Lithium ion conducting polymer electrolytes based on polyvinyl Alcohol (PVA-OH) complexed with salt Li2SO4 and different weight percent ratios of PEG400 plasticizer have been prepared by solution cast technique using deionized water as solvent. The thermogravimetric analysis (TGA) showed that the thermal stability of the materials depended on the plasticizer content. The FTIR study confirmed the polymer - salt complex formation. The modulus spectra indicated the non-Debye nature of the material; a dominant relaxation process is visible being associated with the dynamic glass transition, relaxation-α. The maximum of each peak is shifted to higher frequencies as the plasticizer increases due to an enhancement of dipolar mobility in the origin of cooperative motions. A power law frequency dependence of the real part of the electrical conductivity is observed, which is characteristic of the effects of ion-ion and/or ion-chain correlations in ion motion. This variation is well fitted to a Jonscher′s expression.

Electrolitos poliméricos conductores de iones de litio, basados en alcohol de polivinilo (PVA-OH) complejado con la sal Li2SO4 y diferentes relaciones de porcentaje en peso de plastificante PEG400 fueron preparados por la técnica de solución utilizando agua desionizada como disolvente. El estudio FTIR confirma la formación del complejo polímero-sal. Las curvas de descomposición térmica obtenidas por termogravimetría (TGA) muestran que la estabilidad térmica de los electrolitos depende del porcentaje de plastificante. Un proceso de relajación es visible en el formalismo del módulo eléctrico, asociado con la dinámica de la transición vítrea, relajación-α. El máximo de cada pico se desplaza a frecuencias más altas cuando aumenta el plastificante, debido a una mejora de la movilidad dipolar en el origen de los movimientos cooperativos. La dependencia de la parte real de la conductividad eléctrica como función de la frecuencia exhibe una ley de potencias, esta variación es ajustada a la expresión Jonscher.

This article discusses the adsorption kinetics of a L-cysteine monolayer onto a gold surface by means of information obtained through the QCM technique. The results indicate that the adsorption process is rapid and follows the Langmuir isotherm, in which adsorption and desorption are considered. From these measurements the following parameter values were obtained: k d = (4.2 ± 0.4) x 10-3 s-1, k a = 75 ± 6 M-1 s-1, Keq=(1.8 ± 0.3) x 10(4) M-1 and ΔGads = - (5.8 ± 0.2) kcal mol-1.

The microstructure and electrical properties of varistors composed of (95-x) ZnO + x Pr6O11 + 5 CoO (ZPC), (x = 0.1, 0.5 and 1.0) and sintered at 1300 and 1350 °C, were investigated. According to X-ray diffraction, several phases (ZnO, Pr2O3 and Pr2CoO4) are present when x = 1.0. Using Scanning Electron Microscopy, all of these compositions contain precipitates. These phases are important regarding the development of the microstructure and the electrical properties. The samples with x = 0.1 introduce the best nonohmic behavior (α = 9.0), however when x = 0.5 the electrical properties are highly degraded due to the small quantity of effective barriers. The density of superficial states N IS and donor concentration Nd decreases with Pr6O11 addition. The decrease in the donor concentration is attributed to the annihilation of the donor defects according to the transformation of praseodymium oxides from Pr6O11 to Pr2O3.

Porous nano and micro crystalline tin oxide films were deposited by RF Magnetron Sputtering and doctor blade techniques, respectively. Electrical resistance and impedance spectroscopy measurements, as a function of temperature and atmosphere, were performed in order to determine the influence of the microstructure and working conditions over the electrical response of the sensors. The conductivity of all samples increases with the temperature and decreases in oxygen, as expected for an n-type semiconducting material. The impedance plots indicated the existence of two time constants related to the grains and the grain boundaries. The Nyquist diagrams at low frequencies revealed the changes that took place in the grain boundary region, with the contribution of the grains being indicated by the formation of a second semicircle at high frequencies. The better sensing performance of the doctor bladed samples can be explained by their lower initial resistance values, bigger grain sizes and higher porosity.

The dielectric behavior of composite materials (epoxy resin - barium titanate and epoxy - CCTO) was analysed as a function of ceramic amount. Composites were prepared by mixing the components and pouring them into suitable moulds. In some compositions, the matrix was reduced by tetrahydrofuran (THF) incorporation. Samples containing various amounts of ceramic filler were examined by TG/DTA and scanning electron microscopy analysis. Dielectric measurements were performed from 20 Hz to 1 MHz and 30 to 120 °C. It was demonstrated that the epoxy - CCTO composites possessed higher permittivity than classic epoxy - BaTiO3 composites. However, the low resin permittivity prevailed in the composite dielectric performance.

The present paper aims to verify the inuence of rare earth oxide such as lanthanum (La2O3) and neodymium (Nd2O3) doping SnO2 + 0.25%CoO + 0.75%MnO2 + 0.05%Ta2O5 system. The analysis focus on microstructural inuence on electrical properties. Microstructural analysis were made by using Transmission Electron Microscopy (TEM) at different regions of the samples. From such analysis it was found that La2O3 and Nd2O3 oxides cause heterogeneous segregation and precipitation at grain boundary concerning cobalt and manganese, decreasing the nonohmic electrical properties, as discussed, likely due to the increasing of grain boundary non-active potential barriers.

In the present text we discuss on electronic properties arising from polycrystalline semiconductor ceramics of SnO2, TiO2 and (Sn xTi1-x)O2 solid solution rutile-type structure. This is intended to be a short overview of the most recent papers in this area. One of the most important content discussed in this text is based on sinterability of these polycrystalline ceramics, which depends on the target application used to project porous or highly dense microstructure. The majority of discussion is focused in two main applications: varistor and sensor. In both applications there are similarities involved in the control of the sensor and varistor properties, which can mainly ascribed to the grain boundary structure and composition. The similarities found are consistently explained by the fact that all of these n-type semicondutor ceramics have the tendency to establish a grain boundary region with a "p-type semiconductor nature" (due to metal transition atoms segregated at the grain boundary region and then favors negative charged species to adsorb and enrich this region). This configuration enables electrons to become localized on the surfaces, giving rise to a negative surface and, as a result, electron depletion layers are formed, acting as potential barriers which control the properties of the mentioned devices.

The present paper describes the nonohmic behavior of the SnO2.MnO-based system and analyzes the influence of the sintering time and the Nb2O5 concentration on this system's electrical properties. A nonlinear coefficient of ~7 was obtained for a 0.2 mol%-doped Nb2O5 composition, which is comparable to other values reported in the literature for the ternary SnO2-based systems. A recent barrier formation model proposed in the literature to explain the nonlinear electrical behavior of SnO2-based systems is used to clarify the role of the MnO constituent in the formation of the barrier, taking into account the influence of segregated atoms, precipitated phase and oxygen species in the grain boundary region.