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In this work, we have studied the preparation and properties of an alumino-phosphate glass with composition 13Na2O-13K2O-16BaO-4Al2O3-54P2O5 (mol%). The first part of the work deals with the study of the processing conditions of the dehydroxylation of the phosphate glass, which was performed by remelting under N2 flow using graphite crucibles. Glass samples from 5 to 50 g and Nd2O3 doped were submitted to dehydroxylation and the influence of temperature, time, mass of glass and viscosity were correlated with the content of water in the glasses through the coefficient of absorption of OH ions. The network structure of the glasses was also determined by means of 31P and 27Al 1D/2D nuclear magnetic resonance and the local environment of Nd3+ ions was probed by electron paramagnetic resonance. The optimized conditions of processing were then used to obtain a dehydroxylated glass with a 2.5 wt% Nd2O3 whose spectroscopic and laser emission properties were studied. The spectroscopic properties of Nd3+ ions which include, Judd-Ofelt calculation, stimulated emission cross-section of the laser transition, lifetime, and quantum efficiency are presented. Site-selective laser spectroscopy and stimulated emission obtained under selective wavelength pumping along the 4I9/2→4F5/2 absorption band were performed to determine the distribution of crystal field in which the rare earth is located, together with its influence in the pump wavelength dependence of the spontaneous and laser emissions of Nd3+ in this glass matrix.

The application of oxynitride glasses in optics has been limited due the issues inherent in their preparation that result in bubbles, metallic inclusions or opacity. Although the synthesis of oxynitride phosphates is easier than in silicates, due to their lower melt viscosity, the remaining water in the form of OH causes, for instance, the neodymium luminescence to be negatively affected. We report on the preparation of oxynitride Nd phosphate glasses that are submitted first to a dehydroxylation, so that their structure and properties can be studied as a function of the nitrogen content taking a completely homogeneous OH-free glass as the starting point of each synthesis. Raman and Brillouin Spectroscopy confirmed the segregation in oxide and N-enriched regions, and NMR of the glasses has been used to calculate the O/P ratio from the distribution of P(O,N)4 groups. The difference between this and the experimental one obtained from the elemental analyses confirms the segregation in oxide and oxynitride regions that is produced during the ammonolysis of the phosphate glass. The oxynitride glass network could thus be considered a non-homogeneous mixture of the oxide and the nitrided phases that are segregated due to the non-randomness of the nitridation reaction.

[EN] Brillouin spectroscopy is a well-established technology in condensed matter physics to characterize the mechanical properties of inert materials, and it has been extended very recently to the study of biological samples. Transparency is beneficial for samples to be properly analyzed by Brillouin spectroscopy. Here, we explored the efficacy of optical tissue clearing techniques to improve the acquisition of Brillouin spectra from biological tissues in order to analyze their biomechanical properties. We describe the first application of Brillouin scattering to optically cleared biological tissues with CUBIC protocol. We conclude that, within the range of error, tissue clearing does not modify the mechanical properties of the studied biological tissues.

The elastic constants of high-quality, single-crystal hexagonal boron nitride (h-BN) have been measured by means of high resolution Brillouin spectroscopy using a modified reflected light microscope. The sound propagation velocity in the c-axis direction and perpendicular to the c-axis have been obtained from the Brillouin frequency shift, with a proper account taken of the vast difference between the ordinary and extraordinary refractive indices recently reported in the highly anisotropic layered h-BN crystal. The elastic constants c11 and c33 obtained from the Brillouin experiments are somewhat lower than previous determinations based on inelastic x-ray measurements and confirm the overestimation of the h-BN elastic constants by ab initio calculations based on density functional perturbation theory in the local density approximation.

Rhombohedral NASICON compounds with general formula LiTiSc(PO) (0 ≤ x ≤ 0.5) have been prepared using a conventional solid-state reaction and characterized by X-ray diffraction (XRD), nuclear magnetic resonance (NMR), and impedance spectroscopy. The partial substitution of Ti by Sc and Li in pristine LiTi(PO) increases unit-cell dimensions and the number of charge carriers. In Sc-rich samples, the analysis of XRD data andLi/Li,P, andSc MAS NMR spectra confirms the presence of secondary LiScO and LiScPO phases that reduce the amount of lithium incorporated in the NASICON phase. In samples with x < 0.3, electrostatic repulsions between Li ions located at M1 and M3 sites increase Li mobility. For x ≥ 0.3, ionic conductivity decreases because of secondary nonconducting phases formed at grain boundaries of the NASICON particles (core-shell structures). For x = 0.2, high bulk conductivity (2.5 × 10 S·cm) and low activation energy (E = 0.25 eV) measured at room temperature make LiTiSc(PO) one of the best lithium ionic conductors reported in the literature. In this material, the vacancy arrangement enhances Li conductivity.

Deep eutectic solvents (DESs) offer a suitable alternative to conventional solvents in terms of both performance and cost-effectiveness. Some DESs also offer certain green features, the greenness of which is notoriously enhanced when combined with water. Aqueous DES dilutions are therefore attracting great attention as a novel green medium for biotechnological processes, with the aqueous dilutions of reline-a DES composed of urea and choline chloride-being one of the most studied systems. Despite their macroscopic homogeneous appearance, both H NMR spectroscopic studies and molecular dynamics simulations have revealed the occurrence of certain dynamic heterogeneity at a microscopic molecular level. Ultrasonic measurements were also used with the aim of getting further insights but nonconclusive results were obtained. Herein, we have studied aqueous reline dilutions by Brillouin spectroscopy given its proved suitability for detecting local structure rearrangements in liquid mixtures of H-bonded co-solvents. Brillouin spectroscopy revealed the formation of a co-continuous structure resulting from local structure rearrangements and micro-segregation into aqueous and DES phases. Interestingly, there is agreement between H NMR and Brillouin spectroscopy when pointing to the DES content where microphase segregation and formation of co-continuous structures occurred.

The NASICON series, with formula BaLiTi(PO) (0.4 ≤ x ≤ 1), has been prepared by solid-state reaction and characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR), Raman, nuclear magnetic resonance (NMR) and impedance spectroscopy (IS). XRD patterns of samples indicated the formation of single phases with rhombohedral structure (space group R-3c). The Rietveld analysis of XRD patterns was performed to deduce location of Li and Ba ions. FTIR, Raman, and NMR techniques showed the only presence of isolated PO groups in analyzed phosphates. P MAS-NMR spectra were used to investigate Li and Ba distribution and Li MAS-NMR spectra to discriminated Li ions with different mobility in conduction paths. A maximum total conductivity of 2.5 × 10 S cm and a minimum activation energy of 0.47 eV were obtained at room temperature for BaLiTi(PO) (x = 0.6).

Porous carbons are really interesting materials for applications such as gas adsorption, electrocatalysts or energy harvesting and conversion.[1] Among others, spinodal decomposition (SD) processes have proved effective for the synthesis of macro- and mesoporous materials.[2] Despite the theoretical aspects of SD processes are well understood, finding the proper experimental conditions to obtain bicontinuous structures via SD processes is a non-predictable and quite tedious process, typically based on trial and error. The challenge is therefore finding a ¿tool¿ capable to predict the suitability of a particular starting solution to undergo a spinodal decomposition process. We have used aqueous solutions of different DESs containing common carbon precursors (i. e. resorcinol) for the preparation of bicontinuous porous carbons via polycondensation of resorcinol with formaldehyde. Scanning electron microscopy analysis of the different carbons allowed us to determine which solutions leads to bicontinuous structures via SD. Moreover, we studied the starting DES/H2O binary mixtures by Brillouin spectroscopy given the capability of this technique to observe local structure rearrangements resulting from non-ideal mixing of the components. In our case, we found that the representation of data obtained by Brillouin spectroscopy allows predicting the range of molar fractions of DES in H2O for which bicontinuous structures via SD are ultimately obtained.

The substitution of nitrogen for oxygen in phosphate glasses improves the chemical, thermal and mechanical properties and particularly reduces their very high hygroscopic character, although the preparation of homogeneous and free of defects oxynitride bulk phosphate glasses through ammonolysis represents a big challenge. This work reports on the synthesis and properties of a series of Nd-doped oxynitride phosphate glasses with composition Na0.3K0.3Ba0.2PO3-3x/2Nx that may find application as laser hosts. Whereas the glass transition temperature, elastic modulus and index of refraction show a regular increase with the nitrogen content that agrees with previous studies, the effect of nitrogen onto the luminescence of Nd3+ ions appears to be more complicated. The average lifetime of the decay from the 4F3/2 level decreases with the N/P ratio of the glasses, which is thought to be mainly due to the presence of water from the ammonolysis reaction. However, further thermal treatments under N2 flow of an oxynitride glass have shown an important reduction of the water content as well as a drastic increase of the luminescence lifetime of Nd3+, this being a promising method for the development of laser phosphate glasses having good chemical and mechanical properties.

Spinodal decomposition (SD) processes have proved effective for the synthesis of macro- and mesoporous materials. Despite the theoretical aspects of SD processes are well understood, finding the proper experimental conditions – both the components as well as the ratio in which they have to be combined – to attain co-continuous structures is a non-predictable and quite tedious process, typically based on trial and error. The challenge is finding a “tool” capable to predict the suitability of a particular starting solution to undergo SD processes. Here in, we used aqueous solutions of deep eutectic solvents (DESs) for the preparation via SD of co-continuous porous carbons, the morphologies of which ranged from spinodal to aggregates-of-particles-like just depending on dilution. Despite the starting DES/HO binary mixture was macroscopically homogeneous, Brillouin spectroscopy revealed the occurrence of certain nanostructural rearrangements within a dilution range that coincided with that used for preparation of carbons with morphologies transitioning from spinodal to aggregates-of-particles-like. Moreover, carbons exhibited a noticeable degree of heteroatom co-doping – e.g. N and P – and proved particularly effective for CO capture with adsorptions of up to 4.7 mmol/g at 0 °C and 760 mbar.

In this work, we extend, review and jointly discuss earlier experiments conducted by us in hyperaged geological glasses, either in Dominican amber (20 million years old) or in Spanish amber from El Soplao (110 million years old). After characterization of their thermodynamic and elastic properties (using Differential Scanning Calorimetry around the glass-transition temperature, and measuring mass density and sound velocity), their specific heat was measured at low and very low temperatures. By directly comparing pristine amber samples (i.e. highly stabilized polymer glasses after ageing for millions of years) to the same samples after being totally or partially rejuvenated, we have found that the two most prominent universal >anomalous> lowerature properties of glasses, namely the tunnelling two-level systems and the so-called >boson peak>, persist essentially unchanged in both types of hyperaged geological glasses. Therefore, non-Debye low-energy excitations of glasses appear to be robust, intrinsic properties of non-crystalline solids which do not vanish by accessing to very deep states in the potential energy landscape.

It is shown that direct information from surface acoustic waves (SAWs) of bulk transparent materials can be obtained by using Brillouin light scattering (BLS). The study of surface phonons by means of an optical spectroscopy such as BLS has been historically constrained to nontransparent and highly reflecting bulk and film samples or even to very thin films deposited on reflecting substrates. Probably due to its low signal and to the narrow window in experimental conditions, it was assumed for years that bulk transparent samples were not suited for Brillouin spectroscopy in order to get information on SAWs, negating this optical technique in the search for SAW properties. The reported experiments on transparent glasses and single crystals (cubic MgO and trigonal sapphire) prove that there is no intrinsic physical reason not to collect SAW propagation velocity data from transparent bulk samples and opens a challenge to apply the Brillouin spectroscopy in a wider scenario to obtain direct information, in a nondestructive and contactless way, about SAWs in bulk materials.

The Na-Yb (or Er) co-substitution of Ca in CaNbGaO (CNGG) laser crystal is studied. In contrast to other garnets whose structural disorder is exclusively based on the presence of differently sized cations on the same crystal sites, Na incorporated in the dodecahedral site (a site also shared by Ca and trivalent lanthanides) creates diverse electric charge distributions over the dodecahedral sublattice, which adds to the disorder associated with Nb and Ga simultaneous occupation of the octahedral and tetrahedral sites. The currently determined cationic compositions of Czochralski grown congruent CNGG and Na-modified CNGG crystals show that Na incorporation reduces the cationic vacancy concentration on dodecahedral and octahedral sites but does not affect that in tetrahedral sites. Physical properties of interest for laser design (optical transmission, elastic constants, hardness, specific heat, thermal conductivity, thermal expansion, refractive index dispersion, group velocity dispersion, and thermo optic coefficients) have been systematically determined at cryogenic temperatures and above room temperature. Na incorporation into CNGG decreases the crystal growth temperature, promotes Yb doping, and importantly, increases the Yb optical bandwidth, offering good prospects for the implementation of ultrashort pulses in mode-locked laser oscillators.

We present high-resolution surface Brillouin scattering measurements on cubic GaN layers grown on GaAs substrate. By using a suitable scattering geometry, scattering by surface acoustic waves is recorded for different azimuthal angles, and the surface acoustic wave velocities are determined. A comparison of experimental results with numerical simulations of the azimuthal dependence of the surface wave velocity shows good agreement and allows a consistent set of elastic constants for c-GaN to be determined. © 2016 The Japan Society of Applied Physics.

We propose a strategy to study the elastic properties of extremely thin graphene oxide (GO) films using Brillouin spectroscopy. The dependence of the surface acoustic wave of a gold capping layer on the structural, chemical and morphological changes occurring to the underneath GO film with temperature is reported and analyzed. At room temperature the shear constant c44 is ∼17 GPa and hardens up to 28 GPa at 100 °C due to the partial elimination of embedded water layers and to interlayer distance shrinking. At 200 °C the almost complete elimination of water induces layer stacking disorder, further GO–GO distance reduction and a significant increase of all elastic constants. The in-plane constants harden due to the partial restoration of the sp2 C network (c11: from 268 to 620 GPa) and the out of plane constants harden due to the H bonds that now directly connect the neighbouring GO layers (c44 ≈ 80 GPa). The obtained Young's moduli are significantly higher than those reported for GO paper because the ultra-thin GO films are highly ordered and there is no macroscopic applied strain during the measurement. The results obtained here are associated with the intrinsic properties of GO as in-plane and inter-layer bonding.

We review and concurrently discuss two recent works conducted by us, which apparently give opposite results. Specifically, we have investigated how extreme thermal histories in glasses can affect their universal properties at low temperatures, by studying: (i) amber, the fossilized natural resin, which is a glass which has experienced a hyperaging process for about one hundred million years; and (ii) ultrastable thin-film glasses of indomethacin. Specific heat Cp measurements in the temperature range 0.07 K < T < 30 K showed that the amount of two-level systems, assessed from the linear term at the lowest temperatures, was exactly the same for the pristine hyperaged amber glass as for the subsequently rejuvenated samples, whereas just a modest increase of the boson-peak height (in Cp/T3) with increasing rejuvenation was observed, related to a corresponding increase of the Debye coefficient. On the other hand, we have observed an unexpected suppression of the two-level systems in the ultrastable glass of indomethacin, whereas conventionally prepared thin films of the same material exhibit the usual linear term in the specific heat below 1 K ascribed to these universal two-level systems in glasses. By comparing both highly-stable kinds of glass, we conclude that the disappearance of the tunneling two-level systems in ultrastable thin films of indomethacin may be due to the quasi-2D and anisotropic behavior of this glass, what could support the idea of a phonon-mediated interaction between two-level systems.

The demixing process of aqueous poly(N-isopropylacrylamide) (PNIPAM) solutions can occur either via a nucleation and growth process or via spinodal decomposition. The ensuing self-assembly, leading to heterogeneous morphologies within the PNIPAM solution, is codetermined by kinetic processes caused by molecular transport. By subjecting PNIPAM solutions to cyclic changes in temperature leading to repeated crossing of the demixing transition, we are able to assess the importance of kinetics as well as of overheating and supercooling of the phase transition within the metastable range delimited by the binodal and spinodal lines. First indications about the location of these stability limits for the low- and high-temperature phases, separated by about 1.6 K, could be gained by detailed kinetic studies of the refractive index. These investigations are made possible due to the novel technique of temperature-modulated optical refractometry.

The two most prominent and ubiquitous features of glasses at low temperatures, namely the presence of tunneling two-level systems and the so-called boson peak in the reduced vibrational density of states, are shown to persist essentially unchanged in highly stabilized glasses, contrary to what was usually envisaged. Specifically, we have measured the specific heat of 110 million-year-old amber samples from El Soplao (Spain), both at very low temperatures and around the glass transition Tg. In particular, the amount of two-level systems, assessed at the lowest temperatures, was surprisingly found to be exactly the same for the pristine hyperaged amber as for the, subsequently, partially and fully rejuvenated samples. © 2014 American Physical Society.

Kinetic processes, which are joined with mass transport, are studied in the vicinity of the sharp LCST-type demixing transition of semi-dilute aqueous poly(N-isopropyl acrylamide) (PNIPAM) solutions. These processes are slow as compared to the highly cooperative collapse of individual polymer chains. Purely elastic properties, that are particularly sensitive to this phase transition, are addressed depending on the temperature, space and time by Brillouin spectroscopy. Above the demixing temperature Tc, we discriminate between kinetics related to the phase separation into PNIPAM-rich and PNIPAM-poor domains and kinetics connected to the impact of gravitation on the on-going phase separation. Using shallow temperature jumps of 0.3 °C, the growth of compact PNIPAM-rich agglomerates with identical gel-like mechanical consistency is provoked independently of temperature and position within the sample above Tc. Astonishingly, the transition temperature does not vary while heating or cooling the solutions across the phase transition, although the elastic properties depend strongly on space and time during the equilibration of PNIPAM concentration gradients following the re-entrance into the low-temperature phase. © 2013 The Royal Society of Chemistry.

Functional polymers containing Lewis bases are known as promising materials for the elaboration of highly sensitive micro-sensors for acid gas detection. In this work, poly(urethane-imide)s (PUIs) with Lewis bases were synthesized in two steps only from various functional diols (N-methyldiethanolamine, N-tert-butyldiethanolamine, N-phenyldiethanolamine and 1,4-diethanolpiperazine) containing one or two tertiary amine groups with different chemical structures. The synthesis led to high yields, high molecular weights and a good control of the PUI amine content. These good film-forming polymers were then used as SO2 sensitive coatings on Love surface acoustic wave (L-SAW) micro-sensors. The physical and mechanical properties required for an optimal micro-sensor design were determined by High Resolution Brillouin Spectroscopy of PUI thin layers. Three-layer micro-sensors were developed by respecting the conditions for the L-SAW generation. The three-layer structure included Quartz ST-90 as the piezoelectric substrate, a ZnO guiding layer and a PUI sensitive layer. These micro-sensors were weakly sensitive to temperature and thus compatible with the targeted application. The experimental results for SO 2 detection showed that all the PUI coatings greatly improved the sensitivity compared to a micro-sensor without polymer coating. The basicity of the amine groups was not determining for the micro-sensor sensitivity to the SO2 acid gas and the key factor was their steric hindrance. Finally, the micro-sensor sensitivity increased with the accessibility of the amine groups in the order Piperazine-diol < tBu-DEA ≅ Ph-DEA ≪ MDEA. © 2013 Elsevier B.V. All rights reserved.

We discuss our work on simple aliphatic glass-forming monoalcohols at low temperatures, including experiments on specific heat, thermal conductivity, Brillouin scattering and x-ray diffraction. The family of simple monoalcohols is an interesting model system for exploring molecular glass-forming liquids, the low-temperature universal properties of glasses, and even the glass transition phenomenon itself. More specifically, we examine the role of the molecular aspect ratio in the kinetics of vitrification/crystallization, the reported appearance of particular cases of polymorphism (in ethanol) and polyamorphism (in butanol), and, especially, the influence of positional isomerism and the location of the hydrogen bond on the lattice dynamics and, therefore, on the universal low-temperature properties of glasses. © 2013 AIP Publishing LLC.

Boron-carbon-nitrogen films were grown by RF reactive sputtering from a B4C target and N2 as reactive gas. The films present phase segregation and are mechanically softer than boron carbide films (a factor of more than 2 in Young's modulus). This fact can turn out as an advantage in order to select buffer layers to better anchor boron carbide films on substrates eliminating thermally induced mechanical tensions. © 2013 AIP Publishing LLC.

Temperature-dependent surface acoustic wave (SAW) propagation velocity and temperature coefficient of frequency (TCF) have been determined for the first time in InxGa1-xN alloys by means of high-resolution Brillouin spectroscopy (HRBS). HRBS offers an alternative way of determining TCF. The obtained TCF values present a non-linear behavior with the In concentration. TCF of pure InN (-13.75 ppm/K) is similar to those of AlN and GaN (-19 and -17.7 ppm/K, respectively). InxGa1-xN samples exhibit frequency values that are very stable against temperature changes, which makes InxGa1-xN a good candidate for current SAW-based technological applications.

We have determined the surface acoustic wave velocity in In xGa 1-xN layers for 0.34 x 0.75 by means of high resolution Brillouin spectroscopy. The sagittal dependence of the surface acoustic velocity has been analyzed by comparing the experimental results with theoretical simulations based on the Green's function formalism. We find the best agreement with our data when the bowing parameters for the elastic constants recently reported from density functional theory calculations are taken into account. The dependence of the surface acoustic wave velocity on alloy composition is given. © 2012 American Institute of Physics.

We present low-temperature measurements of the specific heat and the thermal conductivity for the three solid phases of n-butanol, namely glass, crystal and “glacial” phases.Whereas crystal and glass ones are found to exhibit the expected thermal behavior for crystalline and non-crystalline solids, respectively (i.e. Debye theory for crystals, and universal low-temperature properties with a boson peak and a concomitant plateau in the thermal conductivity for glasses), the so-called “glacial phase” behaves as a very defective crystal, confirming earlierwork that identifies it as a mixed phase of nanocrystallites and a disordered matrix. We have also measured longitudinal and transverse sound velocities at lowtemperatures for the glass phase. The elastic Debye coefficient and Debye temperature of the glass determined fromthese measurements are found to agree verywellwith the calorimetric ones obtained from a SPM analysis of the specific heat. © 2010 Elsevier B.V. All rights reserved.

Au thin films have been deposited by DC magnetron sputtering on Si (001) substrates at different substrate temperatures, ranging from 200 K to 450 K. With increasing temperature, the expected crystallinity and morphology of the Au thin film are clearly improved, as shown by x ray diffraction, atomic force microscopy and scanning electron microscopy experiments. Parallel to this, the surface acoustic wave propagation velocity shows a clear enhancement toward the ideal values obtained from numerical simulations of a Au thin film on Si (001) substrate. Moreover, a very thin and slightly rough interlayer between the Si (001) substrate and the Au thin film is developed for temperatures above 350 K. The composition and nature of this interlayer is not known. This interlayer may be responsible for the steep change in the structural and elastic properties of the Au thin films at the higher temperatures and possibly also for an improvement of the adhesion properties of the Au on the Si (001) substrate. © 2011 American Institute of Physics.

Carbon thin films have been deposited by DC magnetron sputtering at different substrate temperatures ranging from 200 K to 400 K. The influence of the preparation substrate temperature on the elastic properties has been evidenced by means of the High Resolution Brillouin Spectroscopy. Thus, the surface acoustic wave (SAW) velocity evolution could be assessed for the different samples. The observed variation is analysed in terms of the relative population of sp2 allotropes phases forming the film. © EDP Sciences, Societa Italiana di Fisica, Springer-Verlag 2010.

We have conducted x-ray diffraction, calorimetric and Brillouin-scattering experiments on n-butanol between 77 and 300K, aiming to explore the physical nature of the so-called 'glacial state' previously found in n-butanol as well as in triphenyl phosphite. In addition to our structural and thermodynamic studies of the liquid-glass transition and of the stable crystal state in n-butanol, we have found that the metastable 'glacial state' that can be obtained in the temperature range 125-160K is not a second amorphous state, but rather the result of a frustrated or aborted crystallization process that produces plenty of nanocrystallites embedded in a disordered matrix. The crystalline order of these nanocrystallites of the 'glacial phase' is exactly the same as that well observed in the fully ordered stable crystal into which it transforms by heating above 160K. © 2010 IOP Publishing Ltd.

High resolution Brillouin spectroscopy (HRBS) backscattering elastic data in nanocomposites of ethylene-vinyl alcohol copolymer (EVOH) and TiO2 nanoparticles present anomalous dependence with concentration, while Young's modulus and microhardness data show the expected behaviour. When performing HRBS with the 90A scattering geometry to asses the effective elastic constant, the expected behaviour for low concentration of TiO2 nanoparticles is again obtained. This unusual disagreement can be solved assuming that the inclusion of TiO2 nanoparticles induces anomalous refractive index behaviour at the applied laser wavelength for the different EVOH-TiO2 nanocomposites. Comparison with experimental elastic and optical data obtained in isotactic-polypropylene-TiO2 nanocomposites proves that EVOH-TiO2 nanocomposites show an unusual optical behaviour at the laser wavelength, possibly due to a singular bonding between the EVOH polymer and the TiO2 nanoparticles. © 2009 Elsevier Ltd. All rights reserved.

Procedimiento para modular las propiedades eléctricas de óxidos con estructura tipo perovskita derivados del niobato de sodio mediante la creación de vacantes catiónicas. La presente invención se refiere a un procedimiento para modificar controladamente las propiedades eléctricas del óxido NaNbO3 mediante la creación de vacantes catiónicas en la subred A de la estructura tipo perovskita. La introducción progresiva de vacantes en la subred A al dopar con un ión alcalinotérreo como por ejemplo Sr2+ o con un ión de tierra rara como por ejemplo La3+ permite la estabilización de un material ferroeléctrico, y el cambio continuo de comportamiento ferroeléctrico a ferroeléctrico-relaxor característico de las disoluciones sólidas tipo perovskita sin plomo. La presente invención incluye el procedimiento para la obtención de los óxidos que, en función de sus propiedades, pueden ser usados en dispositivos electrónicos como materiales piezoeléctricos y piroeléctricos en sensores y actuadores.