Nanosize zinc ferrite samples with an average particle size of 6–65 nm were prepared by a
new chemical reaction involving nitrates of Zn and Fe and investigated for magnetic
behaviour and defect structure. The sample with an average particle size of 6 nm has
considerable inversion in cation distribution as shown by its hysteresis loop and
increased magnetization. Mössbauer spectroscopy gives a single doublet for all the
samples. Mössbauer parameters like quadrupole splitting and linewidth change
sharply as the average particle size increases from 6 to 7 nm and then afterwards the
changes are slow. The total Mössbauer absorption, on the average, increases with
increase in particle size, the change from 6 to 65 nm being by a factor of 3. Positron
parameters too change sharply as the particle size varies. The changes are related to
inversion of the cation distribution, agglomeration of particles and annihilation at the
surface and in the interior. The picture that emerges from the lifetime studies
and supported by Mössbauer spectroscopy and magnetization studies suggests
that there are at least two characteristic particle size length scales for nanosize
ZnFe2O4
particles prepared by the nitrate route.
Various physical properties of the solution-cast films of the proton conducting polymer polyethylene oxide ͑PEO͒ complexed with ammonium perchlorate ͑NH 4 ClO 4 ͒ have been studied in the temperature range 300-370 K. These properties studied by us include free volume by positron lifetime spectroscopy, ionic conductivity by impedance spectroscopy, ionic mobility by transient ionic current technique, number of charge carriers, dielectric constant, etc. The hole volume and conductivity show a steep rise at TӍT m ͑ϳ333 K͒. It appears that the increase in free volume arises out of the increase in the size of the holes rather than an increase in their number. Although the free volume shows an increase around T m , the measured ionic mobility does not show similar behavior. The increase in the conductivity at T m is, therefore, ascribed to an increase in the number of charge carriers at ϳT m . A suitable dissociation model involving the dielectric constant is proposed to explain this increase. The value of the dissociation energy for PEO:NH 4 ClO 4 has been determined to be 2.4 eV.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.