A New Branch of the Diversity-Oriented Synthesis Based on 4-Oxoalkane-1,1,2,2-tetracarbonitriles: Synthesis of Cyano-Substituted Iminofuran Derivatives

4-Oxo-3,4-diphenylbutane-1,1,2,2-tetracarbonitrile reacted with aliphatic, aromatic, and heterocyclic aldehydes in the presence of ammonium acetate to afford previously unknown iminofuran derivatives, 5-imino-4-(2-oxo-1,2-diphenylethyl)tetrahydrofuran-3,3,4-tricarbonitriles.     

Formation of an internal bias field in chromium-and L, α-alanine-doped triglycine sulfate crystals

The unipolar state of a chromium-and L, α-alanine-doped ferroelectric triglycine sulfate (TGS) crystal has been studied. The experimental data on the distribution of internal bias fields with respect to a seed are considered. The possible mechanisms of the formation of an internal bias field during the growth of TGS crystals with a low impurity concentration are considered.     

Synthesis of 2-(5-aryl-4-methyl-2-oxo-1,2-dihydro- 3<Emphasis Type="Italic">H</Emphasis>-pyrrol-3-ylidene)malononitriles

4-Oxoalkane-1,1,2,2-tetracarbonitriles in the presence of an equimolar amount of morpholine were converted to previously unknown 2-(5-aryl-4-methyl-2-oxo-1,2-dihydro-3H-pyrrol-3-ylidene)malononitriles.     

Kinetics of electron emission from the TGS ferroelectric crystal

A study is reported on the behavior in time of the electron emission current density from a triglycine sulfate ferroelectric crystal measured at fixed temperatures. This relation is shown to have an exponential nature. The characteristic emission relaxation time depends on temperature and decreases as one approaches the phase-transition point. The magnitude of the relaxation time and its temperature dependence can be accounted for both within a mechanism in which the emission decay is associated with the emptying of surface electron states, and in terms of the Maxwellian relaxation process.     

Electron emission in ferroelectrics for different values of the coercive field

Results are presented of experimental studies of electron emission from single crystals of triglycine sulfate, nominally pure and doped with Cr³⁺. The relation between the parameters of the processes of switching and electron emission from ferroelectrics by a coercive field and the threshold field for the onset of emission is investigated. It is shown that the temperature and concentration dependences of the threshold field can be explained by the corresponding dependences of the coercive field. Fiz. Tverd. Tela (St. Petersburg) 41, 1675–1678 (September 1999)     

Electrical properties of the metal-insulator nanoparticles-metal structure

The electrical properties of the metal-insulator-metal (MIM) structure with a monolayer of Al₂O₃ or ZrO₂ spherical nanoparticles as an insulator have been investigated. It has been experimentally found that the MIM structure can be in a weakly conducting or highly conducting state, depending on the applied voltage. A phenomenon has been revealed that the differential resistance of the MIM structure is negative and approaches zero (reversibly) with an increase in the electric current. After treatment of the MIM structure in the medium of atomic oxygen or atomic hydrogen, the electrical conductivity of the structure increases and depends on the polarity of the applied voltage. It has been established that the differential resistance of the structure in the form of a monolayer of nickel and copper spherical nanoparticles located between the planar metal electrodes is positive and decreases with an increase in the applied voltage.     

Ferroelectricity in nanocomposites based on porous glass with inclusions of NaNO<Subscript>2</Subscript>

The dielectric nonlinearity and pyroeffect in matrix composite based on porous glass with inclusions of sodium nitrite are investigated. It is found that the composite polarization turns to zero at a temperature below that of the phase transition in the bulk NaNO₂. The obtained dependence of the pyrocoefficient on temperature also corroborates the existence of the phase transition in sodium nitrite nanoparticles included in the porous matrix.     

Ferroelectrical properties of SiO<Subscript>2</Subscript>-TGS nanocomposite

Dielectric properties of the composites based on nanodisperse silica hydrosol and ferroelectric triglycinesulfate (TGS) are investigated. The studies allow us to expect the presence of the ferroelectric state in the composites.