Osman Murat Ozkendir

Influence of Rare-Earth Substitution on the Crystal and Electronic Properties of a Li2MnO3 Battery Cathode

Rare-earth Nd, Ce and Yb substitutions into the Li2MnO3 structure via the general formula Li2Mnx(Nd, Ce, Yb)1−xO3 were investigated according to the crystal structure transitions and the influences on their electronic structure properties. The results of the x-ray diffraction patterns were studied in coordination with the electronic structure properties by the x-ray absorption near-edge spectroscopy technique. 4f levels were selected as the main playground in the study due to their interesting relations yielding fruitful physical phenomena in the materials that were reported in so many studies. Among the substituted samples, the sample for Ce 80% was determined to be the most interesting sample showing band broadening with the strongest overlapped electronic levels that built larger molecular bands.

Chromium Substitution Effect on the Magnetic Structure of Iron Oxides

The local magnetic and electronic structures of chromium substituted iron oxide polycrystalline samples are investigated via Fe L-edge x-ray absorption near-edge structural and magnetic circular dichroism measurements. A strong dependence of atomic magnetic levels on the applied external magnetic field is observed. The magnetic behavior of Cr-doped iron oxides are determined to be dominantly governed by the d—d hybridization between Fe and Cr valence levels. In addition, the formation of CrO2 and Cr2O3 chromium oxide clusters in the sample are observed to determine the magnetic ordering, i.e. anti-ferromagnetic or ferromagnetic with the changing external magnetic fields. The results highly agree with the previous studies.

Crystal and Electronic Structure of (Y,Pr) x Sm 1− x BO 3 Oxide

The effects of Y and Pr substitution on the electronic and crystal structure of triclinic SmBO3 have been investigated using x-ray diffraction (XRD) analysis and x-ray absorption fine-structure spectroscopy. Polycrystalline structure was observed on substitution of Y3+ and Pr4+ ions with Sm3+ coordination. Yttrium-substituted samples were found to contain BO3 ligands around Sm atoms, while the crystal structure of YBO3 presented hexagonal geometry, not preserving the triclinic crystal structure. Also, praseodymium ions (Pr4+) formed isolated Pr2B5 crystal structure by distorting some BO3 ligands. Moreover, electronic structure studies revealed that 4f levels of Sm and Pr were inactive in bonding interaction and did not support strong coupling between neighboring Sm and Y/Pr atoms.

The influence of Cerium doping on the crystal and electronic properties of FeBO3 oxides

Cerium substituted FeBO3 samples were investigated according to their crystal and electronic properties via the general formula CexCuFe1-x BO3. With the doping of the heavy fermion “Cerium”, samples were determined in polycrystalline structure. With the incressing Ce in the samples, disturbances on the Cu-Fe planes became more clear that supports the formation of geometrically different crystal structures. To obtain the electronic mechanisms in the crystals, X-ray Absorption Fine Structure Spectroscopy (XAFS) technique were used to study the electronic properties of the samples in coordination with the X-ray diffraction (XRD) patterns. As a result of the analysis, f-levels of the Cerium atoms were determined as the main playground of interplays and strongly correlated electrons of 4f-3d levels were determined to emerge dominant interactions causing phase transitions.