Positron Annihilation And Electrical Conductivity Studies Of Cu Substitution Effect In Li_(0.5-0.5x)Cu_(x)Fe_(2.5-0.5x)O_(4) Spinel Ferrite

摘要

Positron annihilation lifetime (PAL), and electrical conductivity studies were carried out on a series of polycrystalline spinel ferrite with composition Li_(0.5-0.5x)Cu_(x)Fe_(2.5-0.5x)O_(4) where (x velence 0.2, 0.4, 0.6, 0.8, 1). The radii of the tetrahedral A-sites (r_(A)) and the octahedral B-sites (r_(B)) were studied as a function of composition. The infrared spectra have been analyzed in the frequency range 200-1000 cm~(-1) and two bands were observed. The bands around 589 cm~(-1) (v_(A)) and 400 cm~(-1) (v_(B)) were assigned to the tetrahedral and octahedral complexes, respectively. The compositional dependence of the dc electrical conductivity (sigma)_(dc) showed a maximum at x(velence)0.4 then decreases with increasing Cu~(2+) ions content. For lifetime measurements, a conventional fast-fast coincidence system was used. The variations in positron lifetime parameters with Cu~(2+) ions substitution are attributed to positron trapping in A- and B- sites.