Scopus İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/8651
Browse
3 results
Search Results
Article Analysis of the α-β Transition in Bismuth Titanate as a Function of Pressure and Temperature(Taylor & Francis Ltd, 2026) Kiraci, A.The temperature and pressure dependence of the damping constant (half-width) for the soft Raman mode in bismuth titanate, Bi2Ti4O11, was calculated using the pseudospin-phonon coupled (PS) and the energy fluctuation (EF) models in the vicinity of the transition at T-C = 513 K and P-C = 3.7 GPa. The order parameter that is associated with the observed soft Raman mode frequency and also the pressure-temperature phase diagram was used for this calculation of the damping constant. Our calculated values of both the Raman frequency and the damping constant were compared with the observed data from the literature. Finally, the values of the activation energy were deduced using our calculated damping constant via the Arrhenius plots.Article Citation - WoS: 1Citation - Scopus: 1Calculation of the Spin-Lattice Relaxation Time and the Activation Energy Near the Iv-Iii Phase Transition in Pyridinium Fluorosulfonate (C5nh6)fso3(Taylor & Francis Ltd, 2022) Kara, N.; Kiraci, A.; Yurtseven, HamitThe spin-lattice relaxation time T-1(H) for protons nuclei is calculated in term of the pseudospin-phonon (PS) coupled and the energy fluctuation (EF) models close to the IV-III solid-solid phase transition of T-C = 235 K in (C5NH6)FSO3. This calculation was performed by associating the observed second moment of the H-1 as the order parameter below k and the disorder parameter above T-C. Values of the activation energy for the cation reorientation in this crystal are also deduced by using both models. In addition, the observed dielectric permittivity of this crystal is analyzed within the framework of the Landau theory and values of the spontaneous polarization (P-s) are determined as a function of temperature. The normalized values of P-s are used in the PS and EF models to extract the activation energy for the reorientation of the dipole moment of this compound arising from cation-anion interaction. Our results show that the PS and EF models can describe the observed behavior of the spin-lattice relaxation time adequately for the IV-III solid-solid transition in (C5NH6)FSO3.Article Calculation of the Halfwidth and the Activation Energy for the Soft Raman Modes in the Brominated Compounds of Tris-Sarcosine Calcium Chloride(Walailak University, 2022) Kiraci, A.This letter contributes how to calculate the anomalous behavior for the damping constant (halfwidth) of the ferroelectric Tris-Sarcosine Calcium Chloride (TSSC) and its brominated compounds TSSC1−xBrx (x = 0.13, 0.42 and 0.60) from the wavenumber data of the soft modes below the phase transition temperature of TC. The pseudospin-phonon coupled (PS) and the energy fluctuation (EF) models derived from the dynamical Ising model were used. Both PS and EF models have been used to contribute understanding the temperature dependence of the phase transition mechanism of TSSC1−xBrx. In addition, values of the activation energy for TSSC1−xBrx (x = 0, 0.13, 0.42 and 0.60) were extracted from the damping constant as calculated from both models (PS and EF). Our results indicate order-disorder type phase transition for TSSC1−xBrx. © 2022, Walailak University. All rights reserved.