O3 system gradually narrows. Ti doping causes a red shift in the peak of the absorption spectrum and effectively improves the conductivity of the system. The O vacancy reduces the conductivity of the system, while the interstitial H increases the conductivity of the system. Thus, Ti-doped β-Ga2O3 material is helpful for preparing new optoelectronic devices.

Effect of Ti Doping on the Microstructure and Properties of SiCp/Al Composites by Pressureless Infiltration.

The effects of Ti doping on the microstructure and properties of SiCp/Al composites fabricated by pressureless infiltration were comprehensively investigated using first-principles calculations and experimental analyses. First-principles calculations revealed that the interface wetting and bonding strength in an Al/SiC system could be significantly enhanced by Ti doping. Subsequently, the Ti element was incorporated into SiC preforms in the form of TiO2 and TiC to verify the influence of Ti doping on the pressureless infiltration performance of SiCp/Al composites. The experimental results demonstrated that the pressureless infiltration of molten Al into SiC preforms was promoted by adding TiC or TiO2 due to the improved wettability. However, incorporating TiO2 leads to the growth of AlN whiskers under a N2 atmosphere, thereby hindering the complete densification of the composites. On the other hand, TiC doping can improve wettability and interface strength without deleterious reactions. As a consequence, the TiC-doped SiCp/Al composites exhibited excellent properties, including a high relative density of 99.4%, a bending strength of 287 ± 18 MPa, and a thermal conductivity of 142 W·m-1·K-1.

Achieving High Rate and Long Cycle Performance of Na2FePO4F Cathode Through Co-Modification of Ti Doping and Carbon Coating.

Layered Na2FePO4F (NFPF) cathode material has received widespread attention due to its green nontoxicity, abundant raw materials, and low cost. However, its poor inherent electronic conductivity and sluggish sodium ion transportation seriously impede its capacity delivery and cycling stability. In this work, NFPF by Ti doping and conformal carbon layer coating via solid-state reaction is modified. The results of experimental study and density functional theory calculations reveal that Ti doping enhances intrinsic conductivity, accelerates Na-ion transport, and generates more Na-ion storage sites, and pyrolytic carbon from polyvinylpyrrolidone (PVP) uniformly coated on the NFPF surface improves the surface/interface conductivity and suppresses the side reactions. Under the combined effect of Ti doping and carbon coating, the optimized NFPF (marked as 5T-NF@C) exhibits excellent electrochemical performance, with a high capacity of 108.4mAhg-1 at 0.2C, a considerable capacity of 80.0mAhg-1 even at high current density of 10C, and a high capacity retention rate of 81.8% after 2000 cycles at 10C. When assembled into a full cell with a hard carbon anode, 5T-NF@C also show good applicability. This work indicates that co-modification of Ti doping and carbon coating makes NFPF achieve high rate and long cycle performance for sodium-ion batteries.

The Effect of Ti Doping on the Thermoelectric Performance of Bi2Te3 and Its Chemical Stability

The Effect of Ti Doping on the Thermoelectric Performance of Bi2Te3 and Its Chemical Stability

Ti-Doping in Silica-Supported PtZn Propane Dehydrogenation Catalysts: From Improved Stability to the Nature of the Pt-Ti Interaction.

Propane dehydrogenation is an important industrial reaction to access propene, the world's second most used polymer precursor. Catalysts for this transformation are required to be long living at high temperature and robust toward harsh oxidative regeneration conditions. In this work, combining surface organometallic chemistry and thermolytic molecular precursor approach, we prepared well-defined silica-supported Pt and alloyed PtZn materials to investigate the effect of Ti-doping on catalytic performances. Chemisorption experiments and density functional calculations reveal a significant change in the electronic structure of the nanoparticles (NPs) due to the Ti-doping. Evaluation of the resulting materials PtZn/SiO2 and PtZnTi/SiO2 during long deactivation phases reveal a stabilizing effect of Ti in PtZnTi/SiO2 with a kd of 0.015 h-1 compared to PtZn/SiO2 with a kd of 0.022 h-1 over 108 h on stream. Such a stabilizing effect is also present during a second deactivation phase after applying a regeneration protocol to the materials under O2 and H2 at high temperatures. A combined scanning transmission electron microscopy, in situ X-ray absorption spectroscopy, electron paramagnetic resonance, and density functional theory study reveals that this effect is related to a sintering prevention of the alloyed PtZn NPs in PtZnTi/SiO2 due to a strong interaction of the NPs with Ti sites. However, in contrast to classical strong metal-support interaction, we show that the coverage of the Pt NPs with TiOx species is not needed to explain the changes in adsorption and reactivity properties. Indeed, the interaction of the Pt NPs with TiIII sites is enough to decrease CO adsorption and to induce a red-shift of the CO band because of electron transfer from the TiIII sites to Pt0.

Inductive effect of Ti-doping in Fe2O3 enhances the photoelectrochemical water oxidation

Inductive effect of Ti-doping in Fe2O3 enhances the photoelectrochemical water oxidation

Effects of Ti Doping on the Electrical Properties and Gate-Bias Stability of Amorphous Zinc–Tin–Oxide Thin-Film Transistors

Multicationic oxide semiconductors are receiving considerable interest in electronic and optoelectronic devices owing to their tunability of physical properties by the cation compositions. Here, we investigated the effects of Ti doping on the electrical properties and gate-bias stability of amorphous zinc–tin–oxide (a-ZnSnO, Zn/Sn = 7:3) thin-film transistors (TFTs) using a cosputtering process. Particularly, by using cosputtering, controllable doping of Ti in a-ZnSnO films was possible in the range of 0.87–3.87 atom %. From various electrical analyses, it was found that the key metrics of Ti-doped ZnSnO (TiZnSnO) TFTs, such as field-effect mobility and gate-bias stability, were highly dependent on the Ti concentration, showing a mobility–stability tradeoff. Based on X-ray photoelectron spectroscopy analysis, the mobility–stability tradeoff is ascribed to the suppression of oxygen vacancy formation by Ti doping. Considering the overall electrical performance and stability of TiZnSnO TFTs, which were processed at 450 °C, the optimal Ti concentration was determined as ∼1.14 atom % with Zn, Sn, and O concentrations of 15.87, 22.92, and 60.07 atom %, respectively. The device exhibited a field-effect mobility of 8.2 cm2 V–1 s–1, a subthreshold slope of 0.208 V decade–1, an on/off ratio of 3.38 × 108, a hysteresis of 2.8 V, and a threshold voltage shift of +5.61 and −2.24 V under positive- and negative-bias stresses, respectively.

Magnetic optimization and regulation mechanism of La2CoMnO6 double-perovskite ceramics by Ti-doping at Mn-site

This work focuses on the magnetic optimization of La2CoMnO6 (LCMO) double-perovskite ceramics by Ti-doping at Mn-site. LCMO ceramics with different Ti-doping contents (LCMTxO, x = 0.1–0.4) were prepared by plasma activated sintering, and the effect of Ti-doping on the structural and magnetic properties of the ceramics is studied systematically. All the ceramics exhibit dense structure and small grain size, with a monoclinic P21/n crystalline structure. With the increasing of Ti-doping content, the proportions of Co2+ and Mn4+ in the LCMTxO ceramics change accordingly, reaching the highest values at x = 0.1. Since the Co2+-O-Mn4+ ferromagnetic super-exchange is the dominant factor affecting the magnetic properties of the LCMTxO ceramics, it is reasonable that a high saturation magnetization (Ms = 4.58μB/f.u) is obtained for the LCMT0.1O ceramic. The effect of Ti-doping on the orbital structure and magnetic regulation of the LCMTxO double-perovskite ceramics is further investigated by the first-principle calculation. It is found that the magnetic moments of Co and Mn ions will increase by the appropriate addition of Ti, which makes most Co ions exist in the form of Co2+, underpinning the La2Co2+Mn4+O6 ferromagnetic state and improving the magnetic properties.

Durability and rejuvenation of electrochromic tungsten oxide thin films in LiClO4–propylene carbonate viscous electrolyte: Effect of Ti doping of the film and polyethylene oxide addition to the electrolyte

Tungsten oxide and titanium doped tungsten oxide thin films, deposited by sputtering, were immersed in a viscous electrolyte comprised of LiClO4 in propylene carbonate and 2.0 wt% of polyethylene oxide (PEO). Electrochromic properties of the films were investigated by electrochemical techniques and in situ transmittance measurements. Cyclic voltammetry data were taken in the voltage ranges 2.0–4.0 and 1.5–4.0 V vs Li/Li+ for up to 500 cycles. A potentiostatic rejuvenation treatment was then performed on the degraded electrochromic films, at 6.0 V for 20 h, which was subsequently followed by another cyclic voltammetry measurement. Titanium incorporation into tungsten oxide resulted in a small cyclic stability improvement in the 2.0–4.0-V range, whereas less pronounced effects were observed for cycling in the 1.5–4.0-V range. Combining the results of the present study with our previous work, we are able to assess the relative merits of titanium incorporation and PEO addition to the electrolyte for the durability of electrochromic tungsten oxide thin films. Titanium addition was found advantageous for electrochemical durability in the 2.0–4.0-V range, but no clear benefits of PEO in the electrolyte were seen. On the other hand, in the wider 1.5–4.0-V range, tungsten oxide exhibited better durability than titanium-containing films, and this was especially so after rejuvenation in the PEO-containing electrolyte.

Structural and magnetic properties of Ti-substituted La0.6Ba0.4Mn1-xTixO3-δ (0.02 ≤ x ≤ 0.08) perovskite manganites: Appearance of the Griffiths phase

We have investigated the effects of Ti-doping at the Mn-site of La0.6Ba0.4Mn1–xTixO3–δ (0.02 ≤ x ≤ 0.08) manganites produced via an auto-combustion technique on the structural and magnetic behavior. All of the compositions crystallize into a cubic structure with Pm3‾m space group as confirmed using Rietveld analysis of the X-ray diffraction data. Unit cell lattice parameter ‘a’ and volume ‘V’ increase upon increasing the doping concentration, which revealed that the larger Ti-ions substitute the smaller Mn-ions in the lattice. Temperature-dependent magnetization measurements revealed that all of the compositions undergo a paramagnetic to ferromagnetic transition at the Curie-temperature (TC). The TC decreases non-linearly from 309 to 212 K as the concentration of Ti-ions increases from x = 0.02 to 0.08. An abnormal behavior in the experimental effective paramagnetic moment was observed in La0.6Ba0.4Mn1–xTixO3–δ (0.02 ≤ x ≤ 0.08), which increases with the substitution of magnetic Mn-ions by Ti-ions. The experimental paramagnetic moment increases non-linearly from 6.10 to 6.52 μB. The downturn deviation in the inverse susceptibility from Curie–Weiss law for the sample with x = 0.08 revealed the appearance of a Griffiths phase. The singularity of the dc inverse susceptibility in the Griffiths phase region provided the numerical values of the Griffiths temperature (TG), critical temperature for random ferromagnet (TCR), and critical exponent (λGP) to be 310 K, 247.7 K, and 0.95(1), respectively. In the low temperature region, the larger value of the experimental saturation moment compared to the corresponding theoretical values observed for the La0.6Ba0.4Mn1–xTixO3–δ manganites indicates the possibility of spin-orbit coupling.

(In)Coherent-bond-networks in Ni-rich layered oxides for durable lithium-ion batteries

An intriguing “coherent-bond-network” effect is suggested here for mitigating anisotropic lattice variations inducing micro-cracks, for durable Ni-rich layered cathodes based on Li[Ni10/12Co1/12Mn1/12]O2 (NCM) and Li[Ni10/12Co1/12Ti1/12]O2 (NCT) oxide models in lithium-ion batteries (LIBs). Upon charging, the c and a lattice strains for NCT are lower than those for NCM, implying that mechanical failures are mitigated in the former. Considering that Ni ions are a major component in compensating for the charge imbalance caused by Li deintercalation, the Ni–O bond populations in the deeply charged state reveal a uniform bond network in NCT, relative to the conventional Ni-rich cathode with NiO6 distortion. For deeper insights, the O–O edge populations are calculated for the two oxide models, and the discretized values over the entire crystal framework are observed for NCM, whereas delocalization is shown in NCT. These results underpin the Ti-induced “coherent-bond-network” that smoothly connects the MO6 octahedral network upon charging for Ni-rich layered oxides, where M denotes a transition metal. In addition, the oxide-model-dependent (in)coherent-bond-networks are consistently identified for the Li–O bond populations of NCT and NCM, and insights into the chemical stiffness of the Ti–O bond reinforces the structural origin of the uniform octahedral environment. The structural concept based on an in-depth understanding of the Ni-rich layered models not only accounts for the fundamental origin of the Ti-doping effect on the anisotropic lattice change but also provides a local-structure-related point of view in restraining the formation of micro-cracks for durable high-energy–density LIBs.

Effect of Ti-doping on photocatalytic activity of ZnO nanocatalyst under sunlight irradiation

• Samples are having single-phase hexagonal wurtzite structure and an average crystallite size of 26-12 nm. • TZO-4 nanoparticle seemed to be approximately spherical in shape. • The high specific surface area of TZO-4 material. • the TZO-4 nanoparticles exhibit the highest degradation efficiency. The present study illustrates the ZnO with different doping concentrations (0.05, 0.075, 0.10, and 0.125 M) were prepared by the chemical precipitation method and are labelled as TZO-1, TZO-2, TZO-3 and TZO-4, respectively. A substantial reduce in crystallite size (26-12 nm) and band gap (3.43-3.14 eV) is gained from the Ti-doped samples. The uneven shape and aggregation of the particles are presented from SEM analysis. Moreover, the photocatalytic efficiency of methylene blue (MB) dye was carried out using the product samples and achieved higher removal efficiency of 95.08% under sunlight irradiation for 120 min than the pristine ZnO and doped samples. The improvement in the catalytic performance of TZO-4 indicates a high surface area (48.09 m 2 g -1 ).

Investigation of optical and physico-chemical properties of titanium-doped V₂O₅ nanofilms

In this paper, undoped and Ti-doped V2O5 thin films were fabricated and deposited onto glass substrates using a «doctor blading» method. Then, the effects of Ti-doping on the optical properties of the thin films were investigated. Titanium doping concentration of 0.25-0.75 at.% has been investigated. After treatment in air at different temperatures, the obtained films was characterised by various techniques such as scanning electron microscopy (SEM), X-ray diffraction (XRD) and photoluminescence (PL). It was found that the as-obtained doped films possessed thermochromic properties and optical switching characters. According to optical tests, thin linings of vanadium dioxide alloyed with Ti have optical properties that are effective for application. Because of their capacity to automatically control interior solar irradiation, lower air-conditioning energy consumption, and maintain a comfortable internal thermal climate, smart windows have drawn increased interest in recent years. The doping strategy and integrating with functional coatings can regulate the properties of obtained V2O5 films.

Effects of Ti-doping on energy storage properties and cycling stability of Pb0.925La0.05ZrO3 antiferroelectric thin films

Pb0.925La0.05Zr1-xTixO3 (PLZT, x = 0.5%∼5.5%) thin film were fabricated on Pt(111)/TiO2/SiO2/Si substrates by sol–gel method. In the Zr-rich region, the saturation polarization strengthens with increasing Ti content due to the change of ion-radius. On the other hand, the switching field decreases, which means the enhancement of ferroelectricity. The phase structure and polarization of the films can be tuned by a small amount of Ti doping, and then the energy storage characteristics of the thin films can be modulated. The results showed that a large energy storage density (Wrec) of 49.7 J/cm3 and efficiency (η) of 54% were achieved in the x = 1.5%. Moreover, the x = 1.5% sample displayed excellent cycling stability up to 1 × 106 cyclings, which demonstrated that La and Ti co-doped films can be considered as potential candidates for future energy storage devices.

Effects of Ti Doping on TaFeSb Half‐Heuslers Estimated by a Single Parabolic Band Model

AbstractRecent discovery of new p‐type Ta1‐xTixFeSb‐based half‐Heusler thermoelectric alloy has drawn much attention due to its high thermoelectric performance, zT of ∼1.52 near 970 K. However, the electronic band parameters of TaFeSb nor Ti‐doped TaFeSb have not been studied so far. Here we report the band parameters of Ta1‐xTixFeSb (x=0–0.16) calculated by the Single Parabolic Band model. Ti doping (x=0.12) both increases the density‐of‐states effective mass and non‐degenerate mobility by 27 and 29 times compared to those of the pristine TaFeSb (x=0). This simultaneous increase results in weighted mobility improvement by a factor of 4000 with Ti doping of x=0.12. Based on the estimated weighted mobility and the lattice thermal conductivity, the 300 K zT of Ta0.88Ti0.12FeSb (x=0.12) can be further increased by 10% once the carrier concentration is appropriately tuned.

Titanium doping effect on the sensing performance of ZnO nanosheets toward phosgene gas

The density functional B3LYP was utilized for scrutinizing the effect of Ti-doping on the sensing performance of a ZnO nano-sheet (ZnONS) in detecting phosgene. Pure ZnONS had a weak interaction with phosgene, and the sensing response (SR) was approximately 9.4. There was an increase in the energy of adsorption (Ead) for phosgene from −5.5 to −22.8 kcal mol−1 after the doping of a Ti atom onto the surface of ZnONS. Following the doping of Ti, there was also a dramatic increase in the SR to 84.2. The recovery time (RT) for the desorption of phosgene from the ZnONS that was doped with Ti was 16.4 s. This suggested that Ti-doped ZnONS might be used as a phosgene sensor with a high sensitivity and a shorter RT.

Electronic, thermoelectric, and optical studies of cubic Hf1-xTixO2: An attempt to enhance the key parameters

In this work, we explore the effect of Ti-doping on the structural, electronic, transport and optical properties of c-HfO2 using first principles calculations for their possible applications in thermoelectric (TE) and optoelectronic devices. Seebeck coefficient of Hf1-xTixO2 shows the p-type behaviour in the entire studied temperature range. It attains a maximum value of 320.311 μVK-1 at 300 ​K for x ​= ​0.03 owing to the new flat band region. Ti doping leads to a significant decrease in electronic thermal conductivity (ke) of c-HfO2, which results in high figure of merit (ZTe) ​∼ ​0.82 ​at 400 ​K for x ​= ​0.03 and at 1200 ​K for x ​= ​0.12, which is the highest value ever reported for c-HfO2. We also calculated various parameters such as dielectric constant and refractive index depicting the effect of Ti doping on optical properties of c-HfO2. The present study predicts the applicability of Hf1-xTixO2 in thermoelectric, optoelectronics.

Effects of Ti Doping on Structure and Internal Stress of Amorphous Carbon Films on the γ-Fe Substrate: Molecular Dynamics Simulation.

In this paper, C and Ti were used as the deposition atoms in the molecular dynamics model. The effects of Ti doping percentages (2, 8, 14, and 20 atom %) on the structure and internal stress of a-C films were investigated. The results showed that with the increase in the Ti percentage, the density of the intrinsic zone is gradually increased, while the growth rate is slowly decreased. The internal stress is gradually changed from compressive stress to tensile stress. Among them, when the Ti percentage is 14 atom %, the internal stress is closer to 0. The C percentage with sp3 hybridization is decreased, while those with sp2 and sp hybridizations are increased. The positions of the first and second peaks in the RDF were shifted to the left. Moreover, the distribution of bond lengths and bond angles in the intrinsic zone tend to change from diamond to graphite, which proves that Ti doping leads to the graphitization of a-C films. In addition, Ti doping affects the internal stress of a-C films by changing the C percentage with sp3 hybridization in them.