Study on α-β Quartz phase transition and its effect on dielectric properties

In this paper, the Landau theory and ab initio molecular dynamics are applied to study the temperature induced α-β quartz phase transition, and its influences on dielectric properties are measured experimentally. Based on the Landau theory, the quartz phase transition is found to be a displacive second order transition. Moreover, the atomic displacements in different directions during the phase transition are obtained. The phase transition temperature is accurately estimated from the calculated structural parameters based on ab initio molecular dynamics. The dielectric experiments are carried out to study the effects of phase transition on dielectric properties, and strong anisotropy in different directions is observed. In [100] direction, a strong peak in the real part of dielectric function occurs near the phase transition temperature especially at the low frequency. However, the dielectric properties in [001] direction are hardly affected by phase transition. These phenomena can be interpreted successfully based on the calculated atomic displacements in different directions. In addition, the observed peaks of experimental dielectric spectra near the transition temperature can be also explained in terms of the dipole orientation polarization caused by atomic displacements during the phase transition.