Исследование пьезоэлектрического резонанса в стехиометрических кристаллах LiNbO-=SUB=-3-=/SUB=- в области высоких температур и проводимости

In order to establish conditions of lithium niobate based piezoelectric resonators application at high temperatures and high conductivity in a wide range of temperatures (~ 300 – 850К) we have researched piezoelectric, ferroelectric, dielectric properties and ion conductivity of near-stoichiometric LiNbO3stoich crystals. We have revealed that piezo-resonance is observed in LiNbO3stoich in a certain temperature range ΔТ (correspondingly, in certain static conductivity relaxation time Δtau_V range) and frequencies range Δomega_R provided that tau_V-1<<omegaR. Such patterns are probably applicable not only to LiNbO3stoich crystals, but also to other piezoelectric materials.

Compliance of the Stokes–Einstein model and breakdown of the Stokes–Einstein–Debye model for a urea-based supramolecular polymer of high viscosity

Viscosity dependences of dc conductivity, conductivity relaxation time and dipolar relaxation time are measured for the neat hydrogen-bonded supramolecular polymer N,N′-di(2-ethylhexyl)urea (EHU).

Study of Motion of Impurity Ions Making Influence on Electrical Properties of Polymer Solids in Low Frequency Range

The motion of impurity ions affects the electrical properties of polymer solid. The ions move through free spaces which exist in the non-crystalline part between polymer crystallites. The free spaces have inhomogeneous size distribution depending on a property of polymers or crystallization conditions. The homogeneity or inhomogeneity of the size of the free space affects the ionic motion, and consequently it also affects the electrical properties of polymer solids. In order to study the electrical properties of polymer solids in relation with such motion of impurity ions, the conductivity relaxation time was calculated for isotactic poly (propylene) (iPP), low density poly (ethylene) (LDPE) and plasticized poly (vinyl chloride) with dioctyl phthalate (p-PVC) from the electric modulus as a function of frequency which was observed by means of the Broadband Dielectric Spectroscopy (BDS). The value of the conductivity relaxation time reflects the non-crystalline structure of these polymers.

Conductivity Vs Nmr Correlation Times, and Decoupled Cation Motion in Polymer-In-Salt Electrolytes

We report 7Li spin lattice relaxation times at 12.82 MHz over a range of temperatures for liquid electrolytes of various salt:polymer ratios, and compare the NMR correlation time obtained at the temperature of the T1 minimum with the conductivity relaxation time at the same temperature. We find that at low salt contents the two relaxation times have the same value, but beyond the “salt-inpolymer to polymer-in-salt transition” zone at the Tg maximum, the two times increasingly separate. This is taken as evidence for the onset of cation-matrix mobility decoupling, which maximizes at the pure salt extreme.