Electrical conductivity measurements show that
Ln 1−x Sr x CoO 3 , (Ln = Pr or Nd) undergoes a
non-metal-metal transition when x≈0 3. The d.c. conductivity of compositions with 0<x<0.l
obeys the T −1/4 law up to 400 K and the a.c. conductivity data follow the
ω δ law with δ in the range 0.6-0.8. Surprisingly, however, δ seems to
increase with increasing temperature. Thermopower measurements show clear evidence for a change in the
mechanism of conduction (around 350 K) from variable range hopping to transport at E c . All these
transport properties suggest that Co 4+ ions in
Ln 1-x Sr x CoO 3 (0<x<0.1), considered as moving in a
lattice of Co 3+ , form a degenerate gas and that the states at the Fermi energy are Anderson
localized.
Discussion(0)
No comments yet. Be the first to comment.