Computer modelling of hafnium doping in lithium niobate

Lithium niobate, LiNbO3, is an important technological material with good electro-optic, acousto-optic, elasto-optic, piezoelectric and nonlinear properties. Doping LiNbO3 with hafnium, Hf has been shown to improve the resistance of the material to optical damage. Computer modelling provides a useful means of determining the properties of doped and undoped LiNbO3, including its defect chemistry, and the effect of doping on the structure. In this paper, Hf doped LiNbO3 has been modelled, and the final defect configurations are found to be consistent with experimental results

Study of Eu3+ -> Eu2+ reduction in BaAl2O4:Eu prepared in different gas atmospheres

The effect of different gas atmospheres such as H2(g), synthetic air, carbon monoxide (CO) and nitrogen (N2) on the Eu3+ → Eu2+ reduction process during the synthesis of Eu-doped BaAl2O4 was studied using synchrotron radiation. The Eu3+ → Eu2+ reduction was monitored analyzing XANES region when the sample are excited at the Eu LIII-edge. The results show that the hydrogen reducing agent are the most appropriate gas for Eu2+ stabilization in BaAl2O4 and that only a part of the Eu ions can be stabilized in the divalent state. A model of Eu reduction process, based on the incorporation of charge compensation defects, is proposed

Optical properties of Pr and Eu-doped SrAl12O19: A theoretical study

This paper describes a computational study of extrinsic defect and optical properties of SrAl12O19 induced by trivalent rare earth dopants. Solution energies for a range of possible doping mechanisms are calculated, and predictions made of doping sites and charge-compensation schemes. Atomistic modelling is used to calculate the symmetry and detailed geometry of the dopant ion-host lattice system, and this information is then used to calculate the crystal field parameters. It is found that the preferred doping mechanism for Pr is a substitution at Sr2+ sites, with charge compensation by anti-site and for Eu is a substitution at the Al3+ site. Crystal field parameters have been calculated and the results discussed in terms of optical properties of the doped systems. Bkq values indicate that the site symmetry is D2h. The transition levels are then calculated for the Pr3+ and Eu3+-substituted material, and comparisons made with experimental results have a good agreement

Optical spectroscopy study of Eu-doped ions in BaAl2O4 phosphors

Computational and experimental methodology is employed to study optical properties in Eu-doped BaAl2O4 phosphors. The symmetry and detailed geometry of the Eu-dopant site, predicted by atomistic simulation, are used to calculate the crystal field parameters and the intensity parameters (Ω2 and Ω4) based on a Judd-Ofelt approach to the Eu3+ ion. The phenomenological intensity parameters are obtained from the emission spectra of the Eu-doped BaAl2O4 and compared to the theoretical results. Experimental and calculated values for the 7F1 energy sub-levels of the Eu3+ and maximum Stark splittings (ΔEmax) are also obtained