Effect Of Ti-doping Research Articles

Electronic structure of Ti-doped Sr4Sc2Fe2As2O6 as a possible parent phase for the new FeAs superconductors

Abstract First principle FLAPW-GGA calculations have been performed with the purpose to understand the effect of Ti-doping on the electronic properties for the newly discovered tetragonal iron arsenide-oxide Sr4Sc2Fe2As2O6 (abbreviated as FeAs42226) as the possible parent phase for the new FeAs superconductors. Our results show that the insertion of Ti into Sc sublattice of this five-component iron arsenide-oxide phase leads to the resolute change of electronic structure of FeAs42226. Namely, the insulating oxygen-containing [Sr4Sc2O6] blocks in Ti-doped FeAs42226 became conducting, and this differs essentially from the known picture for all others FeAs superconductors where the conducting [Fe2As2] blocks are alternated with insulating blocks. Moreover in sharp contrast with FeAs-based superconductors with Fe 3d bands near the Fermi level, for Ti-doped FeAs42226 in this region the Ti 3d states are dominated, whereas the Fe 3d states are suppressed.

Preparation of high-oxygen-content apatite silicates through Ti-doping: effect of Ti-doping on the oxide ion conductivity

In this paper we show that through Ti-doping it is possible to synthesise high-oxygen-content silicate-based apatites, La10Si6−xTixO27 (0.25 ≤ x ≤ 2.0), and report conductivity data for this series. The results show that Ti-doping leads to a general decrease in the conductivity, and an increase in activation energy, particularly for the range 1.0 ≤ x ≤ 2.0. With reference to computer modelling and 29Si NMR data, this decrease in conductivity is attributed to trapping of the interstitial oxide ions around the Ti dopant. Attempts to prepare similar compositions containing La cation vacancies, i.e. La10−ySi6−xTixO3−3y/2, have a tendency to result in La2Ti2O7 impurities, particularly for high values of y.

Ti-doping effect on the MI transition of hollandite vanadate, K 2V 8O 16

Ti-doping effect on the metal-insulator transition of hollandite vanadate, K 2V 8O 16 has been investigated. The transition is accompanied by the charge ordering and the structural change from tetragonal to monoclinic structures with the increase of volume in the low-temperature monoclinic insulator phase. A slight amount of Ti-substitution for V atoms raises the transition temperature up to 270 K at x = 0.5 in K 2 V 8 - x Ti x O 16 from 170 K at x = 0 . This significant rise of transition temperature can be understood as a negative chemical pressure effect caused by the Ti-substitution. On the other hand, the disorder effect from the Ti-substitution makes the transition broad and finally the transition smears out around x = 1.0 .

Effect of Ti Doping on the Structure and Performance of LiNi_(0.75)Co_(0.25)O_(2)

Effect of Ti Doping on the Structure and Performance of LiNi_(0.75)Co_(0.25)O_(2)

Au and Pd atoms adsorbed on pure and Ti-doped SiO2∕Mo(112) films

The interaction of Pd and Au atoms with a silica surface and SiO2Mo(112) ultrathin films has been studied with periodic density-functional theory-generalized gradient approximation calculations. On both unsupported and supported silica, Pd and Au are weakly bound. No charge transfer occurs to the empty Pd and Au orbitals. Differently from Au, Pd can easily penetrate with virtually no barrier into the hexagonal rings of the supported silica film and binds strongly at the SiO2-Mo interface. The same process for Au implies overcoming a barrier of 0.9 eV. Completely different is the behavior of Ti-doped silica films. Au forms a direct covalent bond with substitutional Ti at the expense of the Ti...O-Mo interface bond which breaks. The global process is exothermic by 1 eV and nonactivated, showing that Ti doping results in solid anchoring points for the adsorbed Au atoms and for nucleation and growth of small gold particles. The effect of Ti doping is less pronounced for Pd but still visible with substantial enhancement of the Pd adsorption strength.

Effect of Ti-Doping on Different Morphologic LiCoO<sub>2</sub>

Effect of Ti-Doping on Different Morphologic LiCoO<sub>2</sub>

Effect of Ti-doping on the dehydrogenation kinetic parameters of lithium aluminum hydride

The effect of Ti-doping on the dehydrogenation kinetics of lithium aluminum hydride has been investigated in this paper. For the decomposition of lithium aluminum hydride into trilithium hexahydridoaluminate apparent activation energies of 81 and 89 kJ/mol are found for the un-doped and Ti-doped sample, respectively. For the decomposition of trilithium hexahydridoaluminate into lithium hydride apparent activation energies of 108 and 103 kJ/mol are found. The differences in apparent activation energies between the un-doped and the Ti-doped sample are within experimental uncertainty, suggesting that the effect of Ti-doping on the kinetic parameters of dehydrogenation of lithium aluminum hydride, is mainly a prefactor effect.

Insights on the origin of the structural phase transition in BaV 10O 15 from electronic structure calculations and the effect of Ti-doping on its structure and electrical transport properties

Band structure calculations at the level of LMTO-ASA provide insight into the electronic structure of BaV 10O 15 and the origin of the structural phase transition. A crystal orbital Hamiltonian population/integrated crystal orbital Hamiltonian population analysis provides evidence that the crystallographic phase transition is driven by V–V bond formation. As well, the energy bands near the Fermi level are very narrow, <1 eV, consistent with the fact that the observed insulating behavior can be due to electron localization via either Mott-Hubbard correlation and/or Anderson disorder. The partial solid solution, BaV 10− x Ti x O 15, was examined to study the effect of Ti-doping at the V sites on the structure and electronic transport properties. In spite of the non-existence of “BaTi 10O 15”, the limiting x = 8 , as indicated by a monotonic increase in the cell volume and systematic changes in properties. This limit may be due to the difficulty of stabilizing Ti 2+ in this structure. For x = 0.5 both the first order structural phase transition and the magnetic transition at 40 K are quenched. The samples obey the Curie–Weiss law to x = 3 with nearly spin only effective moments along with θ values which range from −1090 K ( x = 0.5 ) to −1629 K ( x = 3 ). For x > 3 a very large, ∼2×10 −3 emu/mol, temperature independent (TIP) contribution dominates. Conductivity measurements on sintered, polycrystalline samples show semiconducting behavior for all compositions. Activation energies for Mott hopping derived from high temperature data range from ∼0.1 eV for x = 0 – 1 and fall to a plateau of 0.06 eV for x = 3 – 7 . Low temperature data for x = 3 , 5 and 7 show evidence for Mott variable range hoping (VRH) with a T 1 / 4 law and in one case between 5 and 17 K, a Efros-Shklovskii correlated hopping, T 1 / 2 law, was seen, in sharp contrast to BaV 10O 15 where only the E-S law was observed up to 75 K. Seebeck coefficients are small (<35 μV/K), positive, roughly TIP and increase with increasing x up to x = 5 . This may point to a Heikes hopping of holes but a simple single carrier model is impossible. The compositions for x > 3 are remarkable in that local moment behavior is lost, yet a metallic state is not reached. The failure of this system to be driven metallic even at such high doping levels is not fully understood but it seems clear that disorder induced carrier localization plays a major role.

A comparative study of LiNi 0.8Co 0.2O 2 cathode materials modified by lattice-doping and surface-coating

Lithium nickel cobalt oxides as cathode materials for lithium ion batteries were modified by Ti-doping and TiO 2-coating. The effects of Ti-doping and TiO 2-coating on the structural and electrochemical properties of LiNi 0.8Co 0.2O 2 cathode material were investigated and compared. The results of X-ray diffraction (XRD) show that a solid solution phase (R-3 m) is observed in the range of 0≤ y≤0.1 for LiNi 0.8− y Ti y Co 0.2O 2 materials, and a new hexagonal phase LiTiO 2 appears on the surface of TiO 2-coated materials when the atomic ratio of Ti/(Ni+Co) is larger than 0.06. The ordering degree of layered structure was decreased for Ti-doped materials, and almost no changes of bulk structure occurred for TiO 2-coated materials. Charge–discharge experiments show both lattice-doping and surface-coating improve the cycling stability of LiNi 0.8Co 0.2O 2 cathode material. Ex-situ XRD of delithiated cathode materials confirms that suppression of lattice changes is attributed to the improved cycling stability of doped materials. But the similar suppression mechanism is not suitable for coated materials. Electrochemical Impedance Spectroscopy (EIS) experiments imply that the improvement of cycling performance for coated materials could be interpreted to the interface stability during cycling.

Effect of Ti Doping on the Superconductivities of MgB2/Fe Wires

Mg 1-x Ti x B 2 /Fe (x = 0, 0.1 and 0.2) wires were made by Powder-In-Tube method. XRD patterns indicate the main phase is MgB 2 and there are Ti particles in the Ti doped wires and no other Ti based impurities in the cores. SEM images show that the MgB 2 particles are distributed evenly in porous core. The J c of the wire (Mg 1-x Ti x B 2 /Fe, x = 0.1) measured magnetically is higher than that of those wires (Mg 1-x Ti x B 2 /Fe, x = 0 and 0.2), while the H irr are almost the same for three wires.

Effect of Ti-Doping on the Sintering Behaviour of Transition Alumina

Reference LTP-CONF-2002-005View record in Web of Science Record created on 2005-01-12, modified on 2017-05-10

Study on Anomalous Hall Resistivity of Nd2Mo2-xTixO7

Hall resistivity ρ H has been studied for single crystals of Nd 2 Mo 2 O 7 , which has the ferromagnetic and chiral ordered state. Effects of Ti-doping on ρ H have also been studied down to 3 K und...

Effect of Ti doping on the transport properties of thick films of (Bi, Pb)–Sr–Ca–(Cu, Ti)–O-type glass–ceramic superconductors

Abstract Homogeneous thick films (0.34.35 mm thick) of glassy (Bi3Pb1)Sr3Cu3Cu4−n Ti n Ox, precursors with low (n = 0–0.0075) concentrations of Ti have been prepared by a fast-quenching technique and characterized by X-ray diffraction and scanning electron microscopy studies. By annealing these as-quenched glasses above their respective glass transition temperatures T g, mostly the Bi-2212-type superconducting phase is obtained. The effect of Ti doping is to decrease the glass melting temperature as well as the annealing temperature (for making the ceramic phase, hereafter termed glass-ceramic (GC) phase) by about 20°C. The addition of Ti also reduces the formation of the high-T c 2223 phase. However, the superconducting transition temperature Tc decreases linearly with increasing Ti content. The Abrikosov-Gor'kov pairbreaking mechanism is found to be satisfied. All these GC samples (except the n = 0.00 sample) follow Mott's variable-range hopping conduction mechanism above the superconducting transition ...

V and Ti Doping Effect on In-Ag-Te-Sb Optical Phase Change Rewritable Disc

In-Ag-Te-Sb is known as one of the alloys suitable for optical phase change recording, which has a high erasability at the linear recording velocity of around 7 m/s. The phase change rewritable recording succeeded at the linear recording velocity of 1.4 m/s with 0.5 at.% doping of Ti or V atoms, which delayed the crystallization time drastically, but maintained the high erasability. It was possible to make 103 repetition recordings with jitter in the reproduced signal of less than 40 ns, when the eight-fourteen modulation (EFM) signal, which is generally used for compact discs (CD), was applied.

Lead scandium tantalate -lead titanate materials for field -stabilized pyroelectric device applications

Abstract A preliminary evaluation of the pyroelectric response of selected compositions from the variable order-disorder [VOD] phase region of this system has been conducted under modest DC biasing conditions in order to assess the performance of these materials for application in small area pyroelectric devices. The figure of merit [FD] was observed to be significantly enhanced over that of the pure Pb(Sc½Ta½)O3 material due to the combined effects of Ti doping, ordering, and the application of a biasing field.