Effect Of Titanium Substitution Research Articles

Effect of titanium substitution on magnetic and dielectric properties of BaFe12O19 ceramics prepared by solid-state and co-precipitation methods

Barium ferrite has been modified by addition of titanium ions according to the formula BaTixFe(12-x)O19, with values of x as 0.00, 0.07, 0.14, 0.42, and 0.70. Samples were synthesized via solid-state and co-precipitation methods and then characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) as well as thermal analysis of dielectric constant and magnetization. The majority phase of barium ferrite with a hexagonal structure is observed in all samples, while the presence of Ti 2p was confirmed in the titanium-substituted samples. The saturation magnetization values for samples with x = 0.00, 0.07, and 0.14 are near the 50 emu/g. In contrast, samples with higher x values as 0.42 and 0.70 show significant magnetization loss with some low-temperature magnetic transition observed for x = 0.42. Dielectric characterization performed by thermal scanning of dielectric permittivity shows a substantial increase in the dielectric constant. It reveals the presence of a paraelectric-like transition at high temperatures induced by the addition of titanium.

Effect of titanium substitution and temperature variation on structure and magnetic state of barium hexaferrites

A number of solid solutions based on BaFe12−xTixO19 M-type barium hexaferrite doped with titanium cations up to x = 2.00 were obtained using conventional ceramic technology. The phase composition, crystal structure and unit cell parameters were refined by the Rietveld method using powder X-ray diffraction data up to T = 900 K. It was found that all the compositions have a magnetoplumbite structure satisfactorily described by P63/mmc space group (No. 194). With increasing temperature and doping concentration, the unit cell parameters increase almost monotonically. The minimum volume of V ~ 696.72 Å3 was determined for the composition with x = 1.00 at T = 100 K, while the maximum value of V ~ 714.00 Å3 is observed for the composition with x = 2.00 at T = 900 K. The mechanism of occupation nonequivalent crystallographic positions with titanium cations is established. The spin-glass component of the magnetic phase state is fixed. The Tdif temperature of the difference between the ZFC-FC curves decreases with an increase in the concentration of titanium cations and the magnetic field from ~237.2 K to ~ 44.5 K, while the Tinf inflection temperature of the ZFC curve increases from ~21.0 K to ~23.8 K. With an increase in the doping concentration, both the Dav average and Dmax maximum clusters grow up to ~ 100 nm. As the magnetic field increases above the critical value, the spin-glass component disappears. For compositions with x > 1.00, the magnetization is not saturated in fields up to 6 T. Along with the formation of the spin-glass component, doping with titanium cations for barium hexaferrite lowers the TC Curie temperature down to T ~600 K. The Ms spontaneous and Mr remanent magnetizations, as well as the Bc coercivity, decrease with increasing doping concentration almost monotonically, while the latter has an inflection point at x = 1.00. The minimum values of spontaneous and remanent magnetization, as well as coercivity, are observed for the composition with x = 2.00 and amount to Ms ~17.7 emu/g, Mr ~1.9 emu/g, and Bc ~3.9 × 10−3 T, respectively. An interpretation of the magnetic state of the doped BaFe12−xTixO19 barium hexaferrite is given taking into account the mechanism of occupation nonequivalent crystallographic positions with titanium cations.

Effect of Titanium Substitution in a P2-Na2/3Co0.95Ti0.05O2 Cathode Material on the Structural and Electrochemical Properties.

Worries about lithium supplies have led to the development of research on sodium batteries. Sodium-ion batteries are regarded as the next generation of energy-storage devices thanks to the generous resources of sodium. In spite of that, structural changes in the electrode materials remain the main challenge of this storage technology. NaCoO2 has been widely investigated as a competitive candidate for LiCoO2. It has been found that the electrochemical cycling curves of this material present numerous potential steps as a result of electronic transitions and/or structural ordering. From this standpoint, this paper reports a novel cathode material, Na2/3Co0.95Ti0.05O2, where 5% of cobalt was replaced by titanium, prepared via a facile solid-state route. The sodiation/desodiation mechanism of this layered material was investigated. Na//Na2/3Co0.95Ti0.05O2 exhibits a first initial capacity of 119 mAh/g in the potential window 2-4.2 V with less potential jumps in the potential versus capacity curve compared to NaCoO2. Genuinely, the electrochemistry of this material demonstrated a reversibility upon the insertion/desinertion process with low polarization. In situ synchrotron investigations on Na2/3Co0.95Ti0.05O2 reveal the occurrence of reversible ordered phases. Ex situ magic-angle-spinning NMR disclosed different environments around sodium starting from the pristine state to the end of charge.

Effect of Titanium Substitution on Magnetic Properties and Microstructure of Nanocrystalline Monophase Nd‐Fe‐B Magnets

Nd12.3Fe81.7−xTixB6.0 (x = 0.5–3.0) ribbons have been prepared by rapid quenching and subsequent annealing treatment. Effect of Ti substitution and annealing treatment on the microstructure, magnetic properties, and crystallization behavior of the ribbons was systematically investigated by the methods of differential scanning calorimeter (DSC), X‐ray diffraction (XRD), transmission electron microscopy (TEM), and vibrating sample magnetometer (VSM). It is found that Ti addition may increase the crystallization temperature and stabilize the amorphous phase. Ti element inhibits the grain growth during crystallization process and finally refines the microstructure. The exchange coupling interactions and magnetic properties of the ribbons increase with increasing x from 0.5 to 1 and then decrease with further increasing x ≥ 1.5. Optimum magnetic properties with (BH) max = 151.6 kJ/m3, Hci = 809.2 kA/m, Jr = 1.02 T are achieved in the Nd12.3Fe80.7Ti1B6.0 ribbons annealed at 600°C for 10 min.

ChemInform Abstract: Formation of the Amorphous Phase in Zr2Al by Hydrogen Absorption and the Effects of Titanium Substitution on the Amorphization Behavior.

ChemInform Abstract: Formation of the Amorphous Phase in Zr2Al by Hydrogen Absorption and the Effects of Titanium Substitution on the Amorphization Behavior.

Effect of titanium substitution in layered LiNiO 2 cathode material prepared by molten-salt synthesis

LiNi 1− x Ti x O 2 (0 ≤ x ≤ 0.1) compounds have been synthesized by a direct molten-salt method that uses a eutectic mixture of LiNO 3 and LiOH salts. According to X-ray diffraction analysis, these materials have a well-developed layered structure (R3-m) and are an isostructure of LiNiO 2. The LiNi 1− x Ti x O 2 (0 ≤ x ≤ 0.1) compounds have average particle sizes of 1–5 μm depending on the amount of Ti salt. Charge–discharge tests show that a LiNi 1− x Ti x O 2 (0 ≤ x ≤ 0.1) cathode prepared at 700 °C has an initial discharge capacity as high as 171 mA h g −1 and excellent capacity retention in the range 4.3–2.8 V at a current density of 0.2 mA cm −2.

Effect of titanium substitution on the structure of VSbO 4 catalysts for propane ammoxidation

The effect of titanium substitution on vanadium antimony oxide propane ammoxidation catalysts was investigated by UV Raman spectroscopy and X-ray diffraction. UV Raman spectra exhibit bands in the region of 450–1000 cm −1, which are associated with the rutile structure, a cation vacancy site, and V 2O 5. Calculations of the vibrational frequencies made with the use of CASTEP optimized slab models provide good agreement with experimental results. With titanium substitution, the rutile bands shift and broaden. Comparison of freshly prepared and ground samples shows that crystalline V 2O 5 forms upon grinding in air. Titanium stabilizes vanadium in the vanadium antimonate rutile structure and thus prevents the formation of crystalline V 2O 5. An in situ Raman characterization of titanium-containing vanadium antimony oxide catalysts was made in reducing and oxidizing atmospheres. The band associated with two-coordinate oxygen at cation vacancy sites disappears under reduction conditions, then returns after reoxidation in air. This indicates that this lattice oxygen moiety is key to ammonia activation. The titanium-substituted sample shows additional characteristics that indicate titanium improves the reduction and oxidation capability of the vanadium antimonate catalyst.

Structural, electrochemical and thermal properties of LiNi 0.8− yTi yCo 0.2O 2 as cathode materials for lithium ion battery

Multiple substitution compounds with the formula LiNi 0.8− y Ti y Co 0.2O 2 (0≤ y≤0.1) were synthesized by sol–gel method using citric acid as a chelating agent. The effects of titanium substitution on the structural, electrochemical and thermal properties of the cathode materials are investigated. A solid solution phase ( R-3 m) is observed in the range of 0≤ y≤0.1 for the titanium-doped materials. X-ray photoelectron spectroscopy (XPS) shows that there are Ni 3+, Ni 2+, Co 3+, Co 2+ and Ti 4+ five transition metal ions in titanium-doped materials. Rietveld refinement of X-ray diffraction (XRD) patterns indicates that titanium substitution changes the materials’ structure with different cationic distribution. An increase of the Ni/Co amount in the 3 a Li site is found with the addition of titanium amount. An improved cycling performance is observed for titanium-doped cathode materials, which is interpreted to a significant suppression of phase transitions and lattice changes during cycling. The thermal stability of titanium-doped materials is also improved, which can be attributed to its lower oxidation ability and enhanced structural stability at delithiated state.

Effect of titanium substitution on film structure and ferroelectric properties of Sr-deficient Sr 0.75Bi 2.35Ta 2O 9 thin films

Ferroelectric films of bismuth-containing layered perovskite Sr 0.75Bi 2.35(Ta 2− x Ti x )O 9 ( x=0–0.8) have been prepared using a metal-organic decomposition method. The effects of Ti substitution on the microstructure evolution and ferroelectric properties of Sr 0.75Bi 2.35Ta 2O 9 films were investigated. A maximum remanent polarization of 2 P r=30.7 μC/cm 2 was obtained for the Sr 0.75Bi 2.35Ta 1.8Ti 0.2O 9 film as compared to Sr 0.75Bi 2.35Ta 2O 9 films (19.6 μC/cm 2) annealed at 800 °C in air. The Ti substitution for Ta leads to charge compensation for the self-produced positive Bi Sr due to the occupation of Bi on Sr vacancies and is responsible for the increase in leakage resistance. The leakage current density as low as 2×10 −8 A/cm 2 can be obtained at an applied electric field of 100 kV/cm. Substitution of Ti for Ta shows a positive effect on the fatigue endurance of Sr-deficient Sr 0.75Bi 2.35Ta 2O 9 film.

Effect of titanium substitution on the structure and properties of Fe3Al-based intermetallic alloys

Substitutions (0–16 at%) of titanium for iron in Fe3Al-based alloys rapidly solidified by chill-block melt-spinning stabilize the D03 and B2 ordered structures. Rapid solidification results in total suppression of D03 order in binary alloys, whereas alloys containing titanium have D03 structure. D03 and B2 antiphase domain size, lattice parameter and hardness increase with increasing titanium content of the alloy. The deformation mode changes from single (unit) bcc dislocation in binary alloys to two-fold superdislocation configuration in D03Fe3Al-Ti alloys. Mechanical antiphase boundaries are generated by the movement of these imperfect configurations. All the alloys exhibited cleavage tensile failure. The mechanical properties are correlated with the observed structural changes.

Crystallization behaviors of the hydrogenated Zr-rich amorphous Zr xNi 1−x:H alloys and the effects of titanium substitution

In order to investigate the effect of hydrogen on the thermal stability of the amorphous Zr xNi 1−x alloys, the crystallization of the hydrogenated alloys is examined using differential scanning calorimetry. By hydrogenation, the crystallization reaction is accelerated and the cubic ZrH 2 phase is formed at first. At the next step, cubic ZrH 2 is further transformed to the tetragonal structure. The corresponding mechanism is different from that of the as-received state and it is proposed to be related to the motion of nickel atoms, these having smaller atomic radius. When partially substituting titanium, the crystallization temperature and activation energy are greatly increased for both the as-received and the hydrogenated systems. This is thought to be caused by the retardation of the nickel diffusion and by hardening of the amorphous structure elastically, due to the presence of titanium atoms.

Formation of the amorphous phase in Zr 2Al by hydrogen absorption and the effects of titanium substitution on the amorphization behaviour

To explore the hydrogen-induced amorphization behaviour of Zr 2Al (Ni 2In type), the structural changes of the compound during hydrogen absorption are investigated by means of X-ray diffraction (XRD), transmission electron microscopy (TEM) and differential thermal analysis (DTA). To examine the effects of alloying element substitution, small amounts of zirconium are replaced by titanium, which has similar chemical and physical properties. At low reaction temperatures, the Zr 2Al and (Zr 0.85Ti 0.16) 2Al compounds form crystalline hydride phases with orthorhombic structure initially, and then transform to an amorphous phase gradually. However, at higher temperatures they are decomposed into the stable phases ZrH 2 and Zr 3Al 2. For the titanium-containing alloy, the reaction process and the amorphization mechanism are similar to those of the titanium-free alloy system. The amorphization temperature is increased by the titanium substitution, which is considered as being due to the increase of the elastic modulus owing to the titanium addition. It is suggested that the hydrogen-induced amorphization occurs as a result of the suppression of the decomposition of the crystalline hydride phase into the stable configurations, and the amorphization mechanism is the short-range motion of aluminum atoms.