Fizik Bilim Dalı

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/1819

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Author: search.filters.author.Kiraci, AliSubject: search.filters.subject.Damping Constant

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Now showing 1 - 3 of 3
  • Article
    A Thermodynamic Study on Pbzr0.52ti0.48o3 Ceramic Close To the Tetragonal-Cubic Transition
    (Springer, 2020) Kiraci, Ali
    The isobaric Gruneisen parameter and the wavenumber (frequency) of various Raman modes in PbZr1-xTixO3 (PZT x = 0.48) ceramic were calculated by means of the unit cell volume of this crystal. In addition, the damping constant (linewidth) of the Raman modes studied was computed from the pseudospin-phonon coupled and from the energy fluctuation models close to the tetragonal-cubic transition temperature of T-C = 650 K. This calculation of the damping constant performed in terms of the order parameter (spontaneous polarization), which was associated with the wavenumbers of the Raman modes studied. Furthermore, the inverse relaxation time of the Raman modes in this ceramic calculated and the values of the activation energy were deduced in terms of the Arrhenius plot close to the tetragonal-cubic transition in PZT (x = 0.48) ceramic. Finally, the temperature dependence of some thermodynamic quantities, such as the isothermal compressibility and the specific heat of this ceramic, was predicted.
  • Article
    Citation - WoS: 2
    Citation - Scopus: 2
    Calculation of the Frequency Shifts and Damping Constant for the Raman Modes (A1g, B1) Near the Tetragonal-Cubic Transition in Srtio3
    (Tubitak Scientific & Technological Research Council Turkey, 2017) Yurtseven, Hasan Hamit; Kiraci, Ali
    Raman shifts of the soft mode A(1g) and the B-1 mode are calculated at various pressures at room temperature for the cubic-tetragonal transition (P-c = 9.5 GPa) in SrTiO3. This calculation is performed using the observed volume data through the mode Gruneisen parameters of A(1g) and B-1 which vary with pressure, by fitting to the experimental wavenumbers in this crystalline system. Calculated Raman shifts are then used as order parameters to predict the pressure dependence of the damping constant and the inverse relaxation time for the cubic-tetragonal transition in SrTiO3. Our predictions from the pseudospin-phonon coupling and the energy fluctuation models can be compared with the experimental measurements when available in the literature.
  • Article
    Citation - WoS: 2
    Citation - Scopus: 3
    Analysis of the Integrated Intensity of the Central Peaks Calculated as a Function of Temperature in the Ferroelectric Phase of Lithium Tantalate
    (Vinca inst Nuclear Sci, 2018) Yurtseven, Hamit; Kiraci, Ali
    The integrated intensity of the central peak is calculated as a function of temperature in the ferroelectric phase (T < T-C) of nearly stoichiometric LiTaO3. This calculation is performed using the temperature dependence of the order parameter obtained from the mean field theory at temperatures lower than the transition temperature T-C (T-C = 963 K) of this crystal. The calculated values of the order parameter (squared) are fitted to the integrated intensity of the central peaks as observed from the Raman and Brillouin scattering experiments as reported in the literature in the ferroelectric phase of nearly stoichiometric LiTaO3. Our results are in good agreement with the observed behavior of LiTaO3 crystal. Because of the applications of LiTaO3 in several academic disciplines including the material science and thermal science, it is beneficial to investigate dynamic properties of this crystal such as the damping constant, inverse relaxation time and the activation energy as also we studied here.