O. I. V’yunov

Crystallographic, electrical, and magnetic properties of the system La0.7Sr0.3Mn1−xFexO3

On the basis of x-ray structural data and studies of the electrical, magnetic, and magnetoresistive properties and the ferromagnet resonance spectra of ceramic samples of La0.7Sr0.3Mn1−xFexO3 (0⩽x⩽0.10) it is established that a competition between structural changes influencing the ferromagnetism leads to a monotonic weakening of the ferromagnetism (a lowering of TC by around 5K∕%Fe). The increase of the magnetoresistance in the low-temperature region and the large values of the low-field contribution to the magnetoresistance are indicative of an inhomogeneous character of the electrical conductivity and magnetization of the samples at T<TC, which may be due to the coexistence of the ferro- and paramagnetic phases over a wide temperature region.

Oxidation state of copper ions in (La0.7Sr0.3)(Mn1 − xCux)O3 ± δ ceramics and their magnetic properties

Bulk ceramic samples of (La0.7Sr0.3)(Mn1 − xCux)O3 ± δ manganites are prepared by solid-state reactions. The unit-cell parameters and Mn-O bond distances in the manganites are determined using the Rietveld profile analysis method, and their magnetic properties are studied with the use of ferromagnetic resonance measurements. The results attest to the formation of solid solutions. Their lattice parameters follow Vegard’s law. The way in which the saturation magnetization of the manganites varies with composition depends on x. For x ≤ 0.07, the saturation magnetization is a weak function of composition; for x > 0.07, it drops rapidly with increasing x. These results can be understood under the assumption that the only oxidation state of copper in (La0.7Sr0.3)(Mn1 − xCux)O3 ± δ is 2+.

Intercalation processes influence the structure and electrophysical properties of lithium-conducting compounds having defect perovskite structure

The structural features and electrophysical properties of lithium-conducting compounds having defect perovskite structure based on Li0.5La0.5Nb2O6 and Li0.5La0.5TiO3 were studied using X-ray diffraction and synchrotron analyses, potentiometry, and complex impedance spectroscopy. Intercalated lithium was found to differently influence ion conductance in titanium- and niobium-containing materials. This difference was found to arise from the structural features of the materials. The systems studied have high chemical diffusion coefficients of lithium (DLi+ = 1 × 10−6 cm2/s for Li0.5La0.5Nb2O6 and DLi+ = 3.3 × 10−7 cm2/s for Li0.5La0.5TiO3).

Structural, electrical, and magnetic properties of La0.7Ca0.3 − xNaxMnO3 ± γ solid solutions

AbstractLa0.7Ca0.3 − xNaxMnO3 ± γ (LCNM) solid solutions with x = 0, 0.04, 0.06, 0.08, and 0.10 have been synthesized (rhombohedral structure, sp. gr. R

Structural, electrical, and magnetic properties of La0.7Sr0.3Mn1−y CryO3

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Effect of impurities on the electrical properties of the defect perovskite Li0.33La0.57TiO3

c). Sodium volatility during sintering is shown to lead to the formation of vacancies on the lanthanum and oxygen sites. Ca2+ → Na+ substitution does not increase the fraction of Mn4+ in LCNM, but the increase in the concentration of lanthanum vacancies with increasing sodium content leads to an increase in ferromagnetic ordering temperature TC and magnetoresistance, which depend, in addition, on heat-treatment conditions on account of the sodium volatility.

Ionic and electronic conductivities of yttria- and scandia-stabilized zirconia

The electrical properties of BaTi1−xMxO3 (M = Nb, Ta, Mo, W) ceramics (partial substitution of Group V (Nb, Ta) or VI (Mo, W) metals on the titanium site) have been studied by impedance spectroscopy. The results indicate that the Group VI metals (Mo and W) are less effective as donor dopants of barium titanate than are Nb and Ta because most of the Mo and W ions reside in the outer layer of the grains, raising its resistance.

Sol-gel synthesis and properties of tin-doped lanthanum manganites

Detailed structural data are presented for La0.7Sr0.3Mn1−yCryO3 solid solutions with 0 < y ≤ 0.10. Chromium substitution on the manganese site is shown to reduce the TC of the solid solutions at a rate of 4 K/mol % Cr. The 300-K magnetoresistance of La0.7Sr0.3Mn1−yCryO3 attains 8% in a field of 1.2 MA/m.