Mechanism of hopping conduction in Be–Fe–Al–Te–O semiconducting glasses and glass–ceramics

Electrical properties of beryllium-alumino-tellurite glasses and glass–ceramics doped with iron ions were studied using impedance spectroscopy. The conductivity was measured over a wide frequency range from 10 mHz to 1 MHz and the temperature range from 213 to 473 K. The D.C. conductivity values showed a correlation with the Fe-ion concentration and ratio of iron ions on different valence states in the samples. On the basis of Jonscher universal dielectric response the temperature dependence of conductivity parameters were determined and compared to theoretical models collected by Elliott. In glasses, the conduction process was found to be due to the overlap polaron tunneling while in glass–ceramics the quantum mechanical tunneling between semiconducting crystallites of iron oxides is proposed. The D.C. conductivity was found not to follow Arrhenius relation. The Schnakenberg model was used to analyze the conductivity behavior and the polaron hopping energy and disorder energy were estimated. Additionally, the correlation between alumina dissolution and basicity of the melts was observed.

Ceramic composite membranes based on Bi3Ru3O11 – Bi1,6Er0,4O3 for obtaining of oxygen

Using hot uniaxial pressing in an argon atmosphere with a stress of 35 MPa and with a holding at 800 °C for 1 hour, ceramic composites of Bi3Ru3O11 – 50, 65 wt % Bi1,6Er0,4O3 were obtained. It was found that phase composition of the composites does not change during gas chromatographic testing at 800 °C and well corresponds to the specified one. Microstructure of the obtained composites was tested and the formation of dense composites with a total porosity of less than 1% and with a uniform distribution of the Bi3Ru3O11 and Bi1,6Er0,4O3 components in bulk of material was demonstrated. Transport properties (total conductivity, oxygen fluxes and selectivity of separating oxygen over nitrogen) of the obtained composites at 600 – 800 °C had been investigated. Thus, at 800 °C the electrical conductivity of Bi3Ru3O11 – 50, 65 wt % Bi1,6Er0,4O3 was about 200 and 50 Ohm–1∙cm–1, respectively, while the metallic nature of their temperature dependence of conductivity is correlated to that for the Bi3Ru3O11. The value of oxygen permeability for the obtained ceramic composites of about 7∙10–9 mol·cm–1·s–1 at 800 °C, which is compared to other membrane materials based on bismuth oxide, demonstrated the potential of their further use in the tasks for obtaining of pure oxygen from air.

Investigation of the Mechanism of Electric Conductivity of Strontium Bismuthate Sr6Bi2O11

The paper presents data on the temperature dependence of the conductivity of strontium bismuthate Sr6Bi2O11. It is shown that the temperature dependence of conductivity cannot be described in the framework of existing models. It was found that at a temperature of about 400 K a change in the radius of localization of the charge carrier is observed.

The Electrical Characterization of Hydrogenated Amorphous Silicon Germanium Film Used in Un-Cooled Micro-Bolometer

In this paper, the deposition and the electrical characterization of hydrogenated amorphous silicon germanium (a-SixGey:H) thin films were performed by plasma enhanced chemical vapour deposition (PECVD) at low temperature with different flow ratios of SiH4/GeH4. The temperature coefficient of resistance (TCR) and temperature dependence of conductivity were measured to study the influence of deposition parameter. The resistance uniformity were also investigated. The result showed that the film presented high TCR values of around 3.5%K-1and moderate conductivity value of 1.47×10-3(Ω•cm)-1respectively at room temperature, while the non-uniformity below 5% which indicated the high resistance uniformity in films.

Fabrication and Failure Prediction of Carbon-alum solid composite electrolyte based humidity sensor using ANN

Using low-cost materials, carbon, and alum, a new solid composite electrolyte system was fabricated and characterized using various techniques. Complex impedance spectroscopy was used to measure its ionic conductivity. A maximum conductivity of 3.4×10−5 S/cm was obtained when alum was doped with 40% carbon. An Arrhenius behavior was reported when the temperature dependence of conductivity was analyzed. Scanning electron microscopy was used to study the surface morphology of the synthesized electrolyte. Fourier transform infrared and X-ray diffraction results confirmed the formation of composite material. The synthesized solid composite electrolyte exhibited excellent humidity sensing behavior in the relative humidity range of 15%–65%. Various humidity characteristics of the sample were measured such as hysteresis loop, recovery, and response time of the sensor. An expert system was modeled using artificial intelligence techniques and failure of the sensor was predicted with 97.2% accuracy using artificial neural networks.