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Magnetic metamorphosis of structurally enriched sol-gel derived SnO2 nanoparticles
摘要： Pure SnO2 and aliovalent substituted polycrystalline Sn0.98?xLa0.02ZnxO2 (x = 0.02, 0.04 and 0.06) samples have been synthesized via sol-gel technique. Rietveld re?nement of X-ray di?raction (XRD) patterns con?rm the single phase tetragonal rutile-type (P mnm 42/) crystalline structure for all the synthesized samples. Crystallite size from XRD analysis is found to decrease from 14 nm to 11 nm as x increases from 0 to 0.06 in Sn0.98?xLa0.02ZnxO2 matrix. Transmission Electron Microscopy further reveals the decrease in average crystallite size from 7 nm for pure SnO2 to 5 nm with increase in Zn2+ concentration in system. Morphological study through Field Emission Scanning Electron Microscopy reveals the agglomeration of nanoparticles on increasing the Zn concentration. The room temperature photoluminescence (PL) measurements mark the change in peak intensity centered around 300–450 nm upon La and Zn co-doping into SnO2 lattice. Deconvolution of PL peak unveil the presence of defects/vacancies and local disorders in (La, Zn) co-doped SnO2 matrix. Further, the magnetic properties have been studied using Vibrating Sample Magnetometer, which envisage the room temperature ferromagnetism (RTFM) in nonmagnetic La3+ and Zn2+ ion modi?ed SnO2. The observed RTFM in (La, Zn) co-doped SnO2 is mainly due to oxygen vacancies which is also supported by PL results.
关键词： Rietveld re?nement,RTFM,SnO2 nanoparticles,Defect states
更新于2025-09-23 15:23:52
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Changes of optical transition models caused by crystal structural changes in CaSe2O5
摘要： The present work concerns calcium pyroselenites CaSe2O5 with two independent crystal structures, their di?erence physical properties and phase transformations. α-CaSe2O5 in orthorhombic form shows 2D calcium oxide anionic layers whereas new compound β-CaSe2O5 crystallizes in monoclinic space group C2/c. It's a new structure type with 1D calcium oxide thick chains which are further connected by Se2O5 dimers. Rietveld re?nement indicates that the weight fraction for α/β-CaSe2O5 mixture phase was found to be 84.5% and 15.5% for α- and β-CaSe2O5, respectively. Optical di?use re?ectance spectrum coupled with Kubelka–Munk ?t gives a result that α-CaSe2O5 adopts direct optical transition model while β-CaSe2O5 is an indirect semiconductor. The experimental result matches well with the prediction of theory calculation. The optical bandgap values were ?tted to be 4.74 and 4.12 eV for α- and β-CaSe2O5, respectively. Thermal analysis coupled with variable temperature powder XRD indicates the phase transformation between these two phases.
关键词： Selenite,Optical bandgap,Rietveld re?nement,Phase transformation
更新于2025-09-23 15:23:52