Structural Analysis of the BaWO4 Crystal Doped with Ce and Codoped with Na Ions Based on g-shift Parameters

Abstract

The relationship between the g-shift and the local structure of the Ce3+ paramagnetic center with axial symmetry were investigated for four BaWO4 single crystals doped with Ce and codoped with Na. Based on g-shift the displacements of Ce3+ ions are determined. The g-shift method yields displacements of impurity ions in good agreement with the superposition model (SPM) and the perturbation methods (PM) predictions. The structural analysis of the paramagnetic ions and its surrounding in the BaWO4 unit cell was also conducted.

Theoretical Investigation of the EPR G-Factor for the Axial Symmetry Ce3+ Center in the BaWO4 Single Crystal

“…Ce, 2.0% at. Na [17][18][19][20]. One of these centers is the strongest and occurs in all four monocrystals.…”

“…Rare-earth ions (like Ce 3+ ) substitute Ba 2+ site in the elementary cell of the barium tungstate (BaWO 4 ) [17][18][19][20]25,26,38]. The local symmetry of the Ce Ba site (Ba 2+ place occupied by Ce 3+ ) is S 4 (tetragonal symmetry).…”

“…Thus, no perturbation formula is needed. We get only g-factor parameters obtained from EPR measurements for Ce 3+ in BaWO 4 [17][18][19][20]. The g-factor can be obtained using CDM method using the following equations:…”

“…Structural information can be obtained from spin-Hamiltonian parameters (and/or g-parameters) using a superposition model (SPM) [22,23] or perturbation methods (PM) up to second-order [24]. Previously, we used a simplified Newman model, a g-shift model [20]. In this paper, we choose to use superposition model (SPM) to obtain structural information on trivalent cerium ion (Ce 3+ ) and its surroundings.…”

“…Five paramagnetic centers with axial symmetry and about ten centers with low symmetry (C 2 ) were found [17,18]. In the next step, we were investigated the connection between the g-shift and the environment of the Ce 3+ centers with axial symmetry for four BaWO 4 doped with Ce (cerium) and co-doped with Na (sodium) with different concentrations [20]. We also determined dislocations of Ce 3+ ions.…”