EPR Study of Cu2+Impurity Centre in WO3

EPR measurements on Cu 2+ centre in WO 3 arc made at 131 K using an X-band spectrometer. The determined g and A parameters in the spin Hamiltonian have strong c -axis anisotropy, as g x =2.053, g y =2.050, g z =2.415 and A x =24.5 ×10 -4 cm -1 , A y =18.9×10 -4 cm -1 , A z =-99.0×10 -4 cm -1 (Eulerian angles; θ 1 =11.7°, φ 1 =44.5°, ψ 1 =6.5°). The ground state of Cu 2+ ion is determined to be ∣ x 2 - y 2 > by g -value analysis. Two models for Cu 2+ centre are discussed by comparing with previous EPR results for V 4+ (3d 1 ) ion in WO 3 ; one is Cu 2+ centre associated oxygen vacancy at the nearest site along the c -axis and the other is Cu 2+ centre located at interstitial site.