New opportunity in alkali niobate ceramics processed in low oxygen partial pressure

Abstract

Alkali niobate ceramics, such as (Na_0.5K_0.5)NbO₃, has been considered as a promising candidate for lead free piezoelectrics and been a subject of growing interest. We focused on the effects of low oxygen partial pressure (pO₂) firing of alkali niobate ceramics, and found that piezoelectric and dielectric properties are essentially independent of the firing atmosphere. Furthermore, low pO₂ firing provides better electrical resistivity and microstructure than air firing, which can be explained by the fact that alkali volatilization is suppressed in low pO₂ firing condition. This opens new opportunities for base meal cofired multilayer applications in the alkali niobate perovskite system. We also found that low pO₂ fired NaNbO₃-NaTaO₃ solid state ceramic exhibited a much higher resistivity than conventional ferroelectric ceramics such as BaTiO₃, and also showed relatively high permittivity at high temperatures up to 250 °C, which make this ceramic promising as a capacitor material for the expanding high temperature.