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Item type:Publication, Structural, hyperfine, and magnetic evolution of a natural magnetite–serpentine composite: Effects of magnetic separation and thermal treatment(Elsevier BV, 2026-08-15)In this work, the structural, hyperfine, and magnetic evolution of a natural magnetite–serpentine composite was systematically investigated in its as-collected state, after magnetic separation, and following thermal treatments. X-ray diffraction combined with Rietveld refinement reveals a lizardite-dominated matrix containing magnetite as the primary magnetic phase. Mössbauer spectroscopy identifies Fe2＋ and Fe3＋ cations distributed over distinct octahedral and tetrahedral sites in both lizardite and magnetite, providing insight into cation distribution and oxidation state evolution. Magnetic measurements reveal ferrimagnetic behavior dominated by magnetite, with a saturation magnetization of ∼79 emu g−1 at room temperature. The transition temperature was estimated from the derivative of the ZFC–FC magnetization curve with respect to temperature, which exhibits a relatively broad peak associated with the Verwey transition (118 K). This feature suggests the presence of relatively preserved magnetite within the ultramafic matrix, although the broad character of the transition may reflect structural disorder, particle-size effects, or magnetic interactions. In addition, the magnetic data indicate the coexistence of superparamagnetic behavior and possible spin-glass-like contributions, likely associated with surface disorder and nanoscale magnetic interactions. Water-assisted magnetic separation enhances the magnetic fraction, confirming that magnetite particles are embedded within the lizardite matrix. Thermal treatments at 500 °C and 1000 °C induce progressive dehydroxylation, oxidation of iron-bearing phases, and the formation of hematite, forsterite, silica, and clinoenstatite, leading to significant modifications in both hyperfine parameters and magnetic behavior. The results establish clear structure-hyperfine-magnetic correlations and demonstrate how magnetic separation and thermal processing govern the phase stability and functional magnetic response of natural magnetite–serpentine systems. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Engineering dynamic defect compensation in Sn-Doped In2O3 thin films for enhanced optoelectronic performance(Elsevier BV, 2026-07-15)Sn-doped In2O3 is a typical transparent conducting oxide, yet the mechanisms governing carrier suppression and functional degradation at high doping levels remain unclear. Here, defect engineering via controlled Sn incorporation is employed to tune dynamic defect compensation, enabling direct correlation between defect chemistry and optoelectronic functionality. A non-monotonic evolution of lattice parameter and carrier density reveals two distinct regimes. At low Sn concentrations, enhanced free-electron density induces a Burstein–Moss bandgap widening. Beyond a critical doping threshold, cooperative compensation mediated by Sn4+/Sn2+ coexistence and oxygen interstitials suppresses carrier density, activating competition between bandgap renormalization and the Burstein–Moss shift. Density functional theory calculations confirm the electronic impact of this defect complex. Remarkably, the evolution of photocurrent closely mirrors the methane sensing response, demonstrating that oxygen-related defects regulate charge-transfer dynamics. These findings establish dynamic defect compensation as a tunable design principle for engineering multifunctional transparent conducting oxides. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Effect of the working pressure on the structural, morphological, optical, electrical and gas sensor properties of ZnO films grown by DC magnetron sputtering(Elsevier BV, 2026-02-01)In this work, ZnO thin films were deposited by DC magnetron sputtering under varying working pressures and subsequently annealed in air, followed by vacuum thermal annealing. The increase of working pressure drive to the reduction of the film thickness, crystallite size, lattice constants, and to the strengthening of the (002) X-ray diffraction peak, suggesting changes in the in oxygen vacancy concentration. Scanning electron microscopy revealed the formation of randomly distributed nanorods, while UV–Vis spectroscopy data analysis evidenced the presence of defect-related levels inside the band gap. As the thickness decreases, Hall measurements show a noticeable drop in charge carrier density and mobility, which is linked to the combined impact of defects and the decreasing size of crystallites. This suggests that thicker films exhibited a higher density of zinc interstitials, whereas thinner films exhibit more oxygen vacancies (VO[jls-end-space/]), mainly associated with surface states, as supported by temperature-dependent resistance measurements and photocurrent analysis. Gas detection tests demonstrated a superior response to methane (CH4[jls-end-space/]) for thinner films at 200 °C, attributed to their higher oxygen vacancy concentration. Photocurrent and gas sensing measurements showed similar trends, indicating a common defect-driven mechanism. These results highlight the potential of tuning defect chemistry in ZnO films to optimize their performance for gas sensing and optoelectronic devices.1