Grain‐Oriented Glass‐Ceramics for Piezoelectric Devices

Abstract

Grain‐oriented glass‐ceramics of Li 2 Si 2 o 5 , fresnoite (Ba 2 TiSi 2 O 8 ), and its isomorphs Sr 2 TiSi 2 O 8 , and Ba 2 TiGe 2 O 8 , were prepared by recrystallizing glasses in a temperature gradient. Electromechanical and hydrostatic piezoelectric properties of these glass‐ceramics were measured. Piezoelectric voltage coefficients g 33 and hydrostatic voltage coefficient g h of these glass‐ceramics are comparable to those of polyvinylidene fluoride and an order of magnitude higher than the corresponding values of lead zirconate‐titanate. These glass‐ceramics seem to be attractive candidate materials for hydrophones and several piezoelectric devices. Hydrostatic piezoelectric properties of Ba 2 TiSi 2 O 8 and Ba 2 TiGe 2 O 8 single crystals were also measured. The unusually high values of g h in fresnoite single crystals and glass‐ceramics are supposed to be due to positive d 31 in these materials. A composite model is proposed to explain the positive sign of d 31 in fresnoite based on its crystal structure and internal Poisson's ratio stress.