Alodia Orera

• PhD, Materials Science
• Researcher at University of Zaragoza

We have analyzed by operando neutron diffraction the charge/discharge crystallographic transformation processes inside the positive active mass (PAM) of industrial lead batteries, getting information onthe spatial distribution of the phases. Our study was focused on the positive electrode because it is there where the main limitations to the charge...

Oxide eutectics have great potentiality as structural or functional materials, owing to the outstanding properties derived from the eutectic microstructure. Among them, the eutectic of the ZrO2–MgO system is particularly noteworthy because of the unusual combination of thermomechanical, optical and electrical properties. In a recent application, Zr...

The redox behavior of terbium and praseodymium doped yttria-stabilized zirconia (YSZ) was studied with the aim of identifying spectroscopic probes and a suitable experimental procedure to monitor the oxygen activity in YSZ electrolytes in solid oxide cells with spatial resolution and at operation conditions (e.g. at high temperatures). Sintered cer...

Pr and Mn infiltrated oxide nanoparticles are confirmed as excellent candidates for boosting the performance of standard lanthanum strontium manganese oxygen electrodes.

The laser is a powerful tool for materials processing, incorporated already in many industrial processes and laboratory procedures. In this work, we are concerned with laser processing applied to research and development of ceramics for electrochemical cells and other high temperature oxide ceramics for energy applications. Solidification of single...

Solid oxide fuel cells (SOFC) are reversible devices that generate electric energy by oxidation of a fuel, commonly hydrogen. In electrolyser mode (SOEC), a voltage is applied and hydrogen is generated from water. These processes are highly efficient, although one of the main sources of degradation in these devices arises from extreme oxygen activi...

The insight into the mechanism of the unprecedented formation of pure anatase TiO2 from the macromolecular (Chitosan)▪(TiOSO4)n precursor has been investigated using micro Raman spectroscopy, Scanning Electron Microscopy (SEM) and thermogravimetric/differential thermal analysis (TGA/DTA). The formation of a graphitic film was observed upon annealin...

Due to the limitations of bone autografts, we aimed to develop new composite biomaterials with pro-angiogenic and osteogenic properties to be used as scaffolds in bone tissue engineering applications. We used a porous, cross-linked and slowly biodegradable fibrin/alginate scaffold originally developed in our laboratory for wound healing, throughout...

Solar perovskites have received phenomenal attention and success over the past decade, due to their high power conversion efficiencies (PCE), ease of fabrication and low cost which has enabled the prospect of them being a real commercial contender to the traditional silicon technology. In one of the several developments on the archetypal MAPbI3 per...

Aluminium-doped lanthanum silicate (LSAO) apatite-type compounds have been considered as promising candidates for substituting yttria-stabilized zirconia (YSZ) as electrolytes for intermediate temperature solid oxide fuel cells (IT-SOFC). Nevertheless, not many materials have been reported to work as cathodes in a LSAO apatite-based cell. In the pr...

The conductivity of ceramic ionic materials is highly influenced by dopant segregation at the grain boundaries or interfaces, which usually induces a depletion of charge carriers by space charge effects. Hence, obtaining interfacial configurations that promote the formation of oxygen vacancies is highly desirable. In this paper we have combined hig...

The oxygen storage capacity of Cex Zr1‐x O2‐y compounds arises from the mixed‐valent character of cerium, which makes the system sensitive to external factors such as temperature and oxygen partial pressure through their influence in the Ce valence, cation ordering and oxygen content. In this work, we analyze the phase relations in Ce0.5Zr0.5O2‐y c...

Showcasing recent developments in inorganic materials in an area of societal interest and importance, this book provides an up-to-date introduction to the contemporary use of functional solids in emerging technologies. Energy Storage and Conversion Materials describes the application of inorganic materials in the storage and conversion of energy, w...

In an effort to discover new inorganic UV absorbers, titania included into silica was prepared using a solvent-less solid state method involving the pyrolysis of the as prepared precursor Chitosan·(TiOSO4)/SiO2, as an alternative and versatile way to using these compounds for practical applications. The new TiO2/SiO2 composite was characterized by...

In this work we report a detailed structural study of the K 2-x Na x Mg 2 (SO 4 ) 3 series in order to evaluate the effect of Na incorporation on the structure. The results show that the cubic langbeinite structure is observed at room temperature for high Na levels; K 2-x Na x Mg 2 (SO 4 ) 3 (0 ≤ x ≤ 1.8). Increasing the Na content further, 1.8 < x...

Sodium mixed metal sulphates have attracted considerable attention, both in terms of mineralogy and more recently due to interest in Na ion containing materials for battery applications. The phase, Na2Mg2(SO4)3, has been previously reported to undergo a phase change to langbeinite at high temperatures, which is interesting given that usually the la...

The first fluorination of the cuspidine-related phases of Ln4(Al2O7□)O2 (where Ln = Sm, Eu, Gd) is reported. A low-temperature reaction with poly(vinyl­idene difluoride) lead to the fluorine being substituted in place of oxygen and inserted into the vacant position between the dialuminate groups. X-ray photoelectron spectroscopy shows the presence...

Autografts are still the standard choice of treatment for bone defects. However, their use is limited by disadvantages such as limited availability, donor-site morbidity and the risk of infection1. There exists an unmet clinical need for novel bone graft substitutes that can eliminate the use of autografts. We developed a novel, off-the-shelf pro-a...

The inscription of diffractive elements in ophthalmic polymers and ocular tissues to induce refractive index changes is of great interest in the fields of Optics and Ophthalmology. In this work fabrication of linear periodic patterns in polydimethylsiloxane (PDMS) intraocular lenses by means of the direct laser interference patterning (DLIP) techni...

Proton-exchanged Li-conducting garnets present novel properties compared with their parent compounds, among which proton conductivity may have potential applications. Here we study the structural and dynamical properties of Li5-xHxLa3Nb2O12 garnets with intermediate proton content (x ≈ 2.8) using neutron and X-ray diffraction, Raman and NMR techniq...

Titanium and its alloys or tantalum (Ta) are materials used in orthopaedic and dental implants due to their excellent mechanical properties and biocompatibility. However, their bioactivity and osteoconductivity is low. With a view to improving these materials bioactivity we hypothesised that the surface of Ta and TiAl6V4 can be functionalised with...

Directionally solidified eutectic rods of Al2O3-Y3−xErxAl5O12 (0 ≤ x ≤ 3) composition have been grown using the laser floating zone method at processing rates of 25 mm/h and 750 mm/h. For all the samples the microstructure presents the same morphology, consisting of an interpenetrated 3D eutectic network of both Al2O3 and garnet phases, while eutec...

Titanium and its alloys or tantalum (Ta) are materials used in orthopaedic and dental implants due to their excellent mechanical properties and biocompatibility. However, their bioactivity and osteoconductivity is low. With a view to improving the bioactivity of these materials we hypothesised that the surface of Ta and TiAl6V4 can be functionalise...

The simple reaction of chitosan with metallic salts yields (chitosan) (MLn)x, MLn = MnCl2, CoCl2, NiCl2, macromolecular complexes which, after a thermal treatment at 800 °C under air, give nanostructured Mn2O3, Co3O4 and NiO. The polymer acts as a template in the solid state, which is eliminated after the combustion process. At an intermediate stag...

Rare earth silicate apatites are one-dimensional channel structures that show potential as electrolytes for solid oxide fuel cells (SOFC) due to their high ionic conductivity at intermediate temperatures (500-700 °C). This advantageous property can be attributed to the presence of both interstitial oxygen and cation vacancies, that create diffusion...

With appropriate doping or processing, Li7La3Zr2O12 (LLZO) is an excellent candidate to be used in Li batteries either as a solid electrolyte or as a separator between the Li anode and a liquid electrolyte. For both uses, the reactivity with water either from the air or in aqueous media is a matter of interest. We address here the structural change...

rystal-to-crystal transformations have been crucial in the understanding of solid-state processes, since these may be studied in detail by means of single crystal X-ray diffraction (SCXRD) techniques. The description of the mechanisms and potential intermediates of those processes remains very challenging. In fact, solid-state metastable intermedia...

Despite the large number of NMR studies performed on lithium conductors with the garnet-type structure, the distribution of the lithium ions in Li7La3Zr2O12 (LLZO) and their contribution to ionic conductivity are still a matter of controversy. In this work we present a magic-angle spinning (MAS) NMR study of enriched 6Li7-xHxLa3Zr2O12 (0 ≤x ≤5) gar...

Directionally solidified eutectics in the 8 mol% Yttria stabilised zirconia and manganese oxide system were fabricated by the laser assisted melt float zone (LFZ) method at different growth rates. The eutectic composition was determined to 0.82 mol% of MnOx. The crystal structure and composition of the eutectic phases were determined by XRD, EBSD,...

A single-crystal structure determination of Nd8Sr2Si6O26 apatite, a prototype intermediate-temperature electrolyte for solid oxide fuel cells grown by the floating-zone method, was completed using the combination of Laue neutron diffraction and Raman spectroscopy. While neutron diffraction was in good agreement with P63/m symmetry, the possibility...

The structure, thermal stability, morphology and ion conductivity of titanium perovskites with the general formula Li(3x)Ln(2/3-x)TiO(3) (Ln=rare earth element; 3x=0.30) are studied in the context of their possible use as solid electrolyte materials for lithium ion batteries. Materials are prepared by a glycine nitrate method using different sinter...

La2O3 takes part in a variety of technologically interesting solids, but it has a known tendency to react with water and CO2, which may result in nonstoichiometry of the final product and the appearance of impurities. We apply Raman spectroscopy to study hydration and carbonation effects of La2O3-based materials, using La(OH)3 as starting material....

We address the controversial issue of the structural stability of Li7La3Zr2O12 garnets, focusing on the mechanisms that result in the transformation from tetragonal to cubic symmetry. We show that undoped tetragonal Li7La3Zr2O12 not exposed to humidity at any moment undergoes a reversible phase transition to cubic symmetry at Tc 645 °C that we ascr...

In this paper we present a study into the preparation of dense La8Y2Ge6O27 apatite electrolytes through both conventional and spark plasma sintering (SPS). For the SPS pellets, the effect of the starting precursor was also examined to include precursors prepared via both standard solid state and a new sol gel route. The results show that similar bu...

In this paper we presented the X-ray PDF investigation of orthorhombic Ba(2)In(2)O(5) and cubic Ba(2)In(1.7)P(0.3)O(5.3) and Ba(2)In(1.7)S(0.3)O(5.45) samples. Pure Ba(2)In(2)O(5) was found to be properly described-at the local scale-by the orthorhombic average structure. Ba(2)In(1.7)P(0.3)O(5.3) and Ba(2)In(1.7)S(0.3)O(5.45) cannot be described, a...

Germanium-based apatite compounds are fast oxide-ion conductors for potential use in fuel cells. A combination of solid-state 17O NMR spectroscopy, atomistic modeling, and DFT techniques help to elucidate oxygen defect sites and novel cooperative mechanisms of ion conduction. The picture shows oxygen diffusion in the studied apatite compound from m...

Recently, apatite-type germanates La9.33+xGe6O26+3x/2 have attracted considerable interest due to their high oxide ion conductivities. Research has shown that the key defects are oxide ion interstitials which lead to the conversion of some of the GeO4 units to GeO5. Consequently there has been a large interest in the preparation of high oxygen exce...

Traditionally materials with the fluorite and perovskite structures have dominated the research in the area of oxide ion/proton conducting solid electrolytes. In such cases, the key defects are oxide ion vacancies, and conduction proceeds via a simple vacancy hopping mechanism. In recent years, there has been growing interest in alternative structu...

In this communication we provide a direct insight into the local structure and defects of oxygen excess Ge-apatites, in both dry and deuterated states, by means of pair distribution function analysis.

In this paper we report the successful incorporation of phosphate and sulfategroups into the ionic conductor, Ba2In2O5, with the samples analysed through a combination of X-ray diffraction, NMR, TGA, Raman spectroscopy and conductivity measurements. The results show that such oxyanion incorporation leads to a conversion from an ordered brownmilleri...

The possibility of doping phosphate anions onto the In site of Ba2In2O5 with the aim of reducing the basicity of the system and hence improving long term stability is investigated.

High oxygen content apatite germanates, La(10)Ge(6-x)W(x)O(27+x), have been prepared by doping on the Ge site with W. In addition to increasing the oxygen content, this doping strategy is shown to result in stabilisation of the hexagonal lattice, and yield high conductivities. Structural studies of La(10)Ge(5.5)W(0.5)O(27.5) show that the interstit...

In this communication, we demonstrate the successful incorporation of phosphate into Ba(2)In(2)O(5), which leads to the conversion from an orthorhombic to a cubic unit cell. The resulting increased oxygen vacancy disorder leads to an enhancement in the oxide ion conductivity at low temperatures. In addition, in wet atmospheres, significant proton c...

Apatite-type oxide-ion conductors have attracted considerable interest as potential fuelcell electrolytes. Atomistic modelling techniques have been used to investigate oxygen interstitial sites, protonic defects and water incorporation in three silicate and three germanate-based apatite-systems, namely La8Ba2(SiO4)6O2, La9.33(SiO4)6O2, La9.67(SiO4)...

A Raman spectroscopy study of the apatite series La8+xBa2−x(GeO4)6O2+x/2 is presented. The results show the presence of a new Raman band appearing at 645 cm−1, whose intensity increases with increasing interstitial oxide ion content. This new band is also observed in samples containing cation vacancies, consistent with previous suggestions that the...

Following recent reports of an enhancement in the conductivity of apatite-type germanate systems at intermediate temperatures in wet atmospheres, the ability of a range of apatite-type silicates/germanates to incorporate water has been assessed through a combination of X-ray diffraction studies and thermogravimetric analysis. The results indicate t...

Following growing interest in the use of ammonia as a fuel in solid oxide fuel cells (SOFCs), we have investigated the possible reaction between the apatite silicate/germanate electrolytes, La8+xSr2-x(Si/Ge)6O26+x/2, and NH3 gas. We examine how the composition of the apatite phase affects the reaction with ammonia. For the silicate series, the resu...

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Apatite-type rare earth silicates/germanates have attracted considerable interest recently due to their high oxide ion conductivities. Despite evidence in support of a conduction mechanism involving interstitial oxide ions, the exact location of the interstitial oxide ion sites continues to attract controversy. In this paper we report a neutron dif...

In this review article, new systems being investigated for application in solid oxide fuel cells are discussed. For the electrode materials, materials with the perovskite or related structures continue to dominate the field, due to the need for high electronic conductivity. Research in this field is being directed toward compositions allowing high...

Apatite-like materials are of considerable interest as potential solid oxide fuel cell electrolytes, although their structural vagaries continue to attract significant discussion. Understanding these features is crucial both to explain the oxide ion conduction process and to optimise it. As the composition of putative P6(3)/m apatites with ideal fo...

Despite being proven to be a good lithium-ion conductor 30 years ago, the crystal structure of the ramsdellite-like Li2Ti3O7 has remained uncertain, with two potential models for locating the lithium ions in the structure. Although the model presently accepted states that both lithium and titanium occupy the octahedral sites in the framework, evide...

Despite being proven to be a good lithium-ion conductor 30 years ago, the crystal structure of the ramsdellite-like Li(2)Ti(3)O(7) has remained uncertain, with two potential models for locating the lithium ions in the structure. Although the model presently accepted states that both lithium and titanium occupy the octahedral sites in the framework,...

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 ≤...

There is growing interest in the use of ammonia as a fuel in Solid Oxide Fuel Cells (SOFCs). However, the possible reaction between the electrolyte and ammonia, and its potential effect on performance, has received little attention. In this paper, we report an investigation of the high temperature (950 °C) reaction of the apatite-type oxide ion con...

29Si NMR data have been recorded for the apatite series La8+xSr2-x(SiO4)6O2+x/2 (0 < or = x < or = 1.0). For x = 0, a single NMR peak is observed at a chemical shift of approximately -77 ppm, while as the La : Sr ratio and hence interstitial oxygen content is increased, a second peak at a chemical shift of approximately -80 ppm is observed, which h...

Ti-substituted MnNb2O6 samples have been prepared to enhance conductivity via introduction of oxygen vacancies or hole formation. The single phase MnNb2-xTixO6-δ columbite existence range is narrow (0 < x < 0.2). The effect of the substitution on electrical properties has been evaluated and compared to both nominal MnNb2O6 as prepared in air and re...

A manganocolumbite with nominal composition MnNb2O6 has been prepared under air in order to characterize its electrical behavior. Although powder X-ray diffraction indicates the presence of a single phase, electrical and microscopic characterization reveals two different bulk responses. The origin of these two bulk elements seems to relate to the p...

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Compounds based on polyanions are currently proposed as a promising alternative to layered LiMO 2 materials as cathode for rechargeable batteries. We have recently investigated the electrochemical behaviour of Li 3 Fe(MoO 4) 3 as positive electrode in lithium cells [1]. Li 3 Fe(MoO 4) 3 undergoes a complex electrochemical reaction with lithium, whe...