Valence State Of Ce Ions Research Articles

Mixed valence state of Ce ions in CeNi 2Al 3

X-ray photoelectron spectroscopy (XPS) and magnetic susceptibility ( χ) of CeNi 2Al 3 and of the reference compound YNi 2Al 3 are reported. Both valence band and core level spectra were analyzed. The χ( T) curve of CeNi 2Al 3 shows a maximum around 22 K, characteristic for the intermediate valence state of Ce ions, and at high temperatures obeys a Curie–Weiss law with an effective magnetic moment μ eff=2.48 μ B/f.u. The Ce 3 d and 4 d XPS spectra have confirmed the mixed valence state of Ce ions in CeNi 2Al 3. The f occupancy n f , and coupling Δ between the f level and the conduction states are derived to be about 0.85 and 80 meV, respectively.

Spin and valence fluctuations in CeMn 4Al 8 and CeMn 6Al 6

The magnetic susceptibility and X-ray photoelectron spectra of CeMn 4Al 8 and CeMn 6Al 6 and of the reference compounds YMn 4Al 8, CeCu 4Al 8, YMn 6Al 6 and LaMn 6Al 6 are reported. The occurrence of a Mn moment in the investigated compounds is strongly correlated with the critical value d≃2.6 Å of the Mn–Mn distance below which the Mn moment collapses. It is revealed that the magnetic character of the Mn moment in the crystallographic sites for which d Mn–Mn≤2.6 Å changes from an itinerant electron type to a local moment type with increasing temperature. This behavior is in agreement with the prediction of spin fluctuation theory. Both the magnetic susceptibility and Ce 3d and 4d XPS spectra confirmed the mixed valence state of Ce ions in CeMn 4Al 8 and CeMn 6Al 6. The f occupancy, n f, and coupling, Δ, between the f level and the conduction states are derived to be about 0.83 and 80 meV, respectively. The Mn 3s XPS splitting is discussed in terms of the time scale for the spin fluctuation and photoemission processes.

Correlation between photoluminescent and crystallographic characteristics in Zn xSr 1− xS:Ce thin films: composition

The compositional dependence of luminescent and crystallographic characteristics of the Zn x Sr 1− x S:Ce thin films was investigated by compositional analysis, crystalline characteristics, valence state of Ce ions and photoluminescence (PL) properties. It has been found that the enhanced PL intensity by the incorporation of a small amount of Zn mainly attributes to the improvement of the crystallinity of the film and partially to the valence state of Ce ions in the host crystal.

Luminescent Properties of ZnxSr 1-xS:Ce Thin Film Phosphors for Electroluminescent Devices

The dependence of the luminescent properties of Ce-doped ZnxSr1-xS thin films on composition and annealing temperature is investigated. It has been found that the emission intensity of Ce3+ photoluminescence is enhanced by the incorporation of an optimum amount of Zn and by the increase of the post-annealing temperature. The luminescent intensity depends strongly on the crystallinity of the films and on the valence state of Ce ions. Fabrication of electroluminescent devices introducing ZnxSr1-xS as a host material has been attempted.