Ortak Dersler Bölümü
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Browsing Ortak Dersler Bölümü by Subject "Activation Energy"
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Article Analysis and mathematical computation of some dynamic function for strontium stannate(2021) Aşkun, Ali Rıza; 56475The frequency and full width at half maximum (FWHM) data of the Ag Raman modes (95.4, 231.4 and 263.2 cm−1) in strontium stannate crystal have been analyzed using the Balkanski model and the fitting parameters were determined. Also, the isobaric Grüneisen parameter of Ag Raman modes studied here was computed below the room temperature. This computation was performed from the unit cell volume and the observed frequency data of this crystal. Finally, values of the activation energy were extracted close to the structural phase transition temperatures of 160 and 265 K using the observed FWHM data of strontium stannate.Article Order-disorder transition in the ferroelectric LiTaO3(2019) Kiracı, Ali; Yurtseven, Hamit; 42475The temperature dependences of the damping constant and the relaxation time are calculated by using the Raman frequencies of a* and the lowest A(1) (TO) phonons in the ferroelectric phase close to the ferroelectric-paraelectric transition in LiTaO3 (T-C = 963 K). Both calculations are performed by considering the frequency as an order parameter for the pseudospin-phonon (PS) and the energy fluctuation (EF) models using the observed data from the literature. Values of the activation energies of this crystal are also deduced by using both models in this crystal. Our results show that the PS and EF models can describe the observed behavior adequately for the order-disorder transition in LiTaO3.Article The Important Role of N(2)(CH3)(4) Ion in the Phase-Transition Mechanism of [N(CH3)(4)](2)ZnBr4(2020) Kiracı, AliThe chemical shift of the N(2)(CH3)(4) ion, which has been found to exhibit the similar anomalous behavior of the monoclinic angle $\Delta \beta $ , was related to the order parameter to evaluate the temperature dependence of the linewidth (damping constant) for N-14 nuclear magnetic resonance spectrum of this crystal in terms of the dynamic Ising models, namely the pseudospin-phonon-coupled (PS) and the energy fluctuation (EF) models. The results from both PS and EF models were successful to explain the abnormal behavior of the linewidth in the vicinity of the phase-transition temperature of ${T}_{C}= {287.6}$ K, when compared with the observed linewidth of the transverse acoustic soft mode in this crystal. As an extension of this work, the N-14 relaxation time and the values of the activation free energy were calculated as a function of temperature. The results indicate that the ferroelastic-paraelastic phase transition in this compound is of the order-disorder type.
