Nickel hydroxide thin films were deposited on ITO-coated glass substrates by the chemical bath deposition method. Two formulations using nickel nitrate were employed to obtain the films. The first one is through coordination compounds by using an ammonia complex producing the well crystallized phase β(II)-Ni(OH)2. The second formulation is based on the decomposition of urea at temperatures above of 90 °C, which promotes the deposition of the turbostratic phase α(II)- Ni(OH)2. After thermal annealing in air at temperatures of 250-300 °C, the β(II) films retain their polycrystalline structure, while the α(II) films are partially transformed to NiO. The electrochromic behavior of the films was tested by cyclic voltammetry in a three electrodes configuration cell. Also, chronoamperometry and in-situ single wavelength transmittance measurements were carried out to evaluate the switching time response. From Raman spectroscopy the structural transformations between colored and blanched states were studied. In the colored state most of the films show a mixture of β(III) and γ(III) phases of NiOOH, and in one case the Ni2O3 phase was found. It is shown that the films can exhibit high optical contrast depending on the processing conditions and electrical potential applied.

For almost a decade there have been spurious reports that high specific capacity LiCoO2 can be stabilized through modification of the synthesis protocol, however no basis for this improvement was ever proven. In this study, high specific capacity (190 mAh/g) LiCoO2 with good cycling stability was successfully fabricated in this study with the purpose to identify the basis for, and reproduce the high specific capacity. Extensive physical and electrochemical characterization confirmed the improvement was directly related to the surface chemistry as opposed to bulk modification of the crystal chemistry. In particular, high resolution transmission electron microscopy confirmed the thermodynamic growth of a distinct surface phase of 5-10nm on the best materials. In contrast to extrinsically deposited surface coating, the intrinsic approach enabled a one step synthesis and modification using intrinsic constituents to result in a 5-10nm uniform coating of a cubic cobaltite based on fundamental phase stabilities as dictated by the phase diagram of the Li-Co-O system.

The nanocrystalline samples of 10wt.%Scandia stabilized Zirconia (10ScSZ) and 1wt.%Ceria doped ScSZ (1Ce10ScSZ) prepared via co-precipitation route were characterized and compared to commercially available samples regarding their transport properties and electrical conductivity. The results of oxygen isotope experiments show that for Zirconia-based electrolytes, the rate of heteroexchange is lower than that for Samaria-doped Ceria. The results of Secondary Ions Mass Spectrometry (SIMS) indicate that all admixed components are present both in the surface layer and the bulk of the studied samples with pronounced segregation on the grain boundary. The highest total conductivity is observed for DKKK sample. In the range of 600-400°C the highest conductivity observed for synthesized nanocrystalline 1Ce10ScSZ sample is explained by the effect of segregated Scandia doped Ceria surface layers.

In this research we investigated the sintering behavior of (La0.9Sr0.1)0.95Cr0.85Mg0.1Ni0.05O3 perovskite which is a potential candidate material for enhancing the oxidation reactions in oxygen separation and syngas production. It was found that solid state sintering occurs as a single step event and it was possible to produce gas tight ceramics after using cold isostatic pressing followed by sintering at 1700°C in air. Grain size, porosity, and lattice parameter measurements of the presureless sintered ceramics were performed as a function of sintering temperature. A small amount of secondary phases was also detected by XRD and EDS analysis.

Nanometric 20% molar Sm-doped ceria (SDC20) powders were synthesized by tetrametylethylen ammine (TMDA) co-precipitation method. SDC20 was sintered in several conditions to control the final microstructure. Fast firing and conventional sintering were performed. LiNO3 was used as an additive to promote liquid phase sintering of ceria at low temperatures (900-1200°C). Powders and dense pellets were analysed using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM). Electrochemical impedance spectroscopy (EIS) measurements were performed on dense pellets in air to estimate the contribution of grain boundary and bulk to the electrical conductivity. Liquid phase sintering produced the densest samples with the highest conductivity.

The sintering behavior and structural changes of fluorite Gd0.2Ce0.8O2-δ(GDC) with one of three perovskites: LaMnO3 (LMO), (La0.7Sr0.3)0.98MnO3 (LSM) and La0.6Sr0.4Fe0.8Co0.2O3 (LSFC) composite ceramics were studied. Sintering was carried out for two hours at five different temperatures: 1100°C, 1200°C, 1300°C, 1400°C, and 1500°C. The highest sinterability has been found in LSFC + GDC. LSM + GDC appear to undergo two-step sintering mechanisms. Of all types of ceramics, only sintered LMO experiences a phase change, from rhombohedral R C to orthorhombic Pnma structure, with respect to its powder phase at sintering temperatures ≥1200 °C. The transition is notably suppressed when LMO is part of an LMO + GDC composite. GDC in a fluorite and/perovskite composite, when sintered, undergoes a temperature-dependent expansion in its unit cell that is not observed in pure GDC ceramics. This structural change will impact the function of composite ceramics as a fuel cell cathode, or oxygen separation membranes.

Nanostructured coatings have recently attracted increasing interest because of the possibilities of synthesizing materials with unique physical-chemical properties. In this report we describe our efforts at developing a methodology for the fabrication of SrFeO3-X based thin films using a modified Pechini method. Thin films of SrFeO3-X were fabricated using a spin coating and PLD method on Al2O3. The films annealed at 600 °C for one hour show a perovskite phase. The sensors based on SrFeO3-X thin films on alumina were fabricated using spin coating and PLD techniques. The sensing properties were determined using propane and propene as the probing gases. Response characteristics and temperature dependency of spin coated and PLD fabricated samples were compared. The effect of the electrode material, Au and/or Pt, on the gas detection sensitivity of the SrFeO3-X thin films was also investigated.

Vanadium oxide-collagen hybrid nanocomposites were prepared by adding a V2O5 sol to a dilute collagen solution. 51V MAS NMR spectroscopy shows that the inorganic phase is composed of the decavanadate [H2V10O28]4− polyanion and V2O5 ribbon-like particles. The broadening of the 51V signals and the absence of Bragg peaks in the XRD pattern suggest a strong disorder concerning the organization of the V2O5 particles and of the decavanadate species in the composites. Analogous hybrid nanocomposites were obtained with a solution that contains only the decavanadate species, showing that the cohesion in the hydrid material results mainly from electrostatic interactions between decavanadate [H2V10O28]4− polyanions and positively-charged collagen helices.

We present the properties of the carbon layer deposited at the surface of the LiFePO4 particles. Characterizations include scanning electron microscopy, high-resolution transmission electron microscopy, and Raman scattering spectroscopy. Analuysis of Raman spectra reveals that the carbon deposit is hydrogenated with very small hydrogen/carbon ratio, so that it belongs to the family of the amorphous graphitic carbon. It is expected to have the same properties (small hardness, high electronic conductivity) that favor both the Li diffusion from the LiFePO4 bulk and the charge-discharge rate of the cell.

Sol-gel derived Nb2O5 thin films were intercalated with Mg2+,using the non-aqueous solution of Mg(ClO4)2 in propylene carbonate (pc) as the electrolyte. 2% and 4% ( volume %) water was added to the electrolyte to study the effect of water on the electrochromic properties of Nb2O5. This paper presents the changes in optical and structural properties of the intercalated films with and without water in the electrolyte. The ratio (x) of the Mg2+ and Nb atoms has been controlled by optimizing the intercalation duration under a constant current density. The fall in transmittance on intercalation (for x= 0.8) increased by 15% with 4% water in the electrolyte, compared to the film intercalated without water. FTIR studies show that water is incorporated in the films on intercalation and small quantities of Mg(OH)2 and Nb-OH are formed along with Mg-O-Nb bonds. The presence of water in electrolyte decreases water content in the films and enhances the formation of Mg(OH)2, Mg-O-Nb and Nb-OH bonds. The recovery of Mg2+ on deintercalation is slightly reduced in presence of water in the electrolyte. The cyclic stability of the films intercalated without water is more than that of the films intercalated in presence of water.

Well-crystalline LiFePO4 particles were successfully prepared in the temperature range between 120 and 220°C, and complete ion ordering was obtained above 175°C where the unit cell dimensions were identical to high temperature material. The use of a soluble reductant, such as sugar or ascorbic acid, was found to minimize the oxidation of the iron to ferric. The electronic conductivity was enhanced by the deposition of carbon from the sugar, or by the addition of carbon nanotubes to the hydrothermal reactor when over 90% of the lithium could be de-intercalated electrochemically. We have extended the hydrothermal synthesis method to the Mn, Co and Ni analogs as well as to the mixed phosphates, such as LiMnyFe1-yPO4.

The fast and reproducible electrical response of the new, metastable fluorite phase of Bi3TiNbO9 to ambient humidity is reported. Pellets were prepared by high energy mechanochemical activation of the precursor powders, pellet pressing, sintering, and sputter deposition of Pt electrodes. Thermal analysis shows exothermic peaks at 465 and 594 °C. X ray diffraction analysis identifies a metastable fluorite like phase, isomorphous to the δ phase of Bi2O3, between the first and the second peaks, and the stable Aurivillius phase after the second peak.

Over a wide (-40 to 20 °C) dew point (DP) range, at 23 °C ambient temperature, the conductivity increases close to exponentially, from nearly 10−3 to 102 pS/cm. Upon removal of the bias, and under DP cycling, the relaxation current responds to humidity steps, on top of the long term current decay, in a manner similar as under bias. In addition, upon a step into humidity, after a dry spell, the current overshoots (before proceeding to the long term decay) to a maximum value (Im) which depends on the duration of the previous dry spell. If this is short, Im remains below the current value (Iph) at the end of the previous humidity stage. If the dry spell is long, Im overshoots above Iph. This behavior is unlike that of any discharge current through a leaky capacitor. A preliminary model for understanding it proposes the surface transport of a charge carrier, assisted by diffusion of some species from the interior of the ceramic grains.

A series of LixFePO4 samples (0≤x≤1) have been synthesized in the vitreous state by fast quenching technique. Characterization methods include XRD, TG, FTIR, magnetic susceptibility and electrical measurements. FTIR studies reveal that in the entire composition range the local structure is identical to the olivine lattice including PO4 3− oxo-anions linked to FeO6 octahedra. Magnetic susceptibility data show that the antiferromagnetic ordering does not exist so far and the paramagnetic behaviour follows the Curie-Weiss law above 30 K. Both the Curie parameter and the Weiss temperature suggest a strong weakness of the superexchange interactions that are consistent with the analysis of infrared spectra. Electrical conductivity shows an activated conduction mechanism with Ea =0.67 eV.

We report the results of a molecular dynamics simulation study aiming to understand the interfacial structure in ceria/zirconia superlattices and the impact of the interfaces on the energies of oxygen vacancy formation and Gd ion substitution in ceria and zirconia layers of the superlattice structure. It is found that the semi-coherent interface is characterized by misfit dislocations, paired at approximately 3-4 nm, with stacking-fault-like region in between, which agrees with the TEM observations. It is also found that the vacancy formation energy and the Gd substitution energy vary as a function of distance from the interface in the individual layers, and that these energies depend on the layer thickness. In addition, the simulations showed that the defect energy variations across the thickness of the ceria and zirconia layers are consistent with the XPS data for composition profile in the superlattice structure. Finally, in the semi-coherent superlattice structure, the formation energy of oxygen vacancies and the Gd substitution energy are found to depend on the position of these defects relative to the interfacial dislocation core. In particular, the oxygen vacancy formation energy is found to be negative close to the dislocation core, indicating that vacancy concentration will increase in such regions allowing for high conduction parallel to the interface.

Li1+z[Ni0.45Mn0.45Co0.1]1-zO2(0.8≤1+z≤1.2) has been synthesized by the co-precipitation method. It was found that 5% excess lithium must be added to obtain the desired composition. XRD results show that an apparent single-phase structure appears except for the lowest lithium content. The layered character of the structure increases with increasing lithium content and Rietveld refinement reveals that cation disorder decreases rapidly as more lithium is added. This conclusion is further confirmed by magnetic studies in which only Li0.8[Ni0.45Mn0.45Co0.1]1.2O2 and Li0.9(Ni0.45Mn0.45Co0.1)1.1O2 show magnetization hysteresis loops. The electrochemical behavior of this series of samples is compared to figure out the best lithium to transition metal ratio.

The microstructural features of diverse samples are studied by powder X-ray diffraction using different methods for the analysis of the diffraction peak broadening. The results obtained are thoroughly analyzed taking into account the assumptions and simplifications done in each of the chosen methods (Scherrer, Stokes and Wilson, Williamson-Hall and Rietveld refinement) and direct observation of the studied specimens by transmission electron microscopy is used in order to contrast the results obtained. Classic simple methods that consider only size effects (Scherrer, Stokes and Wilson) or the combined effects of size and strains (Williamson-Hall) provide a rapid overview of the origins of line-broadening but the most reliable results are obtained when the whole diffraction pattern is taken into account (Rietveld refinement).

The magnetic properties of layered LiNi0.5Mn0.5O2 and NaNi0.5Mn0.5O2 cathode materials are studied using AC susceptibility and DC magnetization techniques in order to elucidate magnetic interactions within transition metal (TM) layers and between them in samples with various TM distributions. In NaNi0.5Mn0.5O2 antiferromagnetic (AF) ordering transition is found at 60 K and a spin-flop transition at high magnetic field. In LiNi0.5Mn0.5O2 obtained by ion exchange from NaNi0.5Mn0.5O2 ferrimagnetic ordering is found at around 100 K. The saturation magnetization and the hysteresis loop size of ion-exchanged compounds vary from sample to sample, which implies that the Ni2+ ions migrate upon ion exchange process. Magnetic properties of high-temperature and ion-exchanged LiNi0.5Mn0.5O2 are compared; magnetic ordering models for all compounds are proposed based on experimental results and Goodenough-Kanamori rules.

We have developed a new type of FC which shows high performance at intermediate temperatures to solve the disadvantage of using hydrocarbon as fuel to FC system. This new FC is an ultra-thin proton conductor electrolyte supported by a metal hydrogen membrane. We have named it Hydrogen Membrane Fuel Cell

The HMFC using BaCe0.8Y0.2O3 (BCY) as the electrolyte and pure Palladium as the substrate exhibits a high cell performance of 2.7 A/cm2 @0.5V, 873K and 1.8 A/cm2 @0.5V, 673K. But the BCY cell performance drops rapidly during several hours. It was inferred that this phenomenon is caused by BCY electrolyte dissolved by hydrothermal reaction with H2O vapor which was generated by the fuel cell reaction.

We studied the possibility as HMFC electrolyte of Ba(Ce0.5Zr0.5)0.8YO3 (BCZY) and BaZr0.8Y0.2O3 (BZY) which are exchanged the B site of BCY perovskite ceramic from Ce to Zr to improve the resistance against the hydrothermal dissolution. BCZY and BZY confirmed the resistance against the hydrothermal dissolution improved compared with BCY by analyzing after the hydrothermal treatment. The BCZY cell shows the same level of the performance as the BCY cell and the performance stability has improved over the BCY cell.

Quasielastic neutron scattering experiments have been performed on proton-conducting hydrated Y-doped BaZrO3 at temperatures between 473 K and 673 K. Quasielastic broadening is observed at all temperatures, but only at the higher ones the scattering exhibits the characteristics of the proton transport process. Attempts to interpret our data in the framework of the two-state model yield unconvincing results. A simpler approach using the isotropic Chudley-Elliott model yields reasonable values for the proton self-diffusivities but also unusually high values for the jump distance which are close to the mean distance between dopants.