Possible observation of a glassy ferroelectric:Bi1.8Pb0.3Sr2Ca2Cu2.8K0.2Oz

Abstract

A glass sample of composition ${\mathrm{Bi}}_{1.8}{\mathrm{Pb}}_{0.3}{\mathrm{Sr}}_{2}{\mathrm{Ca}}_{2}{\mathrm{Cu}}_{2.8}{\mathrm{K}}_{0.2}{\mathrm{O}}_{z}$ was prepared by the conventional quenched-melt technique. The as-quenched sample has been confirmed to be amorphous by x-ray diffraction measurements. The scanning electron microscopy shows no sign of crystalline grain precipitation. Differential thermal analysis indicates a prominent endotherm at 530 K in addition to the glass transition at 607 K and crystallization at 717 K and melting at 1043 K. This extra endothermic peak could possibly be identified as due to a ferroelectric to paraelectric phase transition. This possibility was explored by performing electrical measurements, which include dielectric constant trace, polarization, and hysteresis loops measurements as a function of temperature. It was also found that the transition is irreversible if the glass-transition temperature was reached.