Abstracts Book - IMRC 2018

• SD6-P018
MAGNETIC STUDY ON A NANO-METRIC SCALE K-Sr-Cr-O SYSTEM.
Gustavo Antonio Jimenez Garcia 1 , Elizabeth Chavira 1 , Jesús Angel Arenas Alatorre 2 , Adriana
Tejeda Cruz 1 , Karla Eriseth Morales Reyes 1 , Omar Novelo 1 , Jorge Barreto 2
1 Instituto de Investigaciones en Materiales, , Mexico. 2 Instituto de Física - Universidad Nacional
Autónoma de México, , Mexico.
This study focuses on the manufacture of polycrystals by solid-state reaction
and nano-crystals by crushing, both in a (K x Sr 1-x )CrO z system. Nano-crystals were
manufactured by milling process in a mechanical mill, for 520 min, at room
temperature (26 °C) and external humidity (43%). By X-Ray Powder Diffraction,
XRD, it was identified the purity and presence of the reagents; SrCO 3 (Powder
Diffraction File, PDF, 00-005-0418) with orthorhombic unit cell, KCr 2 O 7 (PDF 00-
029-1047) with triclinic unit cell and K 2 Sr[CO 4 ] 2 (PDF 00-029-1047) with
rhombohedral unit cell. It was also examined the binary compound and the
formation of the solid solution, by XRD, in polycrystals and nano-crystals (at
room and high temperature). A cationic substitution was observed between K +1
with Sr 2+ in the solid solution when x= 0.50.
With thermogravimetric analysis, TGA, and differential scanning calorimetry,
DSC, of (K 0.50 Sr 0.50 )[CrO 2 ] 4 crushing sample, it was possible to determine the
reaction and transition temperatures corresponding to the analysis in an
ambient temperature range up to 200 °C, the intermolecular water loss was
obtained and as a function of the temperature presence of carbonates occurs
at 300- 350°C, the formation of the binary compound occurs at 750- 950 °C,
obtaining as a final result the degradation of the material; losing 3% of its mass
at 450 °C attributing itself to the decomposition of carbonate. At 900 °C occurs
a 10% of weight dropping. At the end, corroborated by XRD, it remained the
same rhombohedra crystalline structure for K 2 Sr[CrO 4 ] 2 and orthorhombic
crystal structure for SrCrO 4 and Cr 2 O 3 .
The nano-crystals reaction temperatures were, from room temperature to
660ºC. The reaction range temperatures, for polycrystals, were: 450, 580, 660
and 900 °C.
High-resolution Transmition Electron Microscopy, HRTEM, showed crystal
clusters size (4- 12 nm). Finally, the (K 0.50 Sr 0.50 )[CrO 2 ] 4 nanocrystals, resulted in
an insulator and weak ferromagnetic material.