New Antiferromagnetic Perovskite CaCo 3 V 4 O 12 Prepared at High-Pressure and High-Temperature Conditions (original) (raw)
Related papers
Structural and Magnetic Transitions in CaCo3V4O12 Perovskite at Extreme Conditions
Inorganic chemistry, 2017
We investigated the structural, vibrational, magnetic, and electronic properties of the recently synthesized CaCo3V4O12 double perovskite with the high-spin (HS) Co(2+) ions in a square-planar oxygen coordination at extreme conditions of high pressures and low temperatures. The single-crystal X-ray diffraction and Raman spectroscopy studies up to 60 GPa showed a conservation of its cubic crystal structure but indicated a crossover near 30 GPa. Above 30 GPa, we observed both an abnormally high "compressibility" of the Co-O bonds in the square-planar oxygen coordination and a huge anisotropic displacement of HS-Co(2+) ions in the direction perpendicular to the oxygen planes. Although this effect is reminiscent of a continuous HS → LS transformation of the Co(2+) ions, it did not result in the anticipated shrinkage of the cell volume because of a certain "stiffing" of the bonds of the Ca and V cations. We verified that the oxidation states of all the cations did not...
Possible helimagnetic order in Co4+-containing perovskites Sr1−xCaxCoO3
APL Materials
We systematically synthesized perovskite-type oxides Sr1−xCaxCoO3 containing unusually high valence Co4+ ions by a high pressure technique and investigated the effect of systematic lattice change on the magnetic and electronic properties. As the Ca content x exceeds about 0.6, the structure changes from cubic to orthorhombic, which is supported by the first-principles calculations of enthalpy. Upon the orthorhombic distortion, the ground state remains to be apparently ferromagnetic, with a slight drop of the Curie temperature. Importantly, the compounds with x larger than 0.8 show antiferromagnetic behavior, with positive Weiss temperatures and nonlinear magnetization curves at the lowest temperature, implying that the ground state is non-collinear antiferromagnetic or helimagnetic. Considering the incoherent metallic behavior and the suppression of the electronic specific heat at the high x region, the possible emergence of a helimagnetic state in Sr1−xCaxCoO3 is discussed in terms...
Ca 2CoNbO 6: A new monoclinically distorted double perovskite
Solid State Sciences, 2010
The new Ca 2 CoNbO 6 double perovskites has been synthesized by solid-state reaction and its crystal structure has been refined using X-ray powder diffraction data. Rietveld fit to the diffraction data shows that the compound is monoclinically distorted and adopts space group P21/n. The cell parameters are: . The Co and Nb are found to be distributed over the six coordinated octahedral sites in rock salt arrangement. However, nearly identical ionic radii of Co and Nb lead to severe degree of anti-site disorder (31%). The refined CoeO and NbeO bond lengths are 1.9788(2) Å and 2.0642(2) Å respectively.
Science and Technology of Advanced Materials, 2015
We synthesize ScCoO 3 perovskite and its solid solutions, ScCo 1−x Fe x O 3 and ScCo 1−x Cr x O 3 , under high pressure (6 GPa) and high temperature (1570 K) conditions. We find noticeable shifts from the stoichiometric compositions, expressed as (Sc 1−x M x)MO 3 with x = 0.05-0.11 and M = Co, (Co, Fe) and (Co, Cr). The crystal structure of (Sc 0.95 Co 0.05)CoO 3 is refined using synchrotron x-ray powder diffraction data: space group Pnma (No. 62), Z = 4 and lattice parameters a = 5.26766(1) Å, b = 7.14027(2) Å and c = 4.92231(1) Å. (Sc 0.95 Co 0.05)CoO 3 crystallizes in the GdFeO 3-type structure similar to other members of the perovskite cobaltite family, ACoO 3 (A 3+ = Y and Pr-Lu). There is evidence that (Sc 0.95 Co 0.05)CoO 3 has non-magnetic low-spin Co 3+ ions at the B site and paramagnetic high-spin Co 3+ ions at the A site. In the irondoped samples (Sc 1−x M x)MO 3 with M = (Co, Fe), Fe 3+ ions have a strong preference to occupy the A site of such perovskites at small doping levels.
A comparative study of high temperature properties of cobalt-free perovskites
Journal of Electroceramics, 2014
Co-free perovskites with chemical composition Ba 0.5 Sr 0.5 Fe 0.8 M 0.2 O 3-δ (M = Ni, Cu, Zn) were synthesized by the modified Pechini method, and their structure and microstructure were characterized by XRD and SEM. Oxygen content, electrical resistivity and Thermal Expansion Coefficient (TEC) were evaluated in air between room temperature and 900°C. The high-temperature properties of these perovskites were compared with those of Co containing Ba 0.5 Sr 0.5 Fe 0.8 Co 0.2 O 3-δ perovskite. The highest electrical conductivity was obtained for Ba 0.5 Sr 0.5 Fe 0.8 Cu 0.2 O 3-δ, with values of 47.6 Scm −1 at 544°C. This same composition also exhibits the highest oxygen vacancies concentration: 3-δ = 2.61 at room temperature. In contrast, the Ba 0.5 Sr 0.5 Fe 0.8 Zn 0.2 O 3-δ, showed lower electrical conductivity suggesting that the Zn +2 ions block electron transport. Cofree perovskites seem to be stable at high temperatures for long term periods. However, these compounds suffered degradation at room temperature in samples stored in air.
The Synthesis and Properties of the Chemically Oxidized Perovskite, La1–xSrxCoO3−δ(0.5≤x≤0.9)
Journal of Solid State Chemistry, 1998
The series of La1-xSrxCoO3-B B (0.54x40.9) perovskites have been prepared using the Pechini gel technique. The products were chemically oxidized by stirring in a sodium hypobromite solution. The samples have been characterized by powder X-ray diffraction, thermal analysis, iodometric titration, Co K edge X-ray absorption spectroscopy, temperature-dependent SQUID magnetic susceptibility, and temperature-dependent electrical resistivity. The Sr-rich samples (x > 0.7) have the brownmilleritetype structure prior to oxidation and the cubic perovskite structure after treatment with sodium hypobromite. Iodometric titration shows as much as a &14% increase in Co(IV) concentration in the Sr-rich samples after chemical oxidation. The Co K edge spectra show that there is very little change in the formal cobalt valence with increasing Sr content. The effective magnetic moments of the oxidized compounds level off with increasing Sr concentration. All of the chemically oxidized samples exhibit small-bandgap semiconducting behavior. The data lead to the postulation of an equilibrium between Co(IV) and O ؊ in the series. 1998 Academic Press 388
Magnetic and electric studies of a new Co(II) perovskite-like material
Phase Transitions, 2004
Structural phase transitions in the perovskite-like material [(CH 4 ) 12 (NH 3 ) 2 ]CoCl 4 have been observed using differential thermal scanning. The material shows an order-disorder transition at T 1 ¼ 396 AE 5 K with entropy, (ÁS 1 ) ¼ 12.8 J/mole/K. A ''chain melting'' transition with a major endothermic peak at T 2 ¼ 337 AE 3 K and a minor one at T 0 ¼ 316 AE 2 K, has total entropy ÁS ¼ 28 J/mole/K. At low temperatures, the transitions at T 3 ¼ 288 AE 3 K and at T 4 ¼ 188 AE 3 K, have entropies of ÁS 3 ¼ 14.4 J/mole/K and ÁS 4 ¼ 2.6 J/mole/K respectively. AC magnetic susceptibility in the temperature range 78-290 K, in a magnetic field of 160 A/m and at a frequency of 320 Hz is presented. The results indicate changes in symmetry at 188 K.
New Remarks on the High-Polarizability Perovskite-Related Material CaCu3Ti4O12
Ferroelectrics, 2004
The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden.