Browsing by Author "Ali, Ahmed I."

Now showing 1 - 3 of 3

Enhancement of piezoelectric and ferroelectric properties of BaTiO3 ceramics by aluminum doping
(ELSEVIER SCI LTD, 2013) Ali, Ahmed I.; Ahn, Chang Won; Kim, Yong Soo
Ferroelectric and piezoelectric properties of BaTiO3 and Al-doped BaTiO3 ceramics were investigated. The ferroelectric study demonstrated that, by doping Al3+ ions in the A-site of BaTiO3, the polarization electric field loop exhibited enhanced remnant polarization (from 12 to 17.5 mu C/cm(2)), saturation and switching. In addition, the piezoelectric constant (d(33)) increased with Al-doping for both static and dynamic strain values (from 75 to 135 and from 29.2 to 57.9 pC/N, respectively, at a maximum applied electric field of 16 kV/cm). Furthermore, the dielectric constant values increased and both the dielectric loss factor and leakage current decreased, even though the transition temperature shifted to lower temperature (from 121 to 113 degrees C) for the Al-doped sample. Therefore, the Aldoped BaTiO3 has adjustable piezoelectric and ferroelectric properties. (C) 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
Ferroelectric enhancement of La-doped BaTiO3 thin films using SrTiO3 buffer layer
(ELSEVIER, 2014) Ali, Ahmed I.; Park, Kibog; Ullah, Amir; Huh, Rock; Kim, Y. S.
Pulsed laser deposition (PLD) was used to fabricate La0.01Ba0.99TiO3 (LBTO) thin films on MgO/TiO2/SiO2/Si substrates with and without SrTiO3 (STO) buffer layer. LBTO films deposited on STO layers exhibited enhanced ferroelectricity and decreased leakage current (9 x 10(-7) A/cm(2) at 50 kV/cm), conductivity, and Hall mobility, compared to those of LBTO films on MgO substrate. The remanent polarization (P-r) and coercive field (E-c) for LBTO thin films on STO buffered MgO substrate dramatically improved, 36.5 mu C/cm(2) and similar to 220 kV/cm, compared to those for LBTO thin films on MgO substrate, 3 mu C/cm(2) and similar to 60 kV/cm. The degradation of P-r and E-c after 10(5) switching test is less than 0.1% for LBTO thin films on STO buffered MgO substrate. This work demonstrates a route to a lead-free ferroelectric thin film for nonvolatile memories and electro-optic devices. (C) 2013 Elsevier B.V. All rights reserved.
Ferroelectric, and piezoelectric properties of BaTi1-xAlxO3, 0 <= x <= 0.015
(AMER INST PHYSICS, 2015) Ali, Ahmed I.; Hassen, A; Nguyen Cao, Khang; Kim, Y.S
Single phase polycrystalline samples of BaTi1-xAlxO3, 0 <= x <= 0.015, have been prepared by a conventional powder processing method. The Rietveld refinements of X-ray powder diffraction patterns at room temperature indicate that the samples crystallize in tetragonal structure with group symmetry P4mm. Because of the oxygen vacancies, the volume of the unit cell increases with increasing x. Field emission scanning electron microscopy revealed that the particle size of pure BTO ceramics was affected by the Al content. Dielectric, ferroelectric and piezoelectric properties of pure BTO as well as Al-doped BTO were studied. It was found that the dielectric permittivity (epsilon') increases significantly with increasing x while the transition from ferroelectric phase to a paraelectric phase changes slightly. The Curie-Weiss law is verified over a wide temperature range. Both ferroelectric and piezoelectric properties of BTO are enhanced by the substitution of Ti4+ by Al3+ ions. Piezoelectric strains of Al-doped BTO showed a suitable behavior for application compared with that of pure BTO compound. Finally, the results obtained in this work are discussed and compared with those for similar materials. (C) 2015 Author(s).