Structural and Surface Study of Praseodymium-Doped SnO₂ Nanoparticles Prepared by the Polymeric Precursor Method

Abstract

In the present study, we report on the successful synthesis of Pr-doped SnO 2 (SnO 2 :Pr) nanoparticles using a polymeric precursor method while setting the Pr-content in the range from 0 to 10.0 mol %. The as-prepared samples were characterized in regard to their structural, morphological and surface properties. X-ray diffraction (XRD) patterns recorded from all samples revealed the tetragonal rutile-type structure with a systematic average size reduction (in the range from 11 to 4 nm) while enhancing the residual strain (in the range of 0.186 to 0.480%) as the Pr-content was increased. From the Rietveld refinement analysis we found that the lattice parameters (a, c, u, and V) showed a linear behavior, indicating a solid solution regimen for the Pr-doping. Transmission electron micrographs provided mean particle sizes of 8.7 ± 0.5 nm, for 2.5 mol % Pr-content, and 5.2 ± 0.5 nm,for 10.0 mol % Prcontent, which are in very good agreement with values obtained from the XRD data analysis: 7.4 ± 1.0 nm and 4.0 ± 1.0 nm, respectively. From X-ray photoelectron spectroscopy (XPS) measurements [O]/[Sn] = 1.44 ratio has been estimated at the surface of the undoped SnO 2 nanoparticles, which is below the expected value for bulk compound ([O]/[Sn] = 2), suggesting that the system is strongly nonstoichiometric at the nanoparticle surface. Actually, we found the [O]/[Sn] ratio value increasing monotonically as the Pr-content was increased, which was interpreted as due to the elimination of the surface chemisorbed oxygen and/or oxygen-related vacancies. Moreover, a redshift of the Sn(3d) XPS peaks has been determined as the Pr-content was increased, evidencing the change of the oxidation state of tin ions from Sn 4+ to Sn 2+ . Our analyzes of the Pr(3d) XPS peaks indicated the preference of the Pr-ions for the Pr 3+ oxidation state, although small amounts of the Pr 4+ -ions could not be completely ruled out, particularly for the lower Pr-doping samples.

Magnetic Properties of Rare Earth Doped SnO2, TiO2 and CeO2 Nanoparticles

“…Due to the larger radius of the dopant ions we obtain tensile strain also in Pr doped TiO 2 NPs (Ti 4+ 0.69 Å ) in qualitative agreement with the experimental data of Strengl et al, Fengping et al, Jiang et al, and Reszczynska et al, as well as in Pr doped SnO 2 NPs (Sn 4+ − 0.76 Å ) in agreement with the reported increasing of the lattice parameters of Aragon et al The grain size decreases with increasing Pr concentration in TiO 2 NPs . So we predict that M would decrease with increasing Pr and Er dopant content in TiO 2 and SnO 2 NPs and hope that experiments in the future would confirm this behavior (Figure , curves 3 and 2).…”

“…This strain could decrease the exchange interaction constants in our model and could lead to a decrease of the magnetization M . This would be in qualitative agreement with the observed suppression of the magnetization by Paunovic et al Aragon et al have studied the role of Er and Pr ions (1.08 Å) in the long‐range ferromagnetic order. It seems to be fundamental, since they provoke more oxygen vacancies in the SnO 2 matrix.…”

“…For example Paunovic et al observed a strongly decrease of the magnetization M in Pr‐doped CeO 2 NPs till , whereas Niu et al reported a maximum in M at (). Sharma et al observed a decrease of the lattice parameters in Pr doped CeO 2 NPs, whereas Paunovic, Kim et al, and Aragon et al an increase. The crystal size decreases in Er doped SnO 2 NPs by Aragon et al whereas it increases by Sambasivam et al Moreover, the last authors reported an antiferromagnetic behavior in Er doped SnO 2 , whereas paramagnetism is obtained by Sharma et al The magnetization M in CeO 2 NPs increases with increasing Sm ion (max at 15%) and Dy ion (max at 11%) doping, respectively.…”

Surface and grain‐boundary excess of ZnO‐doped SnO2 nanopowders by the selective lixiviation method

“…Tin oxide is an interesting inorganic material for segregation studies because of the high stability: the rutile structure is stable from room temperature to approximately 1300°C, the additive solubility is low, and the water solubility is low. 35 Furthermore, SnO 2 nanoparticles can be prepared using many different chemical routes, [36][37][38][39] and some authors have reported the segregation of additives on SnO 2 nanopowders. 20,[40][41][42][43] However, the quantification of interface excess in oxides, particularly SnO 2 , is less reported in the literature.…”

High-performance photoluminescence-based oxygen sensing with Pr-modified ZnO nanofibers

“…The high-resolution Pr 3d XPS spectrum (Fig. 3c) reveals Pr 3d 3/2 and Pr 3d 5/2 peaks at, respectively, 953.7 eV and 933.6 eV with an energy separation of 20.1 eV, implying that the Pr in the PZNF sample is present as Pr 3+ or Pr 4+ [43]. The high-resolution Zn 2p spectra of the two samples ( Fig.…”