Local symmetry of Cu2+ ions in sodium silicate glasses from data of EPR spectroscopy

Sodium silicate glasses with a constant ratio of oxide concentrations (mol %) SiO2/Na2O = 2.4 and with copper ions introduced in the form of CuO (from 1 to 10 mol %) are studied by the EPR method. The shape and width of the EPR line of copper ions are analyzed, and the spin-Hamiltonian parameters g(parallel to), g(perpendicular to), A(parallel to), and A(perpendicular to) are determined by simulating the EPR spectrum and comparing the simulated and experimental spectra. The EPR spectrum of copper ions (1 mol %) is characterized by the parameters g(parallel to) = 2.35, g(perpendicular to) = 2.065, A(parallel to) = 135 x 10(-4) cm(-1), A(perpendicular to) = 7 x 10(-4) cm(-1), and DeltaH = 25 G. An analysis of this spectrum shows that the nearest environment of the Cu2+ ion has the shape of an elongated octahedron. The EPR spectrum of the sodium silicate glass containing 10 mol % Cu is a superposition of the spectrum of an octahedral complex (g(parallel to) = 2.35, g(perpendicular to) = 2.075, A(parallel to) = 135 x 10(-4) cm(-1), DeltaH = 40 G) and the spectrum of a cluster (g(parallel to) = 2.35, g(perpendicular to) = 2.075, A(parallel to) = 135 x 10(-4) cm(-1), DeltaH = 50 G).