Investigations of the local distortions and EPR parameters for Cu²⁺ in xNa₂O‐(30–x)K₂O‐70B₂O₃ (5 ≤ x ≤ 25 mol%) glasses

Abstract

The local distortions and electron paramagnetic resonance parameters for Cu in the mixed alkali borate glasses xNa O-(30-x)K O-70B O (5 ≤ x ≤ 25 mol%) are theoretically studied with distinct modifier Na O compositions x. Owing to the Jahn-Teller effect, the octahedral [CuO ] clusters show significant tetragonal elongation ratios p ~19% along the C axis. With the increase of composition x, the cubic field parameter Dq and the orbital reduction factor k exhibit linearly and quasi-linearly decreasing tendencies, respectively, whereas the relative tetragonal elongation ratio p has quasi-linearly increasing rule with some fluctuations, leading to the minima of g factors at x = 10 mol%. The composition dependences of the optical spectra and the electron paramagnetic resonance parameters are suitably reproduced by the linear or quasi-linear relationships of the relevant quantities (i.e., Dq, k, and p) with x. The above composition dependences are analyzed from mixed alkali effect, which brings forward the modifications of the local crystal-fields and the electronic cloud distribution around Cu with the variation of the composition of Na O.

Theoretical investigation on the optical and EPR spectra for Cu2+‐doped ZnO‐CdS nanocomposites

“…Our calculations suggest that A ‖ and A ⊥ is negative and positive, respectively (see Table ). There are many reports on the negative A ‖ and positive A ⊥ of the hyperfine structure constants for the tetragonally elongated [CuO 6 ] 10− octahedral clusters . Consequently, the signs of hyperfine structure constants were determined in this work and can be regarded as reasonable.…”

“…Consequently, the signs of hyperfine structure constants were determined in this work and can be regarded as reasonable. The studies of hyperfine structure constants for Cu 2+ ions in many crystals given κ is in the range 0.2 κ 0.5 . The adopted κ is in the range and can be regarded as suitable.…”

An investigation on the EPR parameters and tetragonal distortion for Cu$$^{\mathrm {2+}}$$ center in Mg(CH$$_{\mathrm {3}}$$COO)$$_{\mathrm {2}}\cdot $$ 4H$$_{\mathrm {2}}$$O Crystal

“…[9] and similar tetragonal [CuO 6 ] 10− clusters in Refs. [21][22][23][24][25][26][27] for Cu 2+ in many other crystals and can be regarded as rational. In addition, the investigations of hyperfine parameters for Cu 2+ in many crystals revealed that κ is in the range 0.2-0.35 [23][24][25][26][27].…”

“…This point is also supported by various Cu 2+ centers in ZnGa 2 O 4 [18], ZnSeF 6 • 6H 2 O [19] and Al 2 O 3 crystals [20], where the impurity Cu 2+ centers actually show tetragonal elongation distortion due to the JT effect. Even in oxide glasses materials, the doped Cu 2+ centers still exhibit TEO [10,21]. Thus, the local structure of the center may be described by the relative elongation ratio η along the C 4 axis due to the JT effect, and the Cu-O bond lengths parallel and perpendicular to the C 4 -axis are expressed as follows:…”

A comparable study of the optical spectra and EPR parameters for 3d1‐ and 3d9‐doped MgNH4PO4·6H2O

“…On the basis of the perturbation theory, the high-order perturbation formulas of EPR parameters (g factors g jj , g ⊥ and hyperfine structure constants A jj , A ⊥ ) for 3d 1 ions with the ground state 2 B 2g can determined from the two SOC parameters model and CF theory [23] :…”