Articles you may be interested inMicrostructure and magnetic properties of MFe2O4 (M = Co, Ni, and Mn) ferrite nanocrystals prepared using colloid mill and hydrothermal method J. Appl. Phys. 117, 17A328 (2015) We report by the first time a high pressure X-ray diffraction and Raman spectroscopy study of cobalt ferrite (CoFe 2 O 4 ) nanoparticles carried out at room temperature up to 17 GPa. In contrast with previous studies of nanoparticles, which proposed the transition pressure to be reduced from 20-27 GPa to 7.5-12.5 GPa (depending on particle size), we found that cobalt ferrite nanoparticles remain in the spinel structure up to the highest pressure covered by our experiments. 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 of the nanoparticles (B 0 ¼ 204 GPa) is considerably larger than the value previously reported for bulk CoFe 2 O 4 (B 0 ¼ 172 GPa). In addition, when the pressure medium becomes non-hydrostatic and deviatoric stresses affect the experiments, there is a noticeable decrease of the compressibility of the studied sample (B 0 ¼ 284 GPa). 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 information on the pressure dependence of all Raman-active modes and evidences that cation inversion is enhanced by pressure under non-hydrostatic conditions, being this effect not fully reversible. V C 2015 AIP Publishing LLC. [http://dx

Nanoparticles of V-doped SnO 2 with stoichiometry Sn 1−x O 2 V x (x=0.05, 0.075, 0.125) have been synthesized by a co-precipitation method. Their structural, vibrational, and nuclear properties have been characterized by x-ray Diffraction, Transmission Electron Microscopy, Energy Dispersive x-ray Spectroscopy, Raman Spectroscopy, and Mössbauer Spectroscopy (with 119 Sn probe) at ambient pressure. We also performed high-pressure synchrotron x-ray diffraction experiments. The structural behaviour was studied up to ∼10 GPa under quasi-hydrostatic conditions. It has been found that tin dioxide nanoparticles with V are more compressible than un-doped tin dioxide nanoparticles.

We have studied the high-pressure structural behavior of zinc ferrite (ZnFe2O4) nanoparticles by powder X-ray diffraction measurements up to 47 GPa. We found that the cubic spinel structure of ZnFe2O4 remains up to 33 GPa and a phase transition is induced beyond this pressure. The high-pressure phase is indexed to an orthorhombic CaMn2O4-type structure. Upon decompression the low-and high-pressure phases coexist. The compressibility of both structures was also investigated. We have observed that the lattice parameters of the high-pressure phase behave anisotropically upon compression. Further, we predict possible phase transition around 55 GPa. For comparison, we also studied the compression behavior of magnetite (Fe3O4) nanoparticles by X-ray diffraction up to 23 GPa. Spinel-type ZnFe2O4 and Fe3O4 nanoparticles have a bulk modulus of 172(20) GPa and 152(9) GPa, respectively. This indicates that in both cases the nanoparticles do not undergo a Hall-Petch strengthening.

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