Temperature effect on the structural ferroelectric – paraelectric transition in Li2Ge7O15

Abstract

Li2Ge7O15 (LGO) undergoes the ferroelectric – paraelectric transition at Tc D283.5K. The crystal structure of LGO is orthorhombic with the four formula units in the unit cell in the paraelectric phase (T < TC) . The ferroelectric phase of LGO (T < TC) has also the orthorhombic crystal structure with the pseudotrigonal symmetry of the unit group. In this study, we investigate the structural ferroelectric – paraelectric phase transition in Li2Ge7O15. Temperature effect on various physical properties such as the dielectric constant, spontaneous polarization, reflected intensity related to the order parameter, the Raman frequencies of the lattice (Ag) modes and the linear thermal expansion, is studied here by analyzing the experimental data from the literature close to the ferroelectric - paraelectric transition in Li2Ge7O15. An order-disorder type of transition is indicated on the basis of our analyses of the physical properties studied here within the mean field (molecular field) theory for the ferroelectric - paraelectric transition in Li2Ge7O15.