The dc conductivity (σ) along the polar b-axis of ammonium zinc chloride (AZC) crystals in its four hightemperature phases has been measured as a function of temperature. Doping with Mn2+ in different concentrations changed strongly both values of σ at all temperatures and the dependence of ln σdc on 1/T in the phase transition regions. The activation energy of conduction was calculated from the linear portions of this dependence in each phase. The results were discussed in the light of the decomposition of (NH4)2 in the high-temperature normal phase, the discommensuaration (DC) formation/annihilation in the incommensurate phase and domain wall motion and stripples nucleation in the commensurate- and antiferroelectric-phases. Pinning of DC’s in the crystal lattice and/or by the structural defects and the possibility of dislocation formation was also discussed. The bulk- and the electrode-limited conduction mechanisms were also considered. The current density-voltage gradient relationship according to the usual Richardson-Schottky (RS) equation shows disagreement between extracted parameters and experimentally measured ones. A modified equation was used to solve this difficulty which, in addition, facilitated the calculation of the electronic mobility (μ), the barrier height (ϕ) at the electrode-dielectric interface and the R-S constant (βRS). The effect of Mn2+-content on values of μ, ϕ and βRS in different phases of AZC was also considered

The effect of chemical non-stoichiometry and γ-irradiation on the unit cell parameters of ammonium tetrachlorozincate (NH4)2ZnCl4 (A2ZC4) has been studied. The unit cell parameters of crystal grown from solution with NH4Cl/ZnCl2 molar ratio 1:1, apparently non-stoichiometrric, are nearly the same as those given for ammonium tetrachlorozincate in the literature. The 2:1 ratio is actually ‘pseudo-stoichiometric’ due to the hygroscopic nature of ZnCl2. The unit cell parameters of crystal grown from solution with molar ratio 2:1 match those of the structure (NH4)3ZnCl5 (A3ZC5). The habit of the crystal grown in the former case, from solution with excess ZnCl2, was different from that of the crystal grown in the later case, from solution with excess (NH4)Cl. Between these two limits, a set of four samples were prepared from solutions with an excess of ZnCl2 of 20, 30, 60 and 80 wt % in order to detect exact stoichiometric composition to grow A2ZC4. Analysis by X-ray diffraction shows that the first two crystals out of this set are mixed from A2ZC4 and A3ZC5 The third and fourth crystals still contain traces of A3ZC5. Analysis of the X-ray diffraction was then confirmed by DTA study. Irradiating A2ZC4 with γ-dose of 250 kGy slightly increased the unit cell volume due to imperfections created by irradiation. Two computer programs were used to calculate the lattice constants and the results were compared

The effect of chemical non-stoichiometry and γ-irradiation on the unit cell parameters of ammonium tetrachlorozincate (NH4)2ZnCl4 (A2ZC4) has been studied. The unit cell parameters of crystal grown from solution with NH4Cl/ZnCl2 molar ratio 1:1, apparently non-stoichiometrric, are nearly the same as those given for ammonium tetrachlorozincate in the literature. The 2:1 ratio is actually ‘pseudo-stoichiometric’ due to the hygroscopic nature of ZnCl2. The unit cell parameters of crystal grown from solution with molar ratio 2:1 match those of the structure (NH4)3ZnCl5 (A3ZC5). The habit of the crystal grown in the former case, from solution with excess ZnCl2, was different from that of the crystal grown in the later case, from solution with excess (NH4)Cl. Between these two limits, a set of four samples were prepared from solutions with an excess of ZnCl2 of 20, 30, 60 and 80 wt % in order to detect exact stoichiometric composition to grow A2ZC4. Analysis by X-ray diffraction shows that the first two crystals out of this set are mixed from A2ZC4 and A3ZC5 The third and fourth crystals still contain traces of A3ZC5. Analysis of the X-ray diffraction was then confirmed by DTA study. Irradiating A2ZC4 with γ-dose of 250 kGy slightly increased the unit cell volume due to imperfections created by irradiation. Two computer programs were used to calculate the lattice constants and the results were compared

The acetyl benzo[f]coumarin condensed with phenyl hydrazine to afford the corresponding phenyl hydra zone which cyclized into the pyrazolyl benzocoumarin under Vilsmeier reaction conditions. The pyrazolyla ldehyde was used as starting material for synthesis of other heterocyclic compounds containing pyrazolylben zocoumarin moiety. The ethyl benzo[f]coumarin carboxylate were subjected to react with other reagents to synthesize thiazolidinyl and oxadiazolyl derivatives attached to benzocoumarin system. Some of novel syn thesized compounds showed highly antibacterial and antifungal activities.

The acetyl benzo[f]coumarin condensed with phenyl hydrazine to afford the corresponding phenyl hydra zone which cyclized into the pyrazolyl benzocoumarin under Vilsmeier reaction conditions. The pyrazolyla ldehyde was used as starting material for synthesis of other heterocyclic compounds containing pyrazolylben zocoumarin moiety. The ethyl benzo[f]coumarin carboxylate were subjected to react with other reagents to synthesize thiazolidinyl and oxadiazolyl derivatives attached to benzocoumarin system. Some of novel syn thesized compounds showed highly antibacterial and antifungal activities.

The acetyl benzo[f]coumarin condensed with phenyl hydrazine to afford the corresponding phenyl hydra zone which cyclized into the pyrazolyl benzocoumarin under Vilsmeier reaction conditions. The pyrazolyla ldehyde was used as starting material for synthesis of other heterocyclic compounds containing pyrazolylben zocoumarin moiety. The ethyl benzo[f]coumarin carboxylate were subjected to react with other reagents to synthesize thiazolidinyl and oxadiazolyl derivatives attached to benzocoumarin system. Some of novel syn thesized compounds showed highly antibacterial and antifungal activities.

The effect of temperature on the sequence of the hardening precipitates in Al-1·1 wt-%Mg2Si balanced alloy has been investigated by means of differential scanning calorimetry, scanning electron microscopy and hardness measurements. The non-isothermal DSC thermograms exhibited seven reaction peaks. Out of these seven peaks, five are exothermic (representing precipitation) and two are endothermic (representing dissolution). The activation energy associated with the individual precipitates is calculated. The activation energy of nucleation of GP zones (54·3 kJ mol-1) is close to the migration energy of Si in Al (52·7 kJ mol-1). The activation energy associated with the precipitation of p" is determined as 77·6 kJ mol-1 and that for the formation of β' precipitates is 145·3 kJ mol-1. The latter value is close to that for Si diffusion in Al (124 kJ mol-1) and that of Mg diffusion in Al (131 kJ mol-1). It can be concluded that the precipitation of β' particles might be characterised by both the diffusion of Mg and Si atoms in Al to form β' precipitates

The effect of temperature on the sequence of the hardening precipitates in Al-1·1 wt-%Mg2Si balanced alloy has been investigated by means of differential scanning calorimetry, scanning electron microscopy and hardness measurements. The non-isothermal DSC thermograms exhibited seven reaction peaks. Out of these seven peaks, five are exothermic (representing precipitation) and two are endothermic (representing dissolution). The activation energy associated with the individual precipitates is calculated. The activation energy of nucleation of GP zones (54·3 kJ mol-1) is close to the migration energy of Si in Al (52·7 kJ mol-1). The activation energy associated with the precipitation of p" is determined as 77·6 kJ mol-1 and that for the formation of β' precipitates is 145·3 kJ mol-1. The latter value is close to that for Si diffusion in Al (124 kJ mol-1) and that of Mg diffusion in Al (131 kJ mol-1). It can be concluded that the precipitation of β' particles might be characterised by both the diffusion of Mg and Si atoms in Al to form β' precipitates

The effect of temperature on the sequence of the hardening precipitates in Al-1·1 wt-%Mg2Si balanced alloy has been investigated by means of differential scanning calorimetry, scanning electron microscopy and hardness measurements. The non-isothermal DSC thermograms exhibited seven reaction peaks. Out of these seven peaks, five are exothermic (representing precipitation) and two are endothermic (representing dissolution). The activation energy associated with the individual precipitates is calculated. The activation energy of nucleation of GP zones (54·3 kJ mol-1) is close to the migration energy of Si in Al (52·7 kJ mol-1). The activation energy associated with the precipitation of p" is determined as 77·6 kJ mol-1 and that for the formation of β' precipitates is 145·3 kJ mol-1. The latter value is close to that for Si diffusion in Al (124 kJ mol-1) and that of Mg diffusion in Al (131 kJ mol-1). It can be concluded that the precipitation of β' particles might be characterised by both the diffusion of Mg and Si atoms in Al to form β' precipitates

The effect of temperature on the sequence of the hardening precipitates in Al-1·1 wt-%Mg2Si balanced alloy has been investigated by means of differential scanning calorimetry, scanning electron microscopy and hardness measurements. The non-isothermal DSC thermograms exhibited seven reaction peaks. Out of these seven peaks, five are exothermic (representing precipitation) and two are endothermic (representing dissolution). The activation energy associated with the individual precipitates is calculated. The activation energy of nucleation of GP zones (54·3 kJ mol-1) is close to the migration energy of Si in Al (52·7 kJ mol-1). The activation energy associated with the precipitation of p" is determined as 77·6 kJ mol-1 and that for the formation of β' precipitates is 145·3 kJ mol-1. The latter value is close to that for Si diffusion in Al (124 kJ mol-1) and that of Mg diffusion in Al (131 kJ mol-1). It can be concluded that the precipitation of β' particles might be characterised by both the diffusion of Mg and Si atoms in Al to form β' precipitates