Vis and NIR Diffused Reflectance Study in Disordered Bismuth Manganate ‒ Lead Titanate Ceramics

This work shows a correlation between light reflectance, absorption, and morphologies of series of (1-x) BM–x PT, (x = 0.0, 0.02, 0.04, 0.08, 0.12, 0.16, 0.24) ceramics composite. The (1-x) BM–x PT showed features of a black mirror with a low optical energy gap. The measured Vis-NIR diffused reflectance enabled the calculation of the energy gap using the modified Kubelka-Munk function. The estimated energy gap was lower than 1.5 eV related to low reflectance in the Vis-NIR range. Moreover, obtained histograms of grains, using scanning electron microscope, enabled the correlation between grains size and amount of lead titanate. We deduced from the ceramics surface morphology that marked porosity also induced reflectivity of low magnitude. We correlated the magnitude of the energy gap with phases of the BM-PT composite and with the electrical conductivity activation energy reported in the literature. Our results findings opened prospect studied materials for optical applications.

The Temperature Dependence of the Electrical Conductivity Activation Energy of the of Aqueous Electrolyte Solutions

The procedure for determining the activation energy of conductivity Еκ is analyzed depending on the temperature step ΔT. It is shown that with increasing ΔT, the error in the calculation of Eκ decreases, but the calculated value of Eκ decreases. In order not to lose the temperature dependence of the activation energy, it is necessary to choose the optimal value of Δt. In our opinion, this value should not exceed 5 – 10 °C. Taking into account the decrease in concentration with increasing temperature due to a decrease in density has virtually no effect on the accuracy of determining Eκ, provided that ΔT is 5 – 10 °C. It has been shown that in the temperature range 20 – 80 °C, the activation energy of conductivity decreases with increasing temperature. This decrease is due to the rupture of intermolecular hydrogen bonds of the solvent with increasing temperature. It was suggested that the movement of ions in an aqueous solution may be accompanied by the breaking of hydrogen bond of the solvent.

Electrical Conductivity and Thermoelectrical Parameters of Argyrodite-Type Cu7 – xPS6 – xIx Mixed Crystals

Cu7−xPS6−xIx mixed crystals were grown by the direct crystallization from a melt. The electrical conductivity is measured in the frequency range from 10 Hz to 300 kHz and in the temperature interval 293–383 K. The frequency, temperature, and compositional dependences of the electrical conductivity for Cu7−xPS6−xIx mixed crystals are studied. The measurements of thermoelectric parameters of Cu7−xPS6−xIx mixed crystals are carried out in the temperature interval 293–383 K. The compositional behaviors of the electrical conductivity, activation energy, Seebeck coefficient, and power factor are investigated. The interrelation between the structural, electrical, and thermoelectrical properties is analyzed.

Mechanical behavior and electrical conductivity of zinc-oxide ceramics

Ceramics sintered from zinc oxide powders, which differ in crystal structure, particle size and amount and type of impurities, have been studied for their mechanical behavior (strength and micromechanisms of biaxial bending at room temperature) and electrical conductivity depending on the purity of ZnO powder (99,9% byweight — type I and 99,5% byweight — type II) and its sintering temperature in the interval from 800 to 1250 ºC for 2 hours. It is found that the maximum values of strength and electrical conductivity are achieved in ZnO-ceramics sintered at temperatures of 1100—1200 and 1000—1150 ºC, respectively, and their micromechanism of fracture is the cleavage only. ZnO-powder developed (type II), being twice as large as the purchased (type I), 300—350 nm instead of 150—200 nm, provides close to 100% density at 1100 °C, the type II powder is sintering at almost 100 °C lower temperature than the purchased one. Type I ceramics provide biaxial strength at room temperature of 150—170 MPa; type II — 120—160 MPa. ZnO-ceramics from powders of both types provide maximum electrical conductivities of 8,54 10-3S/ cm and 1,6·10-3 S / cm at temperatures of 265 and 600 ºC, respectively. The activation energy of the electrical conductivity of ZnO-ceramics is dependent significantly on the properties of the powder and, accordingly, the structure of the ceramics and the test temperature. Type I ZnO ceramics have a lower conductivity activation energy than type II, 0,2—0,3 eVand 0,3—0,5 eV, respectively. The mechanism of electrical conductivity of ZnO-ceramics type I is practically unchanged in all the interval of testing temperatures, from the room one to 600 °C. In ZnO-ceramics of the type II, it changes at least twice. Keywords: zinc oxide, ZnO ceramics, sintering temperature, porosity, grain size, micromechanism of fracture, bending strength, electrical conductivity, activation energy.

MEMBRANES BASED ON ACID-DOPED TRIAZOLE POLYMERS

The composition and structure of the membrane based on the acid-base method of elemental analysis, IR and NMR spectroscopy were studied. The ion-exchange capacity, proton conductivity, activation energy, and thermogravimetric analysis of the resulting membranes were studied.

Conductivity and Activation Energy in Polymers Synthesized by Plasmas of Thiophene

The electric conductivity, activation energy and morphology of polythiophene synthesized by radiofrequency resistive plasmas are studied in this work. The continuous collisions of particles in the plasma induce the polymerization of thiophene but also break some of the monomer molecules producing complex polymers with thiophene rings and aliphatic hydrocarbon segments. These multidirectional chemical reactions are more marked at longer reaction times in which the morphology of the polymers evolved from smooth surfaces, at low exposure time, to spherical particles with diameter in the 300-1000 nm interval. Between both morphologies, some bubbles are formed on the surface. The intrinsic conductivity of plasma polymers of thiophene synthesized in this way varied in the range of 10-10 to 10-8 S/m; however, the conductivity resulted very sensitive to the water content in the polymers, which produced variations of up to 5 magnitude orders. The activation energy of the intrinsic conductivity was between 0.56 and 1.41 eV, increasing with the reaction time. Plasma, Polymerization, Polythiophene, Conductivity, Activation Energy

Features of the Structure and Physical-Chemical Properties of Poly-Ortho-Toluidine Doped with Toluenesulfonic Acid

Features of crystal structure, electrical conductivity and thermal stability of poly-ortho-toluidine (PoTi) samples, obtained with method of oxidative polymerization in the environment of sulfuric and toluenesulfonic acids (TSA), were investigated. It was discovered that PoTi-TSA samples are characterized withhigh crystallinity. According to the physico-chemical analysis, doping samples with TSA causes increase of PoTi thermal stability, electrical conductivity and sensor sensitivity on the contrary to samples doped with sulfuric acid. Based on temperature dependence of specific resistance, were calculated the values of the conductivity activation energy, which are within the limits of 0.2-0.4 eV depending on the type of dopant.