25 documents found, page 1 of 3
Study of the effect of the substitution of Fe by Ti on the microstructure and t...
Dhahri, R.; Valente, M. A.; Graça, P.; Costa, B. F. O.La0.67Ca0.2Ba0.13Fe1-xTixO3 samples (x = 0 and 0.03) were synthesized by the auto-combustion method. Analysis of XRD diffractograms revealed that these compounds crystallize in the cubic system with the space group Pm3̄m. The dielectric properties have been studied in the 102-106 frequency range and the 120-280 K temperature range. Analysis of AC conductivity shows that the conduction mechanisms are of polaroni...
Effects of laser floating zone processing on electrical and magnetic properties...
Ferreira, N. M.; Carreira, F.; Kovalevsky, A. V.; Costa, F. M.; Valente, M. A.Manganites present fascinating physical properties which can be tuned according with the method and processing conditions. In this work, Ca1-xPrxMnO3 (x = 0.03, 0.06, 0.1) materials were prepared by the Laser Floating Zone technique (LFZ), under different pulling rates (25 to 100 mm/h) in air and argon atmospheres, obtaining fibres with 2.5 mm diameter. Such processing conditions promote the formation of second...
Investigation of temperature and frequency dependence of the dielectric propert...
Bougoffa, Amira; Benali, E. M.; Benali, A.; Bejar, M.; Dhahri, E.; Graça, M. P. F.; Valente, M. A.; Otero-Irurueta, G.; Costa, B. F. O.In this work we synthesized the multifunctional (La0.8Ca0.2)0.4Bi0.6FeO3 material using a sol-gel process. Structural and morphologic investigations reveal a Pnma perovskite structure at room temperature with spherical and polygonal nanoparticles. A detailed study of the temperature dependence of the dielectric and electrical properties of the studied material proves a typical FE-PE transition with a colossal v...
Synthesis and study of the structural and dielectric properties of La0.67Ca0.2B...
Dhahri, A.; Zaouali, A.; Benali, A.; Abdelmoulla, N.; Massoudi, J.; Nouri, K.; Bessais, L.; Graça, M. P. F.; Valente, M. A.; Costa, B. F. O.The La0.67Ca0.2Ba0.13Fe1-xMnxO3 perovskite compounds with different manganese concentrations (x = 0.0, 0.03, 0.06) were synthesized by the autocombustion method and annealed at 700 C. The X-ray diffraction (XRD) data indicated that all obtained compounds crystallize in the cubic structure with the Pm3m space group. The increase in the substitution rate has been found to lead to the decrease in the crystallite s...
Electrical conductivity and dielectric properties of Sr doped M-type barium hex...
Marouani, Y.; Massoudi, J.; Noumi, M.; Benali, A.; Dhahri, E.; Sanguino, P.; Graça, M. P. F.; Valente, M. A.; Costa, B. F. O.The Raman results showed that the intensity of the resonance band remains unchanged in Ba1 xSrxFe12O19 compared to the undoped compound (x ¼ 0) indicating that the polarizability did not change during the vibrations. The particle sizes, observed by TEM, are reduced from 228 nm to 176 nm with doping. Electrical conductance measurements show that all samples present semiconductor-like behaviors. The Maxwell–Wagne...
Structural, morphological, Raman, dielectric and electrical properties of La1-2...
Benali, E. M.; Benali, A.; Bejar, M.; Dhahri, E.; Graca, M. P. F.; Valente, M. A.; Costa, B. F. O.La1-2x Ba x Bi x FeO3 (0.00 ≤ x ≤ 0.20) nanoparticles were prepared by the auto-combustion method using glycine as a combustion fuel. X-ray diffractometry (XRD) measurements confirmed the orthorhombic structure of the synthesized compounds with the Pnma space group as a principal majority phase and showed the presence of a very minor secondary phase when x > 0.1. The nanosize criterion of the prepared compounds...
Study of the influence of 2.5% Mg2+ insertion in the B-site of La0.8Ca0.1Pb0.1F...
Issaoui, H.; Benali, A.; Issaoui, F.; Dhahri, E.; Costa, B. F. O.; Graca, M. P. F.; Valente, M. A.; Bouazizi, Mohamed LamjedThis work involves the synthesis and study of physical properties of the La0.8Ca0.1Pb0.1Fe0.975Mg0.025O3 compound, which has been characterized by various experimental techniques, such as X-ray diffraction, SEM and complex impedance spectroscopy. The structural study showed that the La0.8Ca0.1Pb0.1Fe0.975Mg0.025O3 compound crystallized in the orthorhombic structure with the Pnma space group. The particle size a...
YAG:Ag nanophosphors – synthesis and characterization
Sundari, S. Shanmuga; Karthika, S.; Durairajan, A.; Graça, M.P.F.; Valente, M. A.Yttrium Aluminium Garnet (Y3Al5O12)-YAG and Ag of four different mol% in YAG (0.5, 1.0, 1.5 and 2.0 mol % of Ag) – YAG:Ag were synthesized by Pechini method. The synthesized pure YAG was white in colour but the incorporation of Ag in the YAG matrix forms colour centre and turns to pink. The intensity of pink Ag doped YAG is increasing with the increase in mol% of Ag. In the present work the synthesis and ...
Investigation of Cr substitution effect on the evolution of La0.67Ca0.2Ba0.13Fe...
Dhahri, Ah.; Bougoffa, Amira; Zaouali, A.; Benali, A.; Graça, M. P. F.; Valente, M. A.; Costa, B. F. O.; Abdelmoula, N.; Mariano, José F. M. L.In this study, La0.67Ca0.2Ba0.13Fe1-xCrxO3 (x = 0 and 0.03) powders were prepared by auto-combustion method. The examination of the purity and crystalline structure of the samples by X-ray diffraction showed a cubic structure formed with the Pm (3) over barm space group. Scanning electron microscopy was used to study the morphology and grains size, indicating an agglomeration of nanometric particles. Impedance ...
Photosensitive activity of fabricated core-shell composite nanostructured p-CuO...
Gunasekaran, S.; Thangaraju, D.; Marnadu, R.; Chandrasekaran, J.; Shkir, Mohd; Durairajan, A.; Valente, M. A.; Alshaharanig, T.; Elango, M.Development of photo detectors based on different semiconducting materials with high performance has been in progress in recent past, however, there is a lot of difficulties in developing the more effective photo detectors-based devices with high responsivity, detectivity and quantum efficiency. Hence, we have synthesized pure CuS and CuO@CuS core-shell heterostructure based photo detectors with high performanc...