An investigation of the local distortions and the EPR parameters for Cu2+ in 40MgO–(10−x)PbF2–50SiO2–xCuO glasses.

The local distortions and electron paramagnetic resonance (EPR) parameters for Cu 2+ in 40MgO–(10−x)PbF 2 –50SiO 2 –xCuO (MPSC) glasses are theoretically studied at various impurity CuO concentrations x (= 0.1, 0.3, 0.5, 0.7, 0.9 and 1.0 mol %) in a consistent way. Due to the Jahn-Teller effect, the [CuO 6 ] 10− clusters are found to experience the moderate tetragonal elongation distortions (characterized by the moderate relative tetragonal elongation ratios ρ ≈ 3%) along C 4 axis. With only five adjusted coefficients a 1 , a 2 , b 1 , b 2 and ω , the relevant model parameters ( Dq , k , ρ, κ and H ) are described by the Fourier type functions, which suitably reproduce the corresponding overall varying tendencies and fluctuations of the measured d–d transition bands and EPR parameters with x. The microscopic mechanisms of the varying rules of the relevant quantities with x are discussed in view of the whole decreasing ability of Si 4+ to accept electrons and the reverse tendencies due to partial Cu 2+ reduced to Cu + at x ≥ 0.7 mol %. The monotonically increasing tendency of the calculated optical basicity reveals decreasing covalency of the whole glass systems with x. [ABSTRACT FROM AUTHOR]