Iron-doped Lithium Research Articles

Lithium adsorption from brine by iron-doped titanium lithium ion sieves

Iron-doped lithium titanium oxides were prepared via a solid-state reaction and transformed into lithium ion sieves by acid treatment. Scanning electron microscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy showed that Fe3+ was doped into the Ti–O lattice and Ti–Fe–O bonds were formed. Iron-doping improved lithium ion adsorption from brines. The saturated adsorption capacity of the iron-doped ion sieves in brine (Li+ 1.56g/L, pH=8.8) was 34.8mg/g. Lithium ion adsorption fitted pseudo-second-order kinetic and Langmuir equations, indicating that lithium ion adsorption on iron-doped lithium ion sieves was chemical and predominantly monolayer. In addition, the iron-doped ion sieves showed excellent selectivity for lithium ion and good recyclability. These iron-doped ion sieves therefore provide effective lithium adsorbents for practical applications.

Optical fabrication of large area photonic microstructures by spliced lens

We experimentally demonstrate a convenient approach to fabricate large area photorefractive photonic microstructures by a spliced lens device. Large area two-dimensional photonic microstructures are optically induced inside an iron-doped lithium niobate crystal. The experimental setups of our method are relatively compact and stable without complex alignment devices. It can be operated in almost any optical laboratories. We analyze the induced triangular lattice microstructures by plane wave guiding, far-field diffraction pattern imaging and Brillouin-zone spectroscopy. By designing the spliced lens appropriately, the method can be easily extended to fabricate other complex large area photonic microstructures, such as quasicrystal microstructures. Induced photonic microstructures can be fixed or erased and re-recorded in the photorefractive crystal.

Superior lithium adsorption and required magnetic separation behavior of iron-doped lithium ion-sieves

The recent research on adsorption-based lithium recovery from lithium-containing solutions has been centred on adsorption capacity and separation of lithium ion-sieves powder from solutions. Herein, an effective iron-doped lithium titanium oxide (Fe-doped Li2TiO3) was synthesized by Fe-doping via solid state reactions followed by acid treatment to form iron-doped lithium ion-sieves (Fe/Ti-x(H)). The resulting solid powder displays both superior adsorption capacity of lithium and high separation efficiency of the adsorbent from the solutions. SEM imaging and BET surface area measurement results showed that at Fe doping levels x≤0.15, Fe-doping led to grain shrinkage as compared to Li2TiO3 and at the same time the BET surface area increased. The Fe/Ti-0.15(H) exhibited saturated magnetization values of 13.76emug−1, allowing effective separation of the material from solid suspensions through the use of a magnet. Consecutive magnetic separation results suggested that the Fe/Ti-0.15(H) powders could be applied at large-scale and continuously removed from LiOH solutions with separation efficiency of 96% or better. Lithium adsorption studies indicated that the equilibrium adsorption capacity of Fe/Ti-0.15(H) in LiOH solutions (1.8gL−1 Li, pH 12) reached 53.3mgg−1 within 24h, which was higher than that of pristine Li2TiO3 (50.5mgg−1) without Fe doping. Competitive adsorption and regeneration results indicated that the Fe/Ti-0.15(H) possessed a high selectivity for Li with facile regeneration. Therefore, it could be expected that the iron-doped lithium ion-sieves have practical applicability potential for large scale lithium extraction and recovery from lithium-bearing solutions.

Light-induced electric field generated by photovoltaic substrates investigated through liquid crystal reorientation

Liquid crystal reorientation is exploited to analyze the electric field generated by light irradiation in iron-doped lithium niobate crystals. The evaluation of the strength of this light-induced field is based on the measurement of the phase shift induced in a probe light beam by a liquid crystal cell built with two z-cut iron-doped lithium niobate crystals as substrates. Then, the field profile has been determined starting from a Gaussian-like surface charge density following the model described in the text. The director profile corresponding to the modelled electric field is in good agreement with the director reorientation evaluated experimentally by means of the light-induced phase shift. This investigation gives a new approach to study the effects based on the photovoltaic response of lithium niobate crystals. Moreover, the characterization of the electric field optically generated inside the LC layer is highly desirable in view of the realization of new all-optical devices to be integrated in optofluidic platforms.

Direct evidence of visible surface plasmon excitation in ITO film coated on LiNbO3 slabs.

An iron-doped Y-cut lithium niobate (Fe:LN) slab was coated with indium-tin-oxide (ITO) thin films by magnetron sputtering. The electron confinement in a sub-nanometer region at ITO/LN interfaces is resulted from electric screening effect. Consequently, the local plasma frequency in the sub-nanometer metallic-like layer is shifted to the UV regime. This makes it possible to excite surface plasmon polaritons (SPPs) in the visible region with photorefractive phase gratings in the LN slab and to transport SPPs much energy-efficiently. Direct evidence of the excitation of SPPs was demonstrated by the presence of deep transmission spectral valleys in the transmission spectra and striking dark bands in the 2D diffraction patterns while using a white reading beam. Theoretical arguments and confirmation experiments are presented to elucidate all the related findings.

Ultralow loss visible surface plasmon based waveguides formed in indium-tin-oxide coated Fe-doped LiNbO3 slabs.

Visible reconfigurable waveguides were evidenced in a composite system formed with indium-tin-oxide (ITO) films coated on iron-doped lithium noibate (LN) slabs. Surface plasmon polaritions (SPPs) excited at the ITO/LN interface were believed to be behind the observed light guiding, which is inherent with superlow loss for its sub-nanometer modified layer. The forward near-surface-normal scattering and accompanying reduction of the specular reflectivity in the front ITO/LN interface are consistent with SPP excitation.

Temperature dependence of small polaron population decays in iron-doped lithium niobate by Monte Carlo simulations

The population decay of light-induced small polarons in iron-doped lithium niobate is simulated by a Monte-Carlo method on the basis of Holstein's theory. The model considers random walks of both bound polarons (NbLi4+) and free polarons (NbNb4+) ending to deep traps (FeLi3+). The thermokinetic interplay between polaron species is introduced by trapping and de-trapping rates at niobium antisites (NbLi). The decay of the NbLi4+ population proceeds by three possible channels: direct trapping at FeLi3+ sites, hopping on niobium antisites and hopping on Nb regular sites after conversion to the free state. Up to three regimes, each one reflecting the predominance of one of these processes, appear with different activation energies in the Arrhenius plots of the decay time. The influence of FeLi and NbLi concentrations on the transition temperatures is evidenced. For both polaron species, the length of the final hop (trapping length) is found much larger than the usual hopping length and decreases at rising temperature. This trap size effect is a natural consequence of Holstein's theory and may explain some unclear features of polaron-related light-induced phenomena, such as the temperature-dependent stretching exponent of light-induced absorption decays and the anomalous increase of the photoconductivity at high doping levels.

Area scalable optically induced photorefractive photonic microstructures

A convenient approach to fabricate area scalable two-dimensional photonic microstructures was experimentally demonstrated by multi-face optical wedges. The approach is quite compact and stable without complex optical alignment equipment. Large-area square lattice microstructures are optically induced inside an iron-doped lithium niobate photorefractive crystal. The induced large-area microstructures are analyzed and verified by plane wave guiding, Brillouin-zone spectroscopy, angle-dependent transmission spectrum, and lateral Bragg reflection patterns. The method can be easily extended to generate other more complex area scalable photonic microstructures, such as quasicrystal lattices, by designing the multi-face optical wedge appropriately. The induced area scalable photonic microstructures can be fixed or erased even re-recorded in the photorefractive crystal, which suggests potential applications in micro-nano photonic devices.

Restoration of the near-diffraction-limited response size at heterodyne detection of microholograms, distorted by spherical aberration.

Spherical aberrations (SAs) are an important factor in limiting the number of recording layers in a multilayer microholographic data storage scheme. This paper discusses the effect of the restoration of the response size, which makes it possible to decrease considerably the requirement of accuracy for the SA correction of the optical pickup system. The restoration occurs at the heterodyne detection of microholograms distorted by aberrations. The effect of restoring is demonstrated experimentally. A study of the dependence of the microholograms' lateral and longitudinal sizes on the medium depth in which they were formed was carried out. To measure the longitudinal size, a special material containing submicron microspheres was used. The size of the microhologram distorted by aberrations was then compared with the response size obtained at detection. In the last step, a conclusion about the restoration of the response size is made. The multilayer microholograms recording was carried out in iron-doped lithium niobate at a depth range from 70 to 520μm. A mathematical model of the microholograms' recording-reading was developed. This model makes it possible to give a qualitative explanation of the processes leading to the restoration of the near-diffraction-limited response size.

Light induced DEP for immobilizing and orienting Escherichia coli bacteria

Manipulating bacteria and understanding their behavior when interacting with different substrates are of fundamental importance for patterning, detection, and any other topics related to health-care, food-enterprise, etc. Here, we adopt an innovative dielectrophoretic (DEP) approach based on electrode-free DEP for investigating smart but simple strategies for immobilization and orientation of bacteria. Escherichia coli DH5-alpha strain has been selected as subject of the study. The light induced DEP is achieved through ferroelectric iron-doped lithium niobate crystals used as substrates. Due to the photorefractive (PR) property of such material, suitable light patterns allow writing spatial-charges-distribution inside its volume and the resultant electric fields are able to immobilize E. coli on the surface. The experiments showed that, after laser irradiation, about 80% of bacteria is blocked and oriented along a particular direction on the crystals within an area of few square centimeters. The investigation presented here could open the way for detection or patterning applications based on a new driving mechanism. Future perspectives also include the possibility to actively switch by light the DEP forces, through the writing/erasing characteristic of PR fields, to dynamically control biofilm spatial structure and arrangement.

Optical fabrication of two-dimensional photorefractive periodic photonic lattices and quasicrystal microstructures by multi-lens board

We experimentally demonstrate a convenient approach to fabricate two-dimensional periodic photonic lattices and quasicrystal microstructures in iron-doped lithium niobate photorefractive crystal by multi-lens board. The method does not require complicated optical adjustment system. We analyze the induced square photonic lattices, elliptic photonic lattices and quasicrystal microstructures by plane wave guiding, far-field diffraction pattern imaging and Brillouin-zone spectroscopy. Induced photonic microstructures can be fixed or erased and re-recorded in the crystal. We also numerically demonstrate that the method can be easily extended to form other complex photonic microstructures by designing the multi-lens board appropriately.

Synthesis and characterization of electrospun iron-doped lithium titanate/carbon nanofiber mats

In this paper, nanofibers composed of spinel Li4Ti5−xFexO12 (x = 0 and 0.1)/carbon were synthetized by electrospinning method. Thermal analysis of the prepared fiber was conducted by differential thermal/thermogravimetric analysis, crystal structure was characterized by X-ray diffraction, morphology and composition was determined by scanning electron and transmission electron microscopy. The results showed that fibers were composed of nanocrystals of lithium titanate with an average diameter from 17 to 25 nm supported in a carbonaceous matrix. The added Fe played an important role in improving the electronic conductivity and the charge-transfer process of the Li4Ti4.9Fe0.1O12/C electrode. Due to the morphological and structural features of these novel nanostructured materials, it can be considered as promising candidates for applications in lithium ion batteries.

Optical fabrication of wavy lattices and photonic lattices with defects in photorefractive crystal by single step projection method

We fabricate several different photonic lattice microstructures in iron-doped lithium niobate photorefractive crystal using single step projection method by a spatial light modulator. Wavy photonic lattice and several lattice structures with different defects were one-step induced inside the crystal. This method makes up the weakness of the conventional multiple beams interference method. The experimental setup is very flexible and easy to operate without complicated programming. Induced photonic structures can be fixed or erased and re-recorded in the crystal. The method can be easily extended to fabricate diverse photonic microstructures by drawing different structural patterns on a computer.

Coupling mediated by photorefractive phase grating between visible radiation and surface plasmon polaritons in iron-doped LiNbO3 crystal slabs coated with indium–tin oxide

Photorefractive (PR) phase gratings were used in coupling energy between visible light and surface plasmon polaritons in indium–tin oxide (ITO)-coated iron-doped lithium niobate (Fe:LN) crystal slabs via electrostatic modification at the ITO/LN interface based on a strong photovoltaic effect. The energy coupling is considered to be responsible for several interesting observations: (1) dynamic reflectivity change from 3.25 to 37.0% of the very first reflection at the entrance slab interface, (2) total light reflectivity as high as 89%, and (3) two-dimensional diffraction patterns without external feedback needed.

Generation of reconfigurable two-dimensional photorefractive photonic heterostructures with composite periods using multi-lens boards

A convenient approach to generate two-dimensional photorefractive photonic heterostructures with composite periods was experimentally demonstrated by multi-lens boards. The approach is pretty simple and does not require any complicated optical adjustment as the conventional methods did. Two kinds of composite periodic lattice structures are numerically simulated and optically induced inside an iron-doped lithium niobate photorefractive crystal. The induced composite photonic microstructures can be fixed or erased even re-recorded in the photorefractive crystal, which suggests potential applications in nonlinear photonic devices. Numerical simulation illustrates that the method can be easily extended to form more complex photonic microstructures by designing the multi-lens board appropriately.

Specially shaped negative lens produced in a lithium niobate crystal

The photorefractivity of iron-doped lithium niobate crystal is utilized for creating a negative lens-like structure. The refractive index inhomogeneity acting as a lens is formed due to illumination of the crystal by an optical field with Gaussian spatial distribution of intensity modified by a proper cylindrical lens. Blue line (488 nm) of an argon ion laser is used as a source of light for inducing the inhomogeneity within the crystal. Imaging properties of the photorefractive inhomogeneity are discussed in terms of wave and ray optics approaches and they are practically demonstrated by means of coherent light coming from a He–Ne laser (633 nm). Finally, the focal lengths of the “lens” are calculated using both the lens equation and the formula resulting from analysis of the phase curvature of the wave of light, which passed through the refractive index inhomogeneity.

Optical properties of iron-doped lithium niobate crystal depending on iron content and temperature

The optical properties of LiNbO3 crystals doped with iron at mol% between 0.015 and 0.1 were studied by optical absorption and Raman spectroscopies. The long wavelength tail below the fundamental absorption band is modeled by Urbach exponent assumed to be due to the tunneling of charged carriers through potential energy barrier bent by micro-electric field. We presume that non-uniform local charge distribution creates micro-electric field. Temperature dependence of the Fe2+ absorption band is reported over the range from 100 to 250 K. The Fe2+ absorption band at around 2.58 eV is red shifted at a rate of 4 × 10−5 eV K−1 as the temperature increases. We conclude that Li deficiency increases with iron, which sit on Li sites.

Optically induced three-dimensional Penrose-type photonic quasicrystal lattices in iron-doped lithium niobate crystal

Three-dimensional Penrose-type photonic quasicrystal lattices are optically induced inside an iron-doped lithium niobate photorefractive crystal for the first time using a single multi-pinhole plate. The setup of this method is simple and compact dispense with complex optical adjustment system. Induced Penrose-type photonic quasicrystal lattices are analyzed and verified by plane wave guiding and far field diffraction pattern imaging. The quasicrystal microstructures can be maintained for a long time inside the crystal in a dark room. Other more complex three-dimensional photonic quasicrystal structures can be fabricated with this method by designing the multi-pinhole plate flexibly.

Synthesis of Iron-Doped Manganese Oxides with an Ion-Sieve Property: Lithium Adsorption from Bolivian Brine

Iron-doped lithium manganese oxides Li1.33FexMn1.67–xO4 (x = 0.15, 0.30, and 0.40) were prepared by calcination of carbonates of Li, Mn, and nitrate of Fe in air at 350, 400, 450, 550, and 650 °C. The calcined samples, characterized by X-ray diffraction (XRD) and chemical analysis, were spinels. The protonated samples after treatment with HCl solution were tested as adsorbents for lithium adsorption from the salt lake brine collected from the Salar de Uyuni, Bolivia. The precursor showed 3.7% Mn extraction upon acid treatment with Fe/Mn ratio of 0.1 obtained from calcination at 450 °C. The amount of Mn extracted in HCl solution decreased with increasing of Fe/Mn ratio, and the amounts of lithium extraction were 90%, 96%, and 91% for Fe/Mn = 0.1, Fe/Mn = 0.2, and Fe/Mn = 0.3, respectively, while the amounts of dissolved iron showed the opposite trend. By studying the lithium adsorption in the raw brine and NaOH-added brine by a batch method, the adsorbent with Fe/Mn ratio of 0.1 obtained from calcination of the precursor at 450 °C was found to be efficient lithium adsorbent with lithium uptake of 18 mg/g at final pH 2.0 from the raw brine (initial pH 6.7) and 28 mg/g at final pH 7.2 from the NaOH-added brine (initial pH 8.2). The adsorbent with Fe/Mn ratio of 0.1 obtained from calcination of the precursor at 450 °C was evaluated for a 4 cycle adsorption/desorption experiment. The amount of manganese extracted (%) in the solution decreased with cycle numbers, 1.1% in the first cycle and 0.70% in the fourth cycle.

Fabrication of two-dimensional elliptic photonic lattices in photorefractive crystal by optical induction method

We fabricate two-dimensional elliptic photonic lattices in iron-doped lithium niobate photorefractive crystal for the first time with optical induction method. The experimental setup of our method is very simple and flexible without complicated optical adjustment system. We analyze and verify the two-dimensional elliptic photonic lattices by plane wave guiding, far field diffraction pattern imaging, and Brillouin-zone spectroscopy. Induced elliptic photonic lattices can stably exist for a long time in the iron-doped lithium niobate crystal. The induced two-dimensional elliptic photonic lattices might offer an easy method to study generic band gap phenomena in anisotropic periodic structures.