Thermochemical properties of new N,O-chelate Sc, Eu, and Tb complexes for OLED-devices

A new class of Sc, Eu, and Tb complexes with N,O-chelate ligands was synthesized for the first time. The mass spectra, thermogravimetric analysis, differential scanning calorimetry data, as well as the data on the saturated vapor pressure of the compounds were obtained. The main thermochemical parameters of the compounds were calculated.     

Antiferroelectric films of deuterated betaine phosphate

Thin films of partially deuterated betaine phosphate have been grown by the evaporation on Al₂O₃(110) and NdGaO₃(001) substrates with a preliminarily deposited structure of interdigitated electrodes. The grown films have a polycrystalline block structure with characteristic dimensions of blocks of the order of 0.1–1.5 mm. The degree of deuteration of the films D varies in the range of 20–50%. It has been found that, at the antiferroelectric phase transition temperature T_c^afe = 100–114 K, the fabricated structures exhibit an anomaly of the electrical capacitance C, which is not accompanied by a change in the dielectric loss tangent tanδ. The strong-signal dielectric response is characterized by the appearance of a ferroelectric nonlinearity at temperatures T >T_c^afe, which is transformed into an antiferroelectric nonlinearity at T <T_c^afe. With a further decrease in the temperature, double dielectric hysteresis loops appear in the antiferroelectric phase. The dielectric properties of the films have been described within the framework of the Landau-type thermodynamic model taking into account the biquadratic coupling ξP²η² between the polar order parameter P and the nonpolar order parameter η with a positive coefficient ξ. The E–T phase diagram has been constructed.     

Effect of electric field on the dielectric permittivity of betaine phosphite crystals in the paraelectric phase

Temperature dependences of the dielectric permittivity of betaine phosphite crystals are studied both without and under application of an electric bias. It is shown that, in view of the fact that the high-temperature improper ferroelastic (antiferrodistorsive) phase transition at T _c1=355 K is nearly tricritical, the nonlinear temperature dependence of inverse dielectric permittivity in the paraelectric phase and the effect of the field on the dielectric permittivity can be described within a phenomenological model containing two coupled (polar and nonpolar) order parameters with a negative coupling coefficient. An analysis of the model revealed that, in the case where two phase transitions, a nonpolar and a ferroelectric one, can occur in the crystal, all of its dielectric properties, including the polarization response in a field, can be described by one dimensionless parameter a. For the crystal under study, we have a=?2.5. This value of the parameter corresponds to a second-order ferroelectric transition far from the tricritical point, at which a=?1. It is shown that the polarization response in the paraelectric phase in an electric field calculated within this model differs radically from that in the ferroelectric phase-transition model for which the Curie-Weiss law holds in the paraelectric phase.     

Experiment on the chemical modeling of the action of alcohol dehydrogenase

Summary Certain chelate compounds, containing nickel and zinc, can serve as chemical models of alcohol dehydrogenase in the dehydrogenation of ethyl alcohol.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimisheskaya, No. 7, pp. 1273–1274, July, 1965     

Permittivity and conductivity of triglycine sulfate films on Al/SiO2 and α-Al2O3 substrates

Triglycine sulfate (TGS) films have been prepared by evaporation from a saturated aqueous solution on substrates of fused quartz coated by a layer of thermally deposited aluminum (Al/SiO₂) and white sapphire (α-Al₂O₃) on whose surface interdigital electrodes have been deposited by photolithography. The TGS films have a polycrystalline structure made up of blocks measuring 0.1–0.3 mm (Al/SiO₂) and 0.1 × 1.0 mm (α-Al₂O₃). The polar axis in the blocks is mostly confined to the substrate plane. The temperature dependences of the capacitance and dielectric losses normal to and in the film plane have maxima at the temperature coinciding with that of the ferroelectric phase transition in a bulk crystal, T _c . The low-frequency conductivity G in TGS/Al/SiO₂ structures displays a frequency dispersion described by the relation G ∼ ω ^s (s ≈ 0.82). The conduction can be tentatively ascribed to the hopping mechanism involving localized carriers with a ground state energy of 0.8–0.9 eV. At temperatures above and below T _c , the low-frequency conductivity in TGS/α-Al₂O₃ films operates through a thermally-activated mechanism with an activation energy of 0.9–1.0 eV. At the phase transition, an additional contribution to conductivity appears in TGS/α-Al₂O₃ films with a dispersion G ∼ ω^0.5, which can be associated with domain-wall relaxation.     

Ferroelectric films of deuterated glycine phosphite: Structure and dielectric properties

Polycrystalline textured films of deuterated glycine phosphite consisting of single-crystal blocks with lateral dimensions ～(50–100) μm and a thickness d ～ (1–5) μm have been grown by evaporation on NdGaO₃(100) and α-Al₂O₃ substrates with preliminarily deposited interdigitated electrodes, as well as on Al substrates. The c* (Z) crystallographic axis in the blocks is normal to the film plane, and the a (X) axis and the polar axis b (Y) are oriented in the film plane. The temperature dependences of the capacitance of the structures measured with the interdigitated electrode system reveal a strong dielectric anomaly at the film transition to the ferroelectric state. The phase transition temperature T _c depends on the degree of deuteration D of the glycine phosphite. The maximum value T _c = 275 K obtained in the structures studied corresponds to a degree of deuteration of the glycine phosphite D ～ 50%. The frequency behavior of the dielectric hysteresis loops in glycine phosphite films differs radically from that of the previously studied films of deuterated betaine phosphite, which evidences that polarization switching in these structures proceeds by different mechanisms. It has been that application of a dc bias to the electrodes changes the shape of the dielectric hysteresis loops and shifts them along the electric field axis. The shift of the loops depends on the sign, magnitude, and time of application of the bias. Possible mechanisms underlying the induced unipolarity are discussed.     

Polynuclear Heteroligand Yb(III)–Er(III) Complexes as Potential Upconversion Materials

Russian Journal of Coordination Chemistry - The synthesis of complexes LnI(C6F5O)2 and LnCp(L)2 (Ln = Er, Yb; L = C6F5O, SONF), which are convenient precursors for the preparation of heteroligand...     

Temperature effect in antiproton channeling

The temperature dependence of axially channeled antiprotons in a Si crystal is studied using computer simulation. The number of channeled particles and the energy and angular distributions are calculated for antiprotons with an energy of 300 keV in the temperature range of 100 to 1000 K in the 〈100〉, 〈110〉, and 〈111〉 channels. The roles of the potential and atomic thermal vibrations are studied thoroughly. It is found that dechanneling depends on the crystal temperature. There exists an optimal temperature, which is dependent on the axis direction, for which dechanneling is minimal.     

Scattering of an Electromagnetic Wave by a Structure Consisting of Several Perfectly Conducting and Dielectric Finite-Length Thin Cylinders

Radiophysics and Quantum Electronics - We generalize a variant of the auxiliary-source method, which was proposed earlier for solving the problem of electromagnetic-wave scattering by a structure...