Cobaltite nanoparticles under high presure

SACCONE, F. D.; BILOVOL, V.; FERRARI, S.; F. GRINBLAT; ERRANDONEA, D; PAMPILLO, L. G.

Madrid

Conferencia; International Conference on High Pressure Science and Technology AIRAPT 2015; 2015

Universidad Complutense de Madrid

We report a high pressure X-ray diffraction and Raman spectroscopy study of cobalt ferrite (CoFe2O4) nanoparticles carried out at room temperature up to 17 GPa. In contrast with previous studies, which proposed the transition pressure to be reduced to 7.5 ? 12.5 GPa (depending on particle size) [1], we found that cobaltite remains in the spinel structure up to the highest pressure covered by our experiments. This result is in agreement with studies carried out in bulk cobaltite [2]. In addition, we report the pressure dependence of the unit-cell parameter and Raman modes of the studied sample.. We found that under quasi-hydrostatic conditions the bulk modulus (K0=267 GPa), calculated using a second-order Birch?Murnaghan EOS, is considerably larger than the value reported for the bulk spinel. In addition, when the pressure medium becomes non-hydrostatic, there is a noticeable decrease of the compressibility of the studied sample. After decompression, the cobalt ferrite lattice parameter does not revert to its initial value, evidencing a unit cell contraction after pressure was removed. Finally, Raman spectroscopy provides evidence that cation inversion is enhanced by pressure under non-hydrostatic conditions, being this effect not reversible. [1] Z. Wu et al. J. Appl. Phys. 93, 9983 (2003). [2] J. Blasco et al., Journal of Solid State Chemistry 221, 173 (2015).