Browsing by Author "Ali, Ahmed"

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The effect of some transition metal oxides on the physical properties of K0.5Na0.5Nb0.95Ta0.05O3 ceramics
(TAYLOR & FRANCIS LTD, 2017) Ali, Ahmed; Ahmed, , M; Hassen, , A
Both K0.5Na0.5Nb0.95Ta0.05O3 (KNNTO) and (K0.5Na0.5Nb0.95Ta0.05O3)(0.99) - M-0.01, M = Co3O4 and Mn2O3 (M/KNNTO) Ferromagnetic behaviour was observed for some M/KNNTO compounds. The hardness and compressive strength of all investigated samples are given. Comparisons with similar materials are discussed. Ceramics were synthesised using a solid-state reaction method. X-ray diffraction patterns of all samples revealed that the crystal structure is orthorhombic. Field-emission scanning electron microscopy was performed. Polarisation hysteresis curves indicated a disruption of ferroelectric order with the addition of M into KNNTO ceramics. The dielectric properties of the investigated ceramics have been studied as a function of frequency and temperature.
The influence of SrTiO3 buffer layer on ferroelectric properties of Al-doped BaTiO3 thin films
(SPRINGER INTERNATIONAL PUBLISHING, 2014) Ali, Ahmed; Senthikuma, , V; Kim, Yong Soo
Fabrication of Al0.01Ba0.99TiO3 (Al-BTO) thin films on SrTiO3/MgO/TiO2/SiO2/Si (STO/MgO) and MgO/TiO2/SiO2/Si (MgO) substrates were comparatively prepared using pulsed laser deposition (PLD). The structures of the prepared thin films were studied using X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM). The SrTiO3 buffer layer between Al-BTO thin film and MgO substrate enhanced the ferroelectric, electrical properties. Moreover, the P-E loops showed a dramatic enhancement in the polarization values from 18 mu C/cm(2) at 600 kV/cm to 52 mu C/cm(2) at 780 kV/cm for Al-BTO thin films on SrTiO3/MgO and MgO substrates, respectively. In addition, the dielectric SrTiO3 buffer layer decreased the leakage current from 3 x 10(-3) to 12 x 10(-6) A/cm(2) and increased breakdown electric field from 10 to 30 kV/cm. The electric properties revealed that, the dielectric SrTiO3 buffer layer also decreased the conductivity, mobility and carrier concentrations. The data of Al-BTO thin films on SrTiO3/MgO substrate exhibited remarkably adjusted polarization and leakage current indicating a good ferroelectric property for non-volatile ferroelectric random access memory (FERAM) applications.
Room Temperature Ferromagnetism in Sm0.5Sr0.5CoO3 Thin Films Deposited by Pulsed Laser Deposition
(AMER SCIENTIFIC PUBLISHERS, 2017) Ali, Ahmed; Kim, Yong Soo
Ferromagnetic Sm0.5Sr0.5CoO3 thin films were deposited on MgO/TiO2/SiO2/Si (MgO) and Pt/InO2/SiO2/Si (Pt) substrates by pulsed laser deposition. The crystallinity and morphology of the films were characterized by X- ray diffraction and field emission scanning electron microscopy, respectively. The electrical properties revealed metallic- like behavior at room temperature, confirming the transition from the metallic state to the insulating state at T > 300 K. The magnetization as a function of the temperature under the zero-field-cooled and field cooled modes for the Sm0.5Sr0.5CoO3 confirm that the Curie temperature higher than 300 K for the films deposited on the MgO substrate. The M-H hysteresis loops show that both films exhibit hard ferromagnetic behavior at 10 K independent of substrate type. However, the films deposited on the MgO substrate show a soft ferromagnetic state, whereas those on the Pt substrate exhibit an antiferromagnetic state at 300 K. The correlation between the ferromagnetic and metal states depending on the double exchange interaction and spin states transition at low and high temperatures is discussed.