Crystallization and Dielectric Properties of Ferroelectric Glass-Ceramics Containing Sodium Niobate Crystals

Abstract

Ferroelectric glass-ceramics of the sodium-niobate-aluminum-silicate (NaO-Nb 2 O 5 -SiO 2 +Al 2 O 3 ) system, with various amounts of ZrO 2 added, were synthesized through melt casting followed by controlled crystallization. The crystallization behavior, microstructure, and dielectric performances of the glass-ceramics were investigated. The addition of 1 mol% ZrO 2 to the glass-ceramics improved the glass forming ability of the phase separated melts and supported the formation of transparent glass-ceramics after precipitation of the NaNbO 3 ferroelectric crystals. The presence of ZrO 2 also promoted a well-defined microstructure which presented as an improvement in the dielectric constant of the glass-ceramic heat treated at 750 • C for 1 h. Dipole polarization was responsible for the dielectric response of the glass-ceramics, but due to structural heterogeneities coupled with high migration of the mobile species, a complicated dielectric relaxation mechanism was also found.