M. M. El-Desoky

Thermal studies on the dielectric constant of some (CnH2n)(NH3)2FeCl4 compounds (n = 2, 7 and 10)

Abstract The dielectric constant of the compounds (CH 2 2 (NH 3 ) 2 FeCl 4 , (CH 2 ) 7 (NH 3 ) 2 FeCl 4 and (CH 2 ) 2 10 (NH 3 ) 2 FeCl 4 is measured at temperatures from liquid nitrogen temperature up to near the melting point of each sample. The phase transitions obtained are confirmed by the DTA thermograph.

Temperature dependence of the electrical conductivity of Salicylaldazinate metal chelates

A study of the temperature dependence of the electrical conductivity of Salicylaldazine and its metal complexes with the d-block elements Ni2+, Cu2+ and Zn2+, is correlated with molecular spectral data. The values of the activation energies obtained from the electrical conductivity measurements, as well as the energy gaps corresponding to the maximum absorption wavelengths in the region of ultraviolet and visible spectra, indicate the important role of chelation in producing the Salicylaldazine semiconducting properties.

The electrical conductivity of some azine compounds

Correlation of the molecular structure and thermal study of the electrical conductivity of benzaldazine (BA) and its NO2-derivatives were carried out. The values of the activation energies, obtained from the electrical conductivity measurements, as well as the energy gaps calculated from ultra violet (u.v.) and visible spectra obtained either in liquid or in solid forms indicate that all compounds behave like a semiconducting material. Both nπ*′s and ππ*′s were found to be the main sources participatiog in the cooduction processes.

Phase transition study of some selected azine compounds

Abstract The dielectric constants (real and imaginary) of benzaldazine and its hydroxy derivatives have been measured at different frequencies up to 100 kHz. The measurements were also carried out at different temperatures up to near the melting point of each sample. Two phase transitions were obtained during measurements at 320 and 370 K. The rotation of the benzene ring around the -CN- axis was responsible for these transitions. The effect of variation of the OH substituent between o -, p - and w -positions on the dielectric loss was discussed. The a.c. conductivities for the different samples were measured and explained.

The photoconductivity of benzaldazine and its o- and p-hydroxy substituents

The photoconductivity of benzaldazine (BA) and its o-, m- and p-hydroxy substituents has been measured. The voltage dependence is described by a linear term (ohmic) and a saturation term, the former of which dominates at low field strengths (up to 300 V). The temperature dependence of the photocurrent has been studied. The m-OH-BA has not shown any photoconductivity response.

Effect of alkali ions on the electrical properties of the ferrite phase of cement clinker

The ferrite phase of cement clinker was prepared from a mixture of pure oxides, and also after mixing this mixture with different weight percentages (1, 3, 10, 20 and 30%) of an alkali oxide (Na2O, MgO, SrO or BaO) at 1300° C. Electrical conductivity measurement (d.c.) was carried out from ice temperature to 570 K. It was found the alkali ions decreased the electrical conductivity with increasing alkali oxide content up to 3 wt% which was attributed to a change of C4AF structure from orthorhomic to tetragonal or monoclinic at elevated temperature, and the reduction of Fe3+ ions. Above 3 wt%, in the case of Na2O or BaO, the conduction increased. As MgO or SrO is similar to CaO the energy gaps ranged from 0.54 to 0.61 eV. The activation energy of pure C4AF is equivalent to 0.5 eV, as alkali ions were introduced this value changed according to th alkali type. This is considered as a quick method to assure the purity of the C4AF phase. This phase with alkali impurities behaves as a semiconductor.

Magnetic susceptibility of the compound (CH2)10(NH3)2FeCl4

Abstract The magnetic susceptibility of the compound (CH 2 ) 10 (NH 3 ) 2 FeCl 4 is measured in the temperature range from liquid nitrogen temperature up to room temperature. The effect of thermal and magnetic history on the data obtained is also discussed. It is shown that the compound is antiferromagnetic with a Neel temperature of 93 K but it appears that the antiferromagnetic intra-layer exchange interaction co-exists with a weak ferromagnetic interlayer interaction.

Electrical and spectral studies of modified solid semiconductors

Diazoaminobenzene shows semiconducting properties and a phenomenon of phase transition. The semiconducting properties arise as a result of high molecular resonance induced by intramolecular hydrogen bonding at the cliazo linkage. The phase transition is probably a consequence of thermal rotation into resolved cis and trans configurations; the frans form conducts electricity with a lower activation energy assisted by the molecular resonance. Thermal rotation into the more thermally stable cis form reduces the molecular resonance so that the resultant form conducts electricity with a higher activation energy. Unexpectedly, chelation with the favoured d-block element, Cu, reduces the electrical conductivity which is evidenced by a reduced electric dipole moment. Chelation appears to proceed favourably at the cis form, since the resultant complex conducts electricity with a similar high activation energy, a result of prohibited proton exchange. Restricted rotation in the Cu chelate explains conduction via a single phase. Consistent data from 1H-NMR, i.r. and u.v.—visible spectra do confirm the proposed structural interpretation.

Photoconductivity and dielectric constant studies of some organic complexes

Abstract The photocurrent of the two-dimensional system for (CH 2 ) 2 (NH 3 ) 2 MCl 4 (M = Co 2+ and Cu 2+ ) as a function of temperature, exposure time and returning time has been measured. The activation energy and photoconductivity values were calculated. Saturation of the photoconducting current was reached after exposure for about 25 min. The photocurrents showed a decrease in value with increasing temperature. The dielectric constant was measured, also as a function of temperature and frequency and the electric dipole moment was calculated at different temperatures.

Electrical conductivity of the compounds (CH2)n(NH3)2FeCl4−xBrx (n= 8, 9, 10 and x= 0, 1 and 2)

The electrical conductivity of the compounds (CH2)n(NH3)2FeCl4-x Brx (n = 8, 9, 10 and x = 0, 1, 2) have been measured in the temperature range from liquid nitrogen up to near the melting points of the samples. The effect of a gradual replacement of Cl- ions by Br- ions as well as the effect of layer spacing on the electrical conductivity are discussed. The phase transition points are determined and the values of the activation energies for the low and high temperature phases are calculated and listed.