34 research outputs found
Unraveling Bulk and Grain Boundary Electrical Properties in La0.8Sr0.2Mn1-yO3 Thin Films
Grain boundaries in Sr-doped LaMnO3 thin films have been shown to strongly
influence the electronic and oxygen mass transport properties, being able to
profoundly modify the nature of the material. The unique behaviour of the grain
boundaries can be correlated with substantial modifications of the cation
concentration at the interfaces, which can be tuned by changing the overall
cationic ratio in the films. In this work, we study the electronic properties
of La0.8Sr0.2Mn1-yO3 thin films with variable Mn content. The influence of the
cationic composition on the grain boundary and grain bulk electronic properties
is elucidated by studying the manganese valence state evolution using
spectroscopy techniques and by confronting the electronic properties of
epitaxial and polycrystalline films. Substantial differences in the electronic
conduction mechanism are found in the presence of grain boundaries and
depending on the manganese content. Moreover, the unique defect chemistry of
the nanomaterial is elucidated by measuring the electrical resistance of the
thin films as a function of oxygen partial pressure, disclosing the importance
of the cationic local non-stoichiometry on the thin films behavior
Thin film oxide-ion conducting electrolyte for near room temperature applications
Stabilized bismuth vanadate thin films are presented here as superior oxide ionic conductors, for application in solid state electrochemical devices operating near room temperature. Widely studied in the 90s in bulk form due to their unbeatable ionic conduction, this family of materials was finally discarded due to poor stability above 500 °C. Here, we however unveil the possibility of using BiVCuO at reduced temperatures in thin film-based devices, where the material keeps its unmatched conduction properties and at the same time shows good stability over a wide oxygen partial pressure range
Active layers based on vertically aligned nanostructures for SOFC applications
One of the most recent strategies to enhance the electrode performance is preparing
composite materials leading to an increase of the triple-phase-boundary (TPB) length. In this
work, thin films VANs based on (La0.8Sr0.2)0.98Fe0.8Ti0.2O3−δ-Ce0.9Gd0.1O1.95 (LSFT-GDC)
deposited by PLD were obtained for their use as functional layers in Solid Oxide Fuel Cells
(SOFCs).Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech
Vertically Aligned Nanostructures for SOFC applications
One of the most recent strategies to enhance the
electrode performance is preparing composite materials
leading to an increase of the triple-phase-boundary (TPB)
length. On this way, heteroepitaxial nanocomposite films
such as vertically aligned nanostructures (VANs)
deposited by Pulsed Laser Deposition (PLD) are one of
the most promising and recent approaches to obtain
nanocomposite active layers for energy applications1. In
this work, thin films VANs based on
(La0.8Sr0.2)0.98Fe0.8Ti0.2O3−δ-Ce0.9Gd0.1O1.95 (LSFT-GDC)
electrodes were obtained for their use as functional layers
in Solid Oxide Fuel Cells (SOFCs).Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech
Engineering Transport in Manganites by Tuning Local Non-Stoichiometry in Grain Boundaries
Interface-dominated materials such as nanocrystalline thin films have emerged
as an enthralling class of materials able to engineer functional properties of
transition metal oxides widely used in energy and information technologies. In
particular, it has been proved that strain-induced defects in grain boundaries
of manganites deeply impact their functional properties by boosting their
oxygen mass transport while abating their electronic and magnetic order. In
this work, the origin of these dramatic changes is correlated for the first
time with strong modifications of the anionic and cationic composition in the
vicinity of strained grain boundary regions. We are also able to alter the
grain boundary composition by tuning the overall cationic content in the films,
which represents a new and powerful tool, beyond the classical space charge
layer effect, for engineering electronic and mass transport properties of metal
oxide thin films useful for a collection of relevant solid state devices
Unveiling the outstanding oxygen mass transport properties of Mn-rich perovskites in grain boundary-dominated La0.8Sr0.2(Mn1-xCox)0.85O3-d nanostructures
Ion transport in solid-state devices is of great interest for current and
future energy and information technologies. A superior enhancement of several
orders of magnitude of the oxygen diffusivity has been recently reported for
grain boundaries in lanthanum strontium manganites. However, the significance
and extent of this unique phenomenon is not yet established. Here, we fabricate
a thin film continuous composition map of the La0.8Sr0.2(Mn1-xCox)0.85O3-d
family revealing a substantial enhancement of the grain boundary oxygen mass
transport properties for the entire range of compositions. Through
isotope-exchange depth profiling coupled to secondary ion mass spectroscopy, we
show that this excellent performance is not directly linked to the bulk of the
material but to the intrinsic nature of the grain boundary. In particular, the
great increase of the oxygen diffusion in Mn-rich compositions unveils an
unprecedented catalytic performance in the field of Mixed Ionic Electronic
Conductors. These results present grain boundaries engineering as a novel
strategy for designing highly performing materials for solid state ionics based
devices
Isotope Exchange Raman Spectroscopy (IERS): a novel technique to probe physicochemical processes
We have developed a novel in situ methodology for the direct study of mass
transport properties in oxides with spatial and unprecedented time resolution,
based on Raman spectroscopy coupled to isothermal isotope exchanges. Changes in
the isotope concentration, resulting in a Raman frequency shift, can be
followed in real time, not accessible by conventional methods, enabling
complementary insights for the study of ion transport properties of electrode
and electrolyte materials for advanced solid-state electrochemical devices. The
proof of concept and strengths of isotope exchange Raman spectroscopy (IERS)
are demonstrated by studying the oxygen isotope back-exchange in
gadolinium-doped ceria (CGO) thin films. Resulting oxygen self-diffusion and
surface exchange coefficients are compared to conventional time-of-flight
secondary ion mass spectrometry (ToF-SIMS) characterisation and literature
values, showing good agreement, while at the same time providing additional
insight, challenging established assumptions. IERS captivates through its
rapidity, simple setup, non-destructive nature, cost effectiveness and
versatile fields of application and thus can readily be integrated as new
standard tool for in situ and operando characterization in many laboratories
worldwide. The applicability of this method is expected to consolidate our
understanding of elementary physicochemical processes and impact various
emerging fields including solid oxide cells, battery research and beyond
The performance of the Italian housing market and its effects on the financial system
Developments in the real-estate sector are of crucial importance for the business cycle and financial stability. This study analyses developments in the Italian housing market on the basis of both real and financial variables. Following the sharp contraction of the market during the financial crisis and the more general fall in economic activity, a few signals suggests that the recession in the housing market is easing somewhat. However, the degree of uncertainty remains considerable. In recent months the ratio between the flow of bad debts to total outstanding loans to households and construction firms has reached the highest levels since the beginning of the decade. The paper also investigates three issues of a more structural nature. First, it examines the performance and the regulatory framework of real-estate investment funds in Italy. Second, it analyses the main characteristics of the taxation of residential housing, with reference to ownership, rentals and transactions. Finally, the paper estimates the impact on residential house prices of the growing demand for housing services by immigrants.housing market cycle, transactions, rentals, residential house prices, mortgages, real-estate investment funds, taxation of residential housing