Three different morphologies of ZnO nanostructures were prepared by vapor transport on Au coated silicon substrates. Randomly oriented nanowires (NWs) mixed with few nanoflakes were obtained at furnace temperature of 750 °C and oxygen flow rate of 20 sccm. While thicker, longer and denser NWs were obtained at furnace temperature of 900 °C with the same oxygen flow rate of ... إقراء المزيد

A study of Mn-site substitution by Ni2þ and the effect of annealing time in polycrystalline bulk La0.7Sr0.3MnO3 in composition range (0x0.1) is presented. This study involves structural, electrical, magnetoresistance, and thermoelectric power (TEP) measurements. X-ray diffraction was used to examine the structure for the as-prepared and annealed samples, and it shows that there is no change in structure with annealing ... إقراء المزيد

Wepresentresultsofacomprehensiveinvestigationofthestructural,frequencydependentacsus- ceptibility,dcmagnetization,magnetoresistanceandthermoelectricpowermeasurementsonpoly- crystalline samplesofLa1xLixMnO3 (0.05rxr0.30). Allsamplesundergoferromagnetictopara- magnetic transitionandmetaltosemiconductortransition.Acuspinthezero field-cooled indcmag- netization andafrequency-dependentpeakintheacsusceptibilityrevealtheglassybehaviors.Theoutof phase componentoftheacsusceptibilityshowsfrequency-dependentpeaksbelowtheCurietempera- ture (indicativeofglassybehavior)whichhavepreviouslybeeninterpretedintermsoffreezingof clusters. Thegrainboundariesplayadominantroleintheconductionprocess.Theframeworkofthe magnon andphonondragconceptanalyzedthermoelectricpowerdataatlowtemperature,whilesmall polaron conductionmechanismexplainedthermoelectricpowerdataathightemperature.Ithasbeen found thatthepercolationthresholdsampleis x¼0.10,sotheauthor’s pointofviewreferstomakespot on thissampleinthefutureworks. إقراء المزيد

(La0.7Sr0.3MnO3)1-x/(ZrO2)x (x = 0.0–0.150, step 0.025) composites have been prepared via solid state reaction process. The X-ray diffraction and scanning electron microscopic observations indicate that there are ZrO2 grains separated from La0.7Sr0.3MnO3 matrix. It has been found that the inclusion of ZrO2 content decreases the conductivity, magnetization and metal–semiconductor transition, whereas it increases the low field magnetoresistance. Possible effects of ... إقراء المزيد

ZnO nanowires (NWs) were synthesized on Au-coated Si (100) substrates by vapor transport method. The effect of high temperature annealing on the structural and chemical composition as well as thermal stability was studied. The as-prepared ZnO NWs was nearly stoichiometric and identified as hexagonal ZnO phase. After annealing at 1,473 K, the atomic ratio of O/Zn, the intensity of the ... إقراء المزيد

The temperature dependence of the electrical resistivity q, thermoelectric power S and the magnetic susceptibility v of La0.7–xBixSr0.3MnO3 (x ¼ 0.05, 0.10, and 0.15 at. %) manganites were investigated. La0.7–xBixSr0.3MnO3 crystallizes in a single phase rhombohedral structure with parasitic phase inclusions. With increasing Bi concentration, a systematic decrease in the ferromagnetic transition temperature (Tc), the metal-semiconducting transition temperature (Tms1) and ... إقراء المزيد

ELECTRONIC AND MAGNETIC PROPERTIES OF LITHIUM DOPED LANTHANUM MANGANITES * Ahmed, G. Papavasilio, E. M. M. Ibrahim and H. F. Mohamed, Advanced Materials World Congress in Izmir on September 16-19, 2013 (Turkey) . إقراء المزيد

LOW- FIELD MR BEHAVIOR IN LA0.7SR0.3MNO3/ZRO2 COMPOSITE SYSTEM A. M. Ahmed, A. K. Diab, H. F. Mohamed, Abd El-Mo'ez. A. Mohamed, A. E. A. Mazen, Aml M. Mohamed, Advanced Materials World Congress in Izmir on September 16-19, 2013 (Turkey) إقراء المزيد

Chalcogenide bulk alloys of Ge10AsxTe90-x (x = 20, 25, 30, 35, 40, 45 and 55) system were prepared by the conventional melt quench-technique. The dc electrical conductivity r and thermoelectric power (TEP) measurements were carried out in the temperature ranges from 83 to 353 K and from 253 to 353 K, respectively. The variations of both r and TEP with ... إقراء المزيد

(x = 0.05, 0.1, 0.15, 0.2 & 0.25 at %) fixed valence doped compounds were studied between 80K and 320K. X-ray powder diffraction (XRD) showed that the samples are single phase. We found the correlation of structures to the mag-netoresistance (MR) and the thermoelectric power (S) which we assigned to change the specific branches of the magnon /phonon spectra with ... إقراء المزيد