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Nanocomposites of polyaniline loaded with different weight-fractions of double-wall carbon nanotubes were fabricated by in situ polymerizations of the polyaniline in the presence of double-wall carbon nanotubes. The composition of the nanocomposites is examined by X-ray diffraction and scanning electron microscopy techniques. The functionality of the synthesized composites was studied by electrical conductivity and fluorescence analyses. The dc conductivity of polyaniline was increased by introducing 2.5 wt% of DWCNTs into polyaniline matrix. The fluorescence emission from the double-wall carbon nanotubes/polyaniline showed a broad emission range in the visible region between 350 and 560 nm with appreciable enhancement in the intensity at 434 nm.

Polyaniline (PANI) coupled with Se0.95Fe0.05 in various weight percentage (5 and 10 wt%) were formed by in situ polymerization method of PANI in the presence of Se0.95Fe0.05. The functionality of the investigated nanocomposites was investigated by X-ray diffraction (XRD), Fourier transform infrared (FTIR), vibrating sample magnetometer (VSM), and photoluminescence (PL) analyses. The structural characteristics of PANI and the existence of Se0.95Fe0.05 together with PANI were confirmed using XRD. The different functional groups of nanocomposite were studied using FTIR. PANI/Se0.95Fe0.05 nanocomposites exhibited a weak ferromagnetic behavior. Law of Approach to saturation was used to determine the saturation magnetization of nanocomposites samples. The PL of PANI and nanocomposites emitted five emissions in violet and blue ranges. The PL intensity of the emission peaks is significantly reduced when Se0.95Fe0.05 is introduced to PANI matrix.

Zn/Ga/Gd-substituted NiFe2O4 was formed by solid state reaction and citrate methods. The influence of substitutions on phase formation, the strain, crystallize size, cations distribution and magnetic properties have been examined by X-ray diffraction, Mossbauer effect spectrometer, Fourier-transform infrared, and vibrating sample magnetometer. Zn/Ga/Gd substituted NiFe2O4 samples prepared by solid state method showed that as gadolinium introduced into the system, a second phase was formed with a small percentage while samples prepared by citrate method exhibited a single phase. The distributions of different cations between different sites were determined by both Mossbauer effect spectroscopy, modified Bertaut and Rietveld analysis. Mossbauer technique at room temperature showed that samples synthesized by the ceramic method have a magnetic order while samples prepared by citrate method have a superparamagnetic nature. The canting angle between magnetic ions was increased by increased the amount of Zn in samples prepared by both methods.

Al-and Mo-doped GaFeO3 (Ga1−x Al x FeO3, GaFe1−x Mo x O3) multiferroic systems were fabricated by double-sintering ceramic method. Single phase of orthorhombic structure with space group Pc21n has been obtained. The structure parameters, bond length, and preferential cation distribution were derived from analyzing XRD applying Rietveld method. Rietveld refinement reveals the decrease and increase of the lattice parameters upon Al and Mo doping, respectively. The magnetic properties were studied thoroughly both doped systems. Curie temperatures (T C) change with increasing Al content amount and reach their maximum value for Al-substituted amounts 15 and 25 % (228 K). On other hand, as the amount of Mo increases, T c for GaFeO3, (GFO) decreases. Photoluminescence (PL) spectroscopic measurements were carried out at room temperature, under 330 nm excitation, to sense the reflection of Al and Mo substitutions on the investigated GFO lattice. The presence of the site disorder and cation redistribution was confirmed by PL emission spectral analysis. Fe 3+ ions at the tetrahedral and octahedral sites show entirely different luminescence. It was also inferred from the spectra that, at lower Mo content (x), the dominated higher intense PL emissions come from tetrahedrally coordinated Ga3+ ions, while in Al-doped GFO at higher Al content (x), the emissions come mainly from the octahedrally sited ions. The luminescent emissions will open up the opportunity of GFO-doped transition metals for both further fundamental studies and technological applications.

Nanostructured Ni 1−x Zn xFe 1.78Al 0.2Gd 0.02 O 4 (x = 0.0, 0.1, 0.3, and 0.5) ferrites have been prepared by citrate precursor method. The samples were characterized by several techniques including X-ray diffraction, FTIR spectroscopy, and magnetic and DC and AC electrical measurements. Rietveld analysis revealed crystallite size ranging from 5.8 to 6.7 nm for all samples with an increase in the lattice parameter upon increasing Zn content. With Zn substitution, the saturation magnetization M S first increases for x = 0.1 then decreases for x ≥ 0.2 indicating variation of cation occupancies upon Zn doping. That behavior of magnetization obeys the Yafet–Kittel (Y–K) model, and canting angles 𝜃 Y−K were obtained for all samples. For the formed spinel structure, zinc substitution was found to induce a significant change in the cation distribution being proposed on the basis of the magnetization data and the lattice parameter obtained from the Rietveld analysis, and then confirmed by using theoretically calculated lattice parameter. DC electrical resistivity increases with the Zn content, and for whole samples, it increases with temperature then decreases, exhibiting two different behaviors. Variation of activation energy of electrical conduction was deduced from DC measurements. The effect of Zn content on dielectric properties was fully characterized from the AC measurements.

Ultrasmall nanocrystalline NiSm0.01Fe1.99O4 and Ni1−x Zn x Sm0.01Ga0.5Fe1.49O4 (x = 0.0, 0.3, 0.5) ferrites were synthesized by sol-gel method. The effect of Ga and Zn substitution on the particle size and structural and magnetic properties was investigated using X-ray diffraction patterns (XRD), transmission electron microscope (TEM), Mossbauer effect spectroscopy (ME), and vibrating sample magnetometer (VSM) techniques. XRD measurements suggest the formation of single-phase spinel ferrites with ultrasmall particles size ranging from 4 to 8 nm. Mossbauer effect measurements show a clear signature of superparamagnetism in the studied samples, where the reduced particle size causes the broadening of the Mossbauer spectra and the presence of a pronounced central doublet in all the measured samples. VSM measurements show a strong reduction of saturation magnetization due to size effects.

A series of Mg0.5Mn0.5Fe2−x Co x O4 (0 ≤ x ≤ 0.5) samples were synthesized by citrate precursor method. The impact of replacing Fe ions by Co on the structural parameters and magnetic properties of the system was investigated utilizing X-ray diffraction and M–H magnetic measurements at room and low temperatures. Phase analysis revealed a single-phase spinel for all samples, and cation distribution was suggested using data of magnetization loops, Rietveld analysis and then confirmed by Bertaut method. Both saturation magnetization and coercivity increase with Co content up to x = 0.3, then decrease slightly. The variation of lattice parameter, the interatomic distances, and the bond angles upon increasing the Co content was determined and then correlated with cation distribution and the magnetic behavior.

Nanocrystalline Ni1−x Zn x Fe1.5Cr0.5O4 (0 ≤ x ≤ 0.5) ferrite was prepared using a citrate method. The influence of Zn2+ ion substitution on structure, magnetic, and electric properties of the Ni1−x Zn x Fe1.5Cr0.5O4 ferrite has been investigated. The X-ray diffraction results confirmed the formation of a single phase with a spinel cubic structure for Ni1−x Zn x Fe1.5Cr0.5O4 samples. The magnetization was found to be influenced by the surface spin canting angles, the porosity percentage, and the cation distributions. The variation of dielectric constant with temperature indicated that the investigated materials can be recommended to be used as good insulating ceramic materials at room temperature and as a semiconductor at higher temperatures.

The doped ZnO system Zn0.94Co0.05Cu0.01O (ZCCO) was prepared as a nano-polycrystalline by a sim- ple sol-gel process, then air annealed at different tempera- tures. Applying X-ray diffraction (XRD) and the Rietveld method, structural analysis showed that Co and Cu replace Zn substitutionally yielding ZCCO single phase. The re- fined u-fractional coordinate of Zn increases monotonically by an annealing temperature from 0.3546 at 500 °C reach- ing 0.3722 at 800 °C, very near from the ideal value 0.375. The Zn tetrahedrons become more symmetric and the dis- tortion is gradually relieved by annealing up to 800 °C. An- nealing at 900 °C introduces tetrahedron distortion in an opposite way. The zero field cooled (ZFC) and field cooled (FC) magnetization versus the temperature at different ap- plied fields and the magnetization versus the applied field at different temperatures were carried out. The system ex- hibits a ferromagnetic behavior at room temperature. As the annealing temperature increases from 550 to 900 °C, the saturation magnetization at 300 K increases from 0.0507 to 0.1088 emu/g.

The doped ZnO systems Zn1−x−y Mg x Al y O (ZMAO) (x=0, 0.05, 0.1 and y=0, 0.05 and 0.1) were prepared as polycrystalline nanoparticle by a simple sol–gel process. Structural and microstructural analyses were carried out applying X-ray diffraction (XRD) and Rietveld method. Analysis showed that Mg2+ and Al3+ replace Zn2+ substitutionally yielding ZMAO single phase. Replacing Zn+2 affects the lattice parameters in opposite ways, the parameter c decreases while a increases with an overall decrease in the ratio c/a, which deviates the ZMAO lattice gradually from the wurtzite hexagonal structure. The magnetization versus temperature was measured with zero-field cooled (ZFC) and field cooled (FC) at different applied fields. Also, measurement of magnetization versus applied field was carried out at different temperatures. The system exhibits ferromagnetic properties at room temperature. The saturation magnetization increases as Al doped amount increases.