Conductivities and silver electrode polarization resistance of solid electrolyte ceramics from ZrO2-Y2O3 powder synthesized in air plasma

Ceramic specimens have been obtained from the powder of ZrO₂-7.5 mol% Y₂O₃ having a specific surface area of 30 m²/g synthesized in air plasma. The novelty of this research lies in the fact that the plasma process makes it possible to prepare so-called nanopowders with a particle size less than 100 nm, possessing specific physical, chemical and technological properties. The sintered density of the specimens was 94–96% of the theoretical value, 6.001 g/cm³. The X-ray diffraction pattern of the specimens corresponded to a face-centered cubic lattice. Impedance in the frequency range of 100 Hz–15 MHz and d.c. polarization curves in a potential range of −10 to 10 mV were measured in the temperature range 200–850 °C in heating and cooling cycles. The intragrain, the grain boundary and the total bulk conductivities, the electrode polarization resistance and their activation energies were determined. The thermal stability of the studied system was proved in three measurement series up to 600–850 °C in heating and cooling cycles. The results obtained have shown that the conductivity of ZrO₂-7.5 mol% Y₂O₃ ceramics is not solely a function of temperature, but also depends on the previous thermal state of the ceramics. Received: 16 October 1997 / Accepted: 19 January 1998     

Phenylene-Bridged Perylene Monoimides as Acceptors for Organic Solar Cells: A Study on the Structure–Property Relationship

A series of non-fullerene acceptors based on perylene monoimides coupled in the peri position through phenylene linkers were synthesized via Suzuki-coupling reactions. Various substitution patterns were investigated using density functional theory (DFT) calculations in combination with experimental data to elucidate the geometry and their optical and electrochemical properties. Further investigations of the bulk properties with grazing incidence wide angle X-ray scattering (GIWAXS) gave insight into the stacking behavior of the acceptor thin films. Electrochemical and morphological properties correlate with the photovoltaic performance of devices with the polymeric donor PBDB-T and a maximum efficiency of 3.17 % was reached. The study gives detailed information about structure–property relationships of perylene-linker-perylene compounds.     

Theoretical stability,thin film synthesis and transport properties of the Mon +1GaCn MAX phase

The phase stability of Mo_{n +1}GaC_n has been investigated using ab‐initio calculations. The results indicate stability for the Mo₂GaC phase only, with a formation enthalpy of –0.4 meV per atom. Subsequent thin film synthesis of Mo₂GaC was performed through magnetron sputtering from elemental targets onto Al₂O₃ [0001], 6H‐SiC [0001] and MgO [111] substrates within the temperature range of 500 °C and 750 °C. High structural quality films were obtained for synthesis on MgO [111] substrates at 590 ºC. Evaluation of transport properties showed a superconducting behavior with a critical temperature of approximately 7 K, reducing upon the application of an external magnetic field. The results point towards the first superconducting MAX phase in thin film form. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Traces of Stochasticity in Electron Trajectories in Gyrotron Resonators

The Hamiltonian approach is used to analyze the equation describing the electron interaction in gyrotron resonators with realistic RF field profiles. A detailed numerical study of the behavior of electron trajectories for some specific values of parameters controlling the interaction is performed. It is found that in some cases chaos-like motions of electrons are possible.     

Addition of Me3SiCN to trifluoromethyl derivates of N‐(pyridylmethylidene) anilines catalyzed by Lewis acids

A series of novel Shiff bases (1a–h) was synthesized by condensation of pyridinecarboxaldehydes (1–4) with 3‐ and 4‐trifluoromethylanilines (5, 6) in the presence of molecular sieves (4 Å). It was found that AlCl₃ and AlBr₃ catalyzed the addition of Me₃SiCN to the C?N bond of the imines obtained, whereas the other Lewis acids studied (YCl₃, LaCl₃, ZnI₂) were not active. The reactivity of the imines in the title reaction, on the whole, correlated with their basicity. Besides the addition giving the expected α‐amino nitriles (2a,b,d–f,h), an unusual reaction leading to unsaturated nitriles (3a–h) was observed. The structures of saturated and unsaturated products 2d and 3c were determined by X‐ray diffraction. Copyright © 2001 John Wiley & Sons, Ltd.     

On constrained Volterra cubic stochastic operators

We consider constrained Volterra cubic stochastic operators and construct several Lyapunov functions for the constrained Volterra cubic stochastic operators. We prove that such kind operators do not have periodic trajectories. Finally, we show that the set of all constrained Volterra cubic stochastic operators is a convex compact set and find the extreme points of this set.     

A Note 0n the Equilibrium Potential of Certain Dirichlet Spaces

There exists an equilibrium potential, an element of a Dirichlet space, for any compact subset, with non-emtpy interior, of R ^m. This potential is constant on the interior of the set. There is a corresponding measure that is 0 outside the set. We prove that the restriction of this equilibrium measure to the interior of the set is absolutely continuous, and we derive an explicit formula for its density.