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Your search keyword '"Jibran Khaliq"' showing total 3 results
Start Over Author "Jibran Khaliq" Journal journal of applied physics
3 results on '"Jibran Khaliq"'

1. Reduced thermal conductivity by nanoscale intergrowths in perovskite like layered structure La2Ti2O7.

Author

Jibran Khaliq, Chunchun Li, Kan Chen, Baogui Shi, Haitao Ye, Grande, Antonio M., Haixue Yan, and Reece, Michael J.

Subjects
*THERMAL conductivity, *NANOSTRUCTURED materials, *PEROVSKITE, *STOICHIOMETRY, *TRANSMISSION electron microscopy, *X-ray diffraction
Abstract

The effect of substitution and oxidation-reduction on the thermal conductivity of perovskite-like layered structure (PLS) ceramics was investigated in relation to mass contrast and non-stoichiometry. Sr (acceptor) was substituted on the A site, while Ta (donor) was substituted on the B site of La2Ti2O7. Substitution in PLS materials creates atomic scale disorders to accommodate the non-stoichiometry. High resolution transmission electron microscopy and X ray diffraction revealed that acceptor substitution in La2Ti2O7 produced nanoscale intergrowths of n=5 layered phase, while donor substitution produced nanoscale intergrowths of n=3 layered phase. As a result of these nanoscale intergrowths, the thermal conductivity value reduced by as much as ∼20%. Pure La2Ti2O7 has a thermal conductivity value of ∼1.3W/m K which dropped to a value of ∼1.12W/m K for Sr doped La2Ti2O7 and ∼0.93 W/m K for Ta doped La2Ti2O7 at 573K. [ABSTRACT FROM AUTHOR]

Published
2015
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2. Reduced thermal conductivity by nanoscale intergrowths in perovskite like layered structure La2Ti2O7.

Author

Jibran Khaliq, Chunchun Li, Kan Chen, Baogui Shi, Haitao Ye, Grande, Antonio M., Haixue Yan, and Reece, Michael J.

Subjects
THERMAL conductivity, NANOSTRUCTURED materials, PEROVSKITE, STOICHIOMETRY, TRANSMISSION electron microscopy, X-ray diffraction
Abstract

The effect of substitution and oxidation-reduction on the thermal conductivity of perovskite-like layered structure (PLS) ceramics was investigated in relation to mass contrast and non-stoichiometry. Sr (acceptor) was substituted on the A site, while Ta (donor) was substituted on the B site of La2Ti2O7. Substitution in PLS materials creates atomic scale disorders to accommodate the non-stoichiometry. High resolution transmission electron microscopy and X ray diffraction revealed that acceptor substitution in La2Ti2O7 produced nanoscale intergrowths of n=5 layered phase, while donor substitution produced nanoscale intergrowths of n=3 layered phase. As a result of these nanoscale intergrowths, the thermal conductivity value reduced by as much as ∼20%. Pure La2Ti2O7 has a thermal conductivity value of ∼1.3W/m K which dropped to a value of ∼1.12W/m K for Sr doped La2Ti2O7 and ∼0.93 W/m K for Ta doped La2Ti2O7 at 573K. [ABSTRACT FROM AUTHOR]

Published
2015
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3. Dielectric relaxation, lattice dynamics and polarization mechanisms in Bi0.5Na0.5TiO3-based lead-free ceramics

Author

Arturas Adomkevicius, Marco Deluca, Jibran Khaliq, Michael J. Reece, Haixue Yan, Xiaojong Wei, Huanpo Ning, and Giuseppe Viola

Subjects
Permittivity, Condensed Matter::Materials Science, Materials science, Nuclear magnetic resonance, Condensed matter physics, Polarizability, Electric field, Ferroelectric ceramics, General Physics and Astronomy, Relaxation (physics), Dielectric, Ferroelectricity, Induced polarization
Abstract

In 0.95[0.94Bi0.5Na0.5TiO3-0.06BaTiO3]-0.05CaTiO3 ceramics, the temperature TS (dielectric permittivity shoulder at about 125 °C) represents a transition between two different thermally activated dielectric relaxation processes. Below TS, the approximately linear decrease of the permittivity with the logarithm of frequency was attributed to the presence of a dominant ferroelectric phase. Above TS, the permittivity shows a more complicated dependence of the frequency and Raman modes indicate a sudden increase in the spatial disorder of the material, which is ascribed to the presence of a nonpolar phase and to a loss of interaction between polar regions. From 30 to 150 °C, an increase in the maximum polarization with increasing temperature was related to three possible mechanisms: polarization extension favoured by the simultaneous presence of polar and non-polar phases; the occurrence of electric field-induced transitions from weakly polar relaxor to ferroelectric polar phase; and the enhanced polarizability of the crystal structure induced by the weakening of the Bi-O bond with increasing temperature. The occurrence of different electric field induced polarization processes with increasing temperature is supported by the presence of additional current peaks in the current-electric field loops.

Published
2013
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