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This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International licence Newcastle University ePrints -eprint.ncl.ac.uk Yeganeh M, Shahtahmasebi N, Kompany A, Karimipour M, Razavi F, Nasralla NHS, Siller L. The magnetic characterization of Fe doped TiO2 semiconducting oxide nanoparticles synthesized by sol-gel method.

The importance of investigating the electronic structure of Fe doped TiO2 nanoparticles lies in understanding their various magnetic and optical applications. In this study Fe doped TiO2 nanoparticles were synthesized by sol gel method in a wide range of Fe/Ti molar ratios (1, 3, 5, 8, and 10 %) and post annealing at 400, 600 and 800 o C in air. The structure and size of nanoparticles were studied by X-ray diffraction and transmission electron microscopy, respectively. Systematic study of the existing states of Fe ions in Fe doped TiO2 and transformation of the existing states as a function of annealing temperature and Fe concentration were carried out utilizing high-resolution X-ray photoemission spectroscopy (XPS). The XPS results showed that Fe was present in all samples while Fe ions were detected in mixed valence (Fe 2+ and Fe 3+ ) states. The Fe 3+ ions were dominant in the surface region of the nanoparticles. Moreover, the Ti in Fe:TiO2 nanoparticles was assigned to the Ti 4+ while a small shift towards lower binding energies was observed upon increasing the annealing temperature and dopant level. This confirms the successful incorporation of Fe into TiO2, and the shifts in binding energies were attributed to the anatase to rutile transformation. The results verify that doping by Fe up to 10% do not exceed the limit of Fe substitutation into TiO2 lattice.

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Ni-doped TiO 2 nanoparticles were synthesized by the non-hydrous complex-polymer sol-gel method. Titanium isopropoxide was used as precursor and acetyl acetone (AcAc) and citric acid were used as polymer and complex agent, respectively. A series of Ni x : Ti 1−x O 2 samples with x = 0.01, 0.03, 0.05 and 0.10 were prepared and subsequently annealed at 400, 600 and 800 • C. The structural and magnetic properties of Ni x : Ti 1−x O 2 were studied by means of x-ray diffraction (XRD) and dc magnetometery. Samples annealed at 400 • C attained a particle size of 12 nm with structural phases of anatase, rutile and cubic NiO. From the blocking temperatures of the zero-field-cooled and field-cooled measurements, similar particle sizes (as from XRD) were obtained. The presence of ferro-and antiferromagnetic (AFM) interactions further confirms that the particles have different structural compositions. At 800 • C the particles have grown to about 30 nm with either a rutile or NiTiO 3 -type structure. The presence of NiTiO 3 is also seen in the magnetic measurements, which show the characteristic AFM peak at 23 K.

In the present study, we have investigated the phonon and thermodynamic properties of bulk zinc-blende CdS by first-principle calculations within the density functional theory (DFT) and the density functional perturbation theory (DFPT) method using the quasi harmonic approximation (QHA). We calculated the phonon dispersion at several high symmetry directions, density of phonon state, temperature dependence feature of Helmholtz free energy (F), internal energy, bulk modulus, constant-volume specific heat, entropy, coefficient of the volume thermal expansion and Grüneisen parameter estimated with the local density approximation (LDA) and generalized gradient approximation (GGA) for the exchange-correlation potential and compared them with each other. For internal energy, Helmholtz free energy, constant volume heat capacity and phonon entropy the LDA and GGA results are very similar. But, the LDA gives lattice constants that are smaller than GGA while phonon frequencies, bulk modulus and cohesive energies are larger. On the other hand, the results obtained through the GGA approximation for the coefficient of the volume thermal expansion and Grüneisen parameter are larger than those obtained from LDA.