Studies of the EPR parameters and tetragonal distortion for the Cu²⁺ center in aluminium oxide

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

“…However, as a JT Cu 2+ ion under octahedra, the [CuO 6 ] 10− cluster will suffer the JT effect via stretching the two Cu-O bonds along the C 4 axis and compressing the other four bonds in the perpendicular plane, which reduces the local symmetry to TEO. 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].…”

“…It is also a well-known fact that Cu 2+ ions tend to form an elongated octahedron in most systems due to the Jahn-teller effect [51]. Interestingly, EPR analysis for Cu 2+ centers in Al 2 O 3 [20] and BaO-TeO 2 -B 2 O 3 glasses [10] have yielded the relative tetragonal elongation ratios τ of 4.8 and 4.3%, respectively, due to the Jahn-Teller effect. These values are very close to τ (≈ 3.7%) obtained in this work, which can be regarded as reasonable.…”

“…For the studied MAT:Cu 2+ , the obtained relative tetragonal elongation ratio η (≈ 3.7% > 0) is in agreement with the positive anisotropy Δg(= g || − g ⊥ ) for a 3d 9 ion in a tetragonally elongated octahedron. Tetragonal Cu 2+ complexes with D 4h generally show g || > g ⊥ > 2.04 and A || > A ⊥ with the ground state 2 B 1g [17][18][19][20]. It is also a well-known fact that Cu 2+ ions tend to form an elongated octahedron in most systems due to the Jahn-teller effect [51].…”