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This paper reports the influence of doping degree and annealing temperature on XRD, Raman, EPR and PL spectra of Sn 1 − x V x O 2 nanoparticles with x = 0, 0.01 and 0.05 annealed at 600 and 800 °C. XRD studies reveal a tetragonal rutile crystalline phases of tin oxide, while the formation of V 2 O 5 secondary phase was evidenced for all doped nanoparticles only by Raman scattering. In function of the doping degree and annealing temperature, from EPR spectroscopy was evidenced the presence of three different positions for V 4+ ions in the samples: isolated ions disposed on the nanoparticles surface, ions which are coupled by dipolar or exchange interactions and cluster ions. The luminescence emissions associated with oxygen vacancies and structural defects are influenced by doping degree and annealing temperature and could be correlated with the crystallite size determined from XRD patterns. [ABSTRACT FROM AUTHOR]

Abstract: This article reports the effects of the annealing temperature on the structural, morphological and spin dynamic properties of SnO2 samples doped with 0.005Mn. The samples were annealed at 400, 600, 700 and 800°C and analyzed by XRD, TEM, XPS and EPR spectroscopy. The XRD spectra show that the average crystallite size increases with the increase of the annealing temperature. The particles size and morphology were characterized by TEM microscopy. The valence bands of Mn were investigated by measuring the XPS spectra of Mn 2p core-level doublet. Regardless of the annealing temperature, the observed EPR spectra are due to (i) Mn2+ ions either interstitially situated on the particle surfaces or isolated ones located substitutionally at Sn sites and (ii) Mn4+ ions which substitute for Sn4+ in SnO2 lattice. The effects of the annealing temperature on the relative fractions of Mn2+ and Mn4+ ions are presented and discussed. In Sn1− x Mn x O2 (x =0.005) sample annealed at 400°C, a FMR line was identified and attributed to a ferromagnetic phase. [Copyright &y& Elsevier]

Abstract: This paper reports the influence of the temperature annealing (T a) on the structural, morphological, Raman and EPR characteristics of Mn-doped ZnO nanoparticles. XRD studies reveal a wurzite-type structure, while the formation of ZnMnO3 secondary phase was evidenced only for the nanoparticles annealed at T a =700°C. This impurity phase was also identified by Raman scattering in the samples thermally treated at 600°C and higher temperatures. TEM investigations reveal that the average particle size of samples starts from 13nm. With the increase of synthesis temperature, the average particle size reaches a value of 55nm for 700°C. From the XPS spectrum of Mn 2p core-level doublet only the 2+ valence state for manganese ions was evidenced. EPR investigations show that depending on the annealing temperature, Mn ions are incorporated either in the interior of ZnO nanoparticles (T a =425 and 500°C) or at their surfaces (T a >500°C). For the sample annealed at T a =425°C, a new broad resonance line arises, which was attributed to a ferromagnetic phase. We assume that this ferromagnetic phase could be due to the interaction between the Mn2+ ions and uncompensated acceptor defects incorporated into the ZnO lattice during the thermal treatment of the samples. Our investigations show that the ferromagnetism in Mn-doped ZnO nanoparticles could appear in the low-temperature annealed samples and disappears in the samples thermally treated at high temperatures. [Copyright &y& Elsevier]