Evidence of Cr³⁺ and Cr⁴⁺ Coexistence in Chromium-Doped SnO₂ Nanoparticles: A Structural and Magnetic Study

Abstract

The present study reports the successful synthesis of Sn 1−x Cr x O 2 nanoparticles with doping content (x) ranging from 0 to 0.20. Samples were synthesized by a polymer precursor method using SnCl 2 •H 2 O and Cr(NO 3 ) 3 •5H 2 O as metal ion suppliers. In all samples X-ray diffraction data show one single-phase formation (rutile-type), with crystalline size (crystal strain) decreasing (increasing) monotonically while increasing the x content, which are assigned to substitutional solution of Cr and Sn ions in the crystalline structure. In addition to a weak magnetic ordering observed in a few samples (x = 0.01, 0.02, 0.03, and 0.05), paramagnetism is the main magnetic contribution in all synthesized samples, which is due to the presence of two chromium ions (Cr 3+ and Cr 4+ ). X-ray photoelectron spectroscopy measurements confirm the coexistence of Cr 3+ and Cr 4+ ions in excellent agreement with the monotonic decrease of the [Cr 3+ ]/[Cr 4+ ] versus doping content (x), assessed from the fitting of the susceptibility versus temperature data using the Curie−Weiss law.

Investigation of the Structural and Luminescent Properties and the Chromium Ion Valence of Li2CaGeO4 Crystals Doped with Cr4+ Ions

“…The narrow-scan spectra of XPS were fitted using Gaussian equations with two peaks centered at 575.6 and 584.4 eV due to Cr2p3/2 and Cr2p1/2, respectively, corresponding to the Cr 4+ ions. In the Gaussian fitting curves, we did not find peaks of the Cr 3+ ions, of which the two peaks centered at 577.0 and 586.7 eV were ascribed to Cr2p3/2 and Cr2p1/2 of the Cr 3+ ions, respectively [44,45]. Therefore, the Li2CaGeO4 sample contained only Cr 4+ ions without the presence of Cr 3+ ions, which is consistent with the results of the fluorescence spectroscopy analysis.…”

Aerosol-assisted facile fabrication of bimetallic Cr2O3–Mn2O3 thin films for photoelectrochemical water splitting

“…The found positions of the Cr 2p peaks are in agreement with reports in the literature, confirming the existence of chromium-ion (Cr 3+ ) in the studied sample. 31–33 The doublet binding energies at 642.1 and 653.9 eV shown in Fig. 2c are depictive of Mn 2p 3/2 and Mn 2p 1/2 , respectively.…”

A non-rare earth ion doped broadband emission phosphor located in NIR-II for ethanol concentration detection

“…In addition to the strong signals from the Ca, Ge, O and Cr ions, a peak is observed near 586.7 eV, corresponding to the binding energy of Cr 4+ 2 P 1/2 . 29…”