Etude spectroscopique de l'ion Cu2+ au niveau de la transition ordre-desordre dans les systemes Li0,5M2,5O4-CuAl2O4 (M = Al, Fe)

Abstract Phase diagrams of (1-s)Li 0,5 M 2,5 O 4 -sCuAl 2 O 4 (M = Al, Fe) were established by quenching, X-ray diffraction at high temperature and IR spectrometry. Cation distributions are deduced from magnetic measurements and neutron diffraction. Electronic spectrum of Cu 2+ (4000–50000 cm −1 ) discloses copper on A and B sites in disordered phases (Fd3m). The octaedral 1:3 ordering in Li 0,5 M 2,5 O 4 (M = Fe, Ga, Al) is not destroyed by migration of lithium from octaedral to tetrahedral sites but seems to be mainly disturbed by nature and valency of substituted cations.