Scopus İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/8651
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Article Investigation of the Anomalous Behavior of the Linewidth (Damping Constant) for the Raman Ag Modes in Srsno3 Ceramic(Taylor & Francis Ltd, 2022) Kiraci, A.The anomalous behavior of the linewidth (damping constant) for the Raman A(g) modes of 223 cm(-1) and 260 cm(-1) that contribute to the phase transition mechanism of SrSnO3 ceramic close to the phase transition temperatures of T-C1= 650 K and T-C2= 530 K, respectively, was calculated as function of temperature from the pseudospin-phonon coupled (PS) and the energy fluctuation (EF) models below (T < T-C) and above (T > T-C) the phase transition temperatures of T-C1 and T-C2. For this calculation, the frequency shift of these modes were associated as the order parameter and disorder parameter below and above T-C, respectively. Our results are in good agreement with the observed linewidth of these 223 cm(-1) and 260 cm(-1) Raman A(g) modes. In addition, these two models (PS and EF) were used to deduce the values of the activation energy for SrSnO3 ceramic below and above the phase transition temperatures of T-C1 and T-C2.Article Analysis and Mathematical Computation of Some Dynamic Functions for the Guanidine Zinc Sulfate(Taylor & Francis Ltd, 2021) Askun, A. R.; Kiraci, A.A power-law formula with a critical exponent alpha was used to analyze the anomalous behavior of the specific heat for guanidine zinc sulfate (GZS) crystal close to the phase transition temperature of T-c = 178.4 K. The obtained values of 0.13 and 0.14 for alpha below (T < T-c) and above (T> T-c) the phase transition temperature, respectively, were almost the same value of 0.13 (1/8) that predicted from the 3-D (sing model. Also, the internal energy U, the entropy S and the free energy G of this crystal were calculated as a function of temperature dose to the phase transition temperature of T-c = 178.4 K.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 Citation - WoS: 2Citation - Scopus: 3A Phenomenological Study on Ferroelectric Β-Glycine(Taylor & Francis Ltd, 2021) Kiraci, A.The anomalous behavior of the specific heat for beta-glycine was analyzed in terms of the compressible Ising model approximately 5 K below and above the ferrelectric-paraelectric phase transition temperature of T-C =252 K. The obtained value of the critical exponent alpha =0.12 in the ferroelectric phase (T < TC) was consistent with that predicted from the 3-d Ising model (alpha =0.13), while the obtained value of alpha =0.32 in the paraelectric phase (T > TC) was consistent with that predicted from the 2-d potts model (alpha =0.30). Some thermodynamic quantities such as the internal energy, the entropy and the free energy of beta-glycine were then predicted in terms of these extracted values of the critical exponents close to the phase transition temperature of TC. Our calculated values of the thermodynamic quantities are in good agreement with the observed data.Article Analysis and Mathematical Computation of Some Dynamic Function for Strontium Stannate(Taylor & Francis Ltd, 2021) Askun, Ali RizaThe frequency and full width at half maximum (FWHM) data of the A(g) 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 Gruneisen parameter of A(g) 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 Citation - Scopus: 1Phenomenological Approaches on the Nd<sup>3+</Sup> Doped Ferroelectric Labgeo5(Taylor & Francis Ltd, 2021) Kiraci, A.; Yurtseven, Hamit; Kara, N.Two phenomenological models, namely the compressible Ising model and Landau model, have been used to analyze the specific heat and the dielectric constant data, respectively for the pure and Nd3+ doped LaBGeO5 (LBG) crystals. The critical exponent of the specific heat was extracted in both ferroelectric and paraelectric phases of the crystals studied here within the temperature intervals of [T - T-C vertical bar < 4 K. The extracted values of the critical exponent were then used to predict some thermodynamic quantities such as the enthalpy, entropy, and the Gibbs free energy. Regarding the analysis of dielectric constant data within the framework of the Landau theory, the observed values of the birefringence were associated with the order parameter below the transition temperature T-c. The Landau coefficients a(0) and a(4) were determined. Our results indicate a second-order phase transition mechanism.Article Analysis of the Specific Heat and the Free Energy and Calculation of the Entropy and the Internal Energy of [N(ch3)4]2mnbr4 Close To the Phase Transition(Taylor & Francis Ltd, 2021) Kiraci, A.The critical behavior of the specific heat and the Gibbs free energy of [N(CH3)(4)](2)MnBr4 was analyzed using the 'sing model close to the phase transition temperature of T-c = 276.5 K. Obtained value of alpha=0.02 from the Gibbs free energy and from the specific heat approximately 2.0 K and 1.4 K, respectively, below Tc (ferroelastic phase) and also deduced value of alpha= 0.04 from the specific heat approximately 0.3 K above T-c (paraelastic phase) can be compared with that predicted from mean field theory (alpha = 0). Also, the entropy and the internal energy of this crystal were predicted.Conference Object Citation - WoS: 4Citation - Scopus: 4Order-Disorder Transition in the Ferroelectric Litao3(Taylor & Francis Ltd, 2019) Yurtseven, Hamit; Kiraci, AliThe 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 Citation - WoS: 3Citation - Scopus: 4Damping Constant and the Inverse Relaxation Time Calculated as a Function of Pressure Using the X-Ray Diffraction Data Close To the Cubic-Tetragonal Phase Transition in Srtio3(Taylor & Francis Ltd, 2019) Kiraci, A.; Yurtseven, H.The damping constant is calculated as a function of pressure at room temperature using the normalized intensity as an order parameter near the cubic-tetragonal phase transition in SrTiO3. The observed X-ray diffraction data are used for the normalized intensities to calculate the damping constant () from the pseudospin-phonon (PS) coupled model and the energy fluctuation (EF) model, which is fitted to the observed FWHM data from the literature for comparison. Using the calculated values, the pressure dependence of the inverse relaxation time () is predicted close to the cubic-tetragonal phase transition in SrTiO3. Our calculated damping constant from both models explains the observed FWHM satisfactorily and our prediction of the inverse relaxation time can also be compared with the experimental measurements when they are available in the literature.Article Citation - WoS: 3Citation - Scopus: 2Calculation of the Infrared Frequencies as a Function of Temperature Using the Volume Data in the Ferroelectric Phase of Nano2(Taylor & Francis Ltd, 2014) Kiraci, A.; Yurtseven, H.We calculate the temperature dependence of the infrared frequencies of the TO and LO modes with the symmetries of A(1), B-1 and B-2 mainly in the ferroelectric phase of NaNO2. This calculation is carried out using the volume dependence of the infrared frequencies through the mode Gruneisen parameter in this crystal. The volume dependences of the infrared frequencies are fitted to the observed frequencies by using constant mode Gruneisen parameter in the ferroelectric phase of NaNO2. Our results show that this method of calculating the infrared frequencies describes the observed behaviour of NaNO2 adequately.