Impedance spectroscopy technique was used to characterize the electrical properties in a wide range of frequency [40–105 Hz] and temperature [80–700 K]. As a result, AC-conductivity spectrum follows the ‘double Jonscher Power Law’ in the temperature range [80–280 K], ‘Jonscher Power Law’ in [300–600 K] range and at 700 Kit is described by the classical Drude model. Moreover, the AC-conductivity analysis reveals the contribution of multiple mechanisms in conduction. In fact, the variation of the frequency exponent ‘s1’ with temperature shows that the correlated barrier hopping mechanism is the dominated model for conduction of charge carriers beyond T = 470 K. The previous model was observed again according to the temperature dependence of the frequency exponent ‘s2.’ Then, the deduced activation energy decreases with increasing frequency suggesting the availability of hopping conduction. The temperature dependence of AC-conductivity proves the existence of metal semi-conductor transition at 200 K. At high temperatures, the DC-conductivity analysis reveals that the conduction process is dominated by thermally activated hopping of small polaron. However, at low temperatures, it is confirmed that the most suitable mechanism for conduction is the Shklovskii–Efros-Variable Range Hopping process.

Transport properties of La0.9Sr0.1MnO3 manganite

The grain size dependence of Young’s modulus and thermal conductivity of alumina and zirconia ceramics is predicted via phase mixture modeling, using both analytical and numerical approaches. Using typical values for the thickness and properties of the grain boundaries, the equivalent volume fraction of “grain boundary phase” is calculated for a given grain shape. Based on this volume fraction estimate and a rough estimate of the grain boundary properties, the effective properties of the polycrystalline materials are calculated and compared in terms of volume-equivalent sphere diameters. For grains of cubic and tetrakaidecahedral shape excellent agreement is found between numerical calculations and analytical predictions based on the lower Hashin-Shtrikman bound. The grain size dependence is extremely weak for Young’s modulus, but can be more significant for thermal conductivity, especially when the intrinsic conductivity of the material is high. The predictions are compared to literature data.

Phase mixture modeling of the grain size dependence of Young’s modulus and thermal conductivity of alumina and zirconia ceramics

Crystal structure and magnetic properties of LaFe1-xNixO3 nanomaterials prepared via a simple co-precipitation method

Structural and magnetic properties of yttrium-substituted La 0.6-xYxSr0.4MnO3(x=0–0.3)

The easiness of preparation and tailored properties of perovskite nanoparticles rendered them an important class of materials in the last decade. In this work, La0.7Sr0.3Fe1-xMxO3 (M=Mn, Co and x=0, 0.5) orthoferrites were synthesized using combustion method and examined using X-ray diffraction. The orthorhombic structure was clearly obvious with Pbnm space group without the need of any thermal treatment. Field emission scanning electron microscopy (FESEM) accompanied by Energy-dispersive spectroscopy studies were also performed, evidencing the similarity of both nominal and chemical compositions for the studied orthoferrites. The thermal dependence of the dielectric properties was investigated (from room temperature to 698 K) in the frequency range (70 Hz - 5 MHz). Magnetic properties were investigated at room temperature and discussed.

Role of B-site cation on the structure, magnetic and dielectric properties of nanosized La 0.7 Sr 0.3 Fe 1−x M x O 3 (M = Mn; Co and x = 0, 0.5) perovskites

Qinghua Chen

Papers

Electrical and magnetic properties of La1−xSrxMnO3 (0.1 ≤ x≤ 0.25) ceramics prepared by sol–gel technique

Improved temperature coefficient of resistance in La1-xCaxMnO3:Ag0.2 (0.25 ≤ x≤ 0.33) ceramics prepared by sol–gel method

Grain size effect on the electrical conductivity of submicron Sm-heavily-doped ceria

Enhanced temperature coefficient of resistance and magnetoresistance of Co-doped La0.67Ca0.33MnO3 polycrystalline ceramics

Effect of different post-annealing durations on electromagnetic properties of La0.67Ca0.33MnO3:Ag0.2 thin films prepared by pulsed laser deposition