Alpha-beta transition in quartz

2^nd International Conference and Exhibition on Materials Science & Engineering

October 07-09, 2013 Hampton Inn Tropicana, Las Vegas, NV, USA

H. Yurtseven

Accepted Abstracts: J Material Sci

Abstract :

Quartz exhibits the α-β transition through the incommensurate phase at Ti= 847.2 K. This intermediate phase (IC) occurs in a narrow temperature interval (~1.3 K) between the α and β phases. In this study, we investigate the temperature dependence of the thermodynamic quantities such as the thermal expansion and specific heat close to the α-β transition in quartz. In the vicinity of the α-IC-β transition, the critical behavior of the specific heat Cp , in particular, is described by a power law formula with the critical exponent a. Also, critical behavior of the Bragg peak intensity related to the order parameter due to a tilting of SiO 2 tetrahedra around the threefold axis is analyzed close to the α-IC-β transition by a power-law formula with the critical exponent b. Other aspects of our study on the α-β transition in quartz are to predict the Raman frequencies of a soft mode which drives this crystalline system to the transition, using the volume data through the mode Grüneisen parameter. We have extended this work to calculate the Raman frequency in the case of SiO 2 -moganite close to the α-β transition. We also predict the temperature dependence of the damping constant (bandwidth) using the Raman frequency related to the order parameter by the soft mode-hard mode coupling model and the energy fluctuation model close to the α-β transition in quartz. For all these analyses and calculations, experimental data from the literature are used and our predicted values are discussed within the framework of some other theoretical models to explain the mechanism of the α-IC-β transition in quartz.

Biography :

H. Yurtseven received his Ph.D. degree at the King?s College London, University of London, England in 1984. He had worked at the Ankara University from 1985 to 1987. For one year (1988-1989), he did research work at the University of Rome, Tor Vergata, Italy. Then, from 1987 to 2003, he worked at the Istanbul Technical University, Istanbul, Turkey. Since 2003, he has been working at the Middle East Technical University.