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    Niobium modification on dielectric, magnetic and structural features of nanocrystalline Ni-Co ferrites
    (Indian Acad Sciences, 2024) Teber, Ahmet; Sarac, Mehmet Fahri
    In this study, we will investigate the structural, characteristic, dielectric and magnetic features of Co0.5Ni0.5NbxFe2-xO4 (0.0 <= x (with 0.2 increments) <= 1.0) nanoparticles, which are prepared via the hydrothermal approach. M-type hexagonal crystal structures are confirmed through XRD, FT-IR, SEM-EDS, TEM-SAED and VSM. Also, we have reported the investigations on dielectric properties and ac conductivity. Based on XRD measurements, it is concluded that all samples have M-type hexagonal crystal structure with nanocrystals ranging from 60 to 97 nm. The diffraction patterns obtained matched well with the calculated patterns from Rietveld analysis. Moreover, from the morphological analysis, it was observed that the small spherical structures of Ni-Co ferrite particles transformed into quadrilateral structures with increasing Nb concentration. The results of the FT-IR study show that the hexaferrite structure is formed as predicted because the expected range of absorption bands is present. According to VSM, Nb-substituted Ni-Co ferrite nanostructures reveal a relatively soft ferromagnetic property. Increasing the concentration of Nb tends to increase the coercive field (H-c) variation. The dielectric factors and ac conductivity were measured in the frequency range of 0.1-10 MHz. The reduction in dielectric factors and tangent losses at low frequencies can be elucidated by both deformation and relaxation polarization mechanisms. Another observation is that ac conductivity is amplified with the applied frequency. In this sense, the electron and hole hopping phenomenon can explain the conduction mechanism.
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    Tailoring the optoelectronic properties of ZnO nanowires via TiO2 coating
    (Indian Assoc Cultivation Science, 2025) Sarac, Mehmet Fahri; Mert, Merve; Solakyildirim, Tuba; Teber, Ahmet
    The photosensing properties of TiO2/ZnO nanowires (NWs) were investigated by sequential deposition using thermal oxidation and sol-gel. It was found that TiO2/ZnO NWs with 5 mM concentration exhibit a higher aspect ratio compared to the 10 mM and 25 mM TiO2/ZnO NWs. The surface-to-volume ratio directly influences the photoluminescence (PL) intensity and electrical properties of the ZnO NWs. XPS confirmed the presence of TiO2 on the surface, while EDS detected titanium, with its concentration increasing as the TiO2 concentration rises. The photosensing performance of ZnO has been significantly improved by modifying it with TiO2. However, determining the optimum concentration is a critical factor in performance improvement. The findings show that high TiO2 concentrations improve surface properties, but excessive coating may limit carrier mobility. Photosensitivity has been increased at lower TiO2 concentration due to a higher surface-to-volume ratio (SVR) and, as a result, higher surface photoactivity. The 25 mM TiO2/ZnO NW array stands out in optimal detectability and photoresponsivity due to the reduced resistance caused by the increased Ti concentration on the surface. The 25 mM TiO2/ZnO NWs achieved the highest photoresponsivity (717 mA/W) and specific detectivity (1.48 x 101 degrees Jones), while the 5 mM TiO2/ZnO NWs exhibited exceptional photosensitivity (320.11%), making them ideal for UV detection. The samples at varying concentrations show promise in photosensitivity, detectability, and photoresponsivity, making them suitable for environmental sensors, UV detectors, and other optoelectronic applications.